Pracownicy

Streszczenie:
In this paper, the fatigue performance of the aluminide layer-coated and as-received MAR 247 nickel superalloy with three different initial microstructures (fine grain, coarse grain and column-structured grain) was monitored using nondestructive, eddy current methods. The aluminide layers of 20 and 40 µm were obtained through the chemical vapor deposition (CVD) process in the hydrogen protective atmosphere for 8 and 12 h at the temperature of 1040 °C and internal pressure of 150 mbar. A microstructure of MAR 247 nickel superalloy and the coating were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). It was found that fatigue performance was mainly driven by the initial microstructure of MAR 247 nickel superalloy and the thickness of the aluminide layer. Furthermore, the elaborated methodology allowed in situ eddy current measurements that enabled us to localize the area with potential crack initiation and its propagation during 60,000 loading cycles.

Słowa kluczowe:
chemical vapor deposition, nickel alloys, aluminide coatings, fatigue, eddy current

Streszczenie:
In this paper, fracture behavior of four types of implants with different geometries (pure titanium locking plate, pure titanium femoral implant, Ti-6Al-4V titanium alloy pelvic implant, X2CrNiMo18 14-3 steel femoral implant) was studied in detail. Each implant fractured in the human body. The scanning electron microscopy (SEM) was used to determine the potential cause of implants fracture. It was found that the implants fracture mainly occurred in consequence of mechanical overloads resulting from repetitive, prohibited excessive limb loads or singular, un-intendent, secondary injures. Among many possible loading types, the implants were subjected to an excessive fatigue loads with additional interactions caused by screws that were mounted in their threaded holes. The results of this work enable to conclude that the design of orthopedic implants is not fully sufficient to transduce mechanical loads acting over them due to an increasing weight of treated patients and much higher their physical activity.

Słowa kluczowe:
medical fixation devices, orthopedic prostheses and implants, titanium, titanium alloy, stainless steel, microscopic fracture analysis

Streszczenie:
The paper reports experimental and numerical study of different deformation mechanisms activated in the AZ31B mag nesium alloy sheet subjected to cyclic in-plane tensile – compressive deformation. The influence ofslip, twinning and detwinning upon the mechanical response and texture evolution of the material is thoroughly investigated. The regime of twinning and detwinning activity is assessed based on the variation of hardening modulus in the course of the process. Velocity-based large strain crystal plasticity model accounting for twinning and detwinning is formulated. The crystal plasticity model parameters are identified using the implementation of the evolutionary algorithm. Predicted activity of deformation mechanisms is discussed with respect to the experimental data.

Słowa kluczowe:
twinning, detwinning, crystal plasticity, magnesium alloys, AZ31B, evolutionary algorithm

Streszczenie:
The aim of this research was to compare the effect of 80 000 h exploitation time in high temperature on mechanical properties and microstructure of X10CrMoVNb9-1 (P91) power engineering steel for pipes. The specimens obtained from two pipes: new, as-received and after exploitation were subjected to fatigue loadings to compare their mechanical responses. Additionally, the uniaxial tensile tests on both types of P91 steel were performed. The microstructure evolution before and after deformation was monitored using optical and scanning electron microscopy. The time intensive, high temperature exposure of P91 power engineering steel led to significant phase transformation and subsequent deterioration of mechanical properties and was further described as a function of the fatigue damage measure, φ, and the fatigue damage parameter D. Further proposed methodology of power exponent approximation of the fatigue damage measure, φ, and fatigue damage parameter D, allowed to successfully determine the fatigue life of P91 steel.

Słowa kluczowe:
fatigue development, damage, P91 steel, microstructure

Streszczenie:
In this paper, mechanical properties of the as-received and aluminide layer coated MAR 247 nickel based superalloy were examined through creep and fatigue tests. The aluminide layer of 20 µm was obtained through the chemical vapor deposition (CVD) process in the hydrogen protective atmosphere for 8 h at the temperature of 1040 °C and internal pressure of 150 mbar. A microstructure of the layer was characterized using the scanning electron microscopy (SEM) and X-ray Energy Dispersive Spectroscopy (EDS). It was found that aluminide coating improve the high temperature fatigue performance of MAR247 nickel based superalloy at 900 °C significantly. The coated MAR 247 nickel based superalloy was characterized by the stress amplitude response ranging from 350 MPa to 520 MPa, which is twice as large as that for the uncoated alloy.

Słowa kluczowe:
chemical vapor deposition, nickel alloys, aluminide coatings, high temperature fatigue, creep

Streszczenie:
This paper focuses on the mechanical properties analysis of the high strength S700MC steel applied in welding joints. The research comprised mechanical tests for checking what the changes of tensile characteristics, mechanical parameters, resistance to impact, and fracture toughness look like in selected regions of the welding joint. Stress-strain curves have shown significant differences in the tensile characteristic shape and the values of Young's modulus, yield stress, ultimate tensile strength, and ductility due to the welding process applied. In the case of Charpy tests, the courses of the accumulated energy, force, deflection, and project velocity are presented, indicating the maximum value of absorbed energy, the same level of force during the first contact of the projectile with the specimens, and the significant variation of the velocity for the impact energy ranging from 50 J up to 300 J. On the basis of the fracture toughness tests, the distributions of the CTOD (Crack Tip Opening Displacement) values are presented for the parent material, HAZ (Heat Affected Zone) and weld. Moreover, the characteristic features of the fatigue pre-crack, transient and crack propagation zones are identified and discussed.

Słowa kluczowe:
high strength steel, weld, HAZ, tensile curve, impact, fracture toughness, CTOD, fractography, S700MC

Streszczenie:
In this paper, aluminide coatings of various thicknesses and microstructural uniformity obtained using chemical vapor deposition (CVD) were studied in detail. The optimized CVD process parameters of 1040 °C for 12 h in a protective hydrogen atmosphere enabled the production of high density and porosity-free aluminide coatings. These coatings were characterized by beneficial mechanical features including thermal stability, wear resistance and good adhesion strength to MAR 247 nickel superalloy substrate. The microstructure of the coating was characterized through scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Mechanical properties and wear resistance of aluminide coatings were examined using microhardness, scratch test and standardized wear tests, respectively. Intermetallic phases from the Ni-Al system at specific thicknesses (20-30 µm), and the chemical and phase composition were successfully evaluated at optimized CVD process parameters. The optimization of the CVD process was verified to offer high performance coating properties including improved heat, adhesion and abrasion resistance.

Słowa kluczowe:
chemical vapor deposition, nickel alloys, coatings, X-ray analysis

Streszczenie:
In this paper, experimental verification of the microstructural evolution model during sintering of aluminum, iron and particulate mullite ceramic powders using self-propagated high-temperature synthesis (SHS) was performed. The powder mixture with 20% wt. content of reinforcing ceramic was investigated throughout this research. The mixed powders were cold pressed and sintered in a vacuum at 1030 °C. The SHS reaction between sintered feed powders resulted in a rapid temperature increase from the heat generated. The temperature increase led to the melting of an aluminum-based metallic liquid. The metallic liquid infiltrated the porous SiO2 ceramics. Silicon atoms were transited into the intermetallic iron-aluminum matrix. Subsequently, a ternary matrix from the Fe-Al-Si system was formed, and synthesis of the oxygen and aluminum occurred. Synthesis of both these elements resulted in formation of new, fine Al2O3 precipitates in the volume of matrix. The proposed microstructural evolution model for growth of ultra-fine Al2O3 oxides from SiO2 silica ceramic decomposition during SHS was successfully verified through scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD).

Słowa kluczowe:
intermetallics, powder methods, electron microscopy, X-ray analysis

Streszczenie:
The present work provides description of fatigue crack initiation in metals subjected to cyclic loading within the nominal elastic or initial elastic-plastic regimes next passing to elastic response during cyclic deformation and shake down process. It is assumed that damage growth proceeds due to action of local stress, specified as the sum of mean stress and its fluctuations induced by material inhomogeneities such as grain boundaries, inclusions, cavities, boundary asperities, also due to design notches or holes introduced into the element. The damage growth model is proposed, based on the critical plane concept. The macrocrack initiation then corresponds to a critical value of accumulated damage. The modelling of damage growth is supported by Electronic Speckle Pattern Interferometry (ESPI) apparatus using the coherent laser light. The damage growth effect is analysed by microindentation tests. The fatigue tests are performed for high strength steel specimens with central hole.

Słowa kluczowe:
fatigue crack initiation, micro-plasticity, damage evolution, optical ESPI method, micro indentation

Streszczenie:
The paper concerns the study of polymer-glass composite under tensile loading in order to determine changes in the tensile characteristics. Mechanical properties and features of damage zones important for operation and assessment of the technical conditions of the components made of this material are considered. Selected details of the experimental technique used are presented. The tensile characteristics of the polymer-glass composite are given. They were determined using specimens taken from various directions, with the main focus on the Young's modulus, elastic limit, yield point and ultimate tensile strength. An influence of the number of reinforcement layers, percentage content of the glass fibres as well as the resin quantity, on the mechanical parameters, are discussed.

Słowa kluczowe:
composite, reinforcement, anisotropy, tensile curve, mechanical properties, structure, degradation, cracking, delamination

Streszczenie:
The mechanical anisotropy of a multifunctional titanium alloy, Gum Metal, is investigated in this paper. The structural characterisation showed a strong <110> texture for Gum Metal, that is a result of the cold-swaging process applied during its manufacture. Gum Metal was treated as a transversally isotropic solid because of this texture. A significant difference from Young's moduli of the alloy was detected from the ultrasonic measurement of parallel and perpendicular directions to the alloy swaging direction. Samples of Gum Metal cubes were compressed in two different orientations. During the deformation process, two perpendicular walls of each sample were monitored by two visible range cameras for further two-dimensional digital image correlation analysis, this confirmed a strong plastic anisotropy in Gum Metal.

Słowa kluczowe:
gum metal, compression, mechanical anisotropy, digital image correlation, ultrasonic measurement, texture, titanium alloy, full-field deformation measurement

Streszczenie:
The paper reports experimental results describing behaviour of the AM60 magnesium alloy under impact test. The material was examined at energy in the range from 170 to 690 J, using impact tower with the projectile of conical shape. Results are presented in a form of variations of accumulated energy, force, projectile velocity and its displacement versus time. The characteristic features appearing in courses of force and accumulated energy are illustrated. Fractography and microstructure of damage zones for distinguishing the alloy degradation are shown. The fracture regions of the material examined are represented by cracks and plug-shaped deformation.

Słowa kluczowe:
magnesium alloy, impact, projectile, perforation, fractography, microstructure

Streszczenie:
The article presents variations of rms Barkhausen noise envelopes in the medium-carbon steel used in automotive and power industry. The material was subjected to different loading processes: monotonic loading at room temperature, and constant loading at elevated temperature. The first one enforced a plastic deformation, whereas the second one a creep. The changes of Barkhausen signal were analysed using microstructural observations including X-ray measurements. In the second part of the paper, the magnetic structure and pinning effect were illustrated by means of the Lorentz microscopy.

Słowa kluczowe:
Barkhausen noise, magnetic structure, plastic deformation, creep, dislocation density

Streszczenie:
W pracy omówiono przyczyny występowania uszkodzeń i ich rodzaje. Zawarto cechy charakterystyczne przełomów zmęczeniowych w odniesieniu do wskazania przyczyn ich występowania. Zaprezentowano wybrane stanowiska badawcze do testowania podzespołów motoryzacyjnych i ich wersje modułowe – wyposażane w specjalistyczne komory oraz rekonfigurowalne – zawierające gabarytową płytę montażową. Przedstawiono szczegóły testów stanowiskowych komponentów pojazdów specjalnych, jak ramy wychylne oraz stałe, w tym wykonane ze stali wysokowytrzymałej S700MC. Zaprezentowano charakterystyki naprężenie-odkształcenie, parametry mechaniczne oraz krzywe Wöhlera wymienionego rodzaju materiału w stanie dostawy i po spawaniu.

Streszczenie:
In this paper, the influences of build orientation and post-fabrication processes, including stress-relief, machining, and shot-peening, on the fatigue behavior of stainless steel (SS) 316L manufactured using selective laser melting (SLM) are studied. It was found that horizontally-built (XY) and machined (M) test pieces, which had not been previously studied in the literature, in both stress-relieved (SR) or non-stress-relieved (NSR) conditions show superior fatigue behavior compared to vertically-built (ZX) and conventionally-manufactured SS 316L. The XY, M, and SR (XY-M-SR) test pieces displayed fatigue behavior similar to the XY-M-NSR test pieces, implying that SR does not have a considerable effect on the fatigue behavior of XY and M test pieces. ZX-M-SR test pieces, due to their considerably lower ductility, exhibited significantly larger scatter and a lower fatigue strength compared to ZX-M-NSR samples. Shot-peening (SP) displayed a positive effect on improving the fatigue behavior of the ZX-NSR test pieces due to a compressive stress of 58 MPa induced on the surface of the test pieces. Fractography of the tensile and fatigue test pieces revealed a deeper understanding of the relationships between the process parameters, microstructure, and mechanical properties for SS 316L produced by laser systems. For example, fish-eye fracture pattern or spherical stair features were not previously observed or explained for cyclically-loaded SLM-printed parts in the literature. This study provides comprehensive insight into the anisotropy of the static and fatigue properties of SLM-printed parts, as well as the pre- and post-fabrication parameters that can be employed to improve the fatigue behavior of steel alloys manufactured using laser systems.

Słowa kluczowe:
selective laser melting, stainless steel 316L, fatigue, defect, fracture

Streszczenie:
The paper presents experimental and numerical results of the TiNi shape memory alloy (SMA) subjected to a modified program of force-controlled tensile loading. The time-dependent development of transformation strain under the constant-force conditions was investigated to describe transformation-induced creep phenomena. (2) Mechanical characteristics of the TiNi SMA were derived using a testing machine, whereas the SMA temperature changes accompanying its deformation were obtained in a contactless manner with an infrared camera. A 3D coupled thermo-mechanical numerical analysis, realized in a partitioned approach, was applied to describe the SMA mechanical and thermal responses. (3) The stress and related temperature changes demonstrated how the transformation-induced creep process started and evolved at various stages of the SMA loading. The proposed model reproduced the stress, strain and temperature changes obtained during the experiment well; the latent heat production is in correlation with the amount of the martensitic volume fraction. (4) It was demonstrated how the transformation-induced creep process occurring in the SMA under such conditions was involved in thermo-mechanical couplings and the related temperature changes.

Słowa kluczowe:
TiNi shape memory alloy, phase transformation-induced creep, martensitic transformation, temperature change, thermomechanical couplings, infrared camera, thermo-mechanical coupled numerical analysis

Streszczenie:
The paper presents experimental results from test on tow truck frame made of the high strength steel S700MC subjected to fatigue loading. The mounting manner of the frame with anti-vibration platform and connection with a coupling ball to apply the loading are presented. Cracks features captured by means of macrophotography and microscopic observations are illustrated. Reasons for the crack occurrence are discussed by the use of fractography, hardness tests, microstructural analysis of the parent material, Heat Affected Zone and weld.

Słowa kluczowe:
cyclic loading, fatigue, fracture, crack, higth strength steel, hardness, microstructure, welding, HAZ

Streszczenie:
The research concerns investigation of yielding and developing of the strain localization in new β-Ti alloy characterized by unique elastic-plastic properties, named Gum Metal. The alloy was subjected to tension on testing machine at three various strain rates up to rupture. Digital image correlation and infrared thermography were applied to analyze the experimental results. Strain distributions were determined on the basis of digital image correlation algorithm. The related temperature variations were found in contactless manner using infrared thermography. Mechanical and the corresponding thermal data were used to study the Gum Metal large nonlinear reversible deformation and localization effects.

Słowa kluczowe:
gum metal, tension, large nonlinear elastic deformation, thermomechanical couplings, temperature change, digital image correlation

Streszczenie:
The change in the dislocation density, induced by plastic deformation, influences strongly the magnetic domain structure inside the material. Being so, classic parameters, like the coercivity or magnetic permeability, can be a good measure of the deformation level, yet their reliable determination in a non-destructive way in industrial environment is problematic. The magnetoacoustic emission (MAE) which results from the non-180o domain walls (DW) movement in materials with non-zero magnetostriction can be used as an alternative. The intensity of the MAE signal changes strongly as a result of plastic deformation for both tensile and compressive deformation. It is however possible to discern those cases by analysing the changes in the shape of the MAE signal envelopes. The set of the martensitic steel samples (P91) deformed up to 10 % (for both tension and compression) was investigated. Due to geometrical limitations imposed by the special mounting system, enabling compression of the samples without buckling, had the shape resulting in low signal to noise (S/N) ratio. Being so the optimization of FFT filtering and wavelet analysis was performed in order to improve sensitivity of the proposed method of deformation level determination.

Słowa kluczowe:
magnetic flux leakage, nondestructive testing, wavelet transform

Streszczenie:
The paper presents an attempt of application of the acoustic birefringence coefficient for early stage degradation assessment of Inconel 718 nickel superalloy after short-term creep. It is shown that it can serve as a good damage sensitive parameter and, moreover, it can be well correlated with hardness variation.

Słowa kluczowe:
creep, nickel superalloy, microstructure, pre-deformation, hardness, acoustic birefringence

Streszczenie:
The paper reports the results of tests carried out for kinematic properties determination of components under cyclic loading. DIC system called 5M PONTOS was employed to follow variations of displacement versus time. It was conducted by the use of markers stuck on selected sections of components tested. The results are presented in 2D and 3D coordinate systems expressing behaviour of such elements as: mechanical coupling device, boat frame and car engine. These data enabled to capture weak and strong sections of the component examined at various loading conditions.

Słowa kluczowe:
Digital Image Correlation System, Cyclic Loading, PONTOS, Motion, Displacement, 3D Coordinate System

Streszczenie:
W pracy zaprezentowano wyniki badań trwałościowych końcówki drążka kierowniczego pojazdu o dmc powyżej 3.5 tony. W badaniach wykorzystywano wielkogabarytową platformę wibroizolowaną, serwohydrauliczny siłownik mobilny oraz cyfrowy kontroler sygnałów IST Instron. Próby prowadzono w warunkach działania obciążenia zmiennego cyklicznie do uzyskania 2×106 cykli. Ze względu na kompleksową ocenę zachowania końcówki drążka kierowniczego testy przerywano, by wykonywać oględziny obiektu badań. Wyznaczono zmiany kąta wychylenia oraz momentu siły w funkcji liczby cykli oraz przedstawiono ich prognozę. Omówiono procedurę badawczą służącą ocenie trwałości przegubu kulistego.

Słowa kluczowe:
przegub, zmęczenie, obciążenie zmienne cyklicznie, liczba cykli, trwałość, pęknięcie

Streszczenie:
The paper describes an application of non-destructive volumetric magnetic and ultrasonic techniques for evaluation of the selected mechanical parameter variations of P91 steel having direct influence on its suitability for further use in critical components used in power plants. Two different types of deformation processes were carried out. First, a series of the P91 steel specimens was subjected to creep and second, one to plastic deformation in order to achieve the material with an increasing strain level up to 10%. Subsequently, non-destructive and destructive tests were performed. Magnetic methods based on measurements of magnetoacoustic emission and magnetic hysteresis loop changes as well as the ultrasonic method based on acoustic birefringence measurements, were applied. Finally, the static tensile tests were carried out in order to evaluate the mechanical parameters. It is shown that some relationships between the selected parameters coming from the non-destructive and destructive tests may be formulated.

Słowa kluczowe:
Creep, Plastic deformation, Acoustic birefringence, Magnetoacoustic emission, Magnetic hysteresis loop

Streszczenie:
The paper presents the results of investigation of the influence of plastic deformation on the magnetic properties of martensitic steel (P91 grade). The properties of the hysteresis loops as well as of the Barkhausen effect (BE) signal are analysed for both tensile and compressive loading up to ε=10% of plastic deformation. The choice of the steel and of the deformation range is unique, since for such combination one can expect high residual stresses (both compressive and tensile) in the material that does not exhibit saturation of the BE intensity as a function of elastic stress. The obtained relationships show that for the low level of deformation the dislocation density changes may play a dominant role, yet for higher deformation level the residual stress becomes a dominant factor. It leads to the strong decrease of the BE signal for tensile deformation and an increase for the case of compression. It agrees well with the assumption that the tensile plastic deformation results in the compressive stresses appearance in the soft (magnetically active) sub-regions of the material whereas for the compression one can expect a residual stress of a tensile nature in those areas. Both deformation modes result in the increase of coercivity of the samples, yet the increase observed for the tensile deformation is significantly higher since both the residual compressive stress and increase of dislocation density have a strong effect on the material coercivity. The change of the hysteresis loops steepness agrees well with the notion of the dominant role of residual stresses too.

Słowa kluczowe:
Barkhausen effect, Plastic deformation, Residual stress, Magnetic hysteresis, Coercivity

Streszczenie:
The present work is devoted to simulation of fatigue crack initiation for cyclic loading within the nominal elastic regime. It is assumed that damage growth occurs due to action of meanstress and its fluctuations induced by crystalline grain inhomogeneity and the free boundary effect. The macrocrack initiation corresponds to a critical value of accumulated damage. The modelling of damage growth is supported by Electronic Speckle Pattern Interferometry (ESPI) apparatus using coherent laser light.

Słowa kluczowe:
fatigue crack initiation, damage evolution, optical methods

Streszczenie:
W pracy omówiono wybrane materiały stosowane w układach hamulcowych, jak: żeliwo szare, kompozyty ceramiczne oraz metalowe o osnowie ze stopu aluminium. Zaprezentowano ich zasadnicze właściwości mechaniczne oraz parametry fizyczne. Ponadto, omówiono zmiany granicy plastyczności i wytrzymałości doraźnej żeliwa szarego w warunkach rozciągania prowadzonego przy dziewięciu poziomach temperatury w zakresie od 20 °C do 700 °C

Streszczenie:
This paper presents an investigation of thermomechanical effects related to the phenomena of stress relaxation occurring in TiNi SMA subjected to modified program of displacement-controlled tension. The deformation data were taken from testing machine, whereas the temperature changes accompanying the exothermic/endothermic martensite forward/reverse transformation were measured by infrared camera. At the advanced stages of the transformations, the strain was kept constant for a few minutes and the SMA load and temperature were recorded continuously. As a consequence, the stress and temperature changed significantly during the loading stops. A large stress drop, caused by the transformation, was observed during the relaxation stage in both courses of the SMA loading and unloading. Moreover, the non-uniform temperature distribution, reflecting macroscopically inhomogeneous transformation, lapsed while the strain was kept constant, yet restarted at the end of the relaxation stop and developed at the reloading stage. Along with the experimental results, the mechanical and thermal responses induced by the transformation were obtained by 3D coupled thermomechanical numerical analysis, realized in partitioned approach. Latent heat production was correlated with an amount of the martensitic volume fraction. The stress and temperature drops recorded during the experiment were satisfactorily reproduced by the model proposed for the SMA thermomechanical coupling

Słowa kluczowe:
TiNi shape memory alloy, Superelasticity, Stress relaxation, Temperature change, Thermomechanical couplings, 3-D model

Streszczenie:
Fatigue loading induces a microstructure evolution leading to the change of macroscopically observed mechanical behavior of a dual phase DP500 steel. It was assumed that stress–strain characteristic of a pre-fatigued material may be determined using constitutive equation taking into account damage parameter. To estimate development of the fatigue damage in specimen a variation of the inelastic strain component was applied.

The flat „dog-bone” specimens were initially loaded using stress controlled cycles. When the strain reached a given value the fatigue process was stopped. Subsequently, the specimens with introduced fatigue damage were subjected to tensile tests. Next, the Johnson-Cook's constitutive equation was calibrated separately for each pre-fatigue case. Finally, a new constitutive relationship, based on the Johnson-Cook's model was proposed. It reflects the hardening and softening effects by taking into account both a change in the dislocation structure and development of fatigue microdamage. Proposed model shows a very good agreement with experimental data.

Słowa kluczowe:
Constitutive model, Dual-phase steel, Fatigue, Stress–strain curve, Fatigue damage, Inelastic strain

Streszczenie:
Materials and semi-manufactured products for aviation equipment are usually subjected to increasingly rigorous demands for the quality control. In many cases, like hardened or carburized wheels or rollers assembled in the gear motors, the control procedures enforce necessity of the selective testing of details coming from production lines using destructive techniques. The main aim of diagnostic investigations carrying out on series of final products is to assess qualitatively and quantitatively the layers obtained due to carburizing and induction hardening. Unfortunately, such processes increase the fabrication costs significantly, especially in the case of complex manufacturing technology applied and small-lot production as well. In order to reduce them the attempts for application of non-destructive testing methods are taken for evaluation of either the layers quality or the products subjected to surface treatments. This paper presents the eddy currents method used for the thickness evaluation of the carburized and induction-hardened layers on the basis of the impedance signal variation. The signal was obtained as a result of the so-called ‘lift off’ effect. A methodology for the quantitative thickness evaluation of the carburized and induction-hardened layers has been elaborated under a range of technological parameters. The measurements ranges were defined in the framework of which an identification of the hardened layer was possible using the commercial defectoscope and reference specimens of the fixed thickness. Tests were carried out on specimens made of the ASM6414 steel and subjected subsequently to carburization and induction hardening. The impedance parameters were measured for selected values of frequency. The results were verified on the basis of metallographic investigations as well as the microhardness measurements captured in the form of profiles taken from specimens’ cross-sections of different layer thickness.

Słowa kluczowe:
eddy current, hardening, carburizing, layers, non-destructive technique

Streszczenie:
Fatigue damage process developing in structural materials under long-term cyclic loading is still an unsolved problem of modern engineering. Attempts to assess a degree of materials degradation under fatigue conditions on the basis of changes in the areas of local strain concentration determined by optical methods can be treated as the promising contemporary research direction of majority of scientific centres in the world. In most cases, fatigue damage has a local character and it is based on damage development leading to generation of cracks appearing around structural defects or geometrical notches. An identification of these areas and their subsequent monitoring requires a full-field displacement measurements performed on the objects surfaces. It seems that modern contemporary optical methods for displacement components measuring on the surfaces of structural elements or tested specimens are suitable for such purpose. Digital Image Correlation (DIC) and Electronic Speckle Pattern Interferometry (ESPI) are nowadays the most widely used testing methods in this area. Both of them enable capturing of displacement and strain components distributions. This paper presents an attempt to use the ESPI method for fatigue damage evaluation and its monitoring on specimens made of the aluminide coated nickel super-alloys. Flat specimens were subjected to cyclic loading. The fatigue tests were interrupted several times in order to perform a static loading during which the optical measurements were carried out. An analysis of the results captured by the ESPI system allowed indication of places of the greatest stress concentration and demonstration of the damage development process as a function of the increasing number of cycles.

Słowa kluczowe:
fatigue, damage, super-alloy, Electronic Speckle Pattern Interferometry

Streszczenie:
W pracy omówiono technike cyfrowej korelacji obrazu (DIC) przeznaczona do bezkontaktowego okreslania rozkładów składowych przemieszczenia i na ich podstawie obliczania składowych odkształcenia oraz naprezenia. Umozliwia ona równiez wyznaczanie parametrów kinematycznych obiektów inzynierskich w postaci predkosci i przyspieszenia, które okreslane sa metoda rózniczkowania po czasie zarejestrowanych wartosci składowych przemieszczenia. Zaprezentowano polowe zmiany rozkładów odkształcenia wzdłuznego oraz rozkładów składowych głównych odkształcenia podczas rozciagania stali konstrukcyjnej, które monitorowano az do chwili zniszczenia materiału. Przedstawiono wyniki próby porównawczej, w której jednoczesnie stosowano ekstensometr oraz system DIC. Dodatkowo zaprezentowano rezultaty prób stanowiskowych mechanicznego elementu sprzegajacego przeprowadzonych przy uzyciu systemu pomiarów cyfrowych w warunkach oddziaływania cyklicznie zmiennego obciazenia.

Streszczenie:
The paper reports experimental results from tests carried out at room temperature on servo-hydraulic system dedicated for examination of the exploitation properties of rocker arms. The ball joint of this element was modified by an application of composite coating such as the tungsten carbide (WC). To apply cyclic loading to rocker arms the griping system was designed and elaborated. Results from tests performed on the composite coated ball joints were compared with data obtained for typical elements. Variations of the following parameters versus time i.e. force, temperature and surface topography of balls were analysed with respect to exploitation properties of the modified ball joints. An increase of the wear coefficient was achieved for sliding joints of the steel ball-steel cups coated by the WC.

Słowa kluczowe:
Ball Joint, Composite, Cyclic Loading, Surface Topography, Tungsten Carbide, Wear

Streszczenie:
W pracy omówiono wybrane zagadnienia z zakresu mechaniki pękania dotyczące wyznaczania współczynnika intensywności naprężenia i jego krytycznej wartości (K IC ). Zaprezentowano projekt zminiaturyzowanej próbki kompaktowej (CT) o wymiarach czterokrotnie mniejszych niż jej wersja standardowa. Zamieszczono wyniki z badań odporności na kruche pękanie materiałów kompozytowych wytworzonych na bazie odlewniczego stopu aluminium 44200 z różną zawartością Al 2 O 3. Analiza rezultatów przeprowadzonych testów wykazała brak wpływu udziału Al 2 O 3 i jego postaci, tj. włókien bądź cząstek, na zmianę krytycznej wartości współczynnika intensywności naprężenia

Streszczenie:
The results of comparative examinations of mechanical behaviour during fatigue loads and microstructure assessment before and after fatigue tests were presented. Composites of aluminium matrix and SiC reinforcement manufactured using the KoBo method were investigated. The combinations of two kinds of fatigue damage mechanisms were observed. The first one governed by cyclic plasticity and related to inelastic strain amplitude changes and the second one expressed in a form of ratcheting based on changes in mean inelastic strain. The higher SiC content the less influence of the fatigue damage mechanisms on material behaviour was observed. Attempts have been made to evaluate an appropriate fatigue damage parameter. However, it still needs further improvements.

Słowa kluczowe:
fatigue, damage, metal matrix composites, microstructure

Streszczenie:
Strength and durability of thin-walled structures are usually calculated with the use of computer simulations. To perform such simulations using Finite Element Method, characteristics of a material subjected to monotonic tension or compression and tension-compression cyclic loading are necessary. Experimental determination of such kind of characteristics is usually performed on specimens cut out from a metal or composite thin sheet. Problems associated with testing on flat specimens under large deformation are discussed in this paper. A new design of fixture proposed by the authors for this kind of testing is shortly described. The results of investigations carried out on brass using the new fixture for flat specimens testing are also presented.

Słowa kluczowe:
fixture, large deformations, tension-compression tests, thin metal sheet

Streszczenie:
The effects commonly related with deformation caused by proportional and non-proportional loading types were identified experimentally. In the case of non-proportional cyclic loading along circular strain path the second order effects such as: phase shift between stress and strain signals was observed. An analysis of experimental data from tests under non-proportional cyclic loading along square strain path exhibited a significant reduction of stress independently on direction of deformation.

The paper also presents experimental results concerning evaluation of an influence of cyclic loading on stress variations during monotonic deformation carried out on the pure copper and X10CrMoVNb9-1 steel. All strain controlled tests were performed at room temperature using thin-walled tubular specimens. The experimental programme contained selected combinations of monotonic and cyclic loadings, i.e. the torsion-reverse-torsion cycles were superimposed on the monotonic tension. It is shown that such cycles associated with monotonic tension caused essential variations of tensile stress. For both materials, a significant decrease of the axial stress was visible. The effects observed during monotonic and cyclic loading combinations were theoretically described using the Mróz and Maciejewski model.

Słowa kluczowe:
Proportional and non-proportional loadings, Hardening, Softening, Tensile stress, Strain energy, Yield surface, Modelling

Streszczenie:
Determination of cyclic properties of a material used for many engineering structures, e.g. airframes, requires preparation of specimens from two-dimensional, shell structures. A specimen must be cut out from the structure component in the way allowing application of a load corresponding to that reflecting service cases. In order to fulfil this requirement, tension–compression testing of the flat specimen is necessary to obtain credible data. Problems associated with such kind of testing are discussed in this paper. In the first part, an extensive review of the anti-buckling fixtures developed up to now is given. Several representative solutions are discussed, with special emphasis on the technique limitations. In the second part of the paper, detailed description of the proposed design is given. Finally, the results of preliminary tests carried out using new fixture to mount the flat specimens cut from steel sheets are presented. Application of the proposed testing technique allowed tension–compression tests to be performed at the displacement amplitude within the range ±5 mm what corresponds to the maximum strain amplitude of ±0.4 for the specimen gauge length to be equal 12.5 mm. Taking into account all data captured by means of new fixture, one can conclude that the technique is promising with respect to providing data for modelling of cyclic deformation behaviour for shell structures.

Słowa kluczowe:
buckling, cyclic loading, fixture, thin sheets

Streszczenie:
The results of analysis of fatigue damage development in the X10CrMoVNb9-1(P91) steel specimens subjected to various cyclic loading combinations are presented. The study concerning a quantitative assessment of damage is based on analysis of the fatigue hysteresis evolution in subsequent loading cycles. According to the elaborated algorithms, damage parameters were determined on the basis of two indicators, i.e., average strain and strain amplitude variations. Each of them was responsible for a single damage development mechanism. The average strain characterized ratcheting effect, which is usually related to local generation of plastic strain surrounding microstructural elements. The second damage mechanism called cyclic plasticity is connected with micro slips preceding slip bands formation. The paper also discusses the results of metallographic and fractographic microscopic (SEM) observations of the tested specimens in order to indicate microstructural aspects of fatigue damage development mechanisms.

Słowa kluczowe:
fatigue test, steels, fracture, scanning electron microscopy, microstructure

Słowa kluczowe:
fatigue, metals and alloys, deformation and fracture, cumulative fatigue damage

Streszczenie:
In this work, an attempt at determination of mechanical properties by means of a method based on magnetic Barkhausen emission measurements was proposed. The specimens made of P91 steel were subjected to creep or plastic flow which were interrupted after a range of selected time periods in order to achieve specimens with an increasing level of strain. Subsequently, measurements of magnetic Barkhausen emission were carried out, and then static tensile tests were performed in order to check variations of basic mechanical parameters. It is shown that evident relationships between the yield point /ultimate tensile strength and some parameters of the Barkhausen emission exist.

Słowa kluczowe:
mechanical properties, magnetic Barkhausen effect, plastic strain

Streszczenie:
W artykule przedstawiono na podstawie dostępnych prac właściwości mechaniczne żywic i włókien powszechnie stosowanych jako składniki materiałów kompozytowych. Omówiono typy zniszczenia tego rodzaju materiałów wynikające z różnej kruchości zbrojenia. Zaprezentowano rodzaje przełomów występujące podczas rozciągania i ściskania kompozytu w zależności od kierunku pobierania próbek. Omówiono kryteria zniszczenia stosowane do oceny odporności materiałów kompozytowych dla różnych wariantów obciążenia.

Streszczenie:
In the paper there is presented a discrete - continuous model of the Split Hopkinson Pressure Bar (SHPB) for numerical simulations of a dynamic behaviour of material specimens under high strain - rates. For this purpose several material theories describing visco-elasto-plastic properties of the tested specimens can be applied. Using this model impact-type dynamic responses are sought by means of the longitudinal elastic wave analytical solution of the d’Alembert type. The proposed model enables us theoretical strength investigations for various elasto-plastic materials under great deformation velocities as well as structural parameter de termination of the real SHPB designed to play a role of the laboratory test-rig.

Słowa kluczowe:
Hopkinson bar, elastic wave propagation, d’Alembert solution, numerical simulation

Streszczenie:
In this paper, a new method for assessing the accuracy of a constitutive model is proposed. The method uses perforation test done by drop weight tower. The assessment is carried out by comparison of striker velocity curve obtained using experiment and FEM simulation. In order to validate proposed method the various constitutive equations were applied i.e. Johnson-Cook, Zerilli-Armstrong and the extended Rusinek-Klepaczko to model mechanical behaviour of X4CrMnN16-12 austenitic steel. The steel was characterized at wide range of strain and strain rates using servo-hydraulic testing machine and split Hopkinson pressure bar. The relative error calculated as a difference between measured and constitutive model based stress-strain curve was applied as a reference data (classic approach). Subsequently, it was compared with relative error determined on the basis of experimental and FEM calculated striker velocity (new approach). A good correlation between classic and a new method was found. Moreover, a new method of error assessment enables to validate constitutive equation in a wide range of strain rates and temperatures on the basis of a single experiment.

Słowa kluczowe:
plastic behaviour, fracture properties, constitutive modeling, perforation, austenitic steel

Streszczenie:
This paper presents the assembly of the miniaturised direct impact compression test method (MDICT) developed at the Institute of Fundamental Technological Research at the Polish Academy of Sciences (IFTR PAS). Additionally, this method was used to investigate the mechanical properties of tantalum at the strain rate of 8×10^5 s−1.To analyse the phenomena occurring during the tests, a numerical model of the testing stand was developed and validated. The finite element (FEM) model was expanded to estimate the sources of error achieved in the results using the analytical methods. The effects related to friction, inertia, specimen ratio, adiabatic heating, stress equilibration and strain rate on the stress-strain characteristic observed before and after the analytical correction were discussed.

Słowa kluczowe:
miaturised Hopkinson bar, tantalum, high strain rates, direct impact, finite element method

Streszczenie:
The paper presents experimental results of tests carried out at room temperature on power engineering steel: 10H2M (11CrMo9-10) using thin-walled tubular specimens under biaxial stress state. The loading programme comprised different types of deformation, i.e. monotonic tension and cyclic torsion in the form of symmetric or asymmetric step-increasing strain amplitude. The main task of the paper was focused on investigation of an influence of the cyclic loading parameters on tensile curve variations. The magnitudes of axial strain and cyclic shear strain amplitude were small and did not exceed 1%. An analysis of the results showed a significant reduction of the axial stress (even equal 90% for the torsional amplitude ±0.8%, in both cases of cyclic loading). An influence of torsion frequency on the tensile stress curve was discovered within the range from 0.005Hz to 0.5Hz.

Słowa kluczowe:
Cyclic Loading, Hysteresis Loop, Stress Variation, Tensile Characteristic

Streszczenie:
This article presents the results of an analysis of the mechanical properties of the AW8S-V polyester composite reinforced by a roving fabric under tensile loading. The stress-strain curves show an increase of the maximum stress and elastic modulus with increasing strain rate. By contrast, an increase of the temperature led to decrease of the maximum stress and elastic modulus. It is also shown that, failure mechanisms are dependent on the loading type. Shear cracks occurred in the specimens under quasi-static loading whereas composite layers damage was observed under dynamic loading. Temperature increase resulted to stronger fragmentation of the specimens.

Słowa kluczowe:
polyester composite, Hopkinson bar, high strain rate, damage

Streszczenie:
This paper presents experimental results of the fracture toughness tests carried out on metal matrix composites. The material was produced using the 44200 aluminium alloy reinforced by Al2O3 in the form of Saffil fibres. Three different contents of Al2O3 were taken into account, i.e. 10%, 15%, 20%. The main aim of the research was to examine an influence of the aluminium oxide content on a critical value of the stress intensity factor, KIC. All tests were performed using a miniature compact specimen, which was four times smaller than the typical one. The results of FEA analysis confirmed a typical distribution of the effective stress at the tip of the notch. In each test the composite specimen was mounted in the loading system of the testing machine by applying special grips. Crack tip opening displacement of the specimen notch was measured by means of the clip on knife edge extensometer having 10 mm gauge length. The results in form of tensile force versus crack tip opening displacement show the first mode of fracture. An inspection of the pre-cracked zone of the composite did not exhibit the typical features usually observed on specimen surface after fatigue. An influence of the Al2O3 Saffil fibres content within the range from 10% to 20% on a critical value of the stress intensity factor was negligible small. The KIC of the composites tested in this research achieved the level of 12 MPa m 1/2.

Słowa kluczowe:
metal matrix composite, fracture toughness test, compact specimen, fatigue zone, stress intensity factor

Streszczenie:
W artykule zaprezentowano współczesne maszyny wytrzymałościowe i przyrządy pomiarowe do badania właściwości mechanicznych materiałów. Zamieszczono oraz omówiono ich schematy ideowe, zalety, wady, ograniczenia i zastosowanie. W przypadku niektórych z nich przedstawiono literaturowe i własne wyniki z badań doświadczalnych.

Streszczenie:
The paper presents behaviour of materials under complex loading being combinations of torsion-reverse-torsion cycles superimposed on monotonic tensile deformation. The 2024 aluminium alloy, P91 steel and M1E copper were investigated under plane stress state using thin-walled tubular specimens. All tests were strain controlled and a total strain was less than 1%. An influence of torsion cycles on tensile characteristic was manifested by lowering of the proportional limit and yield point. This effect was increased with magnification of cyclic strain amplitude and in the case of copper a reduction of yield point was equal around 90%. A character of this effect was checked using the yield surface concept after each test. The papers also presents variations of tangential hardening modulus and plastic strain energy dissipation.

Słowa kluczowe:
complex loading, biaxial stress state, cyclic loading, mechanical parameters

Streszczenie:
Around 20% of CO2 emitted as a result of human activity on Earth comes from transportation. One of the ideas, which lead to diminishing of the greenhouse gases e mission, is reducing of fuel consumption. It may be achieved by introducing a new powertrain solutions as well as lowering overall vehicle weight. The reduction of vehicle weight may be obtained by both a new design of part and structures and application of a new materials i.e. aluminium alloys. It has to be emphasised that weight reduction is very important for combustion engine driven vehicles and electric driven vehicles as well. Mass lowering is especially desirable in the case of electric vehicles because they typically have a very narrow operational range usually lower than 200 km. Therefore even small weight reduction de creases energy consumption of EV and as a consequence increases its range, which is a crucial parameter for users.
The results presented in this article were focused on high strength aluminium alloys of 6082-T6 and 7075-T6 types. Applying of those materials enables mass lowering of structures up to 50%, maintaining original functionality. Moreover, aluminium alloys may be also used in energy absorbing structures. The goal of tests was to obtain data required in FE analysis. In order to simulate dynamic phenomenon i.e. vehicle crash investigation of the stress-strain curves of alloys were carried out at wide range of strain rates using Hopkinson bar.

Słowa kluczowe:
road transport, simulation, combustion engines, air pollution, environmental protection

Streszczenie:
W pracy zamieszczono wyniki z badań doświadczalnych dotyczących określania wpływu obciążenia skręcającego o charakterze cyklicznym na przebieg wyznaczanej jednocześnie charakterystyki rozciągania następujących materiałów: stali P91, stopu aluminium P a7 oraz miedzi M1E. Testy przeprowadzono na cienkościennych, osiowosymetrycznych próbkach rurkowych w warunkach płaskiego stanu naprężenia przy sterowaniu sygnałami odkształcenia. Wyznaczono zmiany granicy proporcjonalności, plastyczności i stycznego modułu wzmocnienia w zależności od amplitudy odkształcenia postaciowego oraz opracowano przebiegi zmian naprężeń głównych i kąta obrotu ich kierunków.

Słowa kluczowe:
mechanika eksperymentalna, obciążenie złożone, obciążenie cykliczne, właściwości mechaniczne, rozciąganie, skręcanie

Streszczenie:
Praca przedstawia charakterystyki naprężenie-odkształcenie stali austenitycznej VP159 oraz staliwa austenitycznego LH556, o dużej zawartości azotu, przy różnych prędkościach odkształcania. Do badań w zakresie obciążeń statycznych zastosowano serwohydrauliczną maszynę wytrzymałościową, natomiast w zakresie obciążeń dynamicznych metodę pręta Hopkinsona. Otrzymane rezultaty przedstawiono w formie wykresów naprężenia rzeczywistego w funkcji odkształcenia rzeczywistego. Na podstawie statycznej próby rozciągania wyznaczono również podstawowe parametry badanych materiałów, takie jak: E, R0,05, R0,2, Rm. Na podstawie badań stwierdzono, że stal VP159 ma znacznie lepszą ciągliwość niż staliwo LH556, natomiast pozostałe parametry i charakterystyki były zbliżone. Otrzymane wyniki można wykorzystać do wyznaczenia parametrów równań konstytutywnych opisujących termomechaniczne właściwości materiałów na potrzeby symulacji komputerowych.

Słowa kluczowe:
mechanika, pręt Hopkinsona, duże prędkości odkształcania, stal wysokoazotowa, charakterystyka naprężenie-odkształcenie

Streszczenie:
An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, multifunctional aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) subjected to creep and low cycle fatigue (LCF) was investigated. The materials were tested to verify their applicability as the cylinder heads in car engines. During creep tests, a strain response of the materials was observed under a range of the step-increased stresses and different temperatures. The LCF tests were carried out under strain control in three blocks of 100 cycles each with a constant strain amplitude. The results of creep and LCF tests were analysed with regard to chemical composition, type of porosity and ageing of the materials tested. An influence of porosity on the creep resistance and lifetime was considered. The results of the LCF tests were compared for the materials in the as-received state and after ageing. An experimental evaluation of cyclic behaviour because of the LCF was carried out to check whether the hardening or softening effects can be observed in the materials. Taking into account the various history of loading, a stress response of the materials was investigated.

Słowa kluczowe:
creep, cylinder heads, fatigue, light alloys

Streszczenie:
The paper presents experimental results concerning evaluation of an influence of cyclic loading on material behaviour under monotonic deformation. Tests were carried out on pure copper and P91 steel. The experimental programme contained the torsion–reverse–torsion cycles superimposed on the monotonic tension. It is shown that the torsion–reverse–torsion cycles associated with monotonic tension caused essential variations of the tensile characteristic. For both materials, a significant decrease in the tensile stress can be observed. The effects observed during monotonic and cyclic loading combinations were theoretically described for the 2024 aluminium alloy using the Mróz and Maciejewski model.

Słowa kluczowe:
Complex loading, Yield point, Yield surface, Mechanical parameters

Streszczenie:
The paper presents experimental investigations of two light aluminium alloys (AlSi8Cu3 and AlSi7MgCu0 5) under loading conditions leading to the creep or fatigue processes. During the creep process, the strains were measured under selected tensile stresses and temperatures. An influence of a step loading during creep, at elevated temperature, on steady creep rate and a course of creep curve, was investigated. Moreover, an effect of porosity degree on creep of both aluminium alloys was also analysed. An influence of aging process at the elevated temperature was experimentally evaluated. Fatigue behaviour of materials was checked under strain control using cylindrical samples. The results of LCF tests were analysed for the materials subjected to three-stage sequence of loading at elevated temperature. A resistance to creep and fatigue processes of the AlSi8Cu3 was weaker than that obtained in the case of the AlSi7MgCu0 5.

Słowa kluczowe:
Creep, Fatigue, Sequence loading, Aluminium alloys

Streszczenie:
The paper presents relationships between strain level generated by creep process and two parameters determined form non-destructive tests, i.e. acoustic birefringence and amplitude of magnetoacoustic emission for three kinds of steel: 40HNMA, P91 and 13HMF. Moreover, the relationships between prior deformation level and selected mechanical parameters resulting from the standard tensile tests subsequently carried out at room temperature were established. As a consequence, this enabled to formulate mutual relationships between these mechanical parameters and parameters obtained from the ultrasonic/magnetic investigations.

Słowa kluczowe:
creep, damage, yield point, ultimate tensile stress, Young’s modulus, acoustic birefringence, magnetoacoustic emission.

Streszczenie:
A consolidation of powders using the KOBO method at elevated temperature was elaborated for production of Al/SiC metal matrix composite (MMC). The observations of the mean strain and inelastic strain range during the force controlled high cycle fatigue (HCF) tests identified the ratcheting mechanism combined with mechanism characterized by cyclic plasticity. Damage parameters were calculated on the basis of strain signal acquisition during fatigue tests. Fatigue properties, creep resistance and life time of Al/SiC MMC were gradually improved with the increase of the SiC particles content. The microstructural observations of the material before and after tests were also performed.

Słowa kluczowe:
MMC, KOBO method, fatigue, creep, monotonic loading, microstructure, damage

Streszczenie:
The paper presents the results of multiparameter analysis of Barkhausen noise (BN) signal properties. In addition to the commonly used quantifiers of the BN signal, such as amplitude, integral of the BN envelope or results of pulse count analysis, we propose an additional analysis based on the change in magnetizing current amplitude. As it turns out the character of the change of the BN signal (as a function of the plastic deformation level) measured for various magnetizing currents differs significantly. Being so, a comparison of the results obtained for at least two magnetizing intensities gives a much better description of a plastic deformation level. In addition to that we observe two monotonic changes in the BN signal properties - a systematic shift of the BN signal peak position and the increase in the frequency for which the maximum in the BN FFT spectra occurs.

Słowa kluczowe:
Barkhausen effect, plastic deformation, nondestructive evaluation

Streszczenie:
The paper presents experimental results of investigations carried out on the P91 steel and 2024 aluminium alloy under complex stress states due to various combinations of an axial force and twisting moment. An influence of out-of-phase sinusoidal and trapezoidal strain signals on the mechanical behaviour of tested materials was considered. The experiments enabled identification of the second order effects connected with the non-proportional cyclic loadings such as the phase shift between stress and strain signals during the deformation along the circular strain path, and a significant stress drop of the one of loading components applied in the case of deformation enforced by the trapezoidal signals. The experimental programme also contained the tests of monotonic tensile deformation realized simultaneously with delayed torsional cycles. They enabled to observe a drastic variations of the proportional limit and yield point of the materials in the tensile direction. This fact manifests an important material feature which can be applied to the optimal designing of some metal forming processes like an extrusion or forging for example

Słowa kluczowe:
cyclic loading, biaxial stress state, circle loading path, square loading path, mechanical parameters, yield surface

Streszczenie:
The AlSi8Cu3 and AlSi7MgCu0.5 cast aluminium alloy s of different composition and heat treatment were investigated to verify their applicability as cylinder heads in the car engines [1]. Creep tests under the step-increased stresses at different temperatures, and low cycle fatigue (LCF) tests for a range of strain amplitudes and temperatures were carried out. The results exhibit a significant influence of the heat treatment on the mechanical properties of the AlSi8Cu3 and AlSi7MgCu0.5. An interesting fact is that the properties strongly depend on the type of quenching. Lower creep resistance (higher strain rates) and lower stress response during fatigue tests were observed for the air quenched materials in comparison to those in the water quenched. Cyclic hardening/softening were also observed during the LCF tests due to the heat treatment applied. The mechanical properties determined during the tests can be used to identify new constitutive equations and to verify existing numerical models.

Słowa kluczowe:
creep, low cycle fatigue, aluminum alloys, heat treatment

Streszczenie:
The paper presents experimental results of investigations carried out on the 2024 aluminium alloy and P91 steel under biaxial stress state. The loading programme comprised a monotonic tension assisted by torsion-reverse-torsion cycles. An influence of the cyclic loading and its delay with respect to uniaxial tension on the selected mechanical parameters taken on the basis of tensile characteristics was investigated. Additionally, a relative variation of the proportional limit and yield point due to the loading history applied was analyzed. A permanency of effects observed during combination of tension and cyclic torsion was experimentally assessed on the basis of an initial yield surface evolution

Streszczenie:
The main idea of energy-based hypothesis of material effort proposed by Burzyński is briefly presented and the resulting failure criteria are discussed. Some examples, based on the own studies, which depict applications of these criteria are discussed and visualisations of limit surfaces in the space of principal stresses are presented.

Słowa kluczowe:
Burzyński yield condition, yield surface, strength differential effect, energy-based yield criteria

Streszczenie:
This work presents an attempt to evaluate a stage of mechanical and structural degradation of 40HNMA steel, used for example in automotive industry, by means of non-destructive and destructive methods. The modern ultrasonic and magnetic investigation were mainly applied

Streszczenie:
Development of creep damage at elevated temperatures and structural degradation due to plastic deformation at room temperature were assessed using destructive and non-destructive methods in steels commonly applied in power plants (40HNMA, 13HMF and P91). As destructive methods the standard tension tests were carried out after every kind of prestraining. Subsequently, an evolution of the selected tension parameters was taken into account for damage identification. In order to assess a damage development during the creep and plastic deformation the tests for the steels were interrupted for a range of the selected strain magnitudes. The ultrasonic and magnetic techniques were used as the non-destructive methods for damage evaluation. The experimental programme also contained microscopic observations.

Streszczenie:
This paper describes the application of acoustic birefringence measurement for evaluation of material degradation due to creep. The problem with ultrasonic investigation of the influence of creep-induced voids on ultrasonic wave velocities is the lack of samples containing well-defined voids. The only way to‘‘produce’’ damaged material with numerous voids is accelerated creep laboratory test or long-term service of material in high temperature and stress. To describe voids it is necessary to perform laborious metallographic examination of damaged material. Paper presents glass samples with artificial semi-flat voids created with laser engraving technique. Results of ultrasonic wave velocities and acoustic birefringence measurements in glass samples proved that laser engraving can be helpful for the experimental investigation of voids influence on solid acoustic properties.

Słowa kluczowe:
Ultrasound, Birefringence, Creep, Artificial voids

Streszczenie:
The paper presents experimental results of creep and low cycle fatigue (LCF) tests carried out on the as-received cast aluminium alloys with different chemical composition and porosity. The test programmes contain creep investigations under step-increased stresses at different temperatures, and cyclic plasticity under different strain amplitudes and temperatures

Słowa kluczowe:
creep, low cycle fatigue, aluminium alloys

Streszczenie:
The paper presents experimental results of investigations carried out under complex stress state on the 2024 aluminium alloy (used by aircraft industry) and P91 steel (used at power plants). Second-order effects associated with cyclic loadings enforced by the trapezoidal signals in the two mutually perpendicular directions are identified. It is shown, how the cyclic loading and its parameters (strain amplitude and frequency) influence the simultaneous monotonic loading in the direction perpendicular with respect to the cyclic one. Moreover, the paper presents an analysis of the selected mechanical properties variations on the basis of an initial yield locus evolution.

Streszczenie:
The correlation between magnetoacoustic emission intensity and mechanical Barkhausen effect intensity has been tested in the case of P91 steel having different microstructure states due to either plastic flow at room temperature or speeded-up creep, performed under stress 290 MPa at temperature 773 K. The plastic strain range for the first set of samples has been from 2.0% up to 10.5% and for the second one from 0.85% up to 10.0%. Both effects revealed analogous monotonous decrease of their intensities as a function of resulting plastic strain. The decrease was higher for plastic flow than for creep. Those results are well consistent with results of tensile tests of the as damaged samples.

Słowa kluczowe:
Magnetic properties, Mechanical factors, Steel, Plastics, Creep, Testing, Temperature distribution, Microstructure, Performance evaluation, Stress

Streszczenie:
The steels of different carbon content were tested with respect to their microstructural and selected mechanical parameters variations. The original combinatorial method, based on the phase quanta theory, was applied in the quantitative metallographic assessment. Hence, the adequate geometrical parameters of steel microstructure were possible to be determined. Moreover, the selected mechanical parameters of the materials were evaluated using non-destructive and destructive methods. The results enabled to formulate some significant quantitative relationships between microstructure and mechanical parameters.

Słowa kluczowe:
Steel, phase composition, quantitative metallography, mechanical behaviour

Streszczenie:
A modified miniaturized version of the Direct Impact Compression Test (DICT) technique is described in this paper. The method permits determination of the rate-sensitive plastic properties of materials up to strain rate∼105s−1. Miniaturization of the experimental setup with specimen dimensions: diameter dS=2.0 mm and thicknesslS=1.0 mm, Hopkinson bar diameter 5.2 mm, with application of a novel optical arrangement in measurement of specimen strain, makes possible compression tests at strain rates from∼103s−1to∼105s−1. In order to estimate the rate sensitivity of a low-alloy construction steel, quasi-static, Split Hopkinson Pressure Bar (SHPB) and DICT tests have been performed at room temperature within the rate spectrum ranging from 5*10−4s−1to5*104s−1. A diabatic heating and friction effects are analyzed and the final true stress versus true strain curves at different strain rates are corrected to a constant temperature and zero friction. The results have been analyzed in the form of true stress versus the logarithm of strain rate and they show two regions of a constant rate sensitivity β¼Δσ.log": relatively low up to the strainrate threshold∼50 s−1, and relatively high above the threshold, up to strain rate∼4.5*104s−1.

Słowa kluczowe:
Direct Impact Compression Test (DICT), Dynamic plasticity, Mild Steel, High strain rate

Streszczenie:
Damage development due to creep under uniaxial tension at elevated temperatures is assessed using destructive and non-destructive methods in steels, commonly used in power plants or chemical industry, and in aluminium alloy used in aircrafts for responsible elements. The results obtained using two different destructive methods for assessments of damage development are critically discussed. In the first method the specimens of steel after different amounts of creep prestraining were stretched up to failure and variations of the selected tension parameters were taken into account for damage identification. In the second one, a damage degree was evaluated by studying variations of an initial yield locus position in the stress space and by determination of the yield loci dimensions. The ultrasonic investigations were selected as the non-destructive method for damage development evaluation.

Słowa kluczowe:
Creep, Damage, Mechanical Parameters, Ultrasound (US), Yield Surface

Streszczenie:
Creep tests are carried out under tension, pure torsion, and combined tension and torsion at an elevated temperature of 523K for pure copper and 423K for an aluminium alloy. Different creep and rupture properties of the materials are observed throughout the deformation process under the different stress states. The effects of stress states on primary creep, secondary creep, the failure and lifetime of the materials are analysed. A new set of multiaxial mechanisms-based creep damage constitutive equations has been formulated on the basis of analysis of previous creep models. The proposed unified creep damage constitutive equations are determined using experimental data achieved for both materials at three effective stress levels. Creep tests for each stress level were carried out for three stress states. The comparison of experimental and computed effective creep strain curves is carried out for all the stress states and stress levels tested for both materials. In addition, it has been verified that the determined multi-stress-state creep damage constitutive equations can be used to predict the isochronous surfaces of the materials very precisely. To compare with conventional constitutive descriptions, a set of multiaxial constitutive equations is also determined for the experimental data of the two materials using the same optimisation techniques. The quality of the fittings is compared and further discussion is carried out for the stress-state variable x.

Streszczenie:
An influence of prior tensile plastic deformation on the basic creep parameters such as minimum creep rate, time to rupture, duration of creep stages and ductility is studied for copper and aluminium alloy. The materials were tested at two different temperatures; copper at 523 K and 573 K; aluminium alloy at 423 K and 473 K. It is shown for both materials, that depending on the deformation history the basic creep parameters may attain values which are more beneficial from engineering point of view than those for the nonprestrained material determined. It is also shown that in some cases prior plastic deformation may lead to the detrimental effects expressed by the lifetime reduction. The experimental data achieved are discussed in detail and used to verify the basic assumptions of the recovery creep theory.

Słowa kluczowe:
Creep, Plastic Deformation, Creep Rupture, Lifetime, Minimum Creep Rate

Streszczenie:
The phenomena arising during proportional and non-proportional cyclic loadings are experimentally investigated for 40H steel and PA6 aluminium alloy. Variations of the mechanical properties due to different two types of cyclic loading are assessed on the basis of the yield surface evolution. Effects of strain rate and magnitude of cyclic loading amplitude are also considered. Analysis of the stress and strain signals during non-proportional cyclic loading along circular path has shown significant effect of a phase shift of the maximum stress with respect to the corresponding maximum strain, which was not observed during tests carried out along proportional loading paths

Słowa kluczowe:
Additional Hardening, Non-Proportional Cyclic Loading, Phase Shift, Yield Surfaces

Słowa kluczowe:
stale wysokowytrzymałe, szum Barkhausena, twardość, wytrzymałość na rozciąganie, mikrostruktura

Słowa kluczowe:
kompozyty, żywice termoplastyczne, badania zmęczeniowe, udarność

Streszczenie:
This paper presents an attempt to use the Electronic Speckle Pattern Interferometry (ESPI) and Digital Image Correlation (DIC) for damage evaluation and its monitoring on specimens made of the P91 steel and aluminide coated nickel super-alloys subjected to monotonic or cyclic loading.

Streszczenie:
The results of experimental and numerical investigations concerning the influence of strain rate on mechanical properties of pure tantalum and VP159 high nitrogen austenitic steel are presented. Experiments were carried out using Split Hopkinson Pressure Bar (SHPB) and Direct Impact Compression Test (DICT) technique. The Perzyna elasto-viscoplasticity theory was applied to predict the dynamic compression yield strength of the tantalum at strain rates from 1.0x10-3 s−1 to 0.5x106 s−1. In the case of the VP159 high nitrogen austenitic steel the experimental results were used to calibrate the Rusinek-Klepaczko model. There are still no sufficient data on the flow stress at higher strain rates than 1.0x105s−1, in particular for large strains. The experimental identification of material parameters required for constitutive modelling are not sufficiently reported. This paper is an attempt to supplement our knowledge in this area. The impact resistance of material in question is analysed numerically with use of ABAQUS/Explicit finite element program. The Huber-Mises-Hencky yield criterion and Perzyna viscoplasticity model with adiabatic conditions are used.

Słowa kluczowe:
Dynamic tests, Direct Impact Compression Test, Hopkinson bar, punching effect

Streszczenie:
In most cases, fatigue damage has a local character and it is based on damage development leading to generation of cracks appearing around structural defects or geometrical notches. An identification of these areas and their subsequent monitoring requires a full-field displacement measurements performed on the objects surfaces. This paper presents an attempt to use the Electronic Speckle Pattern Interferometry (ESPI) method for fatigue damage evaluation and its monitoring on specimens made of the P91 steel and aluminide coated nickel super-alloys. In this work, also a development of fatigue damage was investigated using destructive and non-destructive methods in materials commonly applied in power engineering or automotive industry. The fatigue tests for a range of different materials were interrupted for selected number of cycles in order to assess a damage degree. As destructive methods the standard tensile tests were carried out after prestraining due to fatigue. Subsequently, an evolution of the selected tensile parameters was taken into account for damage identification. The ultrasonic or magnetic techniques were used as the non-destructive methods for damage evaluation. In the final step of the experimental programme microscopic observations were performed. The results show that ultrasonic and magnetic parameters can be correlated with those coming from destructive tests. It is shown that good correlation of mechanical and selected non-destructive parameters identifying damage can be achieved for the materials tested

Słowa kluczowe:
Fatigue, damage, optical methods, non-destructive techniques

Streszczenie:
The paper concerns numerical and experimental investigations carried out for determination of an influence of holes on material behaviour under monotonic tension. The 40Cr steel commonly applied in automotive and power plant branches of industry was tested. The analysis was performed by the use of analytical and Finite Element Method calculations. It enabled identification of stress concentration/maximum stress versus hole diameter relationships, and the HMH stress distribution. Full-field contactless Digital Image Correlation (DIC) system was used for capturing the effective strain variations from the beginning of test up to specimen fracture. It enabled us to indicate the most important stress concentrator, and moreover, distribution of the HMH effective strain in 2D coordinate system. A comparison of tensile characteristic obtained by means of smooth and perforated specimens showed 70% reduction of yield point and 50% lowering of elongation as an effect of the artificial defects introduced.

Słowa kluczowe:
Monotonic tension, holes, steel, stress concentration factor, maximum stress, yield point, ductility, FEM, DIC

Streszczenie:
Modern automobile and airplane structures made of sheet metals or composites require usage of thinner and stronger materials. On the other hand, manufacturers are trying to reduce production costs by shortening the fabrication processes and by application of computed simulation for forming operation. Therefore, it is necessary to better understand and more accurately investigate deformation behaviour of sheet alloys. Testing of flat specimens under compression and cyclic tension-compression within large deformation procures a lot of problems. One of them is the buckling phenomenon. A new version of the device mounted in a standard testing machine was developed and geometry of the specimen for validation of the device was proposed. Specimens of DP690 steel with nominal thickness equal to 1.6 mm were investigated at ambient temperature. Tension-compression cyclic tests within a strain range ± 0.04 were executed starting in tension direction. It is shown that the results are repeatable.

Słowa kluczowe:
Buckling, cyclic loading, fixture, thin sheets

Streszczenie:
Strength and durability of thin-walled structures are usually calculated with the use of computer simulations. To perform such simulations using Finite Element Method the characteristics of a material subjected to monotonic tension/or compression and tension-compression cyclic loading are necessary for example. Experimental determination of such kind of characteristics is usually performed on specimens cut out from metal or composite thin sheet. Problems associated with material testing on flat specimens under large deformation are discussed in detail by this paper. In the first part, a short review of the antibuckling fixtures developed up to now is given. Several representative solutions including the applied design are discussed, with special emphasis on the technique limitations. In the second part, the results of investigations carried out on steel and brass using the new fixture for the flat specimens testing are presented.

Słowa kluczowe:
fixture, large deformations, tension-compression tests, thin metal sheet

Streszczenie:
The effects often taking place during proportional and non-proportional types of loading were identified experimentally and modelled numerically. In the case of non-proportional cyclic loading along circular strain path the second order effects such as: phase shift between stress and strain signals were discovered. An analysis of experimental data from tests under non-proportional cyclic loading along square strain path exhibited a significant reduction of stress independently on direction of deformation. The paper also presents experimental results concerning evaluation of an influence of cyclic loading on mechanical parameters during monotonic deformation carried out on the 2024 aluminium alloy and X10CrMoVNb9-1 steel. All strain-controlled tests were conducted at room temperature using thin-walled tubular specimens. The experimental programme contained selected combinations of monotonic and cyclic loadings, i.e. the torsion-reverse-torsion cycles were superimposed on the monotonic tension. It is shown that such cycles caused essential variations of the tension characteristics. A significant decrease of the tension stress was observed. The effects occured during monotonic and cyclic loading combinations were described using Mróz and Maciejewski model. Reasonable good predictions of: hysteresis loops and stress responses for the square and circular loading paths and tensile curves assisted by torsion cycles were obtained

Słowa kluczowe:
cyclic loading, hardening, softening, complex stress state

Streszczenie:
Selected damage measures applied for degradation description of engineering materials subjected to fatigue loading conditions are presented. In addition to well - known measures the new concepts of fatigue damage development are discussed using known mechanisms of cyclic plasticity and ratcheting. Their usefulness was studied on the basis of experimental results for modern metal matrix composites commonly applied in many branches of the industry.

Słowa kluczowe:
Damage, fatigue, composites

Streszczenie:
This paper presents experimental results of tests carried out at room temperature on power engineering steels: P91 (X10CrMoVNb9-1), 10H2M (11CrMo9-10) using thin-walled tubular specimens under biaxial stress state. The loading programme comprised two different types of deformation obtained by monotonic tension and torsional cycles. The values of axial strain and cyclic shear strain amplitude were small and did not exceed 1%. In the case of both materials tested, a significant reduction of the axial stress was achieved. It was even equal to 90% for the 10H2M steel.

Streszczenie:
This work compares the thermomechanical behavior of TiNi shape memory alloy subjected to the compression test performed under various strain rates. The mechanical characteristics of the material were elaborated. The specimen temperature changes related to the exothermic martensitic forward and endothermic reverse transformation were measured in a contact-less manner by a very fast and sensitive infrared camera. It has been found that in this experimental conditions the stress-induced transformation and reorientation processes occurred homogeneously, since the temperature distribution observed on the specimen surface was uniform. The obtained temperature variation depends on the strain rate applied. At the higher strain rate the higher temperature changes were obtained, because the heat flow to the surroundings was lower and the process was closer to adiabatic conditions. The temperature changes influence significantly the SMA stress-strain curves and their mechanical properties.

Słowa kluczowe:
shape memory alloy, various strain rates, compression tests, exothermic martensitic forward, endothermic reverse transformation, fast and sensitive infrared camera

Streszczenie:
This work presents the impact resistance results of investigation on the VP159 high nitrogen steel. The tests were carried out using the Instron impact system at the projectile velocity equal to 12,5 m/s. The experimental results were compared to the FE predictions. The Rusinek-Klepaczko constitutive model was applied to describe mechanical response of tested material. It was concluded that the FE results were in a good agreement with the experiment.

Streszczenie:
W pracy dokonano analizy wskaźników rozwoju uszkodzenia zmęczeniowego, opracowanych w oparciu o wyniki testów zmęczeniowych próbek ze stali P91, w stanie dostawy i po 80 000 godzin eksploatacji w warunkach pracy instalacji energetycznej. Wykonano badania zmęczeniowe dla dwóch typów próbek i wyznaczono funkcje zmiany parametrów uszkodzeń w zależności od liczby cykli przy różnych amplitudach naprężenia. Uzyskane wyniki wykorzystano do wyznaczenia klasycznej charakterystyki zmęczeniowej, ale również do wyznaczenia ewolucji uszkodzeń w zależności od liczby cykli. Wyniki wskazały na możliwość jej opisania przy pomocy dwóch makroskopowych wskaźników rozwoju zmęczenia. Pierwszy z nich to średnie odkształcenie w kolejnych cyklach obciążenia przy stałej amplitudzie naprężenia. Drugim, jest odkształcenie niesprężyste w cyklu obrazujące szerokość pętli histerezy w kolejnych fazach obciążenia ostałej amplitudzie naprężenia. Rozwój uszkodzenia wstali P91poddanej obciążeniom zmęczeniowym opisano stosując kombinację wyżej wymienionych wskaźników

Słowa kluczowe:
badania zmęczeniowe, ewolucja uszkodzeń, wskaźniki uszkodzenia

Streszczenie:
The paper presents the results of tests on polycrystalline tantalum at very high strain rates (7.5x104 s-1). The measurements were carried out using miniaturized Direct Impact Compression Test (DICT) method. The transmitting bar diameter was 3mm, and the tested specimens were cylindrical shape of 1.5 mm diameter and 0.55 mm thickness. A numerical model of the testing stand was developed in the ABAQUS environment to trace the phenomena occurring during specimen deformation and to evaluate their influence on the final result. The test stand dimensions and the test parameters used in the calculations were this same as for DICT experiments. The results of computer simulations demonstrated good agreement with experimental results, which proves that the Finite Element Method (FEM) reproduces well the behavior of the stand and can be applied in analyses performed to find the reasons of errors in plastic stress flow measurements.

Słowa kluczowe:
Direct Impact Compression Tests, Tantalum, high strain rates, compression tests, Hopkinson bar

Streszczenie:
The paper is devoted to an analysis of creep damage at elevated temperatures and structural degradation due to plastic deformation at room temperature of selected steels commonly applied in power plants (40HNMA, 13HMF). The materials were tested in the as-received state, however, in the case of the 13HMF steel also after different periods of exploitation (76000h and 144000h at elevated temperature (813K) under internal pressure (14 bars)). Destructive and non-destructive testing methods were applied to assess material degradation. As destructive methods the standard tension tests were carried out after every kind of prestraining. Subsequently, an evolution of the selected tension parameters were taken into account for damage identification. In order to assess a damage development during the creep and plastic deformation the tests for both steels were interrupted for a range of the selected strain magnitudes. The ultrasonic and magnetic techniques were used as the non-destructive methods for damage evaluation. The last step of the experimental programme contained microscopic observations. A good correlation of mechanical and selected non-destructive parameters identifying damage was achieved for the tested steels. It gives very promising tool for degradation assessments appearing in pipelines at power stations.

Słowa kluczowe:
medical fixation devices, orthopedicimplants, SEM, fracture analysis, titanium alloy, stainless steel

Słowa kluczowe:
Fatigue Crack Initiation, Damage Evolution, Optical Methods, Indentation Method

Słowa kluczowe:
Fatigue, Damage Evolution, Aluminum Alloy

Słowa kluczowe:
mini-próbka, parametry mechaniczne, rozciąganie, skręcanie, pękanie

Słowa kluczowe:
cyclic loading, damage evolution, laminate composites

Słowa kluczowe:
mini-specimen CT, fracture toughness, CTOD, fatigue pre-cracking, notch, fracture, parent material, weld, HAZ

Słowa kluczowe:
structural components, static loading, markers, displacement, deflection, DIC

Słowa kluczowe:
Barkhausen noise, microstructure, hardness, ultimate tensile strength, structural steels

Streszczenie:
The paper reports results of tests focused on determination of kinematic properties of components under cyclic loading. DIC system called 5M PONTOS was employed to follow variations of displacement and velocity versus time. It was conducted by a use of markers stuck on selected sections of components tested. Results are presented in 2D and 3D coordinate systems expressing behaviour of elements such as: car engine, boat frame and mechanical coupling device. These data enable to capture weak and strong sections of the component tested at various loading conditions.

Słowa kluczowe:
digital image correlation system, cyclic loading, PONTOS, motion, displacement, 3D coordinate system

Streszczenie:
The problem investigated in the present work concerns the damage evolution in elastic-plastic materials subjected to cyclic loading. The modeling of damage mechanisms is supported by Electronic Speckle Pattern Interferometry (ESPI) apparatus using coherent laser light. Such a study can help better understanding of the damage and failure mechanism of modern structural materials for practical engineering problems.

Słowa kluczowe:
damage mechanisms, void growth, optical methods

Streszczenie:
The paper presents selected cruciform specimens recommended for static and fatigue tests. Guidelines for cruciform specimens designing and optimization are presented. Numerical data of FEA analysis of Kelly's cruciform specimen in 3D coordinate systems are shown. Various types of cruciform testing machines and their advantages and disadvantages are discussed. The project of the cruciform specimen for examination of material behaviour under static and cyclic loading types is proposed.

Słowa kluczowe:
cruciform specimen, biaxial stress state, specimen optimization, static test, fatigue test, FEA, effective stress

Streszczenie:
Optimization of sheet metal forming processes requires a very good knowledge of material forming ability. During the forming of industrial parts, very complex strain paths are usually observed and can affect the formability of the sheet. Therefore, it is necessary to better understand and more accurately investigate deformation behaviour of sheet alloys. It should be noted that material testing of flat specimens under compression within a large deformation range procures many difficulties, and the buckling phenomenon seems to be the most im-portant. This paper shows the results of tension-compression tests carried out on specimens made of ultralight magnesium alloys AZ31B with nominal thickness equal to 1 mm using the anti-buckling fixture to avoid buckling problem.

Słowa kluczowe:
Bauschinger effect, cyclic loading, buckling, fixture, thin sheet

Streszczenie:
The paper shows how modern contactless Digital Image Correlation (DIC) method can be implemented for examination of material behaviour under various types of loading. DIC method was used to evaluate material straining under monotonic tension conducted by the use of flat specimens having artificial defects in the form of U and V notches. This technique was also examined during capturing of strain distribution in dynamic tests on Split Hopkinson Pressure Bar. On the basis of DIC results the strain maps at various stages of material deformation were elaborated in order to indicate characteristic features of a material behaviour. It enabled an analysis of damage zone evolution up to specimen fracture.

Słowa kluczowe:
Digital Image Correlation, specimen, monotonic tension, Split Hopkinson Pressure Bar, strain maps

Streszczenie:
In the paper the results of experimental and numerical investigations concerning an influence of strain rate on mechanical properties of pure tantalum are presented. Experiments were carried out using Direct Impact Compression Test (DICT) technique (Malinowski et al. [2007]). The Perzyna elasto-viscoplasticity theory (Perzyna [1966]) was applied to predict the dynamic compression yield strength of the tested material at strain rates from 1.0 x10-3 s−1 to 0.5 x106 s−1.

Streszczenie:
The aim of this work consists a development of the Gurson-Tvergaard-Needleman model (GNT) of damage evolution in elastic-plastic materials. This model is supported by optical method of stress and strain monitoring (ESPI) for early detection, localization and monitoring of damage in materials under fatigue loading.

Streszczenie:
The results of experimental and numerical investigations concerning an influence of strain rate on mechanical properties of pure tantalum are presented. Experiments were carried out using Direct Impact Compression Test (DICT) technique. The miniaturization concept of the experimental setup for the dimensions of specimen (diameter dS = 1.5 mm and thickness lS = 0.50 mm), Hopkinson transmitter bar diameter (dH = 3.0 mm) and the striker (diameter dI = 11.5 mm and the length lI =12 mm), together with application of a novel optical arrangement for measurement of striker velocity, enabled compression tests to be executed at strain rates from 1.0 x103 s−1 to 0.5 x106 s−1. The Perzyna elasto-viscoplasticity theory is applied to predict the dynamic compression yield strength of the tested material at different strain rates. In the course of specimens deformation by means of the DICT technique, it was observed that the peak force obtained from the strain gauge mounted on the transmitter Hopkinson bar was lower than the peak force obtained within the framework of the uniaxial stress wave analysis. An explanation of this discrepancy is provided due to the analysis of the localization of deformation in the tested specimens considered as three-dimensional body subjected to high strain rate loading and the resulting stress wave attenuation as it propagates within the specimen.

Słowa kluczowe:
direct impact test, numerical simulations, tantalum

Streszczenie:
Problems associated with material testing on flat specimens under large deformation due to compression or cyclic tension-compression are discussed. A short review of the anti-buckling fixtures developed up to now is given with special emphasis on the new fixture elaborated at the Institute of Fundamental Technological Research in Poland.

Streszczenie:
Fatigue damage process developing in structural materials under long-term cyclic loading is still an unsolved problem of modern engineering. Attempts to assess a degree of materials degradation under fatigue conditions on the basis of changes in the areas of local strain concentration determined by optical methods can be treated as the promising contemporary research direction of majority of scientific centers in the world. In most cases, fatigue damage has a local character and it is based on damage development leading to generation of cracks appearing around structural defects or geometrical notches. An identification of these areas and their subsequent monitoring requires a full-field displacement measurements performed on the objects surfaces. It seems that modern contemporary optical methods for displacement components measuring on the surfaces of structural elements or tested specimens are suitable for such purpose. Digital Image Correlation (DIC) and Electronic Speckle Pattern Interferometry (ESPI) are nowadays the most widely used testing methods in this area. Both of them enable capturing of displacement and strain components distributions. This paper presents an attempt to use the ESPI method for fatigue damage evaluation and its monitoring on specimens ma de of the aluminide coated nickel super-alloys. Flat specimens were subjected to cyclic loading. The fatigue tests were interrupted several times in order to perform a static loading during which the optical measurements were carried out. An analysis of the results captured by the ESPI system allowed indication of places of the greatest stress concentration and demonstration of the damage development process as a function of the increasing number of cycles.

Słowa kluczowe:
fatigue, damage, super - alloy, Electronic Speckle Pattern Interferometry

Słowa kluczowe:
eddy current, hardening, carburizing, layers, non - destructive technique

Streszczenie:
Development of creep and fatigue damage was investigated using destructive and non - destructive methods in materials commonly applied in power plants or automotive industry. In order to assess such kind of damage the tests for a range of different materials were interrupted for selected time periods (creep) and number of cycles (fatigue). As destructive methods the standard tension tests were carried out after prestraining. Subsequently, an evolution of the selected tension parameters was taken into account for damage identification. The ultrasonic and magnetic techniques were used as the non - destructive methods for damage evaluation. In the final step of the experimental programme microscopic observations were performed

Słowa kluczowe:
creep, fatigue, damage, non - destructive method

Streszczenie:
The paper presents results of numerical and experimental investigations conducted in order to determine an influence of notch type on material behaviour under monotonic tension. Two kinds of specimens having U and V notches were applied. Digital image correlation system was used to detect variations of strain/stress state components from beginning of the test up to fracture of the material in question. Assessments of the results enabled identification of stress concentrations in tips of notches. A comparison of tensile characteristics of unnotched and notched specimens exhibited a great reduction of the yield point independently of the geometrical discontinuities applied. In the case of V-notched specimen 50% lowering of elongation was observed.

Słowa kluczowe:
stress concentration, stress distribution, notches, tensile curve, digital image correlation

Streszczenie:
The paper presents the results of fatigue tests performed on the super-nickel alloy after Chemical Vapor Deposition (CVD). CVD process was carried out for the periods of 4 and 12 hours, and as a consequence, a layer of the aluminum of the thickness 20 μm and 40 μm, respectively, was obtained on the surface of nickel alloy. The specimens with layers were tested on the servo-hydraulic testing machine under dynamic loading at high temperature of 900oC. The profiles of micro hardness on the cross-sections of specimens enabled identification of hardness variations. The main aim of this paper was to evaluate the effect of a film thickness on the fatigue properties of the alloy. Additionally, an identification of crack propagation in the layer subjected to cyclic loading was analysed on the basis of deformation changes in the subsequent cycles.

Słowa kluczowe:
aluminium layer, super nickel alloy, fatigue testing, CVD technique

Streszczenie:
Wpływ karbów jest określany zarówno od strony badań teoretycznych, jak i doświadczalnych. Pierwsze z nich umożliwiają przewidywanie zniszczenia na podstawie analizy zmian wartości współczynnika koncentracji naprężenia (WKN) i pozwalają zilustrować jego zmiany w zależności od geometrii karbu. Z kolei w eksperymentach próbuje się określać, jakie znaczenie na otrzymywane wyniki ma rodzaj próbki. Najczęściej stosowane są w tych badaniach próbki rurkowe lub płaskie. W strefie pomiarowej nacinane są karby o różnym kształcie i wymiarach [1]. Uzyskiwane rezultaty z badań wskazują na 50% obniżenie liczby cykli do zainicjowania pęknięcia wraz ze wzrostem promienia karbu od 0 do 6.35mm [2]. Podobny efekt uzyskano również przy wzroście wartości WKN od 1 do 2.833 [1, 3]. Wyniki tego rodzaju nie ujawniają jednak wystarczająco wpływu nieciągłości geometrycznych w bliskim otoczeniu karbu. Rozwiązanie tego problemu może nastąpić poprzez wykorzystanie nowoczesnej techniki pomiarowej DIC (cyfrowa korelacja obrazu). Dlatego też głównym celem pracy było określenie wpływu karbów na zachowanie materiału w teście rozciągania do zniszczenia przy użyciu wymienionej techniki pomiarowej

Streszczenie:
Problems associated with material testing on flat specimens under large deformation are discussed in this paper. An extensive review of the anti - buckling fixtures developed up to now is given first, and then detailed description of the proposed design is presented. Finally, the results of cyclic tests carried out using new fixture are studied

Streszczenie:
The effects commonly taking place during proportional and non - proportional (circle and square) types of loading were identified experimentally. Experimental results of tests under cyclic loading assisted by monotonic deformation are compared to their predictions using the Mróz - Maciejewski model

Streszczenie:
In this paper original experimental methodologies of dynamic plastic behavior of various structural materials in a wide range of strain rates up to 10 5 s - 1, and at selected temperatures are presented. Identification of constitutive models and their verification are also included

Streszczenie:
The paper reports the experimental data of tests on the 10H2M steel, carried out under complex loading being combination of monotonic tension and cyclic torsion. Two types of torsion cycles were applied, i.e.: symmetrical and asymmetrical, having four blocks of different shear strain amplitude within a range from ±0.1% to ±0.8%,. All tests were conducted using the tubular specimens at room temperature. The main aim of the experimental procedure was focused on examination of axial stress variations due to torsion cycles of step increasing strain amplitude. An analysis of the results showed a significant reduction of the tensile stress. This effect became stronger when the torsion strain amplitude was increased andit achieved 85% stress drop at highest strain amplitude considered in comparison to the standard tensile characteristic.

Słowa kluczowe:
complex loading, biaxial stress state, stress reduction, tensile stress, shear stress, tubular specimen

Streszczenie:
Creep and fatigue damage was investigated in steels commonly applied in power plants (40HNMA, 13HMF and P91) using destructive and non-destructive methods. In order to assess both types of damage the tests for each kind of steel were interrupted for a range of the selected time periods (creep) and number of cycles (fatigue).

Streszczenie:
Fatigue tests and microstructural observations were carried out to perform damage analysis of Al/SiC and AlMg/SiC metal matrix composites ( MMCs ). The materials were manufactured using a KoBo method. Ratcheting was the dominant damage mechanism for Al/SiC and damage parameter on the basis of mean inelastic strain was calculated. For AlMg/SiC, in most cases, cyclic softening followed by hardening during subsequent cycles were noticed. Microstructural observations identified existence of SiC concentrations which influenced the volumetric fraction of defects after fatigue tests

Słowa kluczowe:
metal matrix composites, fatigue damage, microstructure, KoBo method

Streszczenie:
Development of damage due to creep at elevated temperatures and fatigue at room temperature was assessed for power engineering steels using destructive and non-destructive methods. The experimental programme contained also microscopic observations to find feedback between macro- and micro-scopic parameters. Three different power engineering steels were tested, i.e. 40HNMA, 13HMF and P91

Streszczenie:
Development of damage due to creep at elevated temperatures and fatigue at room temperature was assessed for power engineering steels using destructive and nondestructive methods. The experimental programme contained also microscopic observations to find feedback between macro and microscopic parameters

Streszczenie:
Creep tests under a range of step-increasing tensile stresses were carried out on the AlMg/SiC composites produced by means of the KOBO method. The content of reinforced phase was equal to 2.5, 5, 7.5 and 10%. The AlMg/SiC creep characteristics were compared to those of the Al/SiC composites. Structural assessments of materials in the as-received state and after creep were carried out.

Słowa kluczowe:
metal-ceramic composites, KOBO method, creep, silicon carbide (SiC)

Streszczenie:
In order to elaborate more efficient technological processes enabling a lifetime prolongation of some elements of devices and machines a lot of scientific efforts are focused on searching of the optimal loading combinations. As it has been found by Korbel and Bochniak [1, 2], a significant reduction of tensile or compressive forces in technological processes is possible using twisting moment simultaneously applied. They proposed the so-called KOBO method and successfully applied it to extrusion, forging or rolling processes. Up to now the method was checked for large deformations, what requiredalot of energy. Since the available results of the method validation in the range of small deformations are not sufficiently represented,an experimental programmelimiting maximal strain level below 1% (Fig.1)was elaborated. The strain controlled loading programme enables observation of stress/strain components variation as a function of time (Figs 1 and 2)The loading programme(for the 10H2M steel) contained four subsequent blocks of cyclic shear deformation assisted by tension. As it is illustrated in Fig.2, theaxial stress increases at the beginning of the test (first cyclic strain amplitude). However, for higher cyclic strain amplitudes, its lowering is clearly manifested. Figure 3 shows comparison of tensile characteristics in the case of activated and inactivated torsion cycles. It is seen, that while the torsion cycles were applied a gradual decrease of axial stress can be observed. The maximum drop of it was almost equal to 400 MPa for the highest cyclic strain amplitude used in the programme. The effect of similar order was also achieved for this material tested under monotonic tension and torsion-reverse-torsion cycles ofconstant strain amplitude (0.8%), Fig.4. It means that prior cyclic loading history does not influence a magnitude of the tensile stress drop. A reduction of axial stress due to application of cyclic loading by means of reversible torsion was also observed for other materials, i.e. the P91 steel and M1E copper (Fig.5) [3].