Prof. Wiera Oliferuk, Ph.D., Dr. Habil., Eng.

Department of Mechanics of Materials (ZMM)
Thermoplasticity Laboratory (LT)
retiree
telephone: (+48) 22 826 12 81 ext.: 177
room: 223
e-mail: wolif

Habilitation thesis
1999Proces magazynowania energii i jego strukturalny aspekt podczas jednoosiowego rozciągania stali austenitycznej886
 
Professor
2009-09-25Title of professor
Supervision of doctoral theses
1.2012-11-29Wysocka-Fotek Olga  Szacownie wielkości i położenia defektów podpowierzchniowych za pomocą impulsowej termografii podczerwieni653
 
2.2007-10-04Maj Michał  Wpływ kierunku wstępnego odkształcenia na proces magazynowania energii w polikryształach604
 

Recent publications
1.Oliferuk W., Maj M., Zembrzycki K., Determination of the Energy Storage Rate Distribution in the Area of Strain Localization Using Infrared and Visible Imaging, EXPERIMENTAL MECHANICS, ISSN: 0014-4851, DOI: 10.1007/s11340-013-9819-1, Vol.55, pp.753-760, 2015
Abstract:

The presented work is devoted to a new simple method of determination of the energy storage rate (the ratio of the stored energy increment to the plastic work increment) that allows obtaining distribution of this quantity in the area of strain localization. The method is based on the simultaneous measurements of the temperature and displacement distributions on the specimen surface during a tensile deformation. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. It has been experimentally shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. It can be treated as the plastic instability criterion.

Keywords:

Infrared thermography, Energy storage rate distribution, Strain localization, Plastic instability criterion, Texture evolution

Affiliations:
Oliferuk W.-other affiliation
Maj M.-IPPT PAN
Zembrzycki K.-IPPT PAN
2.Wysocka-Fotek O., Maj M., Oliferuk W., Use of pulsed IR thermography for determination of size and depth of subsurface defect taking into account the shape of its cross-section area, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2015-0181, Vol.60, No.2, pp.615-620, 2015
Abstract:

The paper is devoted to reconstruction of size and depth (distance from the tested surface) of artificial defects with square and rectangular cross-section areas using the pulsed IR thermography. Defects in form of flat-bottom holes were made in austenitic steel plate. The defect size was estimated on the basis of surface distribution of the time derivative of the temperature. In order to asses the depth of defects with considered geometries on the basis of calibration relations (i.e. dependence of time of contrast maximum vs. defect depth for given defect diameter) obtained for circular defects, the ‘equivalent diameter’ describing not only the defect cross-section area but also its shape was assigned. It has been shown that presented approach gives satisfactory results.

Keywords:

pulsed IR thermography, defect size, defect depth, cross-section shape of defect

Affiliations:
Wysocka-Fotek O.-IPPT PAN
Maj M.-IPPT PAN
Oliferuk W.-other affiliation
3.Oliferuk W., Maj M., Litwinko R., Urbański L., Thermomechanical coupling in the elastic regime and elasto-plastic transition during tension of austenitic steel, titanium and aluminium alloy at strain rates from 10-4 to 10-1 s-1, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, DOI: 10.1016/j.euromechsol.2011.08.007, Vol.35, pp.111-118, 2012
Abstract:

The temperature variation phenomenon during uniaxial deformation of materials with positive coefficient of linear thermal expansion is studied. The formula for a change in the specimen temperature during non-adiabatic tensile deformation is briefly derived. Thermomechanical behaviour of austenitic stainless steel, titanium and aluminium alloy during initial stage of tension at strain rates from 10−4 to 10−1 s−1 has been investigated. It was confirmed, that with increasing stress the temperature of each tested specimen first decreases linearly, reaches a minimum and then starts to rise. The decrease in the specimen temperature corresponds to elastic deformation whereas the temperature rise is related to the plastic one. Thus, the change in the specimen temperature can be used for study of elasto-plastic transition. From the viewpoint of strict theoretical analysis, the yield point will be defined as the stress corresponding to the lowest temperature, if tensile deformation process is adiabatic. The processes of deformation considered in this work are not adiabatic; there is a heat exchange between the specimen and the surroundings. The influence of this fact on the change in the specimen temperature vs. stress is discussed. The problem of yield point as the value of stress corresponding to minimum temperature of the specimen is considered. The influence of the strain rate on the yield point for tested materials is studied. Comparing of the obtained results with theoretical model, the limit above which the deformation process can be treated as the adiabatic one was determined. The values of the yield points determined on the basis of the thermoelastic effect were compared with the stress corresponding to the 0.2% of plastic strain.

Keywords:

Thermoelastic effect, Yield point, Non-adiabatic deformation

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
Litwinko R.-other affiliation
Urbański L.-IPPT PAN
4.Wysocka-Fotek O., Oliferuk W., Maj M., Reconstruction of size and depth of simulated defects in austenitic steel plate using pulsed infrared thermography, INFRARED PHYSICS AND TECHNOLOGY, ISSN: 1350-4495, DOI: 10.1016/j.infrared.2012.02.004, Vol.55, pp.363-367, 2012
Abstract:

In this paper the size and depth (distance from the tested surface) of defects in austenitic steel were estimated using pulse infrared thermography. The thermal contrast calculated from the surface distribution of the temperature is dependent on both these parameters. Thus, two independent experimental methods of defect size and depth determination were proposed. The defect size was estimated on the basis of surface distribution of the time derivative of the temperature, whereas the defect depth was assessed from the dependence of surface thermal contrast vs. cooling time.

Keywords:

pulsed IR thermography, temperature time derivative, defect size, thermal contrast, defect depth

Affiliations:
Wysocka-Fotek O.-IPPT PAN
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
5.Maj M., Oliferuk W., Analysis of Plastic Strain Localization on The Basis of Strain and Temperature Fields, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/v10172-012-0124-2, Vol.57, No.4, pp.1111-1116, 2012
Abstract:

In the present paper the onset of plastic strain localization was determined using two independent methods based on strain and temperature field analysis. The strain field was obtained from markers displacement recorded using visible light camera. In the same time, on the other side of the specimen, the temperature field was determined by means of infrared camera. The objective of this work was to specify the conditions when the non-uniform temperature distribution can be properly used as the indicator of plastic strain localization. In order to attain the objective an analysis of strain and temperature fields for different deformation rates were performed. It has been shown, that for given experimental conditions, the displacement rate 2000 mm/min is a threshold, above which the non-uniform temperature distribution can be used as the indicator of plastic strain localization.

Keywords:

plastic strain localization, strain field, temperature field, infrared thermography, heat transfer

Affiliations:
Maj M.-IPPT PAN
Oliferuk W.-IPPT PAN
6.Oliferuk W., Termografia podczerwieni i zastosowanie jej do kontroli pracy urządzeń elektrycznych, ELEKTRO.INFO, ISSN: 1642-8722, No.11, pp.1-4, 2011
7.Zimnoch M., Oliferuk W., Maj M., Estimation of Defect Depth in Steel Plate Using Lock-in IR Thermography, ACTA MECHANICA ET AUTOMATICA, ISSN: 1898-4088, Vol.4, No.4, pp.6-9, 2010
Abstract:

The paper deals with the application of lock-in active infrared thermography as one of the non-contact and non-destructive techniques used for estimating defect depth. Preliminary research was done by testing a specimen made of austenitic steel plate with artificially created defects, i.e. flat-bottom holes. The obtained dependence between defect depth and phase shift was presented for different frequencies of “thermal waves” generated inside the sample. The experiment was carried out to determine the application of the lock-in thermography approach in testing materials with a high thermal diffusivity.

Keywords:

non-destructive testing, lock-in thermography, defect depth, phase shift, thermal diffusivity

Affiliations:
Zimnoch M.-other affiliation
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
8.Oliferuk W., Maj M., Stress-strain curve and stored energy during uniaxial deformation of polycrystals, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, DOI: 10.1016/j.euromechsol.2008.06.003, Vol.28, No.2, pp.266-272, 2009
Abstract:

The subject of this paper is an attempt to obtain information about the energy stored during plastic deformation from experimentally measured stress–strain curve. Theoretical analysis of the stress–strain curve for elastic-perfectly plastic polycrystalline material has shown that only the part of stored energy can be calculated from the stress–strain curve. This part is the energy stored during non-homogeneous plastic deformation. The results of such calculation have been compared with the total stored energy determined experimentally. It has been shown that part of total stored energy related to non-homogeneous plastic deformation of investigated materials is much lower than that corresponding to homogeneous one.

Keywords:

stored energy, non-homogeneous plastic deformation, geometrically-necessary dislocations

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
9.Wysocka-Fotek O., Oliferuk W., Maj M., Use of pulse IR thermography for detection and quantitative description of subsurface defects in austenitic steel, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.54, No.11, pp.684-687, 2009
Abstract:

Pulsed IR thermography is a non-destructive testing method that allows detection of subsurface defects in material. In this method the surface of the tested specimen is stimulated by heat pulse and its self-cooling process is analyzed. The temperature decrease rate is different for surface over defect with comparison to that over the sound material. It is caused by difference between values of heat diffusivity of defected zone and sound one. The purpose of this work is to determine the size and depth of the defects in austenitic steel on the basis of thermal contrast analysis. Because the thermal contrast is dependent on both these parameters, two independent experimental methods of defect size and depth determination were proposed.

Keywords:

pulsed thermography, thermal contrast, defect characterization

Affiliations:
Wysocka-Fotek O.-IPPT PAN
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
10.Oliferuk W., Maj M., Components of energy storage rate during plastic deformation and their identification, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.54, No.11, pp.732-735, 2009
Abstract:

The subject of the present paper is decomposition of energy storage rate into terms related to different mode of deformation. The stored energy is the change in internal energy due to plastic deformation determined after specimen unloading. Hence, this energy describes the state of the cold-worked material. Whereas, the ratio of the stored energy increament to the appropriate increament of plastic work is the measure of energy conversion process. This ratio is called the energy storage rate. Experimental results show that the energy storage rate is dependent on plastic strain. This dependence is influenced by different microscopic deformation mechanisms. It has been shown that the energy storage rate can be presented as a sum of particular components. Each of them is related to the separate internal microscopic mechanism. Two of the components are identified. One of them is the storage rate of statistically stored dislocation energy related to uniform deformation. Another one is connected with non-uniform deformation at the grain level. It is the storage rate of the long-range stresses energy and geometrically necessary dislocation energy.

Keywords:

stored energy, non-uniform plastic deformation, geometrically necessary dislocations

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
11.Litwinko R., Oliferuk W., Yield point determination based on thermomechanical behaviour of polycrystalline material under uniaxial loading, ACTA MECHANICA ET AUTOMATICA, ISSN: 1898-4088, Vol.3, No.4, pp.1-3, 2009
12.Oliferuk W., Maj M., Plastic instability criterion based on energy conversion, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2006.02.465, Vol.462, No.1-2, pp.363-366, 2007
Abstract:

The energy conversion in the plastic deformation process is described by the energy storage rate, defined as the ratio of the stored energy increment to the plastic work increment. The experiment was performed on 304L and 316L stainless steels. It has been shown that during straining the material reaches the state at which the energy storage rate is zero and after that it is negative. This means that a part of energy stored during previous deformation begins to release. The point where the energy storage rate is zero turned out to be the point of Considere stability criterion. Therefore, the zero and negative values of the energy storage rate can be used as a plastic instability criterion on the macro-scale and the release of stored energy as an indicator to describe the progressive predominance of damage leading to the fracture of tested materials.

Keywords:

stored energy, plastic work, plastic instability criterion, non-homogeneous deformation, austenitic steel

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
13.Oliferuk W., Maj M., Energy storage rate and plastic instability, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.52, No.2, pp.250-256, 2007
Abstract:

The energy storage rate, defined as the ratio of the stored energy increment to the plastic work increment, versus strain was experimentally estimated in the range of homogeneous deformation as well as in the range of non-homogeneous one. The experiment were performed on 304L and 316L stainless steels. It has been shown, that during straining the material reaches the state at which the energy storage rate is zero and after that it is negative. This means that a part of energy stored during previous deformation begins to release.
It has been found that the point where the energy storage rate is zero turned out to be the point of Considere stability criterion. Therefore the release of stored energy could be used as an indicator to describe the progressive predominance of damage leading to the fracture of a material. This confirms Considere construction that specimen will undergo stable deformation up to the point on the stress-strain curve, for which the strain hardening rate is equal to the flow stress. Some attempts to explain the release of stored energy in terms of microstructure phenomena has been made.

Keywords:

energy storage rate, plastic work, non-homogeneous deformation, Considere stability criterion

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
14.Oliferuk W., Maj M., Identyfikacja składników energii zmagazynowanej podczas jednoosiowego rozciągania, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.52, No.11, pp.695-702, 2007
Abstract:

Podjęto próbę wyznaczenia energii zmagazynowanej na podstawie zależności naprężenie-odkształcenie. Przeprowadzona analiza teoretyczna pokazała, że w ten sposób można wyznaczyć jedynie dolną granicę energii zmagazynowanej. Na podstawie uproszczonego modelu materiału polikrystalicznego, podjęto próbę identyfikacji składników energii zmagazynowanej. Wykazano, że dolną granicę tej energii można traktować jako energię zmagazynowaną na skutek deformacji mikroskopowo niejednorodnej. Wyniki analizy teoretycznej porównano z całkowitą energią zmagazynowaną wyznaczoną eksperymentalnie.

Keywords:

energia zmagazynowana, odkształcenie jednorodne i niejednorodne, rozkład gęstości dyslokacji

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
15.Oliferuk W., Beygelzimer Y., Maj M., Synkov S., Reshetov A., Pakieła Z., Zdolność magazynowania energii podczas rozciągania tytanu po wyciskaniu przez matrycę skrętną, Polska metalurgia w latach 2002-2006; Wydawnictwo Naukowe Akapit (Kraków), Świątkowski K. (Ed.), pp.495-500, 2006
Abstract:

The presented work is devoted to experimental studies of the energy storage process in the tensile test of the ultrafine-grained (UFG) titanium in comparison with the coarse-grained one. The UFG titanium was obtained using severe plastic deformation method (SPD) called twist extrusion (TE) that is briefly presented.
The experiments were performed on three groups of titanium specimens. Two of them (T1 and T2) were cut from the materials obtained by TE method. The T1 titanium was processed by 4 passes through the left twist die, whereas for the T2 titanium the twist direction was changed after the first pass. The last group (T0) was prepared from the annealed sheet of coarse-grained titanium. It was noticed that mechanical properties of the material underwent TE differs considerably from properties of te coarsed-grained one. It was observed that yield point obtained for specimens after TE is about 30% higher then that for coarsed-grained material. However, the elongation decrease was observed for both groups of specimens after TE (T1~60%, T2~25%) with respect to T0 ones.
The energy storage investigations show the differences in the energy storage rate for T1 and T2 specimens. In the case of T1 specimens the energy storage rate decreases rapidly with strain whereas for T2 specimens (where twist direction was changed) the energy storage rate remains constant at the homogeneous deformation range. The experimental results show that the change of the twist direction during TE may improve the mechanical properties of the material. The constant rate of energy storage in specimens after twist direction change may be macroscopic manifestation of homogeneous and more stable structure of the material.

Keywords:

energy storage rate, ultrafine-grained titanium, severe plastic deformation, twist extrusion

Affiliations:
Oliferuk W.-IPPT PAN
Beygelzimer Y.-other affiliation
Maj M.-IPPT PAN
Synkov S.-other affiliation
Reshetov A.-other affiliation
Pakieła Z.-Warsaw University of Technology (PL)
16.Korch M., Oliferuk W., Zobaczyć niewidzialne, Delta, ISSN: 0137-3005, Vol.10, No.377, pp.6-10, 2005
17.Mróz Z., Oliferuk W., Energy balance and identification of hardening moduli in plastic deformation processes, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(00)00103-0, Vol.18, No.3, pp.379-397, 2002
Abstract:

The hardening moduli Hr and Hd of plastic deformation associated with the free energy and dissipation function in a representative material element are defined analytically and specified experimentally for three materials. Besides the stress–strain curve and work expended during the deformation process, variation of the hardening moduli with plastic deformation is also determined for austenitic steel, austenitic-ferritic steel and Fe–Si alloy.

Keywords:

Thermomechanical processes, Hardening modulus, Polycrystalline material, Energy methods, Mechanical testing

Affiliations:
Mróz Z.-IPPT PAN
Oliferuk W.-IPPT PAN
18.Oliferuk W., Proces magazynowania energii i jego strukturalny aspekt podczas jednoosiowego rozciągania stali austenitycznej (Praca habilitacyjna), Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.11, pp.1-108, 1997
19.Kruszka L., Nowacki W.K., Oliferuk W., Badania dynamiczne materiałów kruchych na rozciąganie przy dużych prędkościach odkształcenia, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.34, pp.1-23, 1995
20.Oliferuk W., Świątnicki W.A., Grabski M.W., Wpływ wielkości ziarn na zdolność magazynowania energii podczas jednoosiowego rozciągania stali austenitycznej, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.22, pp.1-29, 1992
21.Gadaj S.P., Oliferuk W., Pieczyska E., Emisja akustyczna podczas deformacji plastycznej stali węglowej, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.5, pp.1-15, 1988
22.Gadaj S.P., Kaczmarek J., Oliferuk W., Proces magazynowania energii podczas rozciągania metalu, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.28, pp.1-13, 1983
23.Gadaj S.P., Kaczmarek J., Oliferuk W., Pieczyska E., Wpływ obróbki powierzchniowej na proces magazynowania energii podczas rozciągania stali 1H18N9T, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.28, pp.1-9, 1983
24.Choroś J., Gadaj S.P., Kaczmarek J., Oliferuk W., Pieczyska E., Emisja akustyczna towarzysząca przemianom fazowym w deformowanej stali 1H18N9T, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.31, pp.1-16, 1982
25.Gadaj S.P., Gałkowska E., Kaczmarek J., Oliferuk W., Wyznaczanie energii zmagazynowanej w metalu podczas procesu rozciągania, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.36, pp.1-24, 1981
26.Malatyński M., Nowacki W.K., Oliferuk W., Określenie temperatury w dynamicznej plastyczności metodą detekcji promieniowania podczerwonego, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.39, pp.1-24, 1981
27.Wicher J., Oliferuk W., Sitarek I., Trinda P., Chmurny R., Wpływ samoistnego nagrzewania się materiału wibroizolacyjnego na jego własności dynamiczne w warunkach obciążeń sinusoidalnie zmiennych, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.54, pp.1-23, 1980

List of recent monographs
1.
115
Oliferuk W., Termografia podczerwieni w nieniszczących badaniach materiałów i urządzeń, Biuro Gamma (Warszawa), pp.1-96, 2007

Conference papers
1.Oliferuk W., Maj M., Distributions of energy storage rate and microstructural evolution in the area of plastic strain localization during uniaxial tension of austenitic steel, IOP Conference Series: Materials Science and Engineering, ISSN: 1757-899X, DOI: 10.1088/1757-899X/89/1/012040, Vol.89, pp.012040-1-8, 2015
Abstract:

The presented work is devoted to an experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using Transmission Electron Microscopy (TEM) and Electron Back Scattered Diffraction (EBSC) were performed. On the basis of microstructural studies it is believed that a 0 value of energy storage rate corresponds to the state in which only two dominant components of the texture appear, creating conditions for crystallographic shear banding.

Keywords:

energy storage rate, strain localization, infrared thermography, microstructure evolution, crystallographic texture

Affiliations:
Oliferuk W.-other affiliation
Maj M.-IPPT PAN
2.Oliferuk W., Maj M., Zembrzycki K., Distribution of energy storage rate in area of strain localization during tension of austenitic steel, IOP Conference Series: Materials Science and Engineering, ISSN: 1757-899X, DOI: 10.1088/1757-899X/71/1/012055, Vol.71, pp.012055-1-8, 2015
Abstract:

The present work is devoted to experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using electron back scattered diffraction (EBSC) were performed.

Keywords:

energy balance, strain localization, infrared thermography, texture evolution

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
Zembrzycki K.-IPPT PAN
3.Oliferuk W., Maj M., Distribution of energy storage rate in area of plastic strain localization during tension, 3rd International Conference Topical Problems of Continuum Mechanics, 2012-10-08/08-12, Tsakhkadzor (AM), No.1, pp.282-286, 2012
Abstract:

The presented work is devoted to the new method of energy storage rate detrmination that allows to obtain distribution of this quantity on the surface of deformed specimen. The method is based on the experimental procedure for simultaneous measurements of themperature and displacement distributions on the surface of tested specimen during tensile deformation. This procedure involves two complementary imaging techniques: CCD technique and infrared thermography (IRT). It has been shown experimentally that during evolution of plastic strain localization the energy storage in some zones of deformed specimen dropes to zero even to negative values. To interpret this results in terms of micromechanisms, microstructural obserwations using electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM) were performed on specimens in different states of deformation.

Keywords:

energy storage rate, infrared thermography, plastic strain localization, texture evolution

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN
4.Maj M., Oliferuk W., Pre-strain direction effect on microstructure evolution and energy storage process during uniaxial tension of austenitic steel, 15th International Conference on the Strength of Materials, 2009-08-16/08-21, Dresden (DE), DOI: 10.1088/1742-6596/240/1/012143, Vol.240, pp.012143-1-4, 2010
Abstract:

In the present paper the influence of pre-strain direction on energy balance during deformation of austenitic steel was investigated and the analysis of microscopic phenomena responsible for this influence was performed. The specimens with different pre-strain directions were prepared and the ratio of the stored energy increment to plastic work increment, called energy storage rate, as a function of plastic strain was experimentally determined. At the initial stage of plastic deformation of annealed materials this quantity vs. plastic strain has a maximum. It has been shown that for specimens strained in the same direction as pre-strain the energy storage rate decreases monotonically with deformation while for specimens where strain path was changed, the maximum of the energy storage rate is observed (as in case of annealed material). The study of slip and microstructure evolution at meso- and micro-scales have shown that the change in pre-strain direction leads to the redistribution of internal stresses generated by incompatible slip in neighbouring grains of different orientation. Just after change in strain direction the accommodation of these stresses takes place not only by generation of geometrically necessary dislocations but also by micro-shear banding.

Keywords:

energy storage rate, pre-strain direction, slip evolution, long-range internal stresses, geometrically necessary dislocations, micro-shear bands

Affiliations:
Maj M.-IPPT PAN
Oliferuk W.-IPPT PAN
5.Oliferuk W., Maj M., Identification of energy storage rate components. Theoretical and experimental approach, 15th International Conference on the Strength of Materials, 2009-08-16/08-21, Dresden (DE), DOI: 10.1088/1742-6596/240/1/012144, Vol.240, pp.012144-1-4, 2010
Abstract:

The subject of the present paper is decomposition of energy storage rate into terms related to different mode of deformation. The stored energy is the change in internal energy due to plastic deformation after specimen unloading. Hence, this energy describes the state of the cold-worked material. Whereas, the ratio of the stored energy increment to the appropriate increment of plastic work is the measure of energy conversion process. This ratio is called the energy storage rate. Experimental results show that the energy storage rate is dependent on plastic strain. This dependence is influenced by different microscopic deformation mechanisms.

It has been shown that the energy storage rate can be presented as a sum of particular components. Each of them is related to the separate internal microscopic mechanism. Two of the components are identified. One of them is the storage rate of statistically stored dislocation energy related to uniform deformation. Another one is connected with non-uniform deformation at the grain level. It is the storage rate of the long range stresses energy and geometrically necessary dislocation energy. The maximum of energy storage rate, that appeared at initial stage of plastic deformation is discussed in terms of internal micro-stresses.

Keywords:

stored energy, deformation mechanisms, statistically stored dislocations, geometrically stored dislocations, long-range internal stresses

Affiliations:
Oliferuk W.-IPPT PAN
Maj M.-IPPT PAN

Conference abstracts
1.Oliferuk W., Maj M., Energy storage rate components, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.137-138, 2014
Abstract:

Decomposition of energy storage rate into terms related to different deformation mechanisms has been presented. The energy storage rate is the ratio of the stored energy increment to the appropriate increment of plastic work. Experimental results show that the energy storage rate is dependent on plastic strain. This dependence is influenced by different microscopic deformation mechanisms. Then, the energy storage rate can be presented as a sum of particular components. Two of them are identified.

Keywords:

Energy storage rate, deformation mechanisms, statistically stored dislocations, geometrically necessary dislocations, long range internal stresses

Affiliations:
Oliferuk W.-other affiliation
Maj M.-IPPT PAN