Eligiusz Postek, Ph.D., Dr. Habil., Eng.

Department of Information and Computational Science (ZIiNO)
Division of Computational Analysis of Advanced Structures (ZeKAZK)
position: specialist
telephone: (+48) 22 826 12 81 ext.: 131
room: 412
e-mail: epostek

Doctoral thesis
1997-06-26Numeryczna analiza wrażliwości na parametry projektowe dużych nieliniowych układów konstrukcyjnych 
supervisor -- Prof. Michał Kleiber, Ph.D., Dr. Habil., Eng., IPPT PAN
533 
Habilitation thesis
2014-09-25Modelowanie numeryczne problemów sprzężonych wraz z paralelizacją 
Supervision of doctoral theses
1.2006
co-supervisor
Rosli Ahmad  
(Swansea UW)
Optimisation of the squeeze forming process 
2.2004
co-supervisor
Luo Chouping  
(Lulea UT)
Finite elements based on the piece-wise linear weight functions in contact problems 

Recent publications
1.Postek E., Sadowski T., Impact model of WC/Co composite, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2019.01.084, No.213, pp.231-242, 2019
Abstract:

WC/Co composite is a standard hard material used for the production of cutting tools. It has both very good thermo-mechanical and wear properties. During the cutting, process tools are subjected to impact loading and gradual degradation due to high-stress concentrations. This loading induced deterioration is complex process still not well investigated and explained.Up till now the dynamic response of the WC/Co composite was analysed under dynamic impulse compressive loading [1]. However, the behaviour of the above two-phase composite under impacts conditions was not investigated in details. In the presented micromechanical approach the real material structure geometry of the internal structure can be performed including spatial distribution of: (1) WC grains and their dimensions, (2) volume content of plastic Co binder with their thickness, (3) system of grain/binder interfaces and (4) cracks initiated and developed during impulse loading, (5) possible brittle grains rotation.The results reveal the dependence of the microcracking processes and the stress distribution on impact velocity and presence of discontinuities in the Co binder and the interface zone between the binders and the grains. The microcracks system was evaluated by the damage parameter according to Kachanov, 1986 [62].

Keywords:

Cermet; Impact load; Microcracking; Cohesive elements; Numerical modelling;

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
2.Postek E., Sadowski T., Temperature Effects during Impact Testing of a Two-Phase Metal-Ceramic Composite Material, Materials, ISSN: 1996-1944, DOI: 10.3390/ma12101629, Vol.12, No.1629, pp.1-13, 2019
Abstract:

Metal-ceramic composite (MCC) materials can be used for manufacturing high-responsibility structures such as jet engines or cutting tools. One example of these materials is a two-phase wolfram carbide (WC) and cobalt (Co) composite. This MCC is a combination of hard WC grains with a Co metallic ductile binder. The resulting microstructure is a combination of two phases with significantly different mechanical behaviors. In this study, we investigate impact conditions, starting with an illustrative example of the Taylor impact bar where—although the process is very rapid—the equivalent plastic strain and temperature are higher in the adiabatic solution than those in the coupled solution. On exposing the WC/Co composite with a metallic binder to impact loading, heat is generated by plastic deformation. If the process is fast enough, the problem can be treated as adiabatic. However, a more common situation is that the process is slower, and the heat is generated in the ductile metallic binders. As a result, the associated grains are heated due to the conduction effect. Consequently, the process should be treated as coupled. When the impact is applied over a short time period, maximum temperatures are significantly lower if the process is analyzed as coupled rather than as adiabatic. The grains are immediately affected by temperature increase in the binders. Therefore, the heat conduction effect should not be omitted

Keywords:

metal-ceramic composite, impact, coupled problem, thermomechanics

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
3.Postek E., Sadowski T., Distributed microcracking process of WC/Co cermet under dynamic impulse compressive loading, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.04.014, Vol.194, pp.494-508, 2018
Abstract:

Cermet Materials (CM), for example, WC/Co, have very good mechanical, thermal and wear properties. They are used for manufacturing of cutting tools. However, their behavior under dynamic loads is still not properly understood.
Experiments, e.g. Siegl and Fischmester (1988) and Ravichandran (1994), indicate that the fracture energy of
WC/Co is expended through ductile failure of the Co: (1) close to the binder/tungsten carbide interface (Liu et al., 2017) [64] or by (2) dimple rupture across the interphase (Sigl and Exner, 1987) [22]. Stress concentrations around grain boundaries lead to initiation of microcracks which are dispersed by dynamic loading.
The main goal of the paper is to investigate the previously formulated models of the two-phase composite (Sadowski et al., 2005, 2006, 2007; Dębski and Sadowski, 2014, 2017) [47–51] in the case of dynamic compressive
pulses that are common in the case of cutting tools. We have taken into account complex spatial distribution of cermet phases, grain/binder interfaces modeled by interface elements, possibility of cracks appearance within binders using interface elements as well, and rotation of brittle grains.
The obtained results show that microcracking process and stress distributions are different for quasi-static and dynamic loadings. Early development of microcracks distribution revealed by damage parameter was observed.

Keywords:

Cermet, Dynamic compressive impulse, Interface elements, Distributed microcracking process

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
4.Postek E., Sadowski T., Dynamic pulse sensitivity of WC/Co composite, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2017.10.092, No.203, pp.498-512, 2018
Abstract:

Cutting tools are manufactured among others from cermet (e.g. WC/Co) having excellent mechanical properties. Geometry of the internal microstructure is complex and mechanical response due to quasi-static or dynamic loading is difficult to be described. Particularly, the dynamic loading is not investigated enough precise up till now.
Experimental evidences, e.g. Siegl and Fischmester (1988), Ravichandran (1994), indicate that the fracture energy of WC/Co is expended through ductile failure of the Co: (1) near the binder/tungsten carbide interface or by (2) dimple rupture across the interphase. Concentrations of stresses around grain boundaries lead to initiation of microcrack system, which is dispersed for dynamic loading.
The aim of the paper is to extend the previously formulated models (Sadowski et al., 2005, 2006, 2007, Dębski and Sadowski, 2014, 2017) of the polycrystalline composite towards more advanced finite element formulation, applicable for description of the cermet behavior under dynamic pulses. The model takes into account: (1) spatial distribution of the cermet constituents, (2) system of grain boundaries/binder interfaces modeled by interface elements, (3) rotation of brittle grains.
The obtained results show that stress distributions and gradual microcracking processes are quite different for quasi-static and dynamic loadings. It was revealed by damage parameter indicating concentration of microcracks.

Keywords:

Metal-ceramic composite, Interface elements, Crack propagation, Dynamic loading,

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
5.Postek E., Sadowski T., Qualitative comparison of dynamic compressive pressure load and impact of WC/Co composite, International Journal of Refractory Metals and Hard Materials, ISSN: 0263-4368, DOI: 10.1016/j.ijrmhm.2018.07.009, Vol.77, pp.68-81, 2018
Abstract:

Degradation of Cermet Materials (CM) under impact and pulse pressure is not thoroughly investigated. In this
study, we qualitatively compare the behaviour of WC/Co samples under these types of loading.
The new models of impact and dynamic compressive load of a WC/Co plate were investigated. We developed two models of the composite plate, namely, a continuous model and a model with crack appearance possibility in the interfaces/binders.
We noted a qualitative difference of the shapes of the deformed structure due to different models and kind of loading. The differences also concern the Mises stress, equivalent plastic strains and damage parameter.
The proposed models are suitable for both impact and pressure load. The possibility of cracks appearance should not be neglected. In case of the model with discontinuities, for both kinds of loads, the grains rotation and sliding is more distinct than in case of the continuous model.

Keywords:

Cermet, Impact, Pressure load, Interface elements, Distributed microcracking process, Numerical models

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
6.Postek E., Sadowski T., Cracks in Interfaces and Around Their Junctions in WC/Co Composite, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, Vol.64, No.4, pp.589-596, 2016
Abstract:

WC/Co ceramic metal-matrix composites are characterized by very high mechanical properties that allow for application of the composites mostly in production of different types of cutting tools. By combining in a composite structure a phase of brittle hard wolfram carbide (WC) grains with a metallic interface of cobalt (Co) that exhibits plastic properties, a geometrically complex microstructure with significantly different mechanical properties of the combined phases is created, see Fig. 1a. The presence of the elastic-plastic interface material, i.e. Co binder, in the composite structure is the reason for initiation of technological defects – mainly material porosity. During material loading pores start to coalesce and finally one can observe creation of microcracks system distributed along interfaces. The aim of the paper is to show the previously formulated model [1, 2] of the polycrystalline composite to be extended towards cracks development around the junctions of the interfaces. The obtained numerical results indicate that in the junctions high stress concentrations were observed, which leads to crack initiation and its further unstable propagation, and finally the composite failure. Results indicate that the first crack appears close to the junction and that the load carrying capacity of the sample is overestimated if a crack model in the interfaces is not assumed.

Keywords:

metal-ceramic composite, interface elements, crack propagation at composite junctions

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
7.Postek E., Parameter sensitivity of a monolayer tensegrity model of tissues, Journal of Coupled Systems and Multiscale Dynamics, ISSN: 2330-152X, DOI: 10.1166/jcsmd.2014.1054, Vol.2, No.4, pp.179-187, 2014
Abstract:

The state of stress in the tissue that we call mechanical environment is important for the cell behavior. In particular, the stresses may trigger the chemical pathways. Therefore, it is important to model structure of the cell. The part of the cell is the cytoskeleton that carries most of the loading. We believe that a good method to understand the importance of particular parts of the cellular structure is the parameter sensitivity analysis. In particular, it is interesting in the case of hierarchical structures. An example of such a structure is the tissue. The single cell is modelled as icosahedral based tensegrity structure. The constitutive model is viscous-elastic. The formulation of the parameter sensitivity problem is done in the Updated Lagrangian reference frame. We observe the sensitivity fields due to change of sizing parameters of the microtubules in a single cell and groups of cells. The change of the sizing parameters simulates the sensitivity to growth of group of cells. The tissue evolves continuosly since each cell undergoes cell cycle. In consequence, the state of mechanical fields evolves as well. The investigation of the rules of the cell cycle is the domain of the computational systems biology. The main novelty of the paper is the presentation of the parameter sensitivity algorithm with the application to a complex biological system.

Keywords:

computer simulation of cell processes, finite-element and galerkin methods, modeling, sensitivity analysis, structures and organization in complex systems

Affiliations:
Postek E.-IPPT PAN
8.Postek E., Concept of an Agent-stress Model of a Tissue, TECHNISCHE MECHANIK, ISSN: 0232-3869, Vol.32, pp.518-529, 2012
Abstract:

This paper stands for a concept of coupling between agent modeling and stress analysis valid for a tissue. The stress analysis of evolving tissue is underestimated in previous studies. The experimental observations and numerical simulations of stress development in a single cell and in particular, in a growing tissue are still rare in the literature. We use a tensegrity model for a single cell that serves for stress evaluation in a growing tissue. We propose to couple the mechanical modeling with the agent one using a staggered scheme for two exemplary scenarios. The first example is devoted to scratching of the epithelium, and the second one to the pins and slits.
We observe the systems sensitivities with respect to the selected groups of design parameters. The groups of parameters have been associated with clusters of cells. We have found that the sensitivities may be used for comparing the complex structures of the tissue.

Affiliations:
Postek E.-IPPT PAN
9.Postek E.W., Sadowski T., Assessing the influence of porosity in the deformation of metal-ceramic composites, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1163/092764410X554049, Vol.18, No.1, pp.57-76, 2011
Abstract:

The aim of the paper is to develop the previously formulated model [19, 20] of the polycrystalline composite to include porosity growth at metallic interfaces of metal-ceramic composites (MCCs). Examples of this kind of MCCs are: (1) a two-phase material composed of brittle grains WC joined by the plastic binder Co, which can contain a small degree of porosity introduced during the cooling process [31], (2) TiC-Mo2C hard phase grains surrounded by tough binder phase Ni [12]. This work focuses on the description of the deformation of the MCC material including the modelling of a real material internal structure taking into account porosity growth during the loading. Experimental observations of the WC/Co composite [10] indicate that the majority of the fracture energy of MCC is expended through ductile failure of the plastic binder Co (dimple rupture across the binder or in the binder near the binder/carbide interface). This process is preceded by porosity growth at metallic interfaces and finally leads to inter-granular cracks propagation.

This paper presents micromechanical modelling of the MCC response in the case of uniaxial tension of 3-D Representative Volume Element (RVE) with the application of the Finite Element Analysis (FEA). The MCC material includes: elastic grains and inter-granular metallic layers containing technological pores that create its real complex internal structure. The quasi-static deformation process of the material comprises elastic deformation of brittle grains, elasto-plastic deformation of inter-granular layers (of different thickness: 2-4 mu m) and additional deformation due to micro-porosity development in the layers. A micro-sample analysis leads to the conclusion that a small amount of technological porosity changes the qualitative behaviour of the MCC including deformation, rotation of grains, roughness, and level of plastic strains. (C) Koninklijke Brill NV, Leiden, 2011

Keywords:

Interface porosity, Gurson-Tvergaard model, polycrystalline ceramic composites, INTER-GRANULAR LAYERS, POLYCRYSTALLINE CERAMICS, FRACTURE, GROWTH, PREDICTION, STRENGTH, BEHAVIOR, TENSION, CERMETS, MODEL

Affiliations:
Postek E.W.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
10.Postek E.W., Lewis R.W., Gethin D.T., Finite element modelling of the squeeze casting process, INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT AND FLUID FLOW, ISSN: 0961-5539, DOI: 10.1108/09615530810853619, Vol.18, pp.325-355, 2008
Keywords:

Finite element analysis, Thermodynamics, Material‐deforming processes

Affiliations:
Postek E.W.-other affiliation
Lewis R.W.-University of Wales (GB)
Gethin D.T.-University of Wales Swansea (UK)
11.Sadowski T., Postek E., Denis Ch., Stress distribution due to discontinuities in polycrystalline ceramics containing metallic inter-granular layers, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, Vol.39, pp.230-236, 2007
12.Sadowski T., Hardy S.J., Postek E., A new model for the time-dependent behaviour of polycrystalline ceramic materials with metallic inter-granular layers under tension, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, Vol.424, pp.230-238, 2006
13.Lewis R.W., Postek E.W., Han Z., Gethin D.T., A finite element model of the squeeze casting process, INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT AND FLUID FLOW, ISSN: 0961-5539, Vol.16, No.5, pp.539-572, 2006
14.Sadowski T., Hardy S.J., Postek E.W., Prediction of the mechanical response of polycrystalline ceramics containing metallic intergranular layers under uniaxial tension, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, Vol.34, pp.46-63, 2005
15.Postek E.W., Lewis R.W., Gethin D.T., Ransing R.S., Influence of initial stresses on the cast behaviour during squeeze forming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/j.jmatprotec.2004.05.022, Vol.159, No.3, pp.338-346, 2005
Abstract:

This paper deals with the evaluation of the effects of initial stresses developed during the pressurized casting process. The stresses are induced by the external pressure applied to the cast and developed due to thermal loading. The effect of the stresses is considered as a second order effect by means of investigating the influence of the ‘geometric’ or ‘initial stresses’ stiffness matrix on the response of the cast. The problem formulation is done in the updated Lagrangian (UL) frame. An implicit time integration scheme is applied to solve the transient thermomechanical problem in a staggered form. The constitutive mechanical model is elasto-viscoplastic with hardening incorporated with a Mises yield function. The finite element method is employed and a few 3D numerical examples are presented.

Keywords:

Squeeze casting, Initial stresses, Coupled problems, Finite elements

Affiliations:
Postek E.W.-other affiliation
Lewis R.W.-University of Wales (GB)
Gethin D.T.-University of Wales Swansea (UK)
Ransing R.S.-other affiliation
16.Sadowski T., Hardy S., Postek E., Modelowanie polikrystalicznej ceramiki z warstwami międzyziarnowymi w stanach jednoosiowego rozciągania, Eksploatacja i niezawodność, ISSN: 1507-2711, No.4, pp.79-82, 2004
Abstract:

W pracy przedstawiono model polikrystalicznego materiału ceramicznego, w którym ziarna połączone są poprzez cienkie warstwy o innych własnościach mechanicznych. Powoduje to powstanie niejednorodnych rozkładów deformacji oraz koncentracje naprężeń inicjujące mikrouszkodzenia.

Keywords:

ceramika, mikrouszkodzenia, polikryształy, modele numeryczne

Affiliations:
Sadowski T.-Lublin University of Technology (PL)
Hardy S.-other affiliation
Postek E.-IPPT PAN
17.Klisiński M., Luo Ch., Postek E., Discussion on application of piece-wise linear weight functions in 2D contact problems, Computer Assisted Mechanics and Engineering Sciences, ISSN: 1232-308X, No.10, pp.265-281, 2003
Abstract:

Standard higher order finite elements often perform unsatisfactory in contact problems. The major difficulties are caused by uneven distribution of nodal forces resulting in oscillating contact pressure. The paper presents a new approach that eliminates this drawback. The weight functions are chosen in such a way that even distributions of nodal forces are obtained. It is achieved by applying piece-wise linear weighting functions. Two new 3D isoparametric quadratic elements are derived: 6-node triangle and 8-node quadrilateral, and tested in many examples. The new elements have unsymmetric stiffness matrices, but the provided examples show their good performance in contact problems.

Keywords:

coontact problems, weighting functions, quadratic finite elements

Affiliations:
Klisiński M.-IPPT PAN
Luo Ch.-other affiliation
Postek E.-IPPT PAN
18.Giżejowski M.A., Karczewski J.A., Postek E., Sotomski W., Wierzbicki S., Witkowski J., Behaviour and modelling of semi-rigid structural frame systems, Botswana Journal of Technology, ISSN: 1019-1593, pp.51-61, 2003
Abstract:

A computational finite element model is developed to predict the load-deflection characteristic of portal frames with semi-rigid welded and bolted joints. Plate components of frame members and joints are modelled by thin shell finite elements while bolt connectors by springs with the force-deformation characteristic evaluated from test results. The computer software ABAQUS is used. Experimental investigations were designed in order to evaluate frame load deflection characteristics, joint local rotations, failure modes, and the contribution of end-plates and bolt connectors to the joint rotations. Theoretical results of frame load-deflection characteristics predicted with use of ABAQUS program are compared with the experimental results. The modelling of friction effect between the contact surfaces of bolted joints is verified to be the most important factor. The comparative analysis leads to the conclusion that the proposed advanced shell model can be very useful in the verification of simplified models being developed for practical applications.

Keywords:

semi-rigid connections, limit states analysis, experiments, variable load, finite element method

Affiliations:
Giżejowski M.A.-Warsaw University of Technology (PL)
Karczewski J.A.-Warsaw University of Technology (PL)
Postek E.-IPPT PAN
Sotomski W.-Warsaw University of Technology (PL)
Wierzbicki S.-Warsaw University of Technology (PL)
Witkowski J.-Warsaw University of Technology (PL)
19.Postek E., Kleiber M., Niezawodność dużych nieliniowych układów konstrukcyjnych – wybrane studium, PRZEGLĄD MECHANICZNY, ISSN: 0033-2259, No.5, pp.33-37, 2002
Abstract:

W artykule przedstawiono sposób postępowania podczas szacowania niezawodnoÊci dużych nieliniowych układów konstrukcyjnych. Nacisk położono na zastosowanie metody różniczkowania bezpośredniego (DDM). Jako przykład wybrano żelbetową konstrukcję budynku osłonowego reaktora nuklearnego.

Keywords:

inżynieria nuklearna, niezawodność, analiza wrażliwości, konstrukcje żelbetowe

Affiliations:
Postek E.-IPPT PAN
Kleiber M.-IPPT PAN
20.Postek E., Siemaszko A., Kleiber M., Reliability Study of a Containment Shell, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.40, No.1, pp.179-203, 2002
Abstract:

Computational time needed for reliability abalysis of realistic structural problems as a rule is very high. Improvements in efficiency are critical to allow solution of large realistic problems. The realiability analysis is usually performed using approximate First Order Reliability Method (FORM). Iterative solution procedures of FORM require extensive design sensitivity computations of high accuracy. The design of realistic structures requires computer-based numerical procedures, such as finite element analysis. The design sensitivity gradients are not explicitly available in terms of design variables. The most intensive computational task of design sensitivity computation should be carried out by highly efficient and accurate methods such as discrete design sensitivity analysis, This paper describes requirements for design sensitivity information for reliability analysis. The way of coupling reliability computationa with discrete AVM and DDM methods of design sensitivity analysis is pointed out. A computational program developed for layered concrete shells allows one to solve large realistic reliability problems. The reliability study of an RC nuclear containment shell is carried out. Reliability studies show which pf mthe parameters have the highest impact on the reliability of the vessel.

Keywords:

Nuclear engineering, reliability, design sensitivity, FEM

Affiliations:
Postek E.-IPPT PAN
Siemaszko A.-IPPT PAN
Kleiber M.-IPPT PAN
21.Janas M., Sokół-Supel J., Postek E., Arching action in slackened structures, FOUNDATIONS OF CIVIL AND ENVIRONMENTAL ENGINEERING, ISSN: 1642-9303, No.2, pp.97-109, 2002
Abstract:

Elastic-plastic composite slabs with no-tension matrix are considered, with unilateral in-plane restraints at supports. In such conditions important compressive membrane forces (arching action) are generated by transversal loads. Because of unstable character of such flexural response it is very sensitive to slackening due to clearances at supports. An approximate method based on the post-yield approach (PYA) was adopted and permits to determine easily the ultimate supportable load for slackened structures. The method was calibrated and verified by the FEM incremental analysis.

Affiliations:
Janas M.-IPPT PAN
Sokół-Supel J.-IPPT PAN
Postek E.-IPPT PAN
22.Rojek J., Zienkiewicz OC., Onate E., Postek E., Advances in FE explicit formulation for simulation of metalforming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/S0924-0136(01)00894-9, No.119, pp.41-47, 2001
Abstract:

This paper presents some advances of finite element explicit formulation for simulation of metal forming processes. Because of their computational efficiency, finite element programs based on the explicit dynamic formulation proved to be a very attractive tool for the simulation of metal forming processes. The use of explicit programs in the sheet forming simulation is quite common, the possibilities of these codes in bulk forming simulation in our opinion are still not exploited sufficiently. In our paper, we will consider aspects of bulk forming simulation. We will present new formulations and algorithms developed for bulk metal forming within the explicit formulation. An extension of a finite element code for the thermomechanical coupled analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. A new formulation based on the so-called split algorithm allows us to use linear triangular and tetrahedral elements in the analysis of large plastic deformations characteristic to forming processes. Linear triangles and tetrahedra have many advantages over quadrilateral and hexahedral elements. Linear triangles and tetrahedra based on the standard formulations exhibit volumetric locking and are not suitable for large plastic strain simulation. The new formulation allows to overcome this difficulty. New formulations and algorithms have been implemented in the finite element code Stampack developed at the International Centre for Numerical Methods in Engineering in Barcelona. Numerical examples illustrate some of the possibilities of the finite element code developed and validate new algorithms.

Keywords:

Explicit formulation, Forming simulation, Split algorithm

Affiliations:
Rojek J.-IPPT PAN
Zienkiewicz OC.-other affiliation
Onate E.-International Center for Numerical Methods in Engineering (ES)
Postek E.-IPPT PAN
23.Giżejowski M., Karczewski J., Postek E., Badania ram z węzłami podatnymi – weryfikacja doświadczalna modeli, INŻYNIERIA I BUDOWNICTWO, ISSN: 0021-0315, No.8, pp.433-439, 2000
Abstract:

W artykule przedstawione zostały badania ram stalowych o węzłach podatnych. Dokonana została weryfikacja doświadczalna modeli teoretycznych. Analiza numeryczna została wykonana dla trójwymiarowych modeli powłokowych ram z uwzględnieniem podatności węzłów łączonyc na śruby oraz dla porównania z węzłami spawanymi. W modelowaniu komputerowym uwzględniono nielinową geometrię, sp®ężyto-plastyczne własności materiału, kontakt-tarcie moędzy płytami doczołowymi. Śruby zostały zastąpione sprężynami o charakterytyce M-Fi. Sprawdzana była nośność graniczna ram.

Keywords:

analiza nieliniowa, węzły podatne, ramy, konstrukcje stalowe, połączenia, nośność graniczna

Affiliations:
Giżejowski M.-Warsaw University of Technology (PL)
Karczewski J.-Warsaw University of Technology (PL)
Postek E.-IPPT PAN
24.Giżejowski M., Postek E., Modelowanie zachowania się ram stalowych z węzłami podatnymi, INŻYNIERIA I BUDOWNICTWO, ISSN: 0021-0315, No.11, pp.645-651, 1999
Abstract:

Opracowane modele numeryczne konstrukcji ram stalowych o węzłach podatnych. Ramy byly konstrukcjami o węzłach spawanych oraz łączonych na śruby. Konstrukcje modelowane byly metodą elementów skończonych przy zastosowaniu elementów powłokowych. W modelach numerycznych uwzględniane byly połączenia śrubowe o nieliniowych charakterystykach oraz powierzchnie kontaktu plyt czołowych w węzłach. Badane bylo zachowanie ram pod obciążeniem rosnącym monotonicznie oraz zmiennym. Opracowany rowniez zostal model numeryczny służący obliczaniu statecznosci ram poslugując sie analogia pręta Roordy. Zostalo to zrealizowane drogą obliczenia obciążenia krytycznego, wartości i postaci własnych dla ukladu idealnego, następnie narzucenia imperfekcji zgodnych z postaciami wlasnymi na konstrukcję idealną i w końcu wykonaniu analizy przyrostowej.

Keywords:

analiza nieliniowa, stateczność, imperfekcje, postacie własne, węzły podatne, ramy, konstrukcje stalowe

Affiliations:
Giżejowski M.-Warsaw University of Technology (PL)
Postek E.-IPPT PAN
25.Rojek J., Onate E., Postek E., Application of explicit FE codes to simulation of sheet and bulk metal forming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/S0924-0136(98)00169-1, No.80-81, pp.620-627, 1998
Abstract:

This paper presents the application of an explicit dynamic finite element code for simulation of metal forming processes, of both sheet and bulk forming. The experiences reported here have been gained during the development and use of our own explicit program Stampack. An original formulation of a triangular shell element without rotational degrees of freedom is reviewed combining the explicit sheet forming simulation with the implicit springback analysis as well as the parallelization of the explicit program described. An extension of a finite element code for coupled thermomechanical analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. Numerical examples illustrate some of the possibilities of the finite element code developed.

Keywords:

Metal forming, Sheet stamping, Finite element simulation, Explicit dynamic analysis, Thermomechanical analysis

Affiliations:
Rojek J.-IPPT PAN
Onate E.-International Center for Numerical Methods in Engineering (ES)
Postek E.-IPPT PAN
26.Kleiber M., Hien T.D., Postek E., Incremental finite element sensitivity analysis for nonlinear applications, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, ISSN: 0029-5981, DOI: 10.1002/nme.1620371906, Vol.37, pp.3291-3308, 1994
Abstract:

Finite element formulations for structural sensitivity analysis of non‐linear systems with fixed overall shape are discussed. Both the direct differentiation and adjoint variable methods are employed. The resulting sensitivity algorithms are consistent with time integration scheme adopted for solving equilibrium problem. Effectiveness and computational aspects of the procedures are discussed and compared. Numerical algorithms are shown to be readily implemented in existing finite element codes. Large‐scale examples illustrate the paper.

Keywords:

sensitivity analysis, nonlinear systems, incremental approach, finite element method

Affiliations:
Kleiber M.-IPPT PAN
Hien T.D.-IPPT PAN
Postek E.-IPPT PAN
27.Kacprzyk Z., Postek E., Biblioteka izoparametrycznych elementów skończonych systemu FEAS, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.2, No.3, pp.89-108, 1993
Abstract:

W artykule przedstawiona została biblioteka izoparametrycznych elementów skończonych opartych o paraboliczinee funkcje ksztaltu. W bibliotece zawarte zostały elementy tarczowe o liczbie węzłów od 4 do 8, bryłowe o liczbie węzłów od 8 do 20, 4 i 8 węzłowe elementy płyyty Mindlina, 3 węzłowy element powtoki osiowo-symetrycznej oraz 8 węzłowy element typu Ahmada. Przedstawiona biblioteka implementowana jest w systemie analizy konstrukcji inżynierskich FEAS i znajdzie sie ona w nowej wersji systemu. Konstrukcje mogq być modelowane przy użyciu elementów znajdujqcych się w tzw. bibliotece inżynierskiej skladającej się z elementów, których macierze sztywności obliczone zostaly analitycznie oraz w bibliotece , parabolicznej. W tym wypadku jednak za poprawność modelu odpowiada calkowicie użytkownik. Nowa biblioteka systemu wykorzystywana będzie zarówno w obliczeniach inżynierskich jak i w procesie nauczania mechaniki na Wydziale Inżynierii Lądowej.

Keywords:

elementy paraboliczne, metoda elementĂłw skończonych, dydaktyka

Affiliations:
Kacprzyk Z.-Warsaw University of Technology (PL)
Postek E.-IPPT PAN
28.Postek E., Hien T.D., On the applications of the sensitivity analysis to the design of spatial bar structures, ARCHIVES OF CIVIL ENGINEERING, ISSN: 1230-2945, Vol.38, No.1-2, pp.17-33, 1992
Abstract:

The paper deals with structural sensitivity analysis and its application in the engineering practice. The considerations are illustrated by numerical results concerning an industrial steel room as 3D structure.

Keywords:

sensitivity analysis, adjoint variable method, direct differentiation method, design codes, steel structures

Affiliations:
Postek E.-IPPT PAN
Hien T.D.-IPPT PAN

List of chapters in recent monographs
1.
402
Postek E., GRAFEN – IPPT PAN COMPUTER OF BIOCENTRUM OCHOTA GRID, rozdział: Parameter Sensitivity of a Tensegrity Model of a Tissue, IPPT Reports on Fundamental Technological Research, Postek E., Kowalewski T.A. (Eds.), 3, pp.81-92, 2014
2.
403
Postek E., GRAFEN – IPPT PAN COMPUTER OF BIOCENTRUM OCHOTA GRID, rozdział: Generic Models of Linear and Non-linear Visco-elastic Surface Deformation above a Fault, IPPT Reports on Fundamental Technological Research, Postek E., Kowalewski T.A. (Eds.), pp.92-101, 2014
3.
404
Postek E., GRAFEN – IPPT PAN COMPUTER OF BIOCENTRUM OCHOTA GRID, rozdział: Reliability Analysis of Reinforced Concrete Structures, IPPT Reports on Fundamental Technological Research, Postek E., Kowalewski T.A. (Eds.), pp.105-127, 2014
4.
405
Postek E., GRAFEN – IPPT PAN COMPUTER OF BIOCENTRUM OCHOTA GRID, rozdział: Development of a Concept of an Agent-stress Model of a Tissue, IPPT Reports on Fundamental Technological Research, Postek E., Kowalewski T.A. (Eds.), pp.127-134, 2014
Editor of monographs
1.
370
Postek E., Kowalewski T.A., GRAFEN – IPPT PAN COMPUTER OF BIOCENTRUM OCHOTA GRID, IPPT Reports on Fundamental Technological Research, 3, pp.1-164, 2014

Conference papers
1.Postek E., Sadowski T., Impact Modelling of Cermet Composites, AMS 2018, 7th International Conference on Advanced Materials and Structures - AMS 2018, 2018-03-28/03-31, Timisoara (RO), DOI: 10.1088/1757-899X/416/1/012088, Vol.416, pp.1-8, 2018
Abstract:

Abstract. The WC/Co is one of broad class of cermet materials (CM) that are applied in
fabrication of machining tools. It means that they are subjected to different kind of dynamic
loadings. They have very good mechanical properties. However, the degradation of the CM
material under dynamic load has not been enough thoroughly investigated. Experimental
results yield that the dissipation of the fracture energy in WC/Co samples is due to Co ductile
failure at the WC and Co interface [1] and/or dimple rupture mechanism [2]. Stress
concentrations about stress raisers such as grain bounds cause microcracking that is further
propagated by dynamic loading. However, there are no such predictions for impact conditions.
The main goals of the presentation are to explore the formerly created models of the two-phase
composite [3, 4] towards impact conditions impacts and give qualitative predictions of the
crack and plastic strains initiation for such cases. It has been found that microcracks
development process and stress fields depend on impact velocity and the existence of
discontinuities: (1) inside the Co binder and (2) the interface between the binder and the grains.
Estimation of the microcracks distribution by means of damage parameter is given.

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
2.Pęcherski R.B., Nowak Z., Postek E., The concept of virtual cellular material in peridynamic modelling of deformation processes, ICPS5, 5th International Conference on Protective Structures, 2018-08-19/08-23, Poznań (PL), pp.718-721, 2018
Abstract:

The study of modern cellular materials due to complexity of their internal structure requires the application of efficient computational methods. One of such methods developed in the last 10 years is peridynamics. This approach resulted in the parallelized code that is used in presented analysis. The subject of the study are alumina foams produced by gelcasting method and metallic cellular materials that can be produced in the process of additive manufacturing. The results of microtomoraphy are used to create numerical model reconstructing the structure of foam skeleton. In this way an example of virtual cellular material is obtained. The peridynamic modelling is applied to investigate dynamic damage process under axial compression.

Keywords:

virtual cellular material, peridynamic modelling, cellular skeleton, deformation and damage simulations, alumina foams, additive manufacturing

Affiliations:
Pęcherski R.B.-IPPT PAN
Nowak Z.-IPPT PAN
Postek E.-IPPT PAN
3.Postek E., Design Sensitivity of a Tensegrity Model of a Tissue, CMM 2011, 19th International Conference on Computer Methods in Mechanics, 2011-05-09/05-12, Warszawa (PL), pp.1-6, 2011
Abstract:

The design sensitivity algorithm for visco-elastic tensegrity structures is presented. We adopt Updated Lagrangian formulation. We have possibility of grouping of the design variables what is particularly useful in the case of hierarchical structures. In our case, the structure is the tissue built of elementary cells. The design sensitivity procedure is implemented with parallel solver.

Keywords:

computational biology, tensegrity structures, design sensitivity

Affiliations:
Postek E.-IPPT PAN
4.Postek E., Sadowski T., Description of the Behaviour of Cellular Composite with Weak Filling Material, IUTAM Symposium on Mechanical Properties of Cellular Materials, 2007-09-17/09-20, Cachan (FR), pp.181-188, 2009
5.Sadowski T., Postek E., An influence of the elastic properties of composite components on the mechanical response of polycrystalline structures at yield level, IUTAM Symposium on Scaling in Solid Mechanics, 2007-06-25/06-29, Cardiff (GB), DOI: 10.1007/978-1-4020-9033-2_19, pp.199-208, 2009
Abstract:

The aim of this paper is to present a constitutive model in the case of an uniaxial tension of the polycrystalline materials including the inter-granular metallic layers, creating its internal structure. The paper is focused on the discussion of the elastic properties of a composite components influence on the overall material response. The effective continuum model was applied to get the constitutive relations. Representative Volume Element (RVE) was analysed taking into consideration an initial internal structure of the material obtained from SME photographs. Owing to a high complexity of the internal structure of the composite material, FEA technique was used to get macroscopic stress-strain correlations. They include gradual changes of the internal structure of the material due to porosity and cracks development under tension.

Keywords:

Polycrystalline ceramics, inter-granular layers, different elastic properties of components

Affiliations:
Sadowski T.-Lublin University of Technology (PL)
Postek E.-IPPT PAN
6.Postek E.W., Smallwood R., House R., Nodal positions displacement sensitivity of an elementary icosahedral tensegrity structure, COMPLAS X, X International Conference on Computational Plasticity, 2009-09-02/09-04, Barcelona (ES), pp.1-4, 2009
7.Lewis R.W., Postek E.W., Gethin D.T., Yang X.S., Pao W.K.S., Chao L., Numerical methods in simulation of industrial processes, AET2006, First International Conference on Advances in Engineering and Technology, 2006-07-16/07-19, Entebbe (UG), No. , pp.764-795, 2006
Abstract:

The paper deals with an overview of some industrial applications leading to a formulation for advanced numerical techniques. The applications comprise squeeze casting processes, forming of tablets and petroleum reservoir modelling. All of the problems lead to solutions of highly nonlinear, coupled sets of multiphysics equations.

Keywords:

squeeze forming, powder compaction, oil fields, coupled problems, thermomechanics, porous media, fluid flow, nonlinear solid mechanics, phase transformations, microstructural solidification models, numerical methods, contact problems, discrete elements, finite elements.

Affiliations:
Lewis R.W.-University of Wales Swansea (UK)
Postek E.W.-IPPT PAN
Gethin D.T.-University of Wales Swansea (UK)
Yang X.S.-University of Wales Swansea (UK)
Pao W.K.S.-University of Wales Swansea (UK)
Chao L.-University of Wales Swansea (UK)
8.Postek E., Sadowski T., Denis C., Modelling of metallic inter-granular layers in polycrystalline ceramics, BMC 8, 8th International Symposium on Brittle Matrix Composites, 2005-10-23/10-25, Warszawa (PL), pp.495-506, 2006
9.Postek E., Sadowski T., Hardy S.J., Numerical modelling of mechanical response of a two-phase composite, IUTAM Symposium on Multiscale Modelling of Damage and Fracture Processes in Composite Materials, Lublin University of Technology, 2005-05-23/05-27, Kazimierz Dolny (PL), pp.193-200, 2006
10.Postek E.W., Hardy S.J., Dłużewski P., Stress analysis of a quantum dot region using an elastic anisotropic model, Plasticity 2006, 12th International Symposium on Plasticity and Its Current Applications, 2006-07-17/07-22, Halifax (CA), pp.304-306, 2006
11.Postek E.W., Hardy S.J., Sadowski T., Finite strain behaviour of a polycrystalline ceramic composite with intergranular layers, Plasticity 2006, 12th International Symposium on Plasticity and Its Current Applications, 2006-07-17/07-22, Halifax (CA), pp.205-207, 2006
12.Ahmad R., Gethin D.T., Lewis R.W., Ransing R.S., Postek E.W., Thermal optimisation of the squeeze-forming process using genetic algorithms, 3rd M.I.T Conference on Computational Fluid and Solid Mechanics, 2005-06-14/06-17, Boston (US), pp.1205-1208, 2005
13.Lewis R.W., Postek E.W., Gethin D.T., Ransing R.S., A model of microstructural solidification during mould filling for squeeze forming processes, 4th International Conference on Computational Heat and Mass Transfer, 2005-05-17/05-20, Cachan (FR), pp.1122-1125, 2005
14.Postek E.W., Lewis D.T., Gethin R.S., Ransing R.S., Celentano D.J., Stress analysis of squeeze forming processes, Plasticity 2005, 11th International Symposium on Plasticity, 2005-01-04/01-08, Kauai (US), pp.136-138, 2005
15.Karczewski J., Postek E., Wierzbicki S., Modelowanie zachowania się nakładkowego sprężonego połączenia śrubowego, Badania nośności granicznej konstrucji metalowych, 1998-10-23/10-25, Wrocław Szklarska Poręba (PL), pp.169-176, 1998
Abstract:

Odkształcalność stalowej konstrukcji nośnej budynków, wynikająca z odkształceń jej elmentow i połączeń, w zasadniczej części przypadków, jest ograniczona czynnikami eksploatacyjnymi. W przypadku potaczeń śrubowych wysętpujące luzy między trzpieniami i otworami są przyczyną zwiększonej podatnosci konstrukcji. Wstępne spreżenie tego typu połączenia powoduje znaczną redukcję odksztacałnosci samego połączenia a co za tym idzie także konstrukcji. Zjawisko to wykorzystano w szeroko obecnie stosowanych połączeniach ciernych. Wadą tych połączeń jest przyjęcie założeenia, w ktorym pojawienie się stanu granicznego nosności utożsamia się z pierwszym poślizgiem. W rzeczywistosci sprężone pola.czenie srubowe nadal jest zdolne do przyjecia dodatkowego przyrostu obci^zenia. Wyniki szeregu prac, głównie doswiadczalnych [2], [3], potwierdzaja. to spostrzeżenie. Zgodnie z nimi, przy mozliwosci dalszego przyjmowania obciążenia, odkształcalnosc połączenia po pierwszym poślizgu byla nadal znacznie mniejsza od odksztalceń analogicznych połączeń śrubowych niesprężonych. W pracy przedstawiono model nakładkowego połączenia srubowego, wstępnie sprężonego. Zastosowano w nim jedną rubę (wstępne ujęcie). Miało to na celu uzyskanie dobrych warunkow poznania zachowania się takich połączeń.

Keywords:

sprężenie, płączenia nakładkowe, rozciąganie, modele numeryczne, experyment

Affiliations:
Karczewski J.-Warsaw University of Technology (PL)
Postek E.-IPPT PAN
Wierzbicki S.-Warsaw University of Technology (PL)
16.Postek E., Rojek J., Antúnez H., Nonlinear static analysis of a guyed mast with finite element method, CMM1993, XI Polish Conference on Computer Methods in Mechanics , 1993-05-11/05-14, Kielce-Cedzyna (PL), No. , pp.743-750, 1993
Abstract:

This paper deals with numerical aspects of nonlinear static analysis of a guyed mast of 649 m height. A concept of a new structure constructed of solid bars instead of tubes is analyzed. Due to decrease of member diameters the wind load declines, thus the horizontal displacements are smaller. A few structural variants of the proposed mast are calculated.

Keywords:

guyed mast, nonlinear analysis, tendons

Affiliations:
Postek E.-IPPT PAN
Rojek J.-IPPT PAN
Antúnez H.-IPPT PAN
17.Kleiber M., Hien T.D., Postek E., Structural Design Sensitivity Analysis by Incremental Procedures, CMM10, X Polish Conference Computer Methods in Mechanics, 1991-05-14/05-17, Swinoujscie (PL), DOI: , pp.357-364, 1991
Abstract:

An incremental formulation based on the Taylor's expansion for nonlinear design sensitivity problems is developed. Computational aspects are discussed. A few numerical benchmark problems illustrate the paper.

Keywords:

design sensitivity, nonlinear geometry, incremental procedure

Affiliations:
Kleiber M.-IPPT PAN
Hien T.D.-IPPT PAN
Postek E.-IPPT PAN

Conference abstracts
1.Postek E., Pęcherski R., Nowak Z., Viscoplasticity effect during impact of metallic foams, CCAM & 3D-Printing, Collaborative Conference on Advanced Materials, 2019-08-26/08-30, St. Julian's (MT), pp.16-17, 2019
Abstract:

In the last 20 years, a new rapidly developing method is applied to calculations of solid mechanics problems, [1]. It is a non-local method. The predecessors of the method that have been applied to crystals were developed in [2] and [3]. In the presentation, we show an application of the method for the evaluation of the viscoplasticity effects [4, 5] in the copper foams. The oxygen free high conductivity copper (OHFC) can be applied to produce the open-cell multifunctional structures, for example, heat exchangers, heat capacitors, using additive manufacturing [6]. We use the highly parallelized program Peridigm for the analysis, [7].
Figure 1(a) shows an exemplary impacting foam sample attacking with a velocity of 20 m/s an elastic block. The highest plastic strains are in the case of ideally elastic-plastic case (b). The equivalent plastic strains are higher when neglecting the strain rate hardening effects (d) than including both strain hardening and strain rate hardening effects (c). We provide dependences of the equivalent plastic strains on impact velocities and strain rate hardening exponents.
Literature;
1. S.A. Silling, Journal of Mechanics and Physics of Solids, 48, 175 (2000).
2. D. Rogula, Nonlocal theory of material media (Springer), 123 (1982).
3. A. Kunin, Elastic media with microstructure, one dimensional models (Springer), (1982).
4. J.A. Mitchell, A Nonlocal, Ordinary, State-Based Plasticity Model for Peridynamics (SANDIA ), (2011).
5. J.T. Foster, S.A. Silling, W.W. Chen, International Journal for Numerical Mechods in Engineering, 81,1242 (2010).
6. R.B. Pęcherski, M. Nowak, Z. Nowak, International Journal for Multiscale Computational Engineering, 15, 431 (2017).
7. M.L. Parks, D.J. Littlewood, J.A. Mitchell, S.A. Silling, Peridigm Users’ Guide (SANDIA), (2012).

Keywords:

metallic foams, composites, impact loading, peridynamics, parallel computing

Affiliations:
Postek E.-IPPT PAN
Pęcherski R.-IPPT PAN
Nowak Z.-IPPT PAN
2.Sadowski T., Postek E., Pietras D., Boniecki M., Szutkowska M., Modelling of Quasi-static and Dynamic Damage Process in Ceramic Matrix Composites, MECHCOMP 2019, 5th International Conference on Mechanics of Composites, 2019-07-01/07-04, Lizbona (PT), pp.80-81, 2019
Abstract:

Quasi-static degradation of brittle composites exhibits different mechanical response under uniaxial
tension and uniaxial compression. In this paper we analysed cracking processes and failure under
quasi-static loading of 2 phase ceramic material made of alumina and zirconia mixture, subjected to
tension and compression. Constitutive modelling of two phase ceramic composites obeys description
of: (1) elastic deformations of initially porous material, (2) limited plasticity and (3) cracks initiation
and propagation. Modelling of polycrystalline ceramics at mesoscopic level under mechanical loading is
related to analysis of a set of grains, which create so called Representative Volume Element (RVE). The
basic elements of the defect structure inside polycrystal are: micro- and meso-cracks, kinked and wing
cracks. To get macroscopic response of the material one can calculate averaged values of stress and strain over the RSE with application of analytical approach. Dynamic degradation process was illustrated
for 2 phase ceramic matix composite and cermet, which was subjected to short compressive impulse.
The pulse duration was 10-7s and the applied pressure level - 480 MPa. In the proposed more advanced
nite elements formulation of the cermet behaviour is was necessary to take into account the following
data and phenomena revealing inside of the RVE: (1) spatial distribution of the cermet constituents,
(2) system of grain boundaries/binder interfaces modelled by interface elemnets, (3) rotation of brittle
grains. The cermet response due to pulse loading is signifcantly different in comparison to the quasistatic
behaviour, i.e. the stress distributions and microcracking processes are quite different.

Keywords:

brittle composites, damage, quasi-static behaviour, dynamics, RVE

Affiliations:
Sadowski T.-Lublin University of Technology (PL)
Postek E.-IPPT PAN
Pietras D.-Lublin University of Technology (PL)
Boniecki M.-Institute of Electronic Materials Technology (PL)
Szutkowska M.-Institute of Advanced Manufacturing Technology (PL)
3.Postek E., Sadowski T., Boniecki M., Impact of Al2O3/ZrO2 Composite, Qualitative Comparison of Compositions, RANM2019, Fourth International Conference on Recent Advances in Nonlinear Mechanics, 2019-05-07/05-10, Łódź (PL), pp.226-228, 2019
Abstract:

The ceramic composites Al2O3/ZrO2 are used for different kind of implants
since they are nontoxic and nonallergic [1]. The composites of different composition
of both compounds are obtained by sintering at the temperature 1600◦C. The amount
of zirconia in the composite is normally up to 30% volume. The investigation of such
properties like Youngs modulus, toughness and flexural strength is presented in [2]. The
properties of ZrO2 compound with stabilization of Y2O3 are described in [3].

Keywords:

Al2O3/Zr02, composite compositions, impact, peridynamics

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
Boniecki M.-Institute of Electronic Materials Technology (PL)
4.Postek E., Scheider Y., Schmauder S., Impact of WC/Co/diamond sample with peridynamics, SCFE2019, Supercomputing Frontiers Europe 2019, 2019-03-11/03-14, Warsaw (PL), pp.1-4, 2019
Abstract:

Metal Matrix Composites (MMCs) are widely used in several strategic industrial sectors, such as defense, aerospace, nuclear power plants, space exploration, being the main source of technological progress in the others, for example machining. In this communication, we use meshless method that is peridynamics for simulation of impact of a sample. Peridynamics is a non-local, meshless quite recently formulated method of stress analysis. Nonlocal methods were developed for crystal analysis [1], [2]. The nonlocal methods were generalized on the coupled problems in [3]. The peridynamics was formulated for the first time by Silling [4, 5].

Keywords:

WC/Co composite, Impact loading, Peridynamics, Numerical model

Affiliations:
Postek E.-IPPT PAN
Scheider Y.-University of Stuttgart (DE)
Schmauder S.-University of Stuttgart (DE)
5.Postek E., Sadowski T., Temperature effect in 2 phase ceramic based composite during impact conditions, ICCS21, 21st International Conference on Composite Materials, 2018-09-04/09-07, Bologna (IT), DOI: 10.15651/978-88-938-5079-7, pp.100, 2018
Abstract:

Cermet Materials (CM) are often used for manufacturing of different cutting tools. They have very good mechanical, wear and thermal properties. In our opinion, the dynamic load is still not enough thoroughly analysed, and the impact load as well. The tools are subjected to different dynamic effects.We have taken into account complex spatial distribution of cermet phases, grain/binder interfaces modeled by interface elements, possibility of cracks appearance within binders using interface elements as well, and rotation of brittle grains.
The main goal of the presentation is to develop further previously formulated models of two-phase composite [1-4] to capture effects of temperature due to impact. The source of the thermal loading is the conversion of plastic work into heat [5, 6]. The increase of temperature takes place in the Co interfaces. We investigate adiabatic and fully coupled solutions.
We note differences in the behaviour of the samples when the thermal loading is not considered. We have found that the thermal softening effect in the interface material is important as well. We enhance the description of the damage mechanism in the presence of temperature increase.
Acknowledgements
This work was financially supported by Ministry of Science and Higher Education (Poland) within the statutory research (IPPT PAN) and National Science Centre (Poland) project No 2016/21/B/ST8/01027 (Lublin University of Technology). The calculations were done at the Interdisciplinary Centre for Mathematical and Computational Modelling, University of Warsaw, Poland. The licenses for the MSC Patran and Abaqus programs were provided by Academic Computer Centre in Gdańsk, Poland.

References:
[1] Sadowski T, Hardy S, Postek E. Prediction of the mechanical response of polycrystalline ceramics containing metallic intergranular layers under uniaxial tension. Comput Mat Sci 2005;34:46-63.
[2] Sadowski T, Hardy S, Postek E. A new model for the time-dependent of polycrystalline ceramic materials with metallic inter-granular layers under tension. Mat. Sci. Eng. A 2006;424:230-238.
[3] Sadowski T, Postek E, Denis C. Stress distribution due to discontinuities in polycrystalline ceramics containing metallic inter-granular layers. Comput Mat Sci 2007;39: 230-236.
[4] Postek E, Sadowski T. Dynamic pulse sensitivity of WC/Co composite, (accepted in Composite Structures).
[5] Wriggers P, Miehe C, Kleiber M, Simo JC. On the coupled thermomechanical treatment of necking problems via finite element methods. Int. J. Num. Meth. Eng. 1992; 33:869–883.
[6] Rojek J, Onate E, Postek E. Application of explicit FE codes to simulation of sheet and bulk metal forming processes. J. Mat. Proc. Tech. 1998; 80–81: 620–627.

Keywords:

cermet composites, coupled solutions, thermomechanics

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
6.Postek E., Sadowski T., Model uderzenia z dużą prędkością płytki wykonanej z kompozytu dwufazowego, początek procesu, PLASTMET, 11 KONFERENCJA ZINTEGROWANE STUDIA PODSTAW DEFORMACJI PLASTYCZNEJ METALI, 2018-11-27/11-30, Łańcut (PL), pp.122-123, 2018
Abstract:

Materiały metaloceramiczne są często stosowane w elementach, które mogą być poddane uderzeniom. Jednak większość prac dotyczących obciążeń dynamicznych dotyczy kompozytów warstwowych. Techniki oceny obciążeń uderzeniowych dla kompozytów dobrze przedstawione są w pracy [1]. Przykładem kompozytu dwufazowego jest WC/Co. Ten rodzaj kompozytu jest często modelowany jako posiadający sprężysto plastyczne wypełnienie oraz sprężyste ziarna. Powodem tego jest wysoka odporność na zniszczenie materiału WC. Przedstawiamy rozszerzenie wcześniej opracowanych modeli [2], w których zakładana była idealna sprężystość ziaren. W nowym modelu zakładamy możliwość zniszczenia ziaren. Badamy układ, w którym próbka uderza o sztywną ścianę z różnymi prędkościami.

Keywords:

Obciążenia uderzeniowe, węglik wolframu, kompozyt dwufazowy, metoda elementów skończonych

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
7.Postek E., Pęcherski R., Nowak Z., Perydynamiczna symulacja procesów zgniatania otwartokomórkowych pianek miedzianych, PLASTMET, 11 KONFERENCJA ZINTEGROWANE STUDIA PODSTAW DEFORMACJI PLASTYCZNEJ METALI, 2018-11-27/11-30, Łańcut (PL), pp.120-121, 2018
Abstract:

W ciągu ostatnich dwudziestu lat opracowano nową metodę bezsiatkową znaną jako perydynamika [1]. Metoda ta posługuje się zrównoleglonym kodem obliczeniowym [2]. Przedmiotem badań jest deformacja miedzianej pianki o strukturze otwartokomórkowej poddanej dynamicznemu ściskaniu, Rys. 1.
Model komputerowy szkieletu pianki otrzymano wykorzystując koncepcję materiału wirtualnego przedstawioną w pracy [3]. W zależności od potrzeb wymiary struktury szkieletu pianki można skalować. Materiałem pianki jest miedź beztlenowa o wysokiej przewodności cieplnej (OFHC), wykorzystywana do wytwarzania wielofunkcyjnych struktur komórkowych takich jak wymienniki lub kondensatory cieplne, itp. W obliczeniach zastosowano lepkoplastyczny model materiału szkieletu pianki, a symulacje przeprowadzono dla różnych prędkości uderzenia. Rezultaty metody perydynamiki porównano z obliczeniami MES podobnych problemów ściskania dynamicznego pianki. Obliczenia wykonano w ICM Uniwersytetu Warszawskiego na komputerze CRAY XC-40 oraz na klastrze HP w centrum TASK w Gdańsku.

Keywords:

Obciążenia uderzeniowe, pianka metaliczna, perydynamika

Affiliations:
Postek E.-IPPT PAN
Pęcherski R.-IPPT PAN
Nowak Z.-IPPT PAN
8.Postek E., Sadowski T., Temperature effects during impact of WC/Co composites, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1, 2018
Abstract:

Generally, the papers on dynamic loading of composites more focus on the layered composites, for example [1]. High attention is paid to blast load. However, in our opinion, the process of impact a gap for analysis of WC/Co composite during impact conditions. During impact of WC/Co composite objects and the other composites with metallic binder heat of plastic work is generated. If the process is fast enough the problem can be treated as adiabatic. However, more common situation is slower process when the heat is generated in metallic interfaces and the neighbouring grains are heated due to conduction. The process should be rather considered as coupled [2]. We developed our model of WC/Co composite towards impact load, [3].

Keywords:

thermomechanics, coupled problems, composites

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
9.Postek E., Nowak Z., Pęcherski R., Impact resistance of crushable foam skeleton, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1-2, 2018
Abstract:

The analyses of the modern cellular materials due to complexity of their internal structure require efficient computer methods and codes. The new method that has been developed mostly in the last 10 years is peridynamics [1, 2]. The developments resulted in highly parallelized code [3] that we use in our analysis.
The subject of the study are alumina foams produced by gelcasting method. The results of microtomography of alumina foams are used to create the numerical model reconstructing the structure of foam skeleton. The numerical simulations of failure strength under compression for alumina foams are performed. The calculations with use of the numerical model are time consuming. Therefore, the simplified method of the assessment of failure strength is proposed. The 3D model of the foam structure is created. The detailed description of the model generation is presented in Nowak et al. [5].
The numerical models of real Al2O3 foam with porosity 96 %, and discussion of theirs mechanical properties have been presented. The method of the assessment of failure strength of real alumina foam produced by the gelcasting is proposed.
We attempt to present the mechanism of damaging of a crushable foam under impact.

Keywords:

foams, damage, impact, peridynamics

Affiliations:
Postek E.-IPPT PAN
Nowak Z.-IPPT PAN
Pęcherski R.-IPPT PAN
10.Postek E., Generation of a tumor model, Supercomputing Frontiers Europe wraz z XX Sesją Sprawozdawczą Użytkowników KDM, 2018-03-12/03-16, Warszawa (PL), pp.1, 2018
Abstract:

The physical environment of living cells and tissues, and more
particularly their mechanical interaction with it, plays a crucial
regulatory role in their biological behaviour such as cell
differentiation, apoptosis, proliferation, tissue growth,
remodelling, tumor growth, etc. However, the way that
mechanical forces at the cellular level (i) influence the cell
functions and (ii) govern the behaviour of cell assemblies as well
as their development, remains unclear and hard to model.
First of all, we investigate a tissue growth model. The model is
generated with PhysiCell [1, 2].

Keywords:

computational biology, tumor growth

Affiliations:
Postek E.-IPPT PAN
11.Postek E., Sadowski T., Impact modelling of cerment composite, The 7th International Conference on Advanced Materials and Structures, 2018-03-28/03-31, Timisoara (RO), pp.111, 2018
12.Postek E., Sadowski T., Impact Models of WC-Co Composite, CERMODEL 2017Modelling and Simulation Meet Innovation in Ceramics Technology, 2017-07-26/07-28, Trento (IT), pp.1, 2017
13.Postek E., Sadowski T., A Crack Model Around Junctions in WC/Co Composite, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), pp.1, 2016
Keywords:

Metal-Ceramic Composite, Interface Elements, Crack Propagation at Composite Junctions

Affiliations:
Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
14.Postek E., Dubois F., Mozul R., Canadas P., Modelling of a Collection of Non-Rigid Particles with Smooth Discrete Element Method, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), pp.1, 2016
Keywords:

cell mechanics, smooth discrete element method, finite element method, finite motions

Affiliations:
Postek E.-IPPT PAN
Dubois F.-Université de Montpellier (FR)
Mozul R.-Université de Montpellier (FR)
Canadas P.-Université de Montpellier (FR)
15.Postek E., Parameter sensitivity of a single layer tensegrity modelled tissue, Mecánica Computacional, ISSN: 2591-3522, Vol.XXXIII, No.43, pp.2797, 2014
16.Postek E., A survey of tensegrity models of cells with design sensitivity analysis, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.44-45, 2012
17.Postek E., Dubois F., Mozul R., Modeling of a collection of tensegrity particles with a nonsmooth discrete element method, SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.28-29, 2012
18.Postek E., Caliendo C., Latino P.M., Numerical model of ALN-based bulk acoustic high-frequency resonators, SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.316-317, 2012
19.Postek E., Concept of an Agent-stress Model of a Tissue, 2nd International Conference on Material Modelling, 2012-08-31/09-02, Paryż (FR), pp.297, 2011
20.Postek E., Smallwood R., Hose R., Finite deformation based model of cytoskeleton, ICCB2009, IV International Congress on Computational Bioengineering including the first European Symposium on Biomedical Integrative Research, 2009-09-16/09-18, Bertinoro (IT), DOI: 10.6092/unibo/amsacta/2646, pp.53-53, 2009
Abstract:

The cytoskeleto is modelled as a tensegrity structure. It consists of tendons and struts [Stamenovic, 2005]. The basic tensegrity structures are developed from icosahedron.
The cells undergo finite deformations behaviour and their response to loading conditions is visco-elastic,
These types of structures are sensitive to initial prestressing what it intuitively natural since without the initial stress state they would not exist, The other factors affecting the mechanical behaviour of the cell are constitutive parameters and positions of the nodes, in fact, the shape of the cell.

Keywords:

cytoskeleton, visco-elasticity, finite strains, prestressing

Affiliations:
Postek E.-IPPT PAN
Smallwood R.-other affiliation
Hose R.-other affiliation
21.Postek E., Parallel version of a design sensitivity tensegrity code, TAM 2009, Transnational Access Meeting, HPC-Europa2 2009, 2009-10-14/10-16, Montpellier (FR), pp.1, 2009
Abstract:

The cytoskeleton is a tensegrity structure, The mechanics is important to the cells: "change the mechanical stresses on cancer cells and they can start to behave like healthy ones" [1] . The displacements and stresses change in the biological materials due to the growth, division and death of the cells. The cells receive signals for the actions. This constitutes the agent-stress based models of the tissue. [1] C. Ainsworth. Stretvhing the examination, Nature, 456, Dec., 696-699, 2008.

Keywords:

cell mechanics, signals, design sensitivity

Affiliations:
Postek E.-IPPT PAN
22.Postek E.W., Houseman G.A., Jimack P.K., Aspects of Non-Newtonian Viscoelastic Deformation Produced by Slip on a Major Strike- slip Fault, AGU FALL MEETING 2008, American Geophysical Union Fall Meeting 2008, 2008-12-15/12-19, San Francisco (US), pp.1, 2008
Abstract:

Non-Newtonian flow occurs in crustal deformation processes on the long
timescales associated with large- scale continental deformation, and also
on the short time-scales associated with post-seismic deformation. The
co-seismic displacement is determined by the instantaneous elastic
response of the rocks on either side of the fault surface to the
distribution of slip on the surface of the fault. The post-seismic
deformation is determined by some combination of visco-elastic relaxation
of the medium and post-seismic creep on the fault. The response of the
crust may depend on elastic moduli, Poisson's ratio, temperature, pressure
and creep function parameters including stress exponent, activation
energy, activation volume and viscosity coefficient. We use the von Mises
function in describing the non-linear Maxwell visco-elastic creep models.
In this study we examine a model of a strike-slip fault crossing a 3D
block. The fault slips at time zero, and we solve for the viscoelastic
deformation field throughout the 3D volume using a 3D finite element
method. We perform parametric studies on the constitutive equation by
varying these parameters and the depth of the fault event. Our findings
are focused on the fact that the system is very sensitive to the above
mentioned parameters. In particular, the most important seems to be the
temperature profiles and stress exponent. The activation energy and the
pressure are of lower importance, however, they have their meaning. We
investigated the relaxation times and the deformation patterns. We took
the material properties as typical to dry quartzite and diabase. Depending
on the parameters the surface can be deformed permanently or the
deformation can decrease. We attempt to compare qualitatively the
calculated post-seismic response in terms of the post-seismic displacement
history of the earth's surface with InSAR patterns determined from recent
major strike-slip earthquakes. Quantitative comparison of the observations
with these numerical model results can in principle provide a better
understanding of the physical properties of the sub-surface and further
insight into the diagnostic properties of the earthquake cycles of major
fault systems.

Cite as: Author(s) (2008), Title, Eos Trans. AGU, 89(53), Fall Meet.
Suppl., Abstract T44B-07

Keywords:

rheology, crust, litosphere

Affiliations:
Postek E.W.-IPPT PAN
Houseman G.A.-University of Leeds (UK)
Jimack P.K.-University of Leeds (UK)
23.Postek E.W., Houseman G.A., Jimack P.K., Generic Models of Linear and Non-linear Visco-elastic Surface Deformation above a Fault, EGU 2008, European Geosciences Union General Assembly 2008, 2008-04-13/04-18, Vienna (AT), pp.1, 2008
Abstract:

The ground displacements measured in the vicinity of a large strike-slip earthquake are
potentially important in diagnosing the state of stress on the fault and in the medium
surrounding. The co-seismic displacement is determined by the immediate elastic response
of the medium and the slip function on the fault-surface. The post-seismic
displacement is determined by a combination of post-seismic creep on the fault, viscoelastic
relaxation in the surrounding medium, and possibly poro-elastic deformation.
There are strong indications from previous earthquake studies that the visco-elastic
relaxation involves non-linear mechanisms, which produce faster deformation in the
early stages and slower deformation in the later stages than would occur with a linear
creep mechanism. In this study we examine a simplified model of a strike-slip fault
cutting a 3D block, and compute the surface displacement versus time functions for
a range of different constitutive relations. We examine linear and non-linear Maxwell
visco-elasticity, and compare with the generalized linear Maxwell visco-elasticity. The
effect of non-linearities in the elasticity (finite strain theory) is also considered.We use
the von Mises flow function in describing the non-linear Maxwell visco-elastic creep
models in which viscous creep strain-rate is proportional to the nth power of the deviatoric
stress (formulated using the 2nd invariant of the stress tensor). We describe
analytical solutions used to validate the 3D code, and then consider the effect of the
exponent n on the time histories of the surface displacement fields above the fault.
We aim here to compare these numerical models with observations from actual fault
systems obtained using InSAR and GPS data. Among the factors affecting the surface deformation patterns are near-surface layering, and lateral variation of material
properties, as well as irregularities on the fault surface. In principle, the comparison
of observations with theory should provide a better understanding of the physical response
of the sub-surface, together with a better understanding of the earthquake cycle
as it operates on specific fault systems.

Keywords:

surface deformation, seismic cycle, visco-elasticity, numerical models

Affiliations:
Postek E.W.-other affiliation
Houseman G.A.-University of Leeds (UK)
Jimack P.K.-University of Leeds (UK)
24.Postek E., Houseman G.A., Jimack P.K., Surface deformation during earthquake cycle for a layered visco-elastic crust, Ada Lovelace Workshops on Modelling Mantle and Lithosphere Dynamics 10th International Workshop on Modeling of Mantle Convection and Lithospheric Dynamics, 2007-09-02/09-07, Carry-le-Rouet (FR), pp.1, 2007
Keywords:

surface deformation, viso-elasticity, seismic cycle

Affiliations:
Postek E.-other affiliation
Houseman G.A.-University of Leeds (UK)
Jimack P.K.-University of Leeds (UK)
25.Postek E.W., Houseman G.A., Jimack P.K., The effect of geometrical nonlinearity in visco-elastic deformation, EGU 2007, European Geosciences Union, General Assembly 2007, 2007-04-15/04-20, Vienna (AT), No.9, pp.03087, 2007
26.Postek E., Houseman G.A., Jimack P.K., Nonlinear effects during post-seismic visco-elastic deformation, IUGG XXIV 2007, International Union of Geodesy and Geophysics General Assembly Earth, Our Changing Planet, 2007-07-02/07-13, Perugia (IT), No.JGS003, pp.207, 2007
Keywords:

deformation, viscosity, power law

Affiliations:
Postek E.-other affiliation
Houseman G.A.-University of Leeds (UK)
Jimack P.K.-University of Leeds (UK)
27.Karczewski J.A., Postek E., Wierzbicki S., Experimental shakedown analysis of double butt, prestressed, bolted connections, 6th International Conference, Modern Building Materials Structures and Techniques, 1999-05-19/05-22, Wilno (LT), pp.196-201, 1999
Abstract:

This paper deals with the experiment on double butt prestressed bolted connections. The goal of the experiment is to verify a 3D computational model of the connection. The connections are loaded cyclically according to a load program based on load variability observed in engineering practice

Keywords:

prestressing, deformability, ultimate load, elastooptic layer

Affiliations:
Karczewski J.A.-Warsaw University of Technology (PL)
Postek E.-IPPT PAN
Wierzbicki S.-Warsaw University of Technology (PL)
28.Postek E., Kleiber M., Design sensitivity of reinforced concrete plate/shell structures, CMM1995, XII Polish Conference on Computer Methods in Mechanics, 1995-05-09/05-13, Warszawa Zegrze (PL), No. , pp.279-280, 1995
Abstract:

Design sensitivity gradients are believed to have great significance in realistic asscsment of structural response. Sensitivity techniques form a tool to follow changes in structural behaviour caused by variations of design parameters. The sensitivity gradients make it also possible to investigate the influence of different type of material or geometrical imperfections on the structural response. One of the first papers considering the design sensitivity analysis (DSA) was presented by Zienkiewicz and Campbell |lj. Recently, efforts of the investigators are mostly focused on the r.onlinear performance of structures. The total Lagrangian formulation with the computer Implementation in Adina was presented in ]2]. A formulation considering path-dependent problems was given in [3] and the updated Lagrangian formulation of the design sensitivity problems for arbitrary nonlinearities was given in [4]. Applications of the DSA to the slate estimation of complex structures were presented in |5). The response of reinforced concrete structures should always be considered nonlinear and thus it may be used as an example illustrating the theory of design sensitivity for nonlinear systems. This paper deals with the design sensitivity of reinforced plate and shell structures. References 1. 0. C. Zicnkiowicz, J.S. Campbell, Shape optimization and sequential linear programmiri R. II. Gallagher and O.C. Xienkicwicz, eds Optimum Structural Design, Wiley, 1973. 2. M. Ilaririan, J.B. Cardoso, J.S. Arora, Use of ADINA for design optimization of nonlinear structures, C'omput. Struct., 26 (1987), pp. 123-133. 3. C.A. Vidal, R.I3. Ilaber, Design sensitivity analysis for rate independent elasl.opla.stjr Comp. Mcth. Appl. Mcch. Eng., 107 (1993), pp. 393-431. 4. M. Kleiber, Shape and nonshapc structural design sensitivity analysis for problems w;; any material .and kinematic nonlincarity, Comp. Mclh. Appl. Eng., 108 (1993), pp. 73-97 5. M. Kleiber, T.D. Hien, E. Postek, Incremental finite eleirint sensitivity analysis for non-linear mechanics applications, Int. .!. Num. Me/It. Eng., 37 (1994), pp. 3291-3308.

Keywords:

parameter sensitivity, plate-shell structures, nonlinear analysis

Affiliations:
Postek E.-IPPT PAN
Kleiber M.-IPPT PAN