Adam Glema | Poznan University of Technology (original) (raw)

Papers by Adam Glema

Research paper thumbnail of Towards the Modelling of Anisotropic Solids

Computational Methods in Science and Technology, 2010

In the paper the material model for metals and its numerical applications are presented. The mate... more In the paper the material model for metals and its numerical applications are presented. The material model is stated in terms of continuum mechanics, in the framework of the thermodynamical theory of viscoplasticity. The fundamental achievement is that the constitutive relation includes a description of anisotropy of metal microstructure. Such approach gives qualitatively and quantitatively new results compared with the existing models because it is possible to trace the directions of softening and predict a damage path in process time. Numerical examples comprise full spatial modelling for HSLA-65 steel in adiabatic conditions (the analysis of anisotropic bodies can be led only on 3D models) including: tension of sheet steel and twisting of thin walled tube. During analyses strain rates of order 10 4-10 7 s-1 are observed and the process time up to full damage (loss of continuity in the localisation zone) is around 100-300 μs.

Research paper thumbnail of Material dispersion in dynamic deformation process of solids under impact action

Pamm, 2007

The dispersion phenomenon is studied to introduce the adequate material model for the advanced st... more The dispersion phenomenon is studied to introduce the adequate material model for the advanced states of dynamic deformation processes. The evolution problem is formulated within the frame of theory of thermodynamics and viscoplasticity. Mathematical analysis for elastic, plastic and viscoplastic material evidence the non-dispersive or dispersive property. Occurrence of dispersion in the analysis problem has the consequences not only for constitutive relation. It influences the whole problem with advantages in formulation and solution. Numerical results of example problems present qualitatively different mechanical response for materials with different dispersion. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Research paper thumbnail of Sensitivity analysis and optimal redesign of columns in the state of initial distortions and prestress

Structural and Multidisciplinary Optimization, 1991

The problem of the optimal distribution of the reinforcing material added to an existing column w... more The problem of the optimal distribution of the reinforcing material added to an existing column with the aim to increase its buckling load is considered in the paper. It is assumed that the stress-strain relation is nonlinear elastic. The authors employ the variational formulation to derive the sensitivity gradients with respect to variable reinforcement distribution, prestress and initial distortions. The formulation of optimal redesign allows for uni- and bimodal buckling. Numerical examples for various geometrical constraints illustrate the theory.

Research paper thumbnail of Sensitivity of plastic strain localization zones to boundary and initial conditions

Computational Mechanics, 2003

The plastic strain localization phenomena are studied with the use of the theory of viscoplastic... more The plastic strain localization phenomena are studied with the use of the theory of viscoplasticity and finite element method. The aim of the study is to check if the strain localization is sensitive to variation of initial and boundary conditions. Total and local plastic deformation energy as candidate response functionals for sensitivity analysis are discussed by selected numerical examples of wave propagation problems. The paper considers sensitivity of the form and intensity of plastic strain localization to the variation of the above parameters. Different response functionals for structures demonstrating plastic strain localization were proposed and studied.

Research paper thumbnail of The Numerical Analysis of the Intrinsic Anisotropic Microdamage Evolution in Elasto-Viscoplastic Solids

International Journal of Damage Mechanics, 2009

The objective of the present article is to show the formulation for elastic-viscoplastic material... more The objective of the present article is to show the formulation for elastic-viscoplastic material model accounting for intrinsic anisotropic microdamage. The strain-induced anisotropy is described by the evolution of the intrinsic microdamage process -defined by the second-order microdamage tensor. The first step of the possibility of identification procedure (calibration of parameters) are also accounted and illustrated by numerical examples.

Research paper thumbnail of Numerical investigation of dynamic shear bands in inelastic solids as a problem of mesomechanics

Computational Mechanics, 2008

The main objective of the present paper is to discuss very efficient procedure of the numerical i... more The main objective of the present paper is to discuss very efficient procedure of the numerical investigation of the propagation of shear band in inelastic solids generated by impact-loaded adiabatic processes. This procedure of investigation is based on utilization the finite element method and ABAQUS system for regularized thermo-elasto-viscoplastic constitutive model of damaged material. A general constitutive model of thermo-elasto-viscoplastic polycrystalline solids with a finite set of internal state variables is used. The set of internal state variables is restricted to only one scalar, namely equivalent inelastic deformation. The equivalent inelastic deformation can describe the dissipation effects generated by viscoplastic flow phenomena. As a numerical example we consider dynamic shear band propagation in an asymmetrically impact-loaded prenotched thin plate. The impact loading is simulated by a velocity boundary condition, which are the results of dynamic contact problem. The separation of the projectile from the specimen, resulting from wave reflections within the projectile and the specimen, occurs in the phenomenon. A thin shear band region of finite width which undergoes significant deformation and temperature rise has been determined. Shear band advance, shear band velocity and the development of the temperature field as a function of time have been determined. Qualitative comparison of numerical results with experimental observation data has been presented. The numerical results obtained have proven the usefulness of the thermo-elasto-viscoplastic theory in the investigation of dynamic shear band propagations.

Research paper thumbnail of Interaction of deformation waves and localization phenomena in inelastic solids

Computer Methods in Applied Mechanics and Engineering, 2000

The main objective of this paper is the investigation of the interaction and re¯ection of elastic... more The main objective of this paper is the investigation of the interaction and re¯ection of elastic±viscoplastic waves which can lead to localization phenomena in solids. The rate type constitutive structure for an elastic±viscoplastic material with thermomechanical coupling is developed. An adiabatic inelastic¯ow process is considered. The Cauchy problem is investigated and the conditions for well-posedness are examined. Discussion of fundamental features of rate-dependent plastic medium is presented. This medium has dissipative and dispersive properties. Mathematical analysis of the evolution problem (the dynamical initial-boundary value problem) is presented. The dispersion property implies that in the viscoplastic medium any initial disturbance can break up into a system of group of oscillations or wavelets. On the other hand, the dissipation property causes the amplitude of a harmonic wavetrain to decay with time. In the evolution problem considered in such dissipative and dispersive medium, the stress and deformation due to wave re¯ections and interactions are not uniformly distributed, and this kind of heterogeneity can lead to strain localization in the absence of geometrical or material imperfections.

Research paper thumbnail of Towards the Modelling of Anisotropic Solids

Computational Methods in Science and Technology, 2010

In the paper the material model for metals and its numerical applications are presented. The mate... more In the paper the material model for metals and its numerical applications are presented. The material model is stated in terms of continuum mechanics, in the framework of the thermodynamical theory of viscoplasticity. The fundamental achievement is that the constitutive relation includes a description of anisotropy of metal microstructure. Such approach gives qualitatively and quantitatively new results compared with the existing models because it is possible to trace the directions of softening and predict a damage path in process time. Numerical examples comprise full spatial modelling for HSLA-65 steel in adiabatic conditions (the analysis of anisotropic bodies can be led only on 3D models) including: tension of sheet steel and twisting of thin walled tube. During analyses strain rates of order 10 4-10 7 s-1 are observed and the process time up to full damage (loss of continuity in the localisation zone) is around 100-300 μs.

Research paper thumbnail of Material dispersion in dynamic deformation process of solids under impact action

Pamm, 2007

The dispersion phenomenon is studied to introduce the adequate material model for the advanced st... more The dispersion phenomenon is studied to introduce the adequate material model for the advanced states of dynamic deformation processes. The evolution problem is formulated within the frame of theory of thermodynamics and viscoplasticity. Mathematical analysis for elastic, plastic and viscoplastic material evidence the non-dispersive or dispersive property. Occurrence of dispersion in the analysis problem has the consequences not only for constitutive relation. It influences the whole problem with advantages in formulation and solution. Numerical results of example problems present qualitatively different mechanical response for materials with different dispersion. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Research paper thumbnail of Sensitivity analysis and optimal redesign of columns in the state of initial distortions and prestress

Structural and Multidisciplinary Optimization, 1991

The problem of the optimal distribution of the reinforcing material added to an existing column w... more The problem of the optimal distribution of the reinforcing material added to an existing column with the aim to increase its buckling load is considered in the paper. It is assumed that the stress-strain relation is nonlinear elastic. The authors employ the variational formulation to derive the sensitivity gradients with respect to variable reinforcement distribution, prestress and initial distortions. The formulation of optimal redesign allows for uni- and bimodal buckling. Numerical examples for various geometrical constraints illustrate the theory.

Research paper thumbnail of Sensitivity of plastic strain localization zones to boundary and initial conditions

Computational Mechanics, 2003

The plastic strain localization phenomena are studied with the use of the theory of viscoplastic... more The plastic strain localization phenomena are studied with the use of the theory of viscoplasticity and finite element method. The aim of the study is to check if the strain localization is sensitive to variation of initial and boundary conditions. Total and local plastic deformation energy as candidate response functionals for sensitivity analysis are discussed by selected numerical examples of wave propagation problems. The paper considers sensitivity of the form and intensity of plastic strain localization to the variation of the above parameters. Different response functionals for structures demonstrating plastic strain localization were proposed and studied.

Research paper thumbnail of The Numerical Analysis of the Intrinsic Anisotropic Microdamage Evolution in Elasto-Viscoplastic Solids

International Journal of Damage Mechanics, 2009

The objective of the present article is to show the formulation for elastic-viscoplastic material... more The objective of the present article is to show the formulation for elastic-viscoplastic material model accounting for intrinsic anisotropic microdamage. The strain-induced anisotropy is described by the evolution of the intrinsic microdamage process -defined by the second-order microdamage tensor. The first step of the possibility of identification procedure (calibration of parameters) are also accounted and illustrated by numerical examples.

Research paper thumbnail of Numerical investigation of dynamic shear bands in inelastic solids as a problem of mesomechanics

Computational Mechanics, 2008

The main objective of the present paper is to discuss very efficient procedure of the numerical i... more The main objective of the present paper is to discuss very efficient procedure of the numerical investigation of the propagation of shear band in inelastic solids generated by impact-loaded adiabatic processes. This procedure of investigation is based on utilization the finite element method and ABAQUS system for regularized thermo-elasto-viscoplastic constitutive model of damaged material. A general constitutive model of thermo-elasto-viscoplastic polycrystalline solids with a finite set of internal state variables is used. The set of internal state variables is restricted to only one scalar, namely equivalent inelastic deformation. The equivalent inelastic deformation can describe the dissipation effects generated by viscoplastic flow phenomena. As a numerical example we consider dynamic shear band propagation in an asymmetrically impact-loaded prenotched thin plate. The impact loading is simulated by a velocity boundary condition, which are the results of dynamic contact problem. The separation of the projectile from the specimen, resulting from wave reflections within the projectile and the specimen, occurs in the phenomenon. A thin shear band region of finite width which undergoes significant deformation and temperature rise has been determined. Shear band advance, shear band velocity and the development of the temperature field as a function of time have been determined. Qualitative comparison of numerical results with experimental observation data has been presented. The numerical results obtained have proven the usefulness of the thermo-elasto-viscoplastic theory in the investigation of dynamic shear band propagations.

Research paper thumbnail of Interaction of deformation waves and localization phenomena in inelastic solids

Computer Methods in Applied Mechanics and Engineering, 2000

The main objective of this paper is the investigation of the interaction and re¯ection of elastic... more The main objective of this paper is the investigation of the interaction and re¯ection of elastic±viscoplastic waves which can lead to localization phenomena in solids. The rate type constitutive structure for an elastic±viscoplastic material with thermomechanical coupling is developed. An adiabatic inelastic¯ow process is considered. The Cauchy problem is investigated and the conditions for well-posedness are examined. Discussion of fundamental features of rate-dependent plastic medium is presented. This medium has dissipative and dispersive properties. Mathematical analysis of the evolution problem (the dynamical initial-boundary value problem) is presented. The dispersion property implies that in the viscoplastic medium any initial disturbance can break up into a system of group of oscillations or wavelets. On the other hand, the dissipation property causes the amplitude of a harmonic wavetrain to decay with time. In the evolution problem considered in such dissipative and dispersive medium, the stress and deformation due to wave re¯ections and interactions are not uniformly distributed, and this kind of heterogeneity can lead to strain localization in the absence of geometrical or material imperfections.