Papers by Keyword: Viscoplasticity

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Authors: Wei Shen Zhu, Jian Hua Liu, Shu Cai Li
Abstract: A brief description is given to the visco-plastic constitutive model of 3-D FLAC software and some treating methods for the numerical analysis. The excavation steps and the exerting time of excavation loads are determined in the light of the real construction process. The rockmass mechanical parameters are determined according to back analysis of in-situ measured displacement data. The analysis results of displacement and stability of the opening complex surrounding rocks in the construction process and in a long period of time after excavation completion are given.
Authors: Fabio de Angelis, Donato Cancellara
Abstract: Constitutive relations are presented for a model of nonlocal viscoplasticity within a variationally consistent suitable setting. The appropriate elastic and dissipative potentials are introduced within a generalized standard material framework. A formulation of variationally consistent constitutive relations is accordingly presented for a model of nonlocal viscoplasticity. The evolutive equations are illustrated for the proposed model in a general form which is able to include different models of nonlocal viscoplasticity and different hardening rules.
Authors: Martina Lovrenić-Jugović, Zdenko Tonković, Ante Bakić
Abstract: The present paper is concerned with an experimental research and numerical modelling of the viscoelastic-viscoplastic-damage behaviour of bovine cortical bone. A one-dimensional constitutive model is proposed to predict the experimental behaviour under creep-recovery load conditions. The material parameters are determined by fitting experimental results. The derived algorithm for the integration of the proposed constitutive model is implemented into finite element formulation. The computational algorithm shows an excellent capability to describe the tensile behaviour of bovine cortical bone for the specific mechanical conditions analyzed.
Authors: Sergei Alexandrov, Elena Lyamina, Li Hui Lang
Abstract: The paper concerns with three-dimensional analysis of the process of bending under tension for incompressible, rigid viscoplastic material at large strains. The constitutive equations consist of the Mises-type yield criterion and its associated flow rule. No restriction is imposed on the dependence of the equivalent stress on the equivalent strain rate. The problem is reduced to evaluating ordinary integrals and solving transcendental equations.
Authors: Xiang Guo Zeng, Hua Yan Chen, Zhan Hua Gao
Abstract: Founded on the energy storing characteristics of microstructure during irreversible deformation, a viscoplastic constitutive model with no yielding surface introduced was developed for single crystals by adopting a spring-dashpot mechanical system. Both plastic dashpots reflecting the material time-independent responses and Newtonian dashpots mirroring the material time-dependent viscous responses were introduced to describe the viscoplasticity of slip systems. The single crystal constitutive model was established based on the thermodynamics of internal variables and the theory of absolute reaction rate. By implementing the KBW self-consistent theory, a polycrystal viscoplastic constitutive model was formed. The numerical analysis in corresponding algorithm was significantly simplified as no searching process for the activation of the slip systems and slip directions was required. The numerical simulation of creep-plasticity behaviors demonstrated excellent agreement with the corresponding experimental data.
Authors: Hao Ju Hu, Jian Yu Zhang, Bin Jun Fei
Abstract: A finite element simulation of a plasma sprayed thermal barrier coating(TBC) system was conducted. Plasma sprayed thermal barrier ceramic coating was treated as either a simple elastic model or an advanced viscoplastic model which includes rate dependence and unequal flow stresses in tension and compression. Predicted tensile stresses emerging in the ceramic plane at the elevated temperature never become large enough to cause surface cracks based on elastic analysis, so does using the viscoplastic model. At the low temperature, these two models identically show that the ceramic coat will locally cracks at the “peak” location. It is shown that although there are some numerical differences in these two models’ predictions, elastic analysis predicts accurate in failure mechanism analysis based on stresses
Authors: Takayuki Koda, Tetsuya Matsuda
Abstract: In this study, the elastic-viscoplastic properties of aluminum honeycomb sandwich panels are investigated using a homogenization theory for free edge analysis. For this, the mathematical homogenization theory is reconstructed for elastic-viscoplastic analysis of honeycomb sandwich panels by introducing a traction free boundary condition. Moreover, the domain of analysis is reduced to a quarter using point-symmetry of internal structures of honeycomb sandwich panels. The present method is then applied to the analysis of macroscopic elastic-viscoplastic behavior and microscopic stress distribution of an aluminum honeycomb sandwich panel subjected to in-plane uniaxial compression. It is shown that the stress concentration arises at face/core interfaces, especially at intersections of core walls.
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