Papers by Keyword: Constitutive Model

Abstract: High manganese content TWinning Induced Plasticity (TWIP) steels are promising for the production of lightweight components due to their high strength combined with extreme ductility, see [1]. This paper deals with the implementation of a constitutive model for the macroscopic deformation behavior of TWIP steels under mechanical loading with the aim of simulating metal forming processes and representing the behavior of TWIP-steel components – for example under crash loading - with the Finite Element code LS-DYNA^® and refers to our recently published papers: [2],[4],[5]. Within the present paper we focus on the implementation of the model formulated in [2] and its extension to stress dependent twinning effects.

Abstract: The thixotropic substances can be found in different industrial sectors, such as chemical, biomedical, manufacturing and oil. These substances show a rheological time-dependent behavior, dependent of their structural level. Generally, a constitutive model for the thixotropic substances is composed by a pair of coupled equations: the constitutive equation (based on viscoelastic models) and the rate equation (that describes the structural evolution). In many works presented in the specialized literature, the shear modulus and viscosity dependencies with the structural nature are not formally considered in the dynamical principles from that the constitutive equation is originated. In the present work, a new, thermodynamically consistent, constitutive model for thixotropic substances, where such dependences are considered, is presented and some rheological tests are analyzed in a numerical simulation point of view (code developed in MATLAB). The constitutive model is based on Jeffreys’ model and the coagulation theory of Smoluchowsky.

Abstract: In this study, the hot deformation experiments of 316LN stainless steel under various deformation temperature and various strain rates were conducted on a Gleeble thermal simulator. The true stain and true stress data were obtained and the Arrhenius-type constitutive model was developed, which can be used to accurately predict the flow stress of the studied steel under certain deformation conditions.

Abstract: Shima model and two different kinds of container designs were described. The final geometries of powder metallurgy (PM) preforms were predicted by using finite element method. Several PM Ti-6Al-4V parts were fabricated through a hot isostatic pressing route for comparison with the prediction from the modelling. FEM simulation can be used for shrinkage prediction of powder during HIPing process. The finite element calculations agreed well with the experimental data for shrinkage of the titanium alloy powder under HIPing. The simulation results is helpful to fabricate near-net-shape PM titanium parts.

Abstract: In this paper, the constitutive model of the asphalt pavement permanent deformation is analyzed, which is based on the asphalt pavement permanent deformation. In order to reasonably predict the asphalt pavement permanent deformation, the domestic and foreign research results are thorough investigated. It shows that the nonlinear viscoelastic - elastoplastic constitutive model of Peng Miaojuan improves the defects of various models. This constitutive model comprehensively reflects the characteristics of permanent deformation of asphalt pavement.

Abstract: Green ecological concrete is a new type of building material. It is important to study the relationship of the green ecological concrete between stresses and strains. In the paper, some constitutive models which are suitable to the green ecological concrete are introduced. These models include the linear elastic constitutive model, cauchy model, kuper-gerstle model, constitutive model based on the rheological theory, constitutive model based on plastic fracture theory etc. The constitutive model based on the rheological theory well describes the mechanical properties of the green ecological concrete.

Abstract: The hot deformation behavior of SiC/6168Al composite was studied by means of hot compression tests in the temperature range of 300-450 °C and strain rate range of 0.01-10 s^-1. The constitutive model was developed to predict the stress-strain curves of this composite during hot deformation. This model was established by considering the effect of the strain on material constants calculated by using the Zenter-Hollomon parameter in the hyperbolic Arrhenius-type equation. It was found that the relationship of n, α, Q, lnA and ε could be expressed by a five-order polynomial. The stress-strain curves obtained by this model showed a good agreement with experimental results. The proposed model can accurately describe the hot flow behavior of SiC/6168Al composite, and can be used to numerically analyze the hot forming processes.

Abstract: It is given stress-strain relationships of concrete and reinforcing deformation under high temperatures. These graphs show material features of deformation, look compact and require least defined parameters.

Abstract: A statistical constitutivemodel, which takes account the effect of strain rate, was presented to describethe stress-strain relationship of unidirectional fiber reinforced metal matrixcomposites (UFRMMC). To verify its reliability, tensile tests on a unidirectionalSiC/Al composite wire, were carried out at different strain rates, and thestress-strain curves were obtained. The testing results show that both thestrength and ductility of the composite wire all increase with increasingstrain rate. Simulated stress-strain curves, derived from the constitutivemodel, fit the tested results well, which indicates that the model is valid andreliable.

Abstract: According to the characteristics of mechanical response of titanium alloy, a new constitutive model for ultra-high strain rate deformation in the process of laser shock peening was established. The constitutive model parameters were obtained by the inverse optimization. The propagation characteristic and residual stress-strain distribution under the shock wave were analyzed. The relationship between residual stress and laser power density and laser impacts was indicated via sensitivity analysis of laser parameters. According the above conclusions, the laser shock peening technic on the titanium simulated blades was optimized to obtain the appropriate residual stress distribution. The fatigue test result indicated that the fatigue strength by the optimized technic was improved by 25%, compared to the anterior technic without optimization.