Papers by Keyword: Constitutive Model

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Authors: Yang Bo Guo, Zhi Ping Tang
Abstract: Shock-induced phase transition under intensive impact loading can strongly change the dynamic behavior of materials and wave propagation features. Dynamic constitutive modeling is one of the key problems in this area. We established a 3D dynamic incremental constitutive equation of phase transition with N transforming phases considering pressure, shear stress and temperature based on the Gibbs free energy. We also proposed an evolution equation for the product phase taking account both the over driving force and the growing space. The dynamic stress-strain response predicted by the model for TiNi specimen undergoing martensitic transition fitted the experimental result well, which demonstrates the present model can describe the dynamic deformation behavior of materials during phase transition process under impact loading.
422
Authors: Jun Li, Gui Qiong Jiao, Bo Wang
Abstract: 2D C/SiC ceramic matrix composite (CMC) displays significant damage characteristic coupled with inelastic strain under tension and shear loads, which should be considered in the constitutive model. In this study, a continuum damage mechanics (CDM) model was proposed for this material, in which the process degradation of the material property was described by introducing a set of scalar damage variables, and the damage-coupling effect was also considered. Meanwhile, isotropic hardening theory was applied to form the evolution rule of inelastic strains. The model was then implemented into the UMAT in ABAQUS software and validated by comparison between the simulation and experiment results.
213
Authors: Xue Hao Li, Wei Wang, Zhen Yuan Tian, Wei Ya Xu
Abstract: In this paper, we present a numerical modeling of chemo-mechanical behaviour of sandstone. An internal variable is introduced in this model for the purpose of describing pH effect on elasto-plastic properties. A new chemo-elasto-plastic model is proposed for sandstone. The proposed model is applied to predict material responses in triaxial compression tests of sandstone after soaking in different pH acidic solutions. We concluded with good agreement between numerical simulations and experimental data.
386
Authors: Irene Guiamatsia, Giang Dinh Nguyen
Abstract: Failure develops and propagates through a structure via a complex sequence of competing micro-mechanisms occurring simultaneously. While the active mechanism of surface debonding is the source of loss of stiffness and cohesion, friction between cracked surfaces, upon their closure, acts as a passive dissipation mechanism behind the quasi-brittleness and hence can increase the toughness of the material under favorable loading conditions. In order to numerically study damage propagation, the constitutive response must be able to faithfully capture, both qualitatively and quantitatively, one of the signature characteristic of failure: the energy dissipation. In this paper, we present an interface decohesive model for discrete fracture that is able to capture the apparent enhancement of interfacial properties that is observed when transverse compressive loads are applied. The model allows to seamlessly account for the additional frictional dissipation that occurs when the loading regime involves transverse compression, whether during debonding or after full delamination. This constitutive model is then used to successfully predict the response of realistic engineering structures under generalized loading conditions as demonstrated with the numerical simulation of a fiber push-out test.
649
Authors: Zhong Zhou, Xiao Jun Wang
Abstract: A damage constitutive model of dry/water-saturated granite is proposed within the framework of continuum mechanics and mixture theory, and the model allows for the simulation of the effects of micro-cracks, micro-pores and saturated water. By implementing the model into wave propagation code, one dimensional stain waves in dry granite induced by a rectangular impulsive loading and spherical waves in water-saturated granite due to underground explosion are studied. The simulation results demonstrate the main features of the model, and it is shown that the theoretical model developed is valid for study on the characteristics of stress waves in rock medium.
583
Authors: Wei Guo Li, Xiang He Peng, Wen Li Pi
Abstract: An incremental form of constitutive model is proposed for shape memory alloys using the modified strain based on experimental results and the finite element analysis, taking into account of the laminar microstructure, the thickness of martensite phase lamina and the interaction between the two phases. The pseudoelastisity of NiTi shape memory alloy micro-tube subjected to pure tension and pure torsion are analyzed and compared with the experimental results respectively. It can be seen that the pseudoelastic behavior, especially the stress drop during tension processes, can be well described with the proposed model.
192
Authors: Bin Chen, X. Peng, Xiang Guo Zeng, X. Wu, S. Chen
Abstract: Casting magnesium alloys are heterogeneous materials containing numerous voids. Assuming the voids are spherical, in the present investigation, the evolution equations of the growth and nucleation of the voids have been presented. Combining the evolution equation of the void growth with that of the void nucleation, the evolution rule of the voids was obtained. Based on the void evolution rule a nonclassical elastoplastic constitutive model involving void evolution was developed. The corresponding numerical algorithm and finite element procedure were developed and applied to the analyses of the elastoplastic response and the porosity of casting magnesium alloy. The calculated results show the satisfactory agreement with experiments.
221
Authors: Dong Mei Yang, Xiang Bo Qiu
Abstract: Cyclic loads are commonly encountered in geotechnical engineering; however most constitutive models do not account for the effect that such loads can have on the mechanical behaviour of soils and rocks. This work is concerned with the behaviour of jointed rock and, as the overall mechanical behaviour of jointed rock is usually dominated by the mechanical behaviour of the joints, it is focused on the behaviour of rock joints under cyclic loads. In particular, an extension of the existed constitutive model for cyclically loaded rock joints is presented. Variations of rock joint stiffness in both the normal and the shear directions of loading due to surface degradation are taken into account. The degradation of asperities of first and second order is considered, while a new relation is proposed for the joint stiffness in the normal direction during unloading. Numerical simulation results show good agreement of model predictions with existing experimental results.
2211
Authors: Yan Liu
Abstract: A constitutive model for unsaturated soils is developed. Based on the SFG approach, the deduced LC curve has a smooth transition from saturated state to unsaturated state. The yield stress does not increase with increasing suction monotonically, and thus could reproduce plastic volume change of a slurry soil caused by drying. The model takes account of the effect of saturation, lead to different yield surface for wetting and drying. Soils with same suction but different saturation can have different yield stress. The model is used to simulate exited test data and the predicted curves agree well with the data points.
11
Authors: Xiao Jing Li, Wei Min Yang, Wei Shen Zhu, Shu Cai Li, Ai Hua Sun
Abstract: The jointed rock mass distributed in the nature widely and its mechanical characteristic influenced the stability of the rock engineering badly. The cracks propagated and coalesced each other and macroscopic failure happened. Bolts were a kind of effective reinforcement instrument and they could prevent the cracks from propagating. However, the anchoring mechanism of bolts was not realized clearly and their reinforcement could not be reflected effectively in the numerical simulation yet. Based on the damage mechanics, a constitutive relation and damage equation of anchored jointed rock mass were presented in this paper. With a project application, the model was proved to be feasible one.
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