Hydrostatic stress

About: Hydrostatic stress is a research topic. Over the lifetime, 1568 publications have been published within this topic receiving 37773 citations.

Model of viscoplasticity for transversely isotropic inelastically compressible solids

Abstract: A transversely isotropic, viscoplasticity model is formulated as an extension of Bodner's model. Account is made of inelastic deformation that can occur in strongly anisotropic materials under hydrostatic stress. The extended model retains the simplicity of the Bodner model, particularly in the ease with which the material constants are determined. Although the proposed model is based on a scalar state variable, it is capable of representing material anisotropy under the assertion that history-induced anisotropy can be ignored relative to strong initial anisotropy. Physical limitations on the material parameters are identified and discussed. The model is applied to a W/Cu metal matrix composite; characterization is made using off-axis tensile data generated at NASA Glenn Research Center.

Modeling the Nonlinear, Strain Rate Dependent Deformation of Shuttle Leading Edge Materials with Hydrostatic Stress Effects Included

Abstract: An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.

Concrete Subjected to Triaxial Stress States: Application to Pull-Out Analyses

Abstract: This paper presents the application of three-dimensional (3D) -constitutive models for concrete formulated in the framework of plasticity theory to structural analyses of anchor devices. For this purpose, two commonly employed concrete material models are considered. The first model, the extended Leon model, is based on one yield surface for the description of compressive and tensile failure of concrete. The second material model is a multisurface plasticity model consisting of three Rankine yield surfaces and a Drucker-Prager yield surface. The predictive capability of the models is demonstrated by means of anchor devices, commonly employed in structural engineering for the connection of steel and concrete members. Such devices induce strongly nonuniform triaxial stress states in the surrounding concrete, ranging from tensile, overcompressive, to confined compressive stress states. In the vicinity of the anchor head, even nearly hydrostatic stress states may occur. The numerical simulations on the basis of the employed 3D material models for concrete give insight into the load-carrying behavior of the investigated anchor devices. Two headed studs characterized by different shapes of the anchor head and an undercut anchor are considered. Comparison of the peak loads and failure modes of the respective anchor device predicted by the numerical models with experimental data highlight the strength and weakness of the employed material models. It is shown that some load cases may lead to rather large differences in peak load depending on the choice of material model. These differences are based on the individual properties of the constitutive models for concrete and, hence, detailed knowledge of the model under consideration is essential for giving accurate estimates of the peak load of the anchor device and the failure mode of concrete.