Multiaxial Constitutive Model Research Articles

An Accurate Prediction of Specific Damping Capacity of TiNi SMA Composite through a Three-Dimensional Constitutive Model

Analytical predictions of the constitutive relations and the damping capacity of TiNi shape memory alloy (SMA) fiber reinforced composite lamina have been presented in this work. The stress induced martensitic (M-phase) and rhombohedral (R-phase) phase transformations of the TiNi SMA fiber are taken into account in the formulation of a multiaxial constitutive model of SMA material. The constitutive relation and the damping capacity corresponding to all the six directions (normal and shear) of the lamina level SMA composite have been derived based on a simple square fiber packing. The predictive capability of the present method is demonstrated by simulating the stress-strain curves under isothermal loading and unloading conditions. The specific damping capacity defined as the ratio of the hysteresis type energy dissipation to the stored strain energy is also numerically computed and furnished.

Multiaxial constitutive modeling of aircraft engine materials

Multiaxial constitutive modeling of aircraft engine materials

Necking of Creep‐Cavitating Bars

This paper is a finite element study of the nonuniform (necking) deformation of creep‐cavitating bars under constant load or constant load with superimposed hydrostatic pressure. The multiaxial constitutive model used in the analysis is a finite strain generalization of a physically based model that incorporates Dyson's micromechanical mechanism of constrained cavity growth. The mechanism governs the phenomenon of coupled grain boundary cavitation and creep in polycrystalline metals at elevated temperatures and within the low‐to‐moderate stress regime. The finite element study, which is based on the principle of virtual work and constitutive model in the convected Lagrangian view, includes calculations of elongation, area, stress, and damage histories. Comparisons of elongation history as well as necked profiles of various cases are carried out. The results predict (1) Transitional behavior of catastrophic necking and brittle fracture to the tendency for diffuse necking and ductile rupture under a constan...

Modelling the multiaxial creep behaviour of alloy 800H

A creep constitutive model, based upon the θ-projection concept, is derived using constant-stress creep curves obtained from miniature creep specimens cut from the walls of Alloy 800H tubing. Initial verification of the model predictions under changing uniaxial stress conditions is made by comparison with a series of constant-load creep results. Two multiaxial constitutive models have been developed based on the θ description of uniaxial behaviour, the first based on a von Mises function of equivalent stress and the second based on the maximum principal stress criterion. These models are used to predict the creep deformation and rupture behaviour of tubular specimens under combined internal pressure and axial load. It is shown that both the multiaxial creep deformation and rupture behaviour of Alloy 800H at 900°C are well predicted by the model based on the maximum principal stress criterion.

An engineering multiaxial constitutive model for nonlinear time-dependent materials

A semi-empirical engineering constitutive law modelling in a unified and continuous manner the main characteristic features of time-dependent materials, including creep, strain softening, relaxation and recovery and tensile brittleness, is briefly reviewed. The model, which contains 13 parameters, is a hereditary single Volterra-type integral representation of material response with stress/strain nonlinearity assumed in the form of a power law, the strain tensor dependent on the entire stress history and the stress-anisotropy/brittleness feature handled by means of a tensile-stress dependent damage function. The capability/versatility of the model is illustrated by examples for several materials.

On the multiaxial behaviour of concrete exposed to high temperature

An attempt is made to formulate a multiaxial constitutive model for concrete in the temperature range up to 800°C. The proposed model can be characterized as isotropic, elastic-viscoplastic-plastic in the compression region. Brittle failure is assumed in the tensile region. The thermal strain increment is assumed to be a function of both temperature and the current stress tensor. This assumption implies that the thermal strain may have deviatoric components. The volumetric thermal strain is used as a scalar damage measure instead of temperature itself. The corresponding softening function is obtained from isothermal, uniaxial tests. Also the elastic properties are taken as functions of the volumetric thermal strain. The response of the model is illustrated and compared with experimental results.