Viscoplastic models for high temperature applications

The information specific to the material deformation behavior in stress ana lyses of structures and manufacturing processes is contained in the materia l model or the constitutive equation. In the past these models had to be li near and simple to perform the stress analyses economically. Large safety ( ignorance) factors made up for the simplicity. The availability of inexpens ive computing power and the demands of society for reliability and safety r equire an improvement of stress analyses by using new and realistic constit utive equations of nonlinear, inelastic behavior of metals and their alloys . Presently used nonlinear models such as plasticity and creep theory are b y far the oldest link in the stress analysis package. Test results obtained with modern mechanical testing machines and theoretical developments durin g the past several decades suggest that viscoplastic models using state var iables are much-improved models. It is recommended that these models be car efully reviewed, further developed when needed and recommended by interdisc iplinary, technology specific committees of materials, mechanics, testing a nd computing expects. Rather than having databases with material constants, databases containing 'the constitutive model' for different alloys and ass ociated constants should be established. The analyst would call up 'the mod el', say, for annealed stainless steel and load it into the stress analysis program. (C) 1999 Elsevier Science Ltd. All rights reserved. reserved.