DESIGN OPTIMIZATION OF NONLINEAR STRUCTURES WITH RATE-DEPENDENT AND RATE-INDEPENDENT CONSTITUTIVE MODELS

A design optimization process for non-linear structures with history-d ependent materials modelled using the endochronic constitutive theory is described. This constitutive model does not use the concept of a yi eld surface and describes plastic, viscoplastic and viscoelastic behav iour with one set of equations. Therefore, development of the yield su rface is not traced in numerical calculations, simplifying the impleme ntation of response and sensitivity analyses. The total Lagrangian for mulation incorporating both geometric and material non-linear effects is used. Shape, non-shape and material design parameters are treated s imultaneously using the control volume concept, and static and dynamic problems are treated. A simple structure is optimized for several cas es of static and impact loading conditions to demonstrate the procedur e. Plastic and viscoplastic material behaviour as well as shape and no n-shape design parameters are treated in the example problems.