Modelling of Rate-dependent Anisotropic Material Behavior by Plasticity Theory

Const i tut ive equations appropriate t o the rate-dependent p l a s t i c deformation of an i so t rop ic mater ials a re developed. The method used i n the der iva t ion cons i s t s of the inclusion of the appropriate r a t e of deformation var iab le i n the func t iona l d e f i n i t i o n of the y ie ld surface and the requirement t h a t the s t a t e p i n t remain on t h i s y ie ld sur face during an increment of p l a s t i c s t r a i n .