TEXTURE DEVELOPMENT AND PLASTIC ANISOTROPY OF BCC STRAIN-HARDENING SHEET METALS

A Taylor-like polycrystal model is adopted here to investigate the pla stic behavior of body centered cubic (b.c.c.) sheet metals under plane -strain compression and the subsequent inplane biaxial stretching cond itions. The < 111 > pencil glide system is chosen for the slip mechani sm for b.c.c. sheet metals. The {110} < 111 > and {112} < 111 > slip s ystems are also considered. Plane-strain compression is used to simula te the cold rolling processes of a low-carbon steel sheet. Based on th e polycrystal model, pole figures for the sheet metal after plane-stra in compression are obtained and compared with the corresponding experi mental results. Also, the simulated plane-strain stress-strain relatio ns are compared with the corresponding experimental results. For the s heet metal subjected to the subsequent in-plane biaxial stretching, an d sheer, plastic potential surfaces are determined at a given small am ount of plastic work. With the assumption of the equivalence of the pl astic potential and the yield function with normality flow, the yield surfaces based on the simulations for the sheet metal are compared wit h those based on several phenomenological planar anisotropic yield cri teria. The effects of the slip system and the magnitude of plastic wor k on the shape and size of the yield surfaces are shown. The plastic a nisotropy of the sheet metal is investigated in terms of the uniaxial yield stresses in different planar orientations and the corresponding values of the anisotropy parameter R, defined as the ratio of the widt h plastic strain rate to the through-thickness plastic strain rate und er in-plane uniaxial tensile loading. The uniaxial yield stresses and the values of R at different planar orientations from the polycrystal model can be fitted well by a yield function recently proposed by Barl at et al. (1997b). (C) 1998 Elsevier Science Ltd. All rights reserved.