Forming limit prediction using a self-consistent crystal plasticity framework: a case study for body-centered cubic materials

A rate-dependent self-consistent crystal plasticity model was incorporated with the Marciniak-Kuczyński model in order to study the effects of anisotropy on the forming limits of BCC materials. The computational speed of the model was improved by a factor of 24 when running the simulations for several strain paths in parallel. This speed-up enabled a comprehensive investigation of the forming limits of various BCC textures, such as γ, σ, α, η and ϵ fibers and a uniform (random) texture. These simulations demonstrate that the crystallographic texture has significant (both positive and negative) effects on the resulting forming limit diagrams. For example, the γ fiber texture, which is often sought through thermo-mechanical processing due to a high r -value, had the highest forming limit in the balanced biaxial strain path but the lowest forming limit under the plane strain path among the textures under consideration. A systematic investigation based on the results produced by the current model, referred to as 'VPSC-FLD', suggests that the r -value does not serve as a good measure of forming limit strain. However, model predictions show a degree of correlation between the r -value and the forming limit stress.