Improving numerical predictability of Springback
To reach a sufficient level of accuracy of springback prediction the following must be taken into account: • evolution of elastic properties of a material during forming; • numerical stabilization technique, variation of friction coefficient, method of unloading and number of integration points through the thickness have a significant influence on springback; • the constitutive model must be able to describe all stages of the Bauschinger effect [1]. Early reyielding may introduce plastic deformations during springback (Figure 3);
A Model of Large-Strain Cyclic Plasticity and its Application to Springback Simulation
This paper presents a framework of constitutive modeling of large-strain cyclic plasticity which describes both the deformation- and texture-induced anisotropies of materials. In this model, the transient Bauschinger effect is described accurately by a new equation of the backstress evolution, and the strain-range and mean-strain dependencies of cyclic strain hardening are expressed by a model of workhardening stagnation. For the description of texture-induced anisotropy, any of widely accepted yield criteria of orthotropic anisotropy is easily incorporated into this model. This paper demonstrates the advantage of the present model in the springback analysis over other classical models by comparing the FE simulations of draw bending with the corresponding experimental results.
Work-hardening behavior of mild steel under cyclic deformation at finite strains
The work-hardening behavior of mild steel under monotonic deformation at large shears and cyclic deformation under a wide range of shear amplitudes (from 3 to 34%) has been experimentally investigated and modeled. The influence of shear amplitude, the effect of the amount of pre-shear and that of pre-cyclic deformation have been studied. Considering the evolution of both polarized persistent dislocation structures and no-polarized low-energy dislocation configurations, a physically-based phenomenological model with four internal variables has been proposed. The model explains the cyclic hardening behavior at large strains, the work-hardening stagnation followed by a resumption of work-hardening under Bauschinger deformation with large pre-strains and under cyclic deformation with moderate strain amplitudes. A good qualitative and quantitative agreement has been achieved between experimental results and model predictions.