A new anisotropic elasto-plastic model with degradation of elastic modulus for accurate springback simulations

Abstract

Springback, a phenomenon that is governed by elastic strain recovery after the removal of forming loads, is of great concern in sheet metal forming. There is no doubt that in this regard, physically reliable numerical modelling of the forming process and predictions of springback obtained by respective computer simulations are crucial for controlling this problem. Unfortunately, by currently available approaches, springback still cannot be adequately predicted in general. In this paper, a new constitutive model is proposed which considers simultaneously sheet anisotropy, damage evolution and strain path-dependent stiffness degradation during sheet metal forming. For parameter identification of the built constitutive model, a particular experimental procedure is developed and an optimization procedure is employed to solve the inverse problem that arises. The proposed approach to constitutive modelling is validated in the end by a simulation of the springback in the formed HSS steel sheet. The simulation results, which prove to be in good agreement with the experimental ones, lead to the conclusion that accurate modelling only of anisotropic yielding is not enough to accurately predict the springback phenomenon; the constitutive model should also include the strain path-dependent change of the elastic moduli.

Effect of bending on radial distribution density, MFA and MOE of bent bamboo

“…5 c), which is likely due to microstructural changes under bending stress. For example, fiber orientation and degree of crystalline orientation would increase during tension, while decrease during compression 34 , 42 , which is similar to an increase and a decrease in MOE during the tension and compression phase, respectively 43 , 44 . The springback in bamboo is caused by multiple factors: (1) uneven distribution of stress along cross section (there is a higher stress in the outside half tube wall than the inside) 41 ; (2) the higher MOE in the outside tube wall than the inside; and (3) the higher MOE in the first half bamboo tube wall than the latter half.…”

Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

“…The inelastic strain released from a plastic deformation state is a major source of additional strain recovery [ 24 ]. The elastic modulus of most metals decreases after plastic deformation [ 25 , 26 ]. The diminution of the elastic modulus during plastic deformation can be more than 10% of the initial value after 5% plastic strain [ 27 , 28 ].…”

“…Similar trends of decreasing elastic modulus with increasing pre-strain during cyclic tension–compression deformation have also been observed in cyclic tests [ 27 ]. As suggested by many authors, the elastic modulus varies with the plastic strain [ 25 – 27 , 29 – 32 ].…”

A Method for Optimal Blank Shape Determination in Sheet Metal Forming Based on Numerical Simulations

“…Nowadays, this can be done virtually, based on computer simulations of the technological process under consideration, see, for example, [1] to [4]. Besides choosing a proper numerical approach and computational technique [5] and [6], advanced constitutive modelling [2], [4], [7] and [8] and proper material characterisation [4] and [7] to [9] is crucial for the computer simulation to be physically objective and trustful. Although, in contrast to direct analysis, a Finite Element (FE) inverse analysis approach, see [10] to [14], could possibly be used in sheet metal forming simulation in order to reduce the computer time consumption, such an approach is not recommended because it results in less accurate strain-stress state determination.…”