Temperature and Strain Rate Dependent Anisotropic Plastic Deformation Behavior of AZ31B Mg Alloy

In the present study, the plastic deformation of commercially available AZ31B alloy at different temperatures (300K-473K) and strain rates (0.1s-1-0.01s-1-0.001s-1) under uniaxial tensile test has been carried out. Three different sheet orientations, viz., rolling direction (RD), transverse direction (TD), and 45° to rolling direction have been used. The outcomes of the experiments have demonstrated a temperature-dependent relationship between mechanical properties such as yield strength, ultimate tensile strength, and percentage elongation. The yield strength and ultimate tensile strength has decreased by 28.58% and 31.03% respectively as temperature increased from 300 K to 473 K. At elevated temperature (473 K) the material has exhibited highest ductility (64.88%) as compare to 300 K. The hardening exponent has been found to decrease with increasing temperature. The flow stress behaviour has been predicted using work hardening models such as the Hollomon and Ludwik. Two-stage work hardening behavior has been observed at all the temperatures. According to statistical parameter comparison, Ludwik equation prediction capability of correlation coefficient (0.9959) has been found to be best in agreement with the experimental results

Formability analysis of pre-strained AA5754-O sheet metal using Yld96 plasticity theory: Role of amount and direction of uni-axial pre-strain

Automotive industries are very much interested in formability of different pre-strained aluminum alloy sheets in the context of multistage stamping to fabricate complex components. In the present work, different uni-axial pre-strains of 6.4% and 12.2% were induced in AA5754-O aluminum alloy both along rolling direction (RD) and transverse direction (TD). The true stress-strain response, limiting dome height (LDH) and strain based forming limit diagram (ε-FLD) of as received and all pre-strained materials were evaluated experimentally. The anisotropy constitutive material model was developed using the Yld96 plasticity theory in-conjunction with the Hollomon isotropic hardening law to predict the yield strength evolution of the pre-strained materials. Also, it was found that the limiting strains in ε-FLD shifted significantly depending on the amount and direction of uni-axial pre-strain. Hence, the limiting strains of the as-received materials were transposed into stress space to estimate the stress based forming limit diagram (σ-FLD) using the anisotropy constitutive material model. Further, the dynamic shifts of ε-FLDs of four different pre-strained materials were predicted by successfully decoupling the σ-FLD of as-received materials within root mean square error of 0.008. Finite element models of both uni-axial pre-straining and subsequent LDH tests were developed, and the forming behavior of the pre-strained materials were predicted implementing the Yld96 plasticity model and estimated σ-FLD. It was found that LDH was significantly influenced by the amount of pre-strain, and the maximum thinning location shifted close to pole in the case of 12.2% pre-strained materials. However, the effect of uni-axial pre-strain direction on both LDH and maximum thinning location in AA5754-O material was very negligible

FE modeling of a complete warm-bending process for optimal design of heating stages for the forming of large-diameter thin-walled Ti–6Al–4V tubes

Warm rotary draw bending (WRDB) of large-diameter thin-walled (LDTW) Ti–6Al–4V tube is a multi-nonlinear thermo-mechanical coupled process. Due to the high-cost, energy-wasting and long-term, the traditional physical experiments based on “trial and error” are no longer suitable for the WRBD process. Considering the non-uniform local heating and multi-tool constraints, a thermal–mechanical coupled 3D FE model of complete WRDB process for LDTW Ti–6Al–4V tube is established on ABAQUS as heating-bending-unloading three-stage. The FE models could predict the overall temperature distribution, describe thermo-mechanical bending deformation considering a modified Johnson–Cook model, and simulate the heating-bending-springback-cooling process. On that basis, the temperature distributions on both tube and dies under various heating schemes are compared, and the optimal heating scheme is determined on the basis of forming quality and efficiency. Combined with the experiments of WRDB, the optimal heating scheme and the established FE models are verified. In conclusion, the FE simulation provides a replacement of physical experiment and a convenient method of deformation prediction for WRDB of LDTW Ti–6Al–4V tube