Warm forming simulations of Al-Mg alloy sheet using a viscoplastic model and advanced yield functions

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ORIGINAL RESEARCH

Warm forming simulations of Al-Mg alloy sheet using a viscoplastic model and advanced yield functions Qing Zhang 1 & Yong Zhang 1

&

Yuantao Sun 1 & Dateng Zheng 2

Received: 22 February 2020 / Accepted: 4 September 2020 # Springer-Verlag France SAS, part of Springer Nature 2020

Abstract Al-Mg alloys have the properties of anisotropy, temperature softening and strain rate hardening in warm forming conditions. The former could be modeled by an advanced non-quadratic yield function. The rate-dependent characteristic could be modeled by viscoplastic constitutive models. Up to now, few investigations have combined a viscoplastic model with advanced yield functions for warm forming simulation, especially by an implicit finite element (FE) program. In this investigation, the warm forming simulation of AA5182-O alloy was presented via Abaqus/Standard, considering the viscoplasticity and anisotropy. The established viscoplastic model could well reflect the nearly rate-independent initial yield stress of the selected material, and its parameters could be easily calibrated. The numerical implementation of the viscoplastic model associated with Yld2000 and Yld2004 yield functions was carried out using an implicit integration algorithm, and the algorithmic tangent was deduced. Results accordance between the simulation and experiment, including warm uniaxial tension test and warm deep drawing test of AA5182-O, showed the rationality of the established material model and the corresponding implicit implementation scheme. Keywords Aluminum alloy sheet . Temperature- and rate-dependent flow stress . Non-quadratic anisotropic yield function . Finite element simulation . Fully implicit Euler scheme

Introduction In recent years the problem of energy shortage and environmental damage is being more and more obvious. The demand for lightweight materials, especially aluminum alloys, has greatly increased nowadays because of their high strengthto-weight ratios and good corrosion resistance [1]. However, it is difficult for the aluminum alloys to achieve its target shape using traditional stamping process at room temperature in automobile industry. The elongation of aluminum alloys can be improved at elevated temperatures lower than its recrystallization temperature, mainly due to the thermally activated dislocation lines while the change of grain size were not significant [2]. In practice, warm blank holder and die with cool * Yong Zhang [email protected] 1

School of Mechanical Engineering, Tongji University, No. 4800 Caoan Road, Shanghai 201804, People’s Republic of China

2

School of Mechanical and Electrical Engineering, Jinggangshan University, No. 28 Xueyuan Road, Ji’an 343009, People’s Republic of China

punch could most increase the formability of an aluminum alloy [3, 4]. This technology is widely known as (nonisothermal) warm forming of aluminum. Among most of the industrial aluminum alloys, 5xxx series (Al-Mg) alloys have obtained lots of attentions from academy and automotive investigators, due to their