Constitutive Behavior and Deep Drawability of Three Aluminum Alloys Under Different Temperatures and Deformation Speeds
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JMEPEG DOI: 10.1007/s11665-017-2837-x
Constitutive Behavior and Deep Drawability of Three Aluminum Alloys Under Different Temperatures and Deformation Speeds Sudhy S. Panicker, K. Sajun Prasad, Shamik Basak, and Sushanta Kumar Panda (Submitted March 2, 2017; in revised form May 8, 2017) In the present work, uniaxial tensile tests were carried out to evaluate the stress–strain response of AA2014, AA5052 and AA6082 aluminum alloys at four temperatures: 303, 423, 523 and 623 K, and three strain rates: 0.0022, 0.022 and 0.22 s21. It was found that the Cowper–Symonds model was not a robust constitutive model, and it failed to predict the flow behavior, particularly the thermal softening at higher temperatures. Subsequently, a comparative study was made on the capability of Johnson–Cook (JC), modified Zerilli–Armstrong (m-ZA), modified Arrhenius (m-ARR) and artificial neural network (ANN) for modeling the constitutive behavior of all the three aluminum alloys under the mentioned strain rates and temperatures. Also, the improvement in formability of the materials was evaluated at an elevated temperature of 623 K in terms of cup height and maximum safe strains by conducting cylindrical cup deep drawing experiments under two different punch speeds of 4 and 400 mm/min. The cup heights increased during warm deep drawing due to thermal softening and increase in failure strains. Also, a small reduction in cup height was observed when the punch speed increased from 4 to 400 mm/min at 623 K. Hence, it was suggested to use high-speed deformation at elevated temperature to reduce both punch load and cycle time during the deep drawing process. Keywords
aluminum alloys, ANN, constitutive modeling, deformation speed, flow stress, warm deep drawing
1. Introduction The formability studies of aluminum alloys are of special interest in fabricating light weight structures for applications in automotive, ship building, aerospace and packaging industries due to their high strength-to-weight ratio and corrosion resistance (Ref 1). The warm forming technology has been investigated as an alternative to conventional forming process especially for stamping low formable aluminum alloy sheets using lower press tonnage (Ref 2, 3). The total elongation till fracture increased up to 300%, while the aluminum alloys deformed under uniaxial tensile mode at temperatures within 473-623 K and low strain rates (Ref 4, 5). This increment was attributed to the increase in the post-uniform elongation due to the exponential rise in strain rate sensitivity of the material (Ref 6). It was reported that the actual three-dimensional stamping of aluminum alloy sheets at elevated temperatures produced a drastic improvement in forming limits, deep drawability and final cup heights (Ref 711). The Al-Mg alloys showed very low, sometimes negative strain rate sensitivity at room temperature due to the activation of dynamic strain aging (DSA) (Ref 12). The stress–strain response of aluminum alloy with the hardening and softening mechanisms is influenced by variation in temperat
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