Abstract
Earings appear easily during deep drawing of cylindrical parts owing to the anisotropic properties of materials. However, current methods cannot fully utilize the mechanical properties of material, and the number of earings obtained differ with the simulation methods. In order to predict the eight-earing problem in the cylindrical deep drawing of 5754O aluminum alloy sheet, a new method of combining the yield stress and anisotropy index (r-value) to solve the parameters of the Hill48 yield function is proposed. The general formula for the yield stress and r-value in any direction is presented. Taking a 5754O aluminum alloy sheet as an example in this study, the deformation area in deep drawing is divided into several equal sectorial regions based on the anisotropy. The parameters of the Hill48 yield function are solved based on the yield stress and r-value simultaneously for the corresponding deformation area. Finite element simulations of deep drawing based on new and existing methods are carried out for comparison with experimental results. This study provides a convenient and reliable way to predict the formation of eight earings in the deep drawing process, which is expected to be useful in industrial applications. The results of this study lay the foundation for the optimization of the cylindrical deep drawing process, including the optimization of the blank shape to eliminate earing defects on the final product, which is of great importance in the actual production process.
Highlights
1 Introduction The Von Mises yield function is the most widely used isotropic yield function for its simple mathematical expression. It is convenient for use in theoretical derivation and finite element (FE) calculation
After several repetitions of rolling and heat treatment, sheet metals, which have a texture formed by the fibrous structure and preferred orientation of crystallization, exhibit obvious anisotropy [1,2,3,4]
The anisotropic behavior of the 5754O aluminum alloy sheet is discussed and FE simulations of the deep drawing test are performed based on different yield functions to predict the earing phenomenon
Summary
The Von Mises yield function is the most widely used isotropic yield function for its simple mathematical expression. The famous plane stress yield function, Yld2000-2d, was proposed by Barlat et al [16] to describe the anisotropic plastic deformation of sheet metals, especially for aluminum alloy. The number and shape of the earing defects in deep drawing cannot be described accurately by the Hill yield function if the parameters are solved with yield stresses or r-values alone [1, 33]. The anisotropic behavior of the 5754O aluminum alloy sheet is discussed and FE simulations of the deep drawing test are performed based on different yield functions to predict the earing phenomenon. The proposed method that uses the Hill yield function to predict the formation of eight earings in the deep drawing of 575O aluminum alloy sheet is validated using experimental results. (2) Eq (2) is appropriate for the FE simulation with shelltype elements in which only the plane stress is considered, but is not appropriate for that with solid elements where the stress along the normal direction should be considered
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