Effect of Anisotropy on Formability

It has been long observed that a material’s anisotropy plays a role in its formability. Initially it was observed in the deep drawing of cylindrical cups, that high normal anisotropy (r-value) led to improved Limiting Drawing Ratios (LDR) and low planar anisotropy (∆r) reduced the effects of earing. Furthermore, Lankford et. al. investigated the effects of anisotropy on asymmetric fender draws, where it was found a range of r-values paired with characteristic magnetic anisotropy curves, predictably lead to good press performance in comparison to materials of similar tensile properties.

Although the phenomena has been obeserved for years, it is not well defined or captured analytically, as many investigations have demonstrated the sensitivity theoretical FLCs have on many material constitutive models(see figure below).

In addition, there are significant challenges in demonstrating the phenomena experimentally, due to the complexities of varying anisotropic characteristics while keeping all other material parameters the same.

Therefore, it is necessary to investigate the problem using a careful, experimental- analytical-numerical approach. Through validation of experimental results, analytical models can be implemented into FEA and used to investigate the effects of r and ∆r on formability.

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