Effects of Strain Rate on the Tensile Deformation of Pure Copper Plate for Busbar Application in Electric Vehicles

This study proposes an empirical relationship between the hardness and tensile strength of a busbar to predict the tensile strength of a bended section in the busbar under different strains and strain rates. Moreover, this study theoretically confirms the contributions of the strain rate to the overall tensile properties of a pure copper (Cu) plate. A commercial pure-grade Cu plate was fabricated through warm rolling from a round billet, and a prototype specimen of a busbar was fabricated using a die-free core bending process. The tensile specimens were subject to a given nominal strain (5-40%) in a strain rate of 4.17 x 10(-5) to 4.17 x 10(-2) s(-1), and their hardness was measured to construct an empirical relationship between their tensile strength and hardness. The empirical relationship could be described as a linear relation, in which the slope increases with increasing strain rate. Additionally, from the empirical relationship, the tensile strength and strain rate applied in the bending process of the busbar prototype could be indirectly evaluated through hardness measurement. The tensile strength of the Cu plate increased with increasing strain rate, and the strain required to reach a specific stress level significantly decreased as the strain rate increased. This increase in the tensile strength and decrease in the tensile strain with increasing strain rate is because while the strength coefficient and strain-hardening exponent increase as the strain rate increases, the strain rate sensitivity decreases.

Automated summary

This study proposes an empirical relationship between hardness and tensile strength of a busbar, and predicts the tensile strength of a bended section using different strains and strain rates. The study also confirms the impact of strain rate on the tensile properties of a pure copper plate. The empirical relationship and hardness measurement can indirectly evaluate the tensile strength and strain rate applied in the bending process of the busbar prototype.