Fatigue assessment of welded pure copper hairpins using notch stress concept

Abstract

New electrical machines for passenger cars are gaining popularity. These electrical machines which contain copper parts need to generate a magnetic field to generate the propulsion of the machine. Laser welding is a fast and an effective joining process for the copper parts. In order to determine the lifetime of the copper parts, it is necessary to assess the fatigue behavior of the laser weld seam. Current guidelines for fatigue assessment do not include copper parts or copper weld seams, hence a fatigue concept must be derived. This proceeding examines the applicability of the notch stress concept with a reference radius of 0.05 mm for copper weld seams and provides a complex and a simplified way of modeling the weld seams. The presented concept takes the geometry of the weld seams and the fracture area surfaces into account. This leads to stress results with a low scatter range and a flat slope of the S-N curve. Furthermore, the results indicate that the notch stresses are transferable.