薄板 Cu–Sn–P 銅合金条材における疲労き裂進展特性

In this study, fatigue crack propagation tests were conducted on thin Cu–Sn–P copper alloy strips, which are required to have both mechanical and electrical reliabilities for use in electric devices. For measuring crack lengths during fatigue tests, an unloaded elastic compliance method is usually used. However, it is difficult to apply this method to thin plates such as 0.15 mm thickness plates used in this study. Therefore, an image processing method and a DC potential difference method were applied to measure the crack length, and the accuracies of crack length measurements were compared. Moreover, the effects of rolling direction on crack growth characteristics were investigated. As a result, the image processing method gave similar results as the visual measurement method in longitudinal direction (LD) specimen, but it is difficult to measure the crack lengths for transverse direction (TD) specimen. The DC potential difference method can measure the crack length at the Region IIa in the fatigue crack propagation, which was difficult to obtain clearly by the visual measurement method, and this method is appropriate for the crack length measurement of thin copper alloy strips. For the effects of the rolling direction on the crack propagation, TD specimens have higher fatigue characteristics than LD specimens in the Region IIa and IIc of the fatigue crack propagation. However, LD specimens have higher fatigue characteristics than TD specimens in the Region IIb of the fatigue crack propagation.