2005 年 2005 巻 50 号 p. 17-22
High durability is required for automotive engine valve springs. To ensure the performance of springs, it is necessary to evaluate and measure the residual stress distribution on surface and inner direction of the spring. Theoretically, it is used to be treated that the residual stress of a shot-peened material surface is uniform. However, the shape of a coil spring causes various peening angles corresponding to the surface location, so the uneven shot peening angles may leads to a non-uniform residual stress on the coil spring surface. On the other hand, an analysis method of non-liner 2θ-sin2 φdiagram (or φ-splitting analysis) is well known to directionally deformed material such as ground, planed or rolled materials. Recently, an φ-splitting analysis has been reported for the shot-peened materials. In this study, the residual stress distribution of slant shot-peened spring material was measured and, φ-splitting (non-linear 2θ-sin2 φdiagram) was studied in the view of chemical compositions and microstructures. As a results, the extent of φ-splitting was mainly affected by the distribution of carbide particles, not the kind of carbide particles itself.