G040033 590MPa級自動車用鋼板を毋材とするスポット溶接継手の局所ひずみ挙動に基づく累積疲労損傷評価手法の検討

Abstract

To establish the fatigue life evaluation method on the spot welded joints under the practical circumstance, random loading fatigue tests were conducted for the joints using a 590 MPa-class automobile base metal. In this study, the fatigue life of the spot welded joints was evaluated using two approaches, which are the external loading and local strain approaches. In the external loading approach, the cumulative damage value satisfied the standard of the automobile industry using the modified fatigue life curve considered with the mean load effect. On the other hand, the cumulative damage value was improved with approximately 20% in maximum compared with the result of the external approach in the case of the local strain approach. To investigate the relationship between the local strain behavior on the surface and near the edge of the slit, the validity of the proposed method should be clarified in future.