缺口试样疲劳短裂纹行为研究

采用复型方法对中碳结构钢单边钝缺口试样的非穿透和穿透疲劳短裂纹的演化过程进行了研究。结果表明：试样的疲劳破坏主要是由形成于缺口根部的表面短裂纹扩展引起的；形成穿透裂纹以前的短裂纹形成和扩展过程占试样疲劳寿命的７０％以上；线弹性断裂力学不适合于描述表面裂纹和穿透裂纹早期阶段的扩展特性；某些条件下，裂纹初始几何形状的影响是导致穿透裂纹早期扩展出现奇异特性的主要原因。

Study on the Behavior of Short Fatigue Cracks in Notched Specimens

The initiation and growth of part through and through cracks in blunt notched specimens of a medium carbon steel were investigated by a replication technique. It was observed that cracks originate principally from the surface of notch root. The fatigue life of a notched speciment is controlled mainly by the life in which short surface cracks propagate as part through cracks before joining up to form a single through thickness carck. Both part through cracks and through crack show in many aspects a different behavior to that predicted on the basis of long crack properties. The original crack profile may be the principal reason causing the anomalous propagation behavior of the through crack in its early stage.