Study on the Behavior of Short Fatigue Cracks in Notched Specimens
Wu Zhixue, Sun Xunfang
(Southwest Jiaotong University, Chengdu 610031, China)

Abstract: 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 throughª²crack in its early stage.
Keywords: medium carbon steel, fatigue, carck initiation , crack propagation.