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在工程上,经常由于应力腐蚀开裂和氢脆引起中强度钢结构件发生滞后破坏。这类脆断往往从结构件中预先存在的疲劳或焊接裂纹处开始,因此,运用传统的光滑试样的检验方法不能反映这类破坏的特点。本文将弹塑性断裂力学中的J积分概念用于滞后破坏的研究,提出用带预制疲劳裂纹的悬臂弯曲试样测定J积分的临界值J_(Ic)和应力腐蚀开裂阈值J_(Iscc)的方法。测定了40CrNiMo钢的J_(Ic)值及其在硫化氢水溶液中的J_(Iscc)值。通过和三点弯曲方法测定的J_(Ic)值的对比,以及和满足线弹性条件时直接测定的应力强度因子K_I值的对比,说明这种方法的可靠性。最后,对悬臂弯曲方法的特点进行了讨论。
In engineering, often due to stress corrosion cracking and hydrogen embrittlement caused by the lag damage to the steel structure. These types of brittle fractures often start with fatigue or weld cracks pre-existing in the structural members. Therefore, the test method using conventional smooth specimens does not reflect the characteristics of such damage. In this paper, the concept of J-integral in elasto-plastic fracture mechanics is applied to the study of hysteresis failure. The method of determining the critical value J_ (Ic) of J integral and the stress corrosion cracking threshold J_ (Iscc) using a cantilever bending specimen with prefabricated fatigue crack . The J_ (Ic) value of 40CrNiMo steel and its value of J_ (Iscc) in hydrogen sulfide solution were measured. The reliability of this method is demonstrated by comparing the value of J_ (Ic) determined by the three-point bending method with the K_I value of the stress intensity factor determined directly when the linear elastic condition is satisfied. Finally, the characteristics of cantilever bending method are discussed.