材料期刊网

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。

The delayed failure of a steel structure occurs as a result of the stress cor-rosion cracking and hydrogen embrittlement and similar brittle fracture mayalso happen at the site of the fatigue or weld cracks. The prediction of suchfailures has attracted the attention of many investigators. The concepts of J-integral in elastic-plastic mechanics have been introducedto investigate the delayed failure, and the method which can determine thecritical values of J-integral J_(Ic) and the threshold values of stress corrosioncracking J_(Iscc) with a cantilever beam bend specimen having a fatigue crackintroduced artificially has been proposed. The J_(Ic) and J_(Iscc) values for 40CrNiMosteel specimens in a solution of hydrogen sulphide have been determined. Sucha method has been examined: (1) by comparing the J(Ic) values with those obtain-ed from the three-point bend method; (2) by comparing the stress intensityfactor K_I with those which can be determined directly by linear elastic fracturemechanics. Based on the above results, the characteristics of the cantilever beammethod has been discussed.