【摘要】 根据Barenblatt的设想,接近裂纹端部的裂纹面间应有内聚应力,应力峰值即为内聚强度。本文采用Schmidt和Woltersdorf考虑内聚应力影响的裂端应力场,在基于立方晶胞因为有氢原子存在而发生四方变形的假设下,建立了氢原子在裂端区的漂流模型。模型指出氢原子可从裂纹面漂流到裂端前的一个小区域,降低了该区域的应变能密度和晶体平面间的内聚强度。研究结果还发现,当变形的晶胞是沿[100]方向延长,且裂纹面是在(100)平面时,裂端有最大的氢浓度,同时内聚强度也减少最多;即氢引致的开裂平面是最可能发生在(100)平面系。讨论中,将模型的预测与实验结果进行了比较,并把模型推广到氢引致晶间开裂的情形。更多还原

【Abstract】 According to the Barenblatt’s concept, the cohesive stress exists between the crack surfaces very near the tip, and the maximum value of the stress is just equal to the cohesive strength of the crystal planes that are open to form the crack surfaces. Taking into account the effect of the cohesive stress, the stress fields derived by Schmidt and Woltersdorf are adopted in this study. A drift flow model is then proposed under the assumption of the tetragonal distortion of a cubic unit cell caused by containing one hydrogen atom and under the action of the stresses on hydrogen atoms. The model indicates that hydrogen atoms can flow from crack surfaces to the small region just ahead of the crack tip and reduces the strain energy density and the cohesive strength between the crystal planes thereby. The model suggests that the hydrogen-induced cleavage failure occurs more likely on the {100} -planes for bcc structure. The prediction of this model compares well to the result of experimental observation. Finally the possibility to extend the model to the cases of hydrogeninduced intergranular cracking is discussed.更多还原