腐蚀疲劳裂尖材料损伤研究

金属环境断裂过程依赖于材料，应力与介质参数间的复杂交互作用，这些交互作用的澄清是实现材料断裂控制的重要基础，而裂纹尖端单元损伤过程的研究则是联接微观机制与宏观断裂规律的桥梁。通过对钝化和活化典型腐蚀体系下恒速长大腐蚀疲劳裂纹受力学与电化学参数扰动后的扩展动力学响应规律的系统研究，并结合多种其它分析手段，考察了不同腐蚀因素对裂尖材料的损伤作用机制。在实验基础上，对腐蚀导致裂纹闭合变化，裂纹扩展过载延

RESEARCH ON MATERIAL DAMAGE AT CRACK TIP OF CORROSION FATIGUE

The environmental cracking susceptibility depends upon complex interactions between material, stress and environmental parameters. An important aspect for the control of this type of material failure is to clarify the processes of these complex interactions. The investigation of damage processes of crack tip material during cracking is a bridge to connect the micro-mechanism and the macroscopical behaviours of environmental cracking.In this paper, the response of the corrosion fatigue crack propagation after an application of single overload or a sudden jumping of applied potential has been examined under the constant stress intensity factor range control for low alloy steels and stainless steel in sodium chloride solution. Combining other techniques, the effect of different corrosion factors on damage processes of crack tip material was studied.Based on the experimental results, the change of crack closure by corrosion, theretardation effect of single overload, the behaviour of plastic deformation of crack tip material, the behaviour of hydrogen atoms at crack tip and the effect of different kinds of hydrogen atoms on the crack tip material damage have been discussed. Some important conclusions were obtained, for exemple, it was found that the corrosive wear of crack surfaces caused a change of crack closure behaviour, resulting in an important effect on the fatigue process under varied stress amplitude, the different effects on fatigue damage were indicated for the surface adsorbed hydrogen, stress and dislocation trapped hydrogen atoms.