腐蚀疲劳裂纹扩展微机辅助测试与分析

 腐蚀疲劳裂纹扩展机制甚为复杂。就钢来说，往往呈现应力腐蚀类型的裂纹扩展机制，裂纹扩展速率受阳极溶解造成的裂尖钝化，裂缝闭塞电池效应，裂纹的宏微观分叉，氢致脆化，腐蚀产物造成的闭合效应等诸多因素的影响，反映在裂纹扩展速率曲线上，就是da/dN的波动较大。因此要求理想的腐蚀疲劳裂纹扩展微机测试系统应既能给出供工程寿命估算的，反映裂纹扩展速率总体趋势的da/dN}OK曲线，又能给出有助裂纹扩展机制 研究的，反映裂纹扩展速率随机波动特征的da/dN}}K曲线。

MICROCOMPUTER AIDED MEASUREMENT AND ANALYSIS OF CORROSION FATIGUE CRACK PROPAGATION

A new microcomputer aided system (MAS) developed in our laboratory for measuring fatigue crack propagation (FCP) rates in corrosive environments is briefly introduced and some parts of algorithms for data processing are given. The MAS mentioned above has been successfully applied to measuring and processing the FCP rates of 40CrMnSiMoVA high strength steel in 3.5% NaCl solution. The test results and analysis show that the FCP rates curve in 3.5% NaCl solution comprises four phases, including a plateau. The existence of the plateau may be due to the process competition model of FCP in corrosive enviroment. The fracture stress intensity factor range in 3.5% NaCl solution is much lower than that in air because of the hydrogen pens-tration. It means that the effect of hydrogen embrittlement is serious.