液体粘滞性裂纹闭合对水溶液中腐蚀疲劳的影响

EFFECT OF LIQUID VISCOSITY INDUCED CRACK CLOSURE ON CORROSION FATIGUE

本文从液体的粘滞流动特性出发，导出了无机盐水溶液引起的裂纹闭合应力强度因子分量的定量表达式，并进行了有关计算．计算结果表明，对于负脉冲波，由液体粘滞性引起的裂纹闭合作用不可忽视．而对非脉冲波形，液体粘滞性作用可忽略不计．文中还对ＧＣ－４（４０ＣｒＭｎＳｉＭｏＶＡ）钢在３．５％ＮａＣｌ溶液中的方波（ＳＱ）与负脉冲波（ＮＰ）腐蚀疲劳裂纹扩展特性进行了试验性对比研究．试验结果表明，△Ｋ＜１５．５８ＭＰａ时，（ｄａ／ｄＮ）ＮＰ＜（ｄａ／ｄＮ）ＳＱ试验结果验证了定量计算结果．

Quantitative expression of crack closure stress intensity factor conlponent (KCL) induced by liquid viscosity of inorganic salt aqueous solution was firstly derived. On the basis of viscous flow behaviour of liquid, the magnitude of KCL of several loading waveshapes was evaluated by using the above mentioned expression. Predicted results show that contribution of crack closure induced by liquid viscosity call not by ignored for negative pulse loading waveshape, while it can be ignored for non-pulse loading waveshape.Comparison of corrosion fatigue crack growth behaviour in 3.5% NaCl solution between negative square waveshape and negative pulse vaveshape was also conducted experimentally for GC-4 (40CrMnSiMoVA)steel. Test results show that (da/dN)NP <(da/dN)SQ as △K<15.58MPa m. which agrees with the quantitative prediction in tendency.