环境介质与应力比对300M钢腐蚀疲劳裂纹萌生寿命的影响

 研究了３．５％ＮａＣｌ溶液（ＳＷ）、蒸馏水（ＤＷ）和空气（ＡＩＲ）３种环境和Ｒ＝０．１、０．５两种应力比对３００Ｍ钢疲劳裂纹萌生寿命（ＦＣＩＬ）的影响。结果表明,腐蚀环境显著降低疲劳强度和ＦＣＩＬ。在同一等效应力幅（Δσｅｑｖ）水平下,３种环境中的ＦＣＩＬ（Ｎｉ）的大小依次为（Ｎｉ）ＡＩＲ＞（Ｎｉ）ＤＷ＞（Ｎｉ）ＳＷ。在同一等效应力幅Δσｅｑｖ水平下,３００Ｍ钢在ＳＷ小的腐蚀疲劳（ＣＦ）裂纹萌生寿命（ＣＩＬ）随应力比的提高而提高。义小给出了Ｎｉ与Δσｅｑｖ,ＣＦ强度损失因子Ｄｓ与Ｎｉ,ＣＦＣＩＬ损失因子ＤＬ与Δσｅｑｖ等的关系人达式。

EFFECT OF ENVIRONMENT MEDIUM AND STRESS RATIO ON CF CRACK INITIATION LIFE FOR 300M STEEL

he effects of three environments of3.5% NaCl solution(SW), distilled water(DW)and air(AIR)and two stress ratios of R=0.1 and 0.5 on corrosion fatigue crack initiation life(FCIL)are experimentally investigated in the present study ior 300M steel,an ultra-high strength steel used in airplane structure. Experimental results show that the two corrosive envi- ronments SW and DW used in the present study, without exception,significantly reduce the fa- tigue strength and FCIL of 300M steel, and when the values of equivalent stress amplitude(Δσeqv)in test are identical to each other for the above mentioned three environments, the se- quence of FCIL(Ni)indecreasing order of magnitude is that(Ni)AIR>(Ni)DW>(Ni)SW. When the values ofequivalent stress amplitude are identical for the ahove mentioned ratios,the CF crack initiation life of 300M steel in SW increases as increasing stress ratio. The concepts of FCIL loss factor DL and Fatigue crack initiation strcngth loss factor Ds induced by corrosive environ- ments are also introduced in this paper Furthermore,several quantitative expressions of Ni vs Δσeqv,Ds vs Ni and DL vs Δσeqv are also given in this paper