铝合金中的腐蚀疲劳裂纹扩展

Corrosion Fatigue Crack Propagation of Aluminium Alloys

提出了一个新的腐蚀疲劳裂纹扩展公式，并利用铝合金的实验结果对其进行了验证。

Althougth several formulas of corrosion fatigue crack propagation rate(CFCPR) have been reported, most of them arc only applicable in the intermediate rCa;ion of crack Dropagation(da/ dNas 10-8 to 10-6m/cycle).Abstract: In this paper, a new ed)rcssion of CFCPR is proposed on 1.he basis of a modified static fracture model developed in Ref.[4] and a linear supcrposition model in In Ref.[6]. The existing test results of aluminium alloys in dry argon, laboratory air, synthetic seawatcr and sump tank water arc analysed and used to check the validity of the new expression. It is shown that this expression can formulate well the CFCPR of aluminium alloys in both intermediate region and ncar-threshold region under various environment-loading combinations. The analytic results indicatic thttt, during the crack propagation in the corrosive environments, there is the competition between the cnviroment-assisted-cracking(EAC) and the crack-closure induced by the corrosion product cxistinjl in the crack wake. The corrosive cnviromcnt and low frequency, which enhance both the EAC aled the crack--closure, can increase the CFCPR in the intermediate region (because the effect of EAC d(3minatcs), but decrease the CFCPR in the near threshold region. where the crack-closure becomes controling. Although stress ratio has a remarkable effect on the near-threshold crack propagation,this c'ffect will be wcakcncd as AK level is raised.