低温下LY12CZ铝合金的疲劳裂纹扩展

FATIGUE CRACK GROWTH OF LY12CZ ALUMINIUM ALLOY AT LOW TEMPERATURES

本文试图提出一种近似估算LY12CZ铝合金疲劳裂纹扩展速率的方法。实验结果表明,降低温度使LY12CZ铝合金的疲劳裂纹扩展速率下降,而其在中区(da/dN=10^(-8)～10^(-6)m/cycle)的疲劳裂纹扩展机制则保持以条带机制进行。不同温度下的疲劳裂纹扩展速率实验数据可用公式da/dN=B(⊿K-⊿K_(th))~2拟合。根据分析讨论,给出了系数B和门槛值⊿K_(th)的估算方法及低温疲劳裂纹扩展速率表达式。利用该表达式,在确定了室温的⊿K_(th)和疲劳极限σ_1之后,即可根据拉伸性能近似估算LY12CZ铝合金的低温疲劳裂纹扩展速率。

An attempt was made in this paper to offer an approximate approach for predictionof fatigue crack growth (FCG) rate at low temperatures. The experimental results show that the FCG rate decreases with drop of temperature, whereas the crack growth mechanism in the intermediate rate region (da/dN = 10-8 to 10-8m/cycle) of FCG is mainly the formation of ductile striation. A good fit to the test dat? of the FCG rate in both room and low temperatures is given by the formula, da/dN = B(ΔK - ΔKth)2. The method to estimate the values of the coeffiecient B and the thres hold ΔKth, as well as the expression for the low temperature FCG rate, are offered. By means of the expi ession proposed, the FCG rate of LY12CZ aluminium alloy at low temperatures can be approximately predicted from the tensile properties if the values of ΔKth and endurance limit Δ-1, have been predetermined.