温度与应力比对6061铝合金疲劳裂纹扩展行为的影响

Effect of temperature and stress ratio on fatigue crack growth behavior of 6061 aluminum alloy

为了研究温度与应力比对航空铝合金疲劳裂纹扩展行为的影响,利用电液伺服疲劳试验机对6061铝合金材料开展了不同温度(室温、-70、150℃)、应力比(0.1、0.5)条件下的疲劳裂纹扩展速率试验,获得不同条件下的疲劳裂纹扩展速率曲线,揭示温度与应力比对疲劳裂纹扩展的影响规律。结果表明,在相同应力比下,室温与高温150℃下的疲劳裂纹扩展速率曲线(da/dN-ΔK)基本一致,低温-70℃下的疲劳门槛值与疲劳裂纹扩展速率明显提高,这表明低温环境下6061铝合金材料具有较高的抗疲劳裂纹扩展性能;在相同温度下,随着应力比的增大,疲劳门槛值降低,疲劳裂纹扩展速率升高。讨论了温度与应力比对疲劳裂纹扩展行为影响的可能原因。

Fatigue crack growth rate tests were carried out in 6061 aluminum alloy under different temperatures(room temperature,-70,150 ℃) and stress ratios(0.1,0.5) by electro-hydraulic servo fatigue testing machine,to investigate the influence of temperature and stress ratio on the growth of fatigue crack.The fatigue crack growth rate curves(da/dN-ΔK) under different conditions were obtained.The results indicated that the fatigue crack growth rate curves at room temperature and high temperature(150 ℃) were basically the same under the same stress ratio,while the fatigue threshold value and fatigue crack growth rate at low temperature(-70 ℃) significantly increased,which suggested that this alloy possessed high fatigue crack growth resistance under low temperature environment.When the temperature remained unchanged,as the stress ratio increased,the fatigue threshold value decreased and the fatigue crack growth rate increased.The possible reason for the influence of temperature and stress ratio on the fatigue crack growth behavior was discussed.