Al-12Si-CuNiMg铸造铝硅合金在多轴加载下的疲劳性能

Fatigue Properties of Al-12Si-CuNiMg Cast Aluminum Silicon Alloy under Multi-axial Loading

在等效应力幅160,150,140MPa下,对Al-12Si-CuNiMg铸造铝硅合金进行比例和90°非比例多轴加载疲劳试验,测试了合金的疲劳寿命,对比了最大主应力模型和临界面损伤参量Matake模型估算2种加载模式疲劳寿命的准确性,分析了疲劳断口形貌。结果表明:在相同等效应力幅下非比例加载试样的疲劳寿命远低于比例加载试样的;比例加载时,最大主应力模型和Matake模型的疲劳寿命估算值均具有较高的精度,非比例加载时,最大主应力模型的估算误差较大,但Matake模型的估算精度仍较高,该模型适用于该材料的多轴加载疲劳寿命估算;非比例多轴加载下合金呈脆性断裂,裂纹源位于近表面的氧化夹杂物处,裂纹扩展区呈准解理穿晶断裂特征,且伴有二次裂纹。

The Al-12Si-CuNiMg cast aluminum silicon alloy was subjected to proportional and 90°nonproportional multi-axial loading fatigue test under 160,150,140 MPa equivalent stress amplitudes.The fatigue life of the specimen was tested.The prediction accuracy of fatigue lives under two loading modes by the maximum principal stress model and the critical surface damage parameter Matake model was compared.The fatigue fracture was analyzed.The results show that under the same equivalent stress amplitude,the fatigue life of the nonproportional loaded specimen was much lower than that of the proportional loaded specimen.The fatigue lives estimated by the maximum principal stress model and the Matake model both had high accuracy under proportional loading.Under nonproportional loading,the fatigue lives estimated by the maximum principal stress model had larger errors while those by the Matake model still had high accuracy.The Matake model model was suitable for multi-axial loading fatigue life estimation of this material.The alloy under nonproportional multi-axial loading showed brittle fracture.The crack source was at the oxide inclusions near the surface,and the crack propagation region showed quasi-cleavage transgranular fracture,accompaning with secondary cracks.