材料期刊网

目的 探讨ZL702A铝合金的微动损伤机理,寻找适合的微动疲劳寿命预估模型.方法 以ZL702A铝合金为研究对象,设计方足桥-试件微动模拟件进行微动疲劳实验,用4XC-PC金相显微镜观察断裂试件表面的磨损形貌,探讨微动损伤机理.建立方足桥-试件有限元模型,编程计算剪应变幅、法向正应力、相对滑移距离等微动特征参数,分别运用FS、KBM、McDiarmid以及Ruiz参数预测ZL702A铝合金微动疲劳寿命.结果 疲劳裂纹主要在局部塑性区成核,剪切应变可以加速裂纹核的形成,疲劳裂纹增长是裂纹尖端剪切带不断聚合的过程,裂纹面上的法向应力/应变使这种聚合加速.法向载荷保持不变,随着最大轴向力的增大,微动损伤增大.4种微动疲劳寿命预估模型的结果表明,微动损伤在试件接触区边缘最大,容易萌生微动裂纹,与实验值一致.微动疲劳寿命预测结果表明,Ruiz参数预测结果与实验结果误差在2倍公差带因子范围内,最接近实验值.结论 微动磨损区分为粘着区、混合区、滑移区,在混合区边界上最容易发生塑性变形,萌生微动疲劳裂纹,用Ruiz参数预测ZL702A铝合金的微动疲劳寿命是可行的.

This work aims to study fretting damage mechanism of ZL702A aluminum alloy and find an appropriate predic-tion model for fretting fatigue life. Fretting fatigue experiment was carried out to ZL702A aluminum alloy by designing fretting simulation item composed of square foot bridge and specimen. Surface morphology of the fractured specimen was observed with 4XC-PC metallographic microscope, and mechanism of fretting damage was discussed. The finite element model com-posed of square foot bridge and specimen was established, fretting characteristic parameters including shear strain amplitude, normal stress and relative slip distance were subject to programmed calculation. FS, KBM, McDiarmid and Ruiz parameters were applied to predict fretting fatigue life of ZL702A aluminum alloy. Fatigue cracks mainly nucleate in local plastic zone, shear strain could accelerate the formation of crack nucleus, fatigue crack growth was a process of continuous polymerization of crack tip, normal stress/strain on the crack surface accelerated this polymerization. When normal load remained constant, fret-ting damage increased with the increase of maximum axial force. Life prediction model results of 4 kinds of fretting fatigue showed that most severe fretting damage was present in edges of specimen contact zone and may produce fretting cracks, which were consistent with experiment value. Prediction results of fretting fatigue life showed that error between results predicted based on Ruiz parameters and experimental results fell within dual factor in tolerance zone, and the prediction results were most close to experiment value. Fretting wear zone can be divided into adhesive zone, mixing zone and sliding zone. Plastic deforma-tion is most likely present along the boundary of mixing zone, and thus producing fretting fatigue cracks easily. The prediction results show that it's feasible to predict fretting fatigue life of ZL702A aluminum alloy based on Ruiz parameters.