Effect of cold expansion on fatigue life of double lap structure

冷挤压强化对双搭接结构疲劳性能影响研究

Received: 7 June 2020

Abstract

The finite element simulation analysis was used to determine the weak parts of the fatigue life of a double lap structure, for which the cold expansion finite element model was established. The effect of the cold expansion of slotted bushings on the residual stress distribution around the hole of the double lap structure under different interferences was deeply studied, and the optimal interference amount was determined to be 2.5%. The effect of reaming on the residual stress distribution around the hole was studied. The residual stress distribution around the edge of the hole under actual loading conditions before and after cold expansion was compared to provide a theoretical analysis basis for extending the fatigue life of the specimen after cold expansion. The China-made and free- forged 7A85 aluminum alloy specimen was used to obtain the fatigue life and DFR value of the double lap structure after ordinary hole making and the cold expansion of slotted bushing. The results show that the fatigue life under 95% confidence and 95% reliability after cold expansion strengthening increases by about 49% and that the tested DFR value increases by about 9.8%.

摘要

通过有限元仿真分析确定双搭接结构疲劳薄弱部位，针对疲劳薄弱部位建立了冷挤压强化有限元模型，深入研究了开缝衬套冷挤压在不同干涉量下对孔周残余应力分布的影响，确定了最佳干涉量为2.5%。研究了铰孔对孔周应力分布的影响，对比分析了冷挤压强化前后实际加载状态下的孔边应力分布，为冷挤压强化后试验件的疲劳寿命提高提供了理论分析基础。基于国产7A85铝合金自由锻件试验件，得到了双搭接结构在普通制孔以及开缝衬套冷挤压后的疲劳寿命以及DFR值。结果表明：冷挤压强化后在95%置信度以及95%可靠度下的疲劳寿命提升了约49%，试验DFR值提升了约9.8%。