芯棒直接孔挤压强化7050铝合金疲劳性能研究

Fatigue Properties of Mandrel Direct Hole Expansion Strengthened 7050 Aluminum Alloy

为了探究实心芯棒、开缝芯棒2种芯棒直接孔挤压强化方法对7050铝合金疲劳性能的影响,建立了芯棒直接孔挤压强化7050铝合金三维有限元仿真模型,开展了芯棒直接孔挤压强化试验,对比分析了未挤压强化、芯棒直接孔挤压强化试样的孔壁应力、疲劳性能。结果表明:芯棒直接孔挤压强化试样铰削加工前后,孔壁最大残余压应力差值小于20 MPa;芯棒直接孔挤压强化后试样孔壁形成的残余压应力能够抵消部分受载过程中产生的拉应力;实心芯棒孔挤压强化试样的中值疲劳寿命是未挤压强化试样的1.46倍,开缝芯棒孔挤压强化试样的中值疲劳寿命是未挤压强化试样的1.52倍;芯棒直接孔挤压强化减小了疲劳源数量,缩小了疲劳裂纹扩展区的疲劳辉纹间距,提高了试样的疲劳寿命。

In order to investigate the effect of two kinds of mandrel direct hole expansion strengthening methods,i.e.solid mandrel and split mandrel,on the fatigue properties of 7050 aluminum alloy,a three-dimensional finite element model of 7050 aluminum alloy of mandrel direct hole expansion strengthening was established;direct hole expansion strengthening test of mandrel was carried out,and hole wall stress and fatigue properties of specimens without expansion strengthening and with mandrel direct expansion strengthening were compared and analyzed.The results show that the difference between the maximum residual compressive stress of the hole wall before and after the ream machining of the mandrel direct hole expansion strengthening specimen is less than 20 MPa.The residual compressive stress formed in the hole wall of the specimen after the direct hole expansion strengthened of the mandrel can offset the tensile stress generated in the process of partial loading.The median fatigue life of the solid mandrel hole expansion strengthened specimen is 1.46 times higher than that of the specimen without expansion strengthening,and the median fatigue life of the split mandrel hole expansion strengthened specimen is 1.52 times higher than that of the specimen without expansion strengthening.The mandrel direct hole expansion process reduces the number of fatigue sources,and the fatigue striation spacing in the fatigue crack propagation zone,and thus improves the fatigue life of specimen.