铝锂合金薄板自动钻铆残余应力特性

Residual Stresses of Al-Li Alloy Sheets in Automatic Drilling Riveting Process

利用主应力法推导了铆接壁板所受压力的力学公式,将壁板等效为厚壁圆筒,根据空间轴对称问题求解方法,得出铆接孔孔壁处径向和周向残余应力的表达式,理论分析结果可以合理解释镦头高度和钉孔直径对孔壁处残余应力的影响规律:随着镦头高度和钉孔直径的变化,孔壁各处径向残余应力的变化并不明显,而周向残余应力的变化十分显著;镦头高度和孔径尺寸的增加使周向残余压应力的绝对值下降,甚至出现残余压应力转变为残余拉应力的情况.对于孔壁处残余应力沿板厚方向的分布,采用有限元方法进行分析.结果表明,上、下壁板间应力存在突变,下壁板孔壁处残余应力呈"C"型分布.得出铝锂合金材料在自动钻铆过程中相关工艺参数的合理取值.

Residual stress induced by riveting process is critical to the fatigue life of riveted structures.In this paper,the principal stress method was employed to calculate the pressure on the surface of rivet hole and the stress between upset head and sheet.The radial and circumferential residual stresses were solved by using the spatial axisymmetric elastoplasticity theory,where the sheets were equivalent to a thickwalled cylinder.The change of residual stresses caused by various process parameters was explained by the analytical results reasonably.The results show that the circumferential residual stress decreases with the increase of the upset head height and the rivet hole diameter.However,the radial residual stress is approximately independent of the two parameters.The distribution of residual stress on the surface of rivet hole along the thickness direction was investigated by using the finite element method.The results indicate that the residual stress on the faying surface is discontinuous.A C-shaped distribution of residual stress was introduced into the surface of rivet hole in the lower sheet.Reasonable process parameters were given for the Al-Li alloy sheets in the automatic drilling riveting process.