汽车桥壳多向充液压制小圆弧成形分析及设计

Forming analysis and design for small arc in multi direction hydro-pressing of automobile axle housing

汽车桥壳是大尺寸复杂形状管件,横截面存在小圆弧,使用传统液压胀形需要超高内压,难以成形。本文简介胀压成形工艺,分析了预成形管坯多向压制过程,揭示出小圆弧的成形机理,并推导出应力大小与内压、外压的表达式,给出小圆弧内壁点近似塑性变形条件及屈服轨迹,分析出小圆弧曲率半径差异及裂纹的原因,并给出小圆弧设计方法。针对某轴荷10 t桥壳管件的胀压成形进行了有限元模拟,小圆弧应力状态的变化趋势同理论分析一致,并揭示了不同压制方式下模具压制力、小圆弧两侧应力及相对内径的变化规律,拟合出剪切应力与圆弧相对内径的表达式,依据小圆弧设计方法确定压制系数、摩擦因数及圆弧相对内径范围。进行了桥壳管件胀压成形工程试验,实测模具压制力及样件横截面的小圆弧尺寸,相同条件下的有限元模拟与试验结果吻合。

Automobile axle housing is a large-scale pipe with complex shape and small arc,and it is difficult for hydroforming which needs high pressure.The technology of bulging-pressing is introduced,and the multi directional pressing process of preformed tube blank is analyzed,then the forming mechanism of small arc is revealed,and the expressions of stress,internal pressure and external pressure are derived.The approximate plastic deformation condition and yield trajectory of the inner wall point of the small arc are given,the reason of the difference of curvature radius and crack of the small arc is analyzed,and the design method of the small arc is also given.The FEA of the bulging-pressing of a 10 ton axle housing was carried out,the trend of the small arc stress state is consistent with the theoretical analysis,and the rules of the die pressing force,the stress on both sides of the small arc and the relative inner diameter under different pressing methods are revealed.The expression between shear stress and the relative inner diameter of arc is fitted,then the pressing coefficient,friction coefficient and the relative inner diameter range of arc are determined according to the design method.Finally,the bulging-pressing test of axle housing tube was carried out,the pressing force and the small arc size of the sample were measured.The finite element simulation under the same conditions is consistent with the experimental results.