7075铝合金环压缩过程摩擦影响的有限元分析

FE analysis of friction effect in 7075 Al alloy ring upsetting process

基于罚函数刚塑性有限元法和网格重划分技术建立了环形件镦粗过程三维热-力耦合求解模型,并对7075铝合金在不同摩擦因子下环形件镦粗过程载荷变化、应力应变以及速度场分布规律进行了数值分析。结果表明:由于加工硬化、高温软化以及摩擦作用,环形件镦粗过程载荷变化分为急剧增加、缓慢增加、后期急剧增加三个阶段。由于摩擦作用内外侧自由表面均出现单鼓和侧面翻平现象,随着摩擦增加,内侧单鼓现象更为明显。环形件镦粗过程中应力为三向压应力,外侧自由表面产生较大轴向拉应力,易于产生裂纹。摩擦系数越大,等效应变梯度越大,变形更为不均匀。随着摩擦系数和压下量增加,分流面区域由环形件内侧向外侧移动,摩擦系数较大时,环形件内侧表面受到较高三向压应力作用,摩擦对分流面位置的影响作用减弱。

The 3D coupled thermal-mechanical model based on penalty function of rigid-plastic FEM and remeshing technology has been established. The change of load, distribution of stress ＆ strain and velocity field with different friction factor in 7075 AI alloy ring upsetting process have been analyzed numerically. The results show that as per the effects of higher temperature softening, work hardening and friction on deformation, the change of load has been divided into sharp increase, slow increase and afterwards sharp increase three stages during ring upsetting process. Furthermore, the single drum and turned flat have been occurred in inner and outer flank of billet because of friction. The single drum in inner flank becomes more significantly with the increment of friction comparing with that of flank. There is three-dimensional compressive stress. The tensile stress in axial and circumferential direction leads to the crack generated easily in the outer side surface.Additionally, equivalent strain grade and inhomogeneous deformation have been much larger as the increase of friction coefficient. The divergent position moves from inner of ring to the outer of ring as the increase of friction coefficient and press-down. However, the influence of friction on the divergent position becomes less with larger friction because of larger compressive stress in circumferential direction of inner flank.