倾斜管件多道次缩径旋压成形的数值模拟及试验

Numerical Simulation and Experimental Investigation on the Multi-pass Neck-spinning of Non-axisymmetric Oblique Tube

以6061T1(退火态)铝合金为研究对象,以MSC.MARC软件为分析手段,采取有限元法对三维非轴对称倾斜管件多道次缩径旋压过程进行数值模拟,并利用网格圆及显微组织的变化从试验的角度验证模拟所得到的应变分布规律。结果表明,倾斜使得工件的应力应变呈不均匀分布规律;等效应力沿轴向呈分层分布的特点,在口部达到最大值;等效应变沿周向0°～180°域逐渐减小,在0°域存在最大值,180°域存在最小值;沿轴向从起旋处到口部,等效应变在0°域具有逐渐增大和在180°域具有逐渐减小的特征。由于返程旋压的明显增厚效应,多道次旋压时,工件变形中间部位壁厚增加。多道次缩径旋压时工件变形中间部位壁厚变化规律的试验结果与模拟结果的相对误差不大于10%,说明所建立的有限元模型是合理可靠的。在理论分析及试验研究的基础上,成功研制出倾斜类汽车排气歧管样件。

The process of multi-pass offset tube neck-spinning is simulated by MARC, the 3D elasto-plastic finite element software. 6061T1 aluminum alloy （annealed） is taken as the the material investigated. The simulation result of the distribution of stress and strain is verified by experimental result based on mesh circle method and variation of microstructure of workpiece. It shows that the distribution of strain and stress is non-uniform due to oblique; the equivalent stress distributes along axial direction section by section and the equivalent stress reaches the maximum at the opening end of the spun workpiece. Along circumferential direction, the equivalent strain decreases gradually from 0° area, where the biggest oblique amount exists, to 180° area, where the smallest offset amount exists; and reaches the maximum at 0° area and the minimum at 180° area. Along axial direction, the equivalent strain increases gradually at 0° area and decreases gradually at 180° area. During multi-pass neck-spinning, the thickness at the middle section of spun workpiece increases due to the remarkable thickening effect in the backward path spinning. The simulation result of the thickness distribution at the middle section of spun workpiece during multi-path neck-spinning conforms well to the experimental result with maximum deviation less than 10%, indicating the validity of the FEA model. The automobile exhaust pipe with oblique tube end has been produced successfully based on the theoretical analysis and experimental research.