管材缩径起皱失稳数值模拟

Numerical simulation on wrinkling instability of tube outer pressure compression

轻质薄壁件越来越多地应用于航空、航天和汽车等高新技术工程领域,但起皱失稳一直是薄壁件成形过程中主要的缺陷之一。因此,轻质薄壁件成形过程中的塑性失稳起皱预测研究就显得尤为重要。本文针对塑性成形中薄壁管件结构由于存在多种初始缺陷(如厚度不均,尺寸偏差等)从而导致失稳模拟预测与实际情况不符的现象,以AA6061固体颗粒介质管材缩径工艺为算例,结合ABAQUS中最适合复杂接触工况的DYNAMIC算法以及Draker-Pager颗粒介质成形数值模拟模型,对无初始缺陷圆柱壳体、引入屈曲模态初始缺陷圆柱壳体、引入厚度不均初始缺陷圆柱壳体以及同时引入屈曲模态和厚度不均缺陷的圆柱壳体进行了缩径成形模拟,将四种条件下的管件失稳波形模拟结果与试验结果进行了比较。结果表明:同时引入屈曲模态和厚度不均缺陷的动态显示有限元法可以准确预测出管材缩径失稳后的形貌,并将模拟仿真与实验的应力-位移曲线进行对比,验证了此模拟方法的可靠性。

The lightweight thin-walled parts are increasingly used in high-tech engineering fields such as aviation,aerospace and automobile.Wrinkling instability has always been one of the major defects in thin-walled parts forming processes.Therefore,the study on prediction of plastic wrinkling instability becomes particularly important in the process of forming lightweight thin-walled parts.Based on the inconsistent between the instability simulation prediction of thin-walled tube structures and the actual situation which are due to various initial defects(such as uneven thickness,dimensional deviations,etc.),this paper takes the example of the AA6061 diameter-reduced tubes by solid granule medium forming technology and combines the DYNAMIC algorithm which is the most suitable for complex contact conditions in ABAQUS,simulates the tube outer pressure compression forming with no initial imperfections,buckling modes initial imperfections,uneven thickness initial imperfections and the last one which contains buckling modes initial imperfections and uneven thickness initial imperfections.The dynamic finite element method with simultaneous introduced buckling modes and thickness unevenness imperfections can accurately predict the instability waveforms of the tube through the comparison between the simulations and the tests.The reliability of the simulation method is verified through the comparison between the simulative and experimental force-displacement curves.