薄壁管材连续矫直拉伸失稳极限弯曲半径模型

Limit Bending-Radius Model of Tensile Instability for Continuous Straightening a Thin-Walled Tube

薄壁管材连续矫直拉伸失稳极限弯曲半径作为重要的工艺参数,直接决定了设备结构和产品质量。而目前现场仍沿用经验图表结合人工经验和反复试矫对其进行估定,为此基于薄壳理论的相关假设,确定了变形区的应力应变,运用Swift分散失稳准则建立了塑性拉伸失稳极限弯曲半径的解析模型,并进行了有限元仿真验证。研究结果表明:解析模型可正确计算薄壁管材矫直时拉伸失稳的极限弯曲半径,该半径随初始弯曲半径的增大而减小,并与管材直径和金属塑性加工能力有关,为继续深入研究矫直相关工艺参数的合理设置、完善薄壁管材矫直理论体系奠定基础。

The limit bending-radius of tensile instability as the main straightening technical parameter, decides the struc- ture of equipment and the quality of products for continuous straightening thin-walled tubes. However, it is usually carried out based on the experiential data and chart by skilled laborers, whose art is based on long experience and experiments. Therefore, by means of the membrane shell theory and it＇ s relevant hypothesis the normal strain and stress components were firstly obtained, and then the limit bending-radius model for the prediction of diffuse plastic instability under pure bending was presented using Swift＇ s criterion, finally the dynamic simulation was done by FEA. The results have shown that： the analytical model can be used to calculate the limit bending-radius of tensile instability for straightening thin- walled tubes correctly, which is decreased with the increase of the initial bending-radius, and it relates to the diameter and the metal plastics deformation capacity of the tube. The basis can be provided for optimizing straightening technical pa- rameters and completing the theory of thin-walled tube straightening.