锥形模机械扩径中失稳起皱分析与扩径力优化

WRINKLING IN MECHANICAL EXPANDING OF FINNED TUBE WITH CONICAL DIE AND OPTIMUM OF EXPANDING FORCE

研究了管材锥形模具机械扩径的特点,分析了扩径过程中失稳起皱的原因,建立了扩径变形区单元体力学模型,考虑材料扩径过程中的加工硬化,采用刚塑性直线硬化规律描述真实的应力-应变关系,通过主应力法推导出了锥形模机械扩径力解析公式,结果表明扩径力与摩擦系数呈近似线性增长关系,而模具半锥角在20°―30°之间存在一个使扩径力最小的最优值,并且最优值随摩擦系数的增大而增大。进一步,通过试验研究和数值模拟证明了结论的正确性。

Tube mechanical expanding with conical die is investigated, the instability and wrinkling causes in expanding process are analyzed, and a unit mechanical model in deformation zone is established. Considering effects of work hardening in expanding process, rigid-plastic line hardening rule is adopted to describe the real stress-strain relationship. Analytic formula of the mechanical expanding is derived by slab method, and the numerical results indicate that the mechanical expanding force increases along with friction coefficients,while the die semi-cone angle exists an optimum value between 20° and 30° which can make the expanding force get a minimum value. Moreover, the optimum value increases along with friction coefficients, and the correctness of conclusions is proved by experiment investigation and numerical simulation.