微构件自由弯曲回弹的数值模拟

回弹是影响弯曲成形精度的一个重要因素,由于尺度效应的存在,微构件的弯曲回弹问题更复杂.利用动态显式与静态隐式算法相结合的方法数值模拟了C1200黄铜V形微构件的自由弯曲,与其超薄板三点弯曲的实验结果吻合度很好,验证了该方法模拟微构件弯曲回弹的可行性.分析了板厚t、晶粒大小d、t/d(板厚与晶粒大小比值)和残余应力对回弹的影响,结果显示t/d可以作为表征回弹的重要参数,回弹量随着t/d减小而增大;随着t和d的增大,工件的残余应力也增大,会影响工件的质量.可以采用适当热处理工艺增大材料的晶粒尺寸来减少回弹,当然也要兼顾残余应力对工件质量的影响.

Numerical Simulation of Micro-Component Spring Back Behavior in Free Micro-Bending

Spring back is an important factor influencing on forming precision in bending process. For micro-components, the spring back behavior is more complex due to the size effect. Bending process of a V-shape micro-component made of C1200 brass was simulated based on both dynamic explicit and static implicit codes. Simulation results are in good agreement with experimental results obtained in three-point bending of a super thin brass sheet metal that shows the simulation feasibility of the spring back in free micro-bending. The influences of sheet thickness t, grain dimension d, the ratio t/d and residual stress on spring back were analyzed. Results show that the ratio t/d can be used as an important parameter to token the spring back, and spring back increases with the decrease of t/d. Results also show that residual stress increases with the increase of t and d and affects the figuration quality of a micro-component. It is pointed out that the spring back decrease can be obtained by increasing grain sizes based on suitable heat treatment and the residual stress control.