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提出一种创新的试验方法——覆层板椭圆胀形试验,利用该试验方程可以实现厚度法向应力的加载和研究。建立覆层板椭圆胀形的理论解析模型,通过试验确定不同椭圆度下板材的等效应力-应变曲线,并研究覆板材料性能和厚度对目标板材流动性能的影响。结果表明,相比无覆板液压胀形,覆层板液压胀形得到的等效应力-应变曲线缩颈前的应变值更大。并且椭圆凹模椭圆度越小,所得的等效应力-应变曲线离圆形凹模(b/a=1)胀形曲线越远。同时,成形过程中选择强度系数K较高、加工硬化指数n较大及适当厚度的覆板有利于目标板材成形性能的提高。
An innovative test method - Elliptical Cladding Test of Cladding Plate is presented. With this test equation, the normal stress of the load can be loaded and studied. The theoretical analytical model of the oval bulge of the clad plate is established. The equivalent stress-strain curve of the slab under different ovality is determined through experiments. The influence of the performance and thickness of the clad plate on the flow properties of the target plate is also studied. The results show that the equivalent strain-strain curve obtained by the hydraulic bulging of the clad plate is larger than that before the constriction. And the smaller ellipticity of the elliptical die, the resulting equivalent stress-strain curve farther away from the bulging curve of circular die (b / a = 1). In the meantime, the higher selection coefficient of strength K, the larger work hardening index n and the appropriate thickness of the sheathing sheet are beneficial to the improvement of the forming properties of the target sheet.