板料FLD试验胀形冲头形状影响研究

Effects of punchers with different shapes in FLD experiments of metal sheet

参考板料成形极限图(FLD)试验国家标准,采用不同形状的胀形冲头进行了板料的FLD对比试验.对试验数据分析后发现:半椭球头形状的冲头相比半球头形状的冲头,其样件的破裂位置更接近中心高点位置;在单向拉伸、平面应变和等双向拉伸的应力状态下,半椭球头形状的冲头和半球头形状的冲头分别引起板料的应变路径有所差异.分析了应变梯度对FLD试验的影响规律,指出FLD试验采用半椭球头凸模有利于提高试验的稳定性和精度.

With different the bulging punch shapes, comparative tests of forming limit diagram （FLD） for metal sheets were done after the national standards of the sheet FLD tests were referenced. After analyzing the experimental data, it is seen that, compared with the hemispherical head shape punch, the position of the half ellipsoid head shape punch, the rupture of the sample location, is closer to the center of the high point. It is also found that under the stress state of uniaxial tension, plane strain and biaxial stretching, the semi-elliptical shape and the hemispherical head shape of ball head punch caused different strain paths. The impact on strain gradient to FLD test result was analyzed. It is founded that the FLD semi-elliptical ball head punch is helpful to improve the stability and accuracy of the test.