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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.
According to the National Standard of Sheet Metal Forming Test (FLD), FLD test of sheet metal was carried out by using bulging punch of different shape.After analyzing the test data, it was found that the shape of the semi-ellipsoid head punch compared with the hemispherical head shape Of the punch, the specimen rupture position closer to the center of the high position; in the uniaxial tension, plane strain and biaxial tensile stress state, the semi-ellipsoid-shaped punch and the hemispherical head punch Which lead to the different strain path of the sheet.The influence of the strain gradient on the FLD test is analyzed and it is pointed out that the semi-ellipsoid head punch used in the FLD test is beneficial to improve the stability and accuracy of the test.