管材拉拔中的不均匀变形与残余应力

INHOMOGENIOUS DEFORMATION AND RESIDUAL STRESS IN TUBE DRAWING

为评价管材拉拔中的不均匀变形 ,提出用管材拉拔前后截面形状变化指数Q描述截面变形的不均匀性。用电阻应变片测试了黄铜管材变形后的表面残余应力 ,用管材截面小圆环法计算了截面径向和周向变形的分布 ,确定了管材拉拔中Q值对管材截面上变形分布及表面残余应力的影响规律。

It is put forward in this article that the cross section deformation index Q can be used to evaluate the inhomogeneity of deformation in tube drawing. The experiments include testing the surface residual stress on deormed brass tube by the use of resistance strain gauge, and calculating the distribution of deformation in radial and circumferential directions. Finally, the relationship between index Q and cross section deformation distribution and residual stress is established.The experiment results show that the inhomogeneity of cross section deformation of tube can be well described by index Q , it is also needed that to keeping index Q within 0 8～0 9 when selecting tube drawing parameters helps for achieveing homogeneous deformation and lower residual stress;when there is a high radius reducing deformation,the Q value will be high,the inner layer metal aggregates under the high circumferential compression, along with increased radial deformation.In this case, a circumferential residual stress can also be generated because the inner layer metal is being compressed and outer layer metal stretched.When there is a high wall reducing deformation, the Q value will be low,and it will produce a circumferential residual stress because of the compressed outer layer metal and the stretched inner layer metal.