薄壁管数控绕弯成形壁厚减薄的主要影响因素研究

Research on main influential factors of wall thinning in NC thin-walled tube rotary-bending process

针对薄壁圆管数控绕弯精确成形过程在多因素作用下容易出现外侧壁厚减薄的物理过程,基于Dynaform建立了数控绕弯三维有限元模型并验证了模型的可靠性。研究了材料参数、顶推装置、弯曲角度、相对弯曲半径、芯棒伸出量、芯头个数对管材数控绕弯成形外侧壁厚减薄的影响规律。结果表明:LF2M铝合金比1Cr18Ni9Ti不锈钢减薄严重,但是截面畸变程度小于1Cr18Ni9Ti;相比尾部没有安装顶推装置的管坯,加装了顶推的弯管壁厚减薄率降低了大约5%;随着弯曲角度和弯曲半径的增大,减薄率也逐渐增大;芯棒伸长量和芯头个数也是影响减薄的重要因素,芯棒伸出越多,弯管壁厚减薄率越大,增加芯头也会增大减薄率。

For the complex physical process of outer wall thickness thinning easily occurred in thin-walled tube NC rotary-bending under action of multi-factors, a 3-D finite element model was established by Dynaform and its reliability was verified. It was studied the influential regularity of forming parameters, such as material parameters, pushing device, bending angle, relative bending radius, mandrel extension length and mandrel heads number on outer wall thickness thinning in NC thin-walled tube rotary-bending process. The results show that the wall thickness thinning ratio of aluminum alloy LF2M tube is higher than that of stainless steel 1Crl8NigTi tube, while its cross-sectional distortion is less than that of 1CrlSNi9Ti, and the wall thickness thinning ratio of tube with pushing device decreases about 5% compared with that without pushing device. Moreover, the thinning ratio of the outer wall increases gradually with the increase of ben- ding angle and relative bending radius. Therefore, the mandrel extension length as well as mandrel balls number are also important factors to effect wall thickness thinning, the more mandrel extension length is, and the greater thinning of outer wall thickness is. Further, in- creasing the mandrel ball numbers can also increase thinning ratio of the outer wall thickness.