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金属材料在弯曲时,其圆角区上外层受拉伸,内层受压缩,内圆半径r越小,圆角区的变形越大。当外层圆角区的拉伸应力超过材料的强度极限,外层材料发生断裂;而内层材料丧失稳定起皱,致使工件报废。据资料介绍,管材弯曲的最小弯曲半径R=3D_0 D_0:管材外径生产中需将φ48×δ2.5的拉制硬铜管弯曲成蛇形管,要求弯曲半径为76mm,内壁不起皱,外壁不开裂。根据技术要求自制弯管机试弯,发生管材外壁开裂和内壁起皱现象。经过分析和对最小弯曲半径的计算,认为原因是材料硬而塑性差,弯曲半径太小
When the metal material is bent, the outer layer is stretched on the fillet area, and the inner layer is compressed. The smaller the inner radius r is, the larger the deformation of the fillet area is. When the tensile stress in the outer corner area exceeds the strength limit of the material, the outer layer material breaks; while the inner layer material loses stability and wrinkles, resulting in scrapped parts. According to the information, the minimum bending radius of the pipe bending R = 3D_0 D_0: the pipe outer diameter of the production required φ48 × δ2.5 drawn hard copper tube bent into a serpentine tube, the required bending radius of 76mm, the inner wall does not wrinkle, The outer wall is not cracked. According to the technical requirements of self-made bending machine bending test, the occurrence of pipe wall cracking and wall wrinkling phenomenon. After analysis and calculation of the minimum bending radius, the reason is that the material is hard and the plasticity is poor and the bending radius is too small