1、 Types of metal stretching processes
(1) Cylinder stretching: stretching of a flanged cylinder. The flange and bottom are both straight faces, and the cylinder is axisymmetric, with uniform deformation on the same circumference. The blank on the flange undergoes deep drawing deformation.
(2) Elliptical stretching: The blank on the flange undergoes stretching deformation, but the deformation amount and deformation ratio change accordingly. The larger the curvature, the greater the deformation of the blank; The smaller the curvature, the smaller the deformation of the blank.
(3) Rectangular stretching: A low rectangular part formed by one stretch. During stretching, the tensile resistance at the corner of the flange deformation zone is greater than that at the straight edge, and the degree of deformation at the corner is greater than that at the straight edge.
(4) Yamagata stretching: The side walls are suspended during the process and do not adhere to the mold until the end of the forming process. The deformation characteristics of different parts of the sidewall during forming are different.
(5) Hill shaped stretching: The deformation of the blank during the forming process of the hill shaped cover plate is not a simple stretching deformation, but a composite forming where stretching and bulging deformation coexist.
(6) Hemispherical stretching with flanges: When stretching a spherical part, the blank partially contacts the spherical top of the punch, while the rest is mostly in a suspended state.
(7) Flange stretching: Perform shallow stretching on the stretched flange section. Its stress-strain situation is similar to compression flanging.
(8) Edge stretching: Perform angular re stretching on the flange, requiring the material to have good deformation.
(9) Deep stretching: It requires two or more times of stretching to complete. The wide flange stretching part is stretched to the required flange diameter during the first stretching, and the flange diameter remains unchanged during subsequent stretching.
(10) Conical stretching: Due to the large degree of deep deformation, deep conical parts are prone to excessive thinning and even cracking of the billet locally, requiring multiple transitions to gradually form.
(11) Rectangle re stretching: The deformation of high rectangular parts formed by multiple stretching is not only different from that of deep cylindrical parts, but also greatly different from that of low box shaped parts.
(12) Surface forming: Surface stretching forming is a stamping method that reduces the outer flange part of a metal flat billet and elongates the inner flange part, forming a non straight wall and non flat bottom surface shape.
(13) Step stretching: The initial stretching is re stretched to form a stepped bottom. The deeper part undergoes deformation in the early stages of stretching, while the shallower part undergoes deformation in the later stages of stretching.
(14) Reverse stretching: Reverse stretching is a type of re stretching that involves stretching the workpiece from the previous process. The reverse stretching method can increase radial tensile stress and achieve good results in preventing wrinkling. It is also possible to increase the stretching coefficient of re stretching.
(15) Thinning stretching: Unlike ordinary stretching, thinning stretching mainly involves changing the thickness of the cylinder wall of the stretched part during the stretching process.
(16) Panel stretching: The surface shape of the panel is complex. In the stretching process, the deformation of the blank is complex, and its forming properties are no longer simple stretching forming, but a composite forming that coexists with deep drawing and bulging.
