Zhongtang Wang

Study of the deformation velocity field and drawing force during the dieless drawing of tube

Abstract Dieless drawing is a newly developed flexible metal forming technique without dies, which is performed only according to the feature that the yield strength of the metal varies with the deformation temperature. The precision and shape of the product are controlled by the drawing speed and the speed of movement of the heating–cooling apparatus. Dieless drawing is a technology that has many advantages, such as high precision, high efficiency, low consumption of energy, no pollution of the environment and flexibility. It can be used to form some materials, i.e. those that have high strength and high frictional resistance and low plasticity at room temperature, which cannot be formed using conventional forming technology. Variable section tubular parts, such as conical and laddertron and wavelike, which are difficult to be formed using conventional metal forming technology, can be formed easily using this technology. On the basis of the analysis of the deformation mechanism and velocity field of tube dieless drawing, the drawing force and velocity field are studied theoretically and relevant equations have been determined by means of the power equilibrium method. The drawing force has a relation to the width of the deformation field, the sectional reduction ratio, the deformation temperature, the drawing speed, the speed of movement of the heating–cooling apparatus and the carbon content. With the increasing of the sectional reduction ratio, the drawing speed, and the speed of movement of the heating–cooling apparatus, the values of the drawing force also increase. With the increasing of the deformation temperature and the deformation width, the values of the drawing force decrease.

Experiment study on the variation of wall thickness during dieless drawing of stainless steel tube

The variation of wall thickness during tube dieless drawing for stainless steel tube has been Studied by experiment. It has been put 1 2 forward that the variation of wall thickness is directly Proportional to the external diameter. the internal diameter, and ( 1 - R-s)(1/2) where R-s is the cross-sectional reduction ratio of the tube. It has been found that for thin wall tube dieless drawing, there exists the relation. t(f) /t(0) = D-if/D-i = D-Of/D-0 = (1 - R-s)(1/2); whilst for thick wall tube dieless drawing, there exists the relation: t(f)/t(0) = k(1)D(if)/D-i = k(2)D(0f) /D-0 =k(3)(1-R-s)(1/2). With the increasing width of deformation, the value of the variation in wall thickness and the derivative of wall thickness variation (t(f)/t(0)) to width of deformation reduces

Finite Element Analysis on Warm Hydroforming of Rectangular Mg Alloy Cups with a Step Cavity

Magnesium alloys, as one of the lightest metal structural materials, are attracting more and more attention. At present, most of Mg alloy products are manufactured by die casting. For enlarging the applications of Mg alloys, many researchers are engaged in developing its plastic forming technology. However, the study on warm sheet hydroforming of Mg alloy is rarely reported. Therefore, a set of warm sheet hydroforming tools was designed for experimental research on the hydroforming of rectangular Mg alloy cups with a step cavity. The corners of the deeper cavity are difficult to form directly because of the severe stretching. Multi-stage hydroforming method was used to improve the sheet thickness reduction in the corners of the deeper cavity. Several different two-stage hydroforming methods were realized by elastic-plastic finite element simulation. According to the results of finite element simulation, the influence of forming methods on the minimum thickness of formed parts and the reasons were analyzed, and the optimal process for the rectangular Mg alloy cup with a step cavity was determined.