| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 99 === There are two types of tube, seam and seamless, in accordance with the different forming methods. Cold roll forming proess is adopted to produce seam tubes; hot extrusion process is used to make seamless tubes on the other hand. The secondary forming process, tube sinking or tube drawing, are usually carried out to change the diameter and the thickness of tube. In this thesis, the die design methods for tube sinking and tube drawing will be studied. FEM method is adopted to evaluate the proposed design methods and study the formed dimensions of different designs.
A limit tube drawing coefficient is proposed in this thesis to determine the required tube drawing pass number. The different die and mandrel designs for tube drawing are proposed and optimized using the Taguchi method and the Response Surface Method(RSM), respectively. For tube sinking process, die designed with conical, single curvature, and double curvature profiles are studied. A Bezier curve die profile design is proposed to cover all of the design characteristics of the above mentioned designs. RSM is adopted to determine the optimum positions of the control points of the Bezier curve die profile. The goal of the optimum design is to minimize the variation of the tube wall thickness.
The study shows the semi angle 15 degrees of mandrel is the best design for the tube drawing with both of the conical die and the single curvature die (the original tube thickness is 1.8mm). The maximum effective strain is increased with increasing of the semi angle of mandrel, and is decreased with increasing of the original tube thickness. The optimum radii of single curvature tube drawing die and mandrel are equal to the outer diameter of tube bille and the inner diameter of the product, respectively. The average effective stress at the exit section is minimized. For tube sinking process, the thickness variation of the sank tube is mainly influenced by the backward extrusion diameter of the performing process (4.2, 4.5, and 4.8 mm, respectively). The variation of the sank tube thickness is smallest in the case of the Bezier die design. The sank tube thickness is about 0.7mm using the 4.8 mm inner diameter of the backward extrusion process and most close to the target value 0.75mm。
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