| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 102 === Titanium with high strength, light weight, and corrosion resistance advantages, are mainly used in aerospace industries. Following the improvement of processing technology and increase of living expenditure ability, titanium are also used in automotive, sports leisure goods and other industries. Because of non-toxicity and high biocompatibility, titanium are widely applied in biomedical fields. At first, Compression tests were carried out under various forming temperatures to obtain the flow stresses which are need in the finite element simulations of heading processes of grade 2 pure titanium screws. A heading process is generally composed of three stages. The first stage is extrusion of the screw shaft. The second stage is preforming of the screw head. The third stage is forging of the inner hexagonal socket part of the screw head. By appropriate process parameters control and die design, defects usually occurring in the heading process can be avoided. The threading process is to identify the appropriate distance of the thread plates, so that the finished product meets the specifications of the ISO metric thread. The effect of friction factor, mesh size and the distance of the thread plates in the threading process are also investigated. Finally, heading and threading experiments are conducted by using a universal testing machine with a self-designed die set. The experimental load and dimensions are compared with the analytical results to verify the suitability and accuracy of finite element model for heading and threading processes.
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