直齒圓柱齒輪之熱間抽擠複合成形製程研究

本研究主要在探討利用抽擠複合成形技術來進行齒輪熱間塑性成形的可行性，並探討此技術各製程參數對齒輪成形的影響。亦即首先採用三維有限元素模擬技術分析擠壓、抽拉及抽擠複合成形等三種方法在正齒輪塑性成形的差異，亦即冀望從瞭解金屬在抽擠過程中的變形流動、齒型充填、材料利用、應力與應變分佈及模具受力等特徵，探討以抽擠複合法進行正齒輪塑性成形的可行性。其後，對抽擠複合成形再進一部分析，探討沖頭壓力、抽拉速度及摩擦因子等製程參數對胚料充填變形、凹模受力及齒輪成形品質的影響。研究發現，雖然抽擠複合塑性成形方法，其凹模受力並無顯著降低，但於齒型充填中，抽擠複合塑性成形比擠壓成形及抽拉成形效果佳且穩定，亦降低了齒輪齒型充填不滿缺陷之虞，而胚料料頭的廢料亦較少，相對的增加了材料的使用率。此外，抽擠複合塑性成形正齒輪件的應力較低，降低了破裂風險，又齒輪應變強化亦均勻分佈在齒型四周，有助於輪齒強化效能。總之，以抽擠複合塑性成形方法來製造正齒輪具有其可行性，塑性成形後亦可達到預期的效果。抽擠複合成形參數對塑性變形、凹模受力及齒輪的應力與應變則有不同程度的影響。當?頭壓力越大其齒形充填效果越好，但相對的凹模受力也越大。又不同抽拉速度及模擦因子的大小對其凹模受力影響則並無顯著差別。此外，當?頭壓力越大齒輪件齒面之應變強化亦均勻分佈在齒型四周，有助於輪齒強化效能。抽拉速度越大時其齒輪件的應力在齒面較高，增加了破裂風險。

關鍵字

抽擠複合成形、擠壓、抽拉、正齒輪、有限元素分析

並列摘要

This research aimed to explore the feasibility of hot plastic forming for spur gear through the drawing-extrusion forming technique, and the effects of the forming parameters on the gears. It firstly employed 3D finite element simulation technique to analyze the forming differences in spur gear through extrusion, drawing, and drawing-extrusion. Specifically, such characteristics as plastic flow of workpiece, filling of die cavity, yield of material, distribution of stress and strain, and load of die were investigated to further understand the feasibility of hot plastic forming for spur gear through the drawing-extrusion forming technique. Then, analysis was made on the effects of the forming parameters—the punch pressure, drawing speed, and fraction factor, on the filling deformation of billet, die load, and the quality of the gear. Results showed that the load on the forming die did not reduce in drawing-extrusion forming, but the filling of die cavity was most effective and stable as compared with extrusion and drawing operations. Filling defect at the die entrance was greatly reduced and hence the yield of production increased. In addition, the forming stress of drawing-extrusion was smaller, which reduced the risk of die fracture. Significant strain appeared on the peripheral of the tooth, which contributed to strengthening the workpiece. Therefore, drawing-extrusion forming technique exhibited more advantages in its feasibility analysis. The desired functionality of the product could be also achieved through plastic forming. It was found that the plastic deformation, load of die, and the stress and strain of gear workpiece were respectively influenced by the forming parameters of drawing-extrusion forming. The higher the punch force was, the better the filling effect of gear profile was; but the load of die server was relatively higher. In addition, the load of die was not influenced by drawing velocity and friction factor. Furthermore, the strength performance of formed gears would improve, owing to the strengthened effect of the strain being distributed around the teeth of gear. However, the higher the drawing velocity was, the higher the stress in the teeth surface of gear was, which in turn increased the fracture risk of formed gears.