本論文以量產製造的自行車避震器鋁冠鍛件為研究，進行了數值分析及鍛造實驗。提出預成型設計方案，以提高鍛件產品之品質並減少生產下料重量，降低加工之製造成本。由於傳統的製程下料過重而毛邊過大之問題，故此研究提出一種具透過有限元(FE)模擬軟體對材料流動、應力和有效應力分佈進行數值分析，再結合軟體之子程序模擬，從不同溫度和應變下的得到了功率耗散值極不穩定性的數值參數，分析了材料成型性、鍛件缺陷及微觀組織結構。透過數值分析對傳統圓棒鍛造進行生產下料尺寸之分析，並分析其產品材料流動及體積分配，並提出設計之預成型方案。 最終透過數值分析結果與實驗鍛造進行驗證，數值分析有效的預測了鍛件之充填性不足及夾料(包料)之缺陷，最終滿足鍛造產品精度公差及產品品質之要求的預成型設計，預成型設計可有效節省材料重量10.26%，材料使用率從79.01%提升至88.08%，改善了毛邊過大之問題並有效降低了鍛造負荷達12.40%，並透過加工圖(processing map)結果分析，鍛件中心圓之應變、應力及溫度條件下可獲得較佳之微觀結構。 ;In this article the conventional aluminum crown forging process for mass production of shock absorber assembly is experimentally and numerically studied. The preform design method was proposed to improve the quality of post-forged product, save the material weight, and decrease manufacturing cost for finishing process. Finite element (FE) simulation software was employed to numerically analyze the material flow lines, strain, temperature, and effective stress distribution to reduce time and cost in obtaining the optimized preform design. Furthermore, the software is used to extract the numerical results power dissipation efficiency and instability from the processing map analysis of stress-strain rate material data in different temperatures and strains, which are useful parameters to analyze formability and microstructures of material. The numerical results have accurately predicted the poor quality and serious underfilling defects in the conventional post-forged product. Then, the new preform designs were proposed based on the previous numerical analysis, and finally the optimized preform design that successfully met precision tolerances and satisfied quality requirements was achieved. The optimized preform design saves material weight up to 10.26%, increases material utilization from 79.01% to 88.08% which improves the problem of excessive flash in the conventional case, and reduces the forging load up to 12.40%. Processing map analysis shows that the fine grain size microstructures can be obtained under stress, strain and temperature conditions that are similar to area around center circular which is also validated well in microstructure examinations.
