在現今3C產品輕量化的前提下,如何在製造產品前即對結構重量做輕量化的設計成為一個相當重要的課題。另一方面,結構在受力產生變形後,可能會造成產品的失效。因此本文探討一個承受扭力作用之鈑金件變形的情形。分析方法是利用商用有限元素分析軟體及程式內部的最佳化模組,對一受扭力作用之鈑金固定件進行應力與結構最佳化分析。在最佳化求解的過程中,定義七個不同的鈑金件幾何設計參數(最大長度、孔邊最小距離、厚度、高度、寬度、上下側圓角)。個案一設定最佳化目標函數為最大位移量最接近目標值,限制條件為最大應力需小於材料的極限應力;個案二設定最佳化目標函數為鈑金固定件的體積,限制條件為最大應力需小於材料的降伏應力。在限定的設計範圍內,對目標函數求其最小值。 在個案一設計空間中找出了一組最佳解,其最大應力不超過材料的極限強度,且其最大位移量能最接近設定的目標值0.2mm。在個案二中,比較原始模型與同厚度之最佳化模型,得到很大的體積改善,其體積減少了184.9mm3,相當於節省了58.59%的材料重量。比較兩個個案可以發現同樣的幾何參數對於結構的最大位移與應力,皆有相同趨勢的影響。
In the present 3C product industry, designing a lightweight structure is one of the important issues in mechanical design. The purpose of this article is to find optimum size of sheet metal parts under twisting load. The commercial finite element program is used to analyze the stress responses, and the optimization modular in program is then used to analyze and optimize the size of sheet metal parts under the objective function, constrained conditions and the design variables. The design variables are the length, the distance between the hole and the edge, thickness, height, width, and the radius of top and bottom fillet. The goal of case1 is to find the predefined displacement of metal part. The constrained condition is that the maximum stress must be below the ultimate strength of the material. The objective of case2 is to minimize the weight of the parts designed. The constrained condition is that the stress yielded at critical point must be below the yield strength of the material. After study, the optimum solution with maximum displacement of 0.2mm for case1 is obtained. And for case2 with thickness of 1mm, an optimum solution is also generated with a weight reduction of 58.59% compared to the original model.