- 學位論文
車輛動態分析與疲勞破壞預測
Vehicle Flexible-Body Dynamic Simulation and Fatigue Prediction
摘要
本研究採用越野沙灘車(Dune buggy)之CAE骨架模型，主要目的是探討零部件相對於不同的道路，產生動態反應力的耐久性試驗模擬，進而對零部件疲勞破壞分析。本論文以Patran作為前處理器，來分解完成劃分網格的越野沙灘車模型，並經由模態分析後，運用模態疊加的理論，將剛性模型以可變形的柔性體取代。並以ADAMS/View軟體為動態模擬平台，透過不同路面回授應力測試，求出零件的應力隨時間之紀錄，將應力-時間歷程再匯入疲勞分析軟體中，求解零件的疲勞壽命。最後分析車架容易損傷的零件，依照分析結果來預測車架容易破壞的位置。運用柔性體的動態模擬技術，較使用剛體模型的計算，更能切確地描述實際物體運動因彈性變形的情況。相對於有限元素法的網格計算方式，可大量減少矩陣方程式自由度，節省軟體計算時間，與計算資料的檔案大小。並對使用不同的路面、調整模型模態以及剛性與柔性體等變數，去相互比較分析差異，結合疲勞分析軟體，用以預測車輛壽命，以車架管壁2.5mm均厚的模型，在隨機不平路面上，以50km/hr速度前進，可持續7.72小時耐久壽命。經此過程以模擬的方式代替實車測試，可減少開發測試成本，加速耐久性測試時間，獲得產品壽命預測，在產品量產前的設計階段上給予參考與改善，完成一連貫的耐久性分析流程。
並列摘要
The objective of this research was to use a CAE (Computer-Aided Engineering) model of an off-road vehicle, Dune buggy, to investigate the bearing loads of each critical parts from different road conditions, and analyze the fatigue damage of components. Patran was chosen as the pre-processor tool to deal with the ATV (All Terrain Vehicle) meshing model, and transformed the FEM (Finite Element Method) mode to the flexible body element used in ADAMS. The results of the stress history of components were simulated in ADAMS. The location of the maximum stress point on the model was predicted, and the analysis of fatigue was calculated according to the stress history of maximum stress point. The flexible body dynamic simulation technology could describe the actual elastic deformation of simulated objects. With this technology, the grid computing approach of finite element method could be replaced with a much smaller equation matrix, and simulation time was significantly reduced. Different road conditions, number of modes of the flexible components used, and component properties were simulated and compared in this research. The frame of the model with a 2.5mm thick wall was predicted to have 7.72 hours durable life in a 50km/hr off-road pace. This process could reduce vehicle development cost and the time required for accelerated durability hardware test, and provided preliminary life predictions of parts in early-design stage. It gave an appropriate reference to improve the durability prior the final production.