機車車架結構之剛性分析與測試

Analysis and Test of Structure Stiffness for a Motorbike Frame

高宗華(Chong-Hua Kao)

指導教授 ： 胡惠文

國立屏東科技大學/工學院/車輛工程系所/碩士(2010年)

摘要

本論文主要目的是利用電腦輔助工程設計分析(CAE)進行機車前車架結構之設計分析，並以測試驗證其模型與分析結果。內容包括：建立有限元素分析模型、結構模態分析與測試、靜態剛性強度分析與測試、以及殘留應變分析。在執行相關之分析前必須先確定有限元素分析模型之等效性，然後再進行模擬分析方能獲得準確的結果。首先採用ANSYS建立機車前車架結構之有限元素分析模型，為提升分析模型的準確性，有限元素分析模型所需之材料機械性質皆透過拉伸試驗來獲取。車架結構有限元素模型之等效性可藉由重量、重心的量測以及實驗模態分析所獲得之模態參數進行驗證比對，其目的為確認有限元素模型質量與剛性的分佈情形，車架結構模型比對完成並確定有限元素模型為等效模型後，即可進行有限元素靜態之剛性與強度分析(扭轉剛性與彎曲剛性)，同時執行剛性測試，初步需依照實際車架組裝過程中，所有零組件之相關位置及作用情形並設計出可取代實際車架結構固定情況之治夾具設計出車架剛性測試平台。測試項目包括剛性與應變之量測，透過分析過程中可預測結構材料的變形以及應力分佈情形，並將分析與測試進行結果之比對。完成模型驗證以及剛性與強度分析之後，可更深入探討車架矯正過程中之殘留應變與強度。有限元素分析模型必須擷取由拉伸試驗獲得塑性區之應力應變曲線並將其曲線輸入有限元素分析模型中，並根據實際車架矯正過程中可能發生之情形加以模擬分析，藉由材料非線性分析結果可得知車架結構以不同之矯正方式其殘留應變位置，最後進一步提出最佳的矯正方式，減少殘留應變發生於銲道位置上。

關鍵字

機車車架 ； 有限元素模型 ； 實驗模態分析 ； 剛性分析與測試 ； 材料非線性 ； 殘留應變與強度分析

並列摘要

The objective of this research is to investigate the design of structural stiffness and strength for a motorbike frame by using the computer-aided engineering and test technique. The working tasks include finite element modeling, experimental modal analysis (EMA), stiffness and strength analysis, stiffness and strength test, and residual strain analysis for the straightening of frame during the manufacturing. The finite element model (FEM) is established by using the commercial code ANSYS. The frame is made by several aluminum alloys. Tensile tests are used to obtain the mechanical properties of the frame materials. The weight and the center of gravity of FEM are first validated. EMA is then conducted on the frame to obtain the natural frequencies and the associate mode shapes, which are used to validate the distribution of mass and stiffness of FEM. This will guarantee the FEM is equivalent to the real frame structure. The analyses and tests of bending and torsion stiffness are performed. The test jig is designed to provide the proper constraint equivalent to the real boundary conditions. The deformations of frame and strains are measured to compute the stiffness and strength of the frame. The residual strain and stress of the frame are of concern due to its straightening in manufacturing. The full stress-strain curves of the materials are obtained from the tensile tests and then entered to the software. Four approaches of straightening are investigated by using the nonlinear analysis to find a proper straightening which generates the minimum residual strain in the welding.

並列關鍵字

motorbike frame ； finite element model ； experimental modal ； stiffness and strength analyses ； stiffness and strength tests ； material nonlinear ； residual strain and stress analyses

參考文獻

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