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標題: | 煞車系統之振動分析及異音預測 Vibration Analysis and Squeal Prediction for the Brake System |
作者: | Cheng-Chang Hsieh 謝正昌 |
指導教授: | 王昭男(Chao-Nan Wang) |
關鍵字: | 煞車異音,不對稱矩陣,模態分析,複數特徵值法,模態耦合, Brake squeal,Unsymmetric matrix,Modal analysis,Complex eigenvalue method,Modal coupling, |
出版年 : | 2008 |
學位: | 碩士 |
摘要: | 過往車輛工業在煞車系統的發展上,煞車異音的議題一直不是主要改善重點,不過,隨著人們生活品質的提高與對行車舒適性的要求,煞車異音的問題才逐漸受到重視以及開始被廣泛研究。本文主要探討目的是研究煞車系統元件對系統本身運動穩定性所造成的影響,利用煞車系統所產生之不穩定振動,進而預測煞車異音的生成。煞車異音的產生,主要是由摩擦襯墊與煞車碟盤接觸面間的摩擦作用力所引起的系統不穩定,在本文裡,利用有限元素分析軟體,建立實際摩托車的煞車系統模型,並推導出接觸面間的摩擦耦合作用力關係,運用線性交接面連結元素建構出一非對稱摩擦耦合勁度矩陣,模擬摩擦襯墊與碟盤交接面之間的耦合作用力影響,並建立煞車系統在接觸摩擦耦合作用力影響下的振動方程式,利用複數特徵值法,從計算所得到的複數特徵值判斷系統運動是否為穩定,進而預測可能發生煞車異音的頻率以及振動模態,從本文中發現產生煞車異音的模態會有模態耦合的現象。最後,藉由分析不同的系統參數值以及改變摩擦襯墊的幾何形狀,探討系統參數及摩擦襯墊的幾何形狀對煞車系統穩定度的影響,並引入一不穩定度指標,除了便於分析結果的表示之外,還可根據指標的大小判斷該振動模態是否容易有異音的發生,進一步利用模態耦合的現象預測系統運動即將發生不穩定時的臨界系統參數值,其模擬分析的結果也許可作為改善煞車異音的建議,其中以增加阻尼效應對消滅煞車異音的幫助最為顯著。 The purpose of this study is to analyze the unstable modes in linear conditions for the brake system and to provide the method for determining the stability characteristics of the brake system assembly. When the motion of brake system is unstable, it is the likelihood of brake squeal. The brake squeal typically occurs at unstable resonant frequencies of brake system. Finite element methods are used to derive the equations of motion for the brake system of motorcycle. The components of brake system are coupled together in the system model including the friction coupling terms between the pad and disc. The proposed friction coupling formulation produces an asymmetric stiffness matrix. This mechanism (varying force) provides necessary for energy to be fed into the vibrating system that will excite the unstable modes of the system. To study the stability of the system by the complex eigenvalue method, the friction effects between the pad and the disc are accounted for by introducing linear elements in an asymmetric stiffness matrix. The application of modal analysis in the finite element friction coupling model of the brake system is used to identify its complex eigenvalues and to relate them to the squeal occurrence. The positive real parts of complex eigenvalues reveal which modes are unstable and tend to generate the brake squeal. The image parts of complex eigenvalues is the frequency of the brake squeal. This analysis can be a predictive tool to squeal. An attempt is made to investigate the effect of the operational parameters (friction coefficient, brake pressure, proportional damping and the stiffness of each component for brake system) and the modification of pad shape on the brake squeal. The simulation results show that a pair of modes merges at the critical value of the operational parameters, i.e., their frequencies and mode shapes become identical. This merging state defines the modal coupling phenomenon and it may be the mechanism of brake squeal. Brake squeal can be reduced by decreasing the friction coefficient and brake pressure. The effect of modifying pad shape on the squeal is also obvious. However, increasing the damping have good results for eliminating brake squeal. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/37783 |
全文授權: | 有償授權 |
顯示於系所單位: | 工程科學及海洋工程學系 |
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