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研究生： 葉俊平
Yeh, Chun-Ping
論文名稱： FC250灰鑄鐵煞車碟盤之整合性數值模擬研究
Integrated Numerical Simulation for a FC250 Gray Cast Iron Brake Disc Casting
指導教授： 黃文星
Hwang, Weng-Sing
學位類別： 博士
Doctor
系所名稱： 工學院 - 材料科學及工程學系
Department of Materials Science and Engineering
論文出版年： 2010
畢業學年度： 98
語文別： 中文
論文頁數： 164
中文關鍵詞： 煞車振動 、灌模充填 、殘留應力 、硬度 、數值模擬
外文關鍵詞： brake judder, mold filling, residual stresses, hardness, numerical simulation
相關次數： 點閱：109  下載：1 
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    • 煞車振動的現象一般認為是由煞車碟盤的厚度變化所造成，此厚度變化是由於碟盤在煞車過程中殘留應力的釋放，或是不均勻的磨耗導致碟盤變形而造成。因此，如何經由調整煞車碟盤的鑄造條件來改善其機械性質，對於降低煞車振動現象極為重要。本研究使用商用鑄造模擬軟體ProCAST來進行FC250灰鑄鐵煞車碟盤鑄件之灌模充填、熱傳凝固、殘留應力及硬度整合性模擬解析，從模擬結果中獲取最佳化鑄造條件來達到降低煞車振動現象的效果。

    灌模充填及熱傳凝固模擬解析用來預測煞車碟盤鑄件的鑄造缺陷。首先針對原始澆流道設計做灌模充填及熱傳凝固模擬解析，並預測鑄造缺陷的位置及程度。為了獲得更佳的鑄造品質，鑄造方案的設計必須改善。經由改變澆流道系統的設計後，煞車碟盤鑄件的澆鑄過程變得更平穩及均勻，鑄造缺陷也明顯減少。

    殘留應力模擬解析用來預測煞車碟盤鑄件的殘留應力及熱裂現象。藉由改變開箱時間的條件來減少煞車碟盤鑄造時的殘留應力，同時也實際量測煞車碟盤的殘留應力，並與模擬結果做比對，模擬結果與實際量測結果相當吻合。模擬結果發現7200秒為最佳開箱時間。將不同開箱時間的煞車碟盤裝至汽車上進行實車測試，測試結果顯示僅有鑄造條件為7200秒開箱時間的煞車碟盤能通過實車測試，此與殘留應力模擬解析結果相符合。此外亦模擬澆流道系統修改前後煞車碟盤鑄件的熱裂現象，模擬結果顯示澆流道系統修改後煞車碟盤鑄件的熱裂現象可獲得改善。

    硬度模擬解析用來預測煞車碟盤的硬度分佈情形。藉由改變開箱時間來尋找煞車碟盤硬度分佈較均勻的鑄造條件。本研究使用Oldfield 模型來模擬煞車碟盤鑄件凝固過程中晶粒成核與成長的現象。首先先鑄造一校正鑄件，運用Oldfield模型並使用不同的晶粒成核與成長係數(Ae, Be)來模擬此校正鑄件的硬度，並與實際鑄件做比對，由此求得一組最佳成核與成長係數。利用此組係數來模擬測試鑄件的硬度，並再次與實際澆鑄之測試鑄件做比對，模擬結果與實際量測結果相當吻合。利用此種方法即可求得一組模擬FC250灰鑄鐵煞車碟盤鑄件硬度所需之晶粒成核與成長係數。除此之外，經由模擬不同開箱時間煞車碟盤鑄件的硬度分佈來尋找最佳鑄造條件，模擬結果發現7200秒同為最佳開箱時間。

    Brake discs are subject to wear and overheating during normal use and may distort, causing disc thickness variation(DTV) and feedback to the driver as brake judder through the brake pedal. Disc thickness variation on the brake disc may be due to relaxation of residual stresses through heating during continuous severe braking or by uneven wear. In order to improve mechanical properties of a brake disc casting to reduce the brake judder phenomena, proper design of casting condition is of great importance. In this study, a computer-aided engineering software; ProCAST, is applied to simulate the mold filling, solidification phenomena, residual stresses and hardness of a FC250 gray cast iron brake disc casting as well as to obtain optimum design. Then, brake judder phenomena can be alleviated.

    First, a numerical model is adopted to simulate the mold filling and solidification phenomena as well as to predict the occurrence of the related casting defects for a brake disc casting. The goal is to conduct numerical experimentation to improve the running and gating system of the brake disc casting to obtain better casting quality. Numerical simulations are conducted for the brake disc casting with a preliminary running and gating system. The mold filling and solidification phenomena are examined to predict the occurrence and extent of the casting defects. They are found to be consistent with the defects observed in the actual casting. Based on the findings of the simulated results, a modified running and gating system is then proposed. The mold filling and solidification phenomena for the modified design are simulated. The results show that the problem of casting defects is alleviated with use of present results.

    The numerical modeling of residual stresses and hot tear prediction model for a brake disc are also presented in this study. The goal is to conduct numerical experimentation to reduce the residual stresses of the brake disc casting to obtain better casting quality. Numerical simulations were conducted for the brake disc casting with different shake-out times. The solidification phenomena were examined to observe distribution of residual stresses and the optimized shake-out time was then proposed based on the simulated results to alleviate residual stresses of the brake disc casting. Experimentation procedures were also conducted to measure residual stresses of the brake disc casting. The predictions of residual stresses were validated by comparison with experimental measurements and consistency was found between the two results. The simulation results shows that 7200 seconds is a better shake-out time design and it can pass actual track testing. Besides, hot tearing phenomena are also simulated both with a preliminary and a modified running and gating system. Simulation results reveal that hot tearing phenomena is alleviated with a modified running and gating system.

    The purposes of hardness simulation are to develop a technique of numerically simulating the hardness of a FC250 gray cast iron brake disc casting and verified by experimental measurements. As the numerical model is proven reliable, numerical experimentation is then conducted to homogenize the hardness distribution of a brake disc to obtain better casting quality. The Oldfield’s model was adopted to simulate the nucleation and grain growth during solidification of the casting. A calibration brake disc casting was first made. By comparing the hardness of the calibration brake disc casting with the simulated results using different nucleation and growth coefficients (Ae, Be) in Oldfield’s model, the most appropriate set of values for Ae and Be was obtained. Then, this set of values was applied to the hardness simulation of a test brake disc casting and confirmed by experimental measurements. Through this approach, a set of nucleation and growth coefficients was obtained for the brake disc casting. Subsequently, numerical simulations were conducted for the brake disc casting with different shake-out times to evaluate its distribution of hardness and an optimized shake-out time was then proposed based on the simulated results. The predictions of hardness were validated by comparison with experimental measurements and actual track testing. The simulation results shows again that 7200 seconds is a better shake-out time design.

    摘要 i Abstract iii 目錄 vii 表目錄 x 圖目錄 xi 符號表 xvi 第一章 緒論 1 1.1 研究背景 1 1.1.1 煞車振動現象簡述 1 1.1.2 碟式煞車系統簡述 2 1.1.3 砂模鑄造製程簡述 3 1.1.4 電腦輔助設計與工程分析技術簡述 4 1.2 文獻回顧 5 1.2.1 鑄造灌模及凝固過程數值模擬技術之回顧 5 1.2.2 凝固過程縮孔形成之理論及預測方式之回顧 8 1.2.3 鑄造應力形成之理論及其回顧 11 1.2.4 硬度數值模擬文獻之回顧 15 1.3 研究內容與目的 17 第二章 理論基礎 27 2.1 灌模充填過程之數值模擬理論 27 2.1.1 灌模充填控制方程式 27 2.1.2 自由液面追蹤法則 29 2.2 熱傳凝固過程之數值模擬理論 29 2.3 縮孔預測指標 31 2.4 應力數值模擬理論 33 2.4.1 基本假設 33 2.4.2 彈塑性力學中基本變量 34 2.4.3 熱彈塑性模型理論 35 2.4.3.1 彈性控制方程式 35 2.4.3.2 塑性理論 37 2.4.3.3 彈塑性控制方程式 40 2.4.3.4 過渡係數和應變硬化率的決定 47 2.4.3.5 熱彈塑性控制方程式 48 2.4.3.6 應力場的數學模型 49 2.5 熱裂預測指標 52 2.6 硬度數值模擬理論 55 第三章 實驗方法與步驟 65 3.1 數值模擬 65 3.1.1 商用鑄造模擬軟體ProCAST之操作介面 65 3.1.2 數值模擬之流程 66 3.2 殘留應力之量測 68 3.2.1 Von Mises等效應力之決定 68 3.2.2 測得的電壓與應變之轉換關係 69 3.2.3 殘留應力量測步驟 70 3.3 硬度之量測 72 3.4 實車測試流程 73 第四章 結果與討論 96 4.1 煞車碟盤鑄件之灌模充填及熱傳凝固模擬解析 96 4.1.1 原始澆流道設計方案 96 4.1.2 原始澆流道設計方案之灌模充填及熱傳凝固模擬解析 97 4.1.3 修正澆流道設計方案 99 4.1.4 修正澆流道設計方案之灌模充填及熱傳凝固模擬解析 99 4.2 煞車碟盤鑄件之應力模擬解析與實驗驗證 101 4.2.1 原始澆流道設計方案之應力模擬解析 102 4.2.2 修正澆流道設計方案之應力模擬解析 103 4.2.3 煞車碟盤鑄件應力模擬解析之實驗驗證 105 4.3 煞車碟盤鑄件之硬度模擬解析與實驗驗證 106 4.3.1 原始澆流道設計方案之硬度模擬解析與實驗驗證 107 4.3.2 修正澆流道設計方案之硬度模擬解析 110 4.4 煞車碟盤鑄件之實車測試 112 第五章 結論 152 參考文獻 154

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