斜圈彈簧致動聚四氟乙烯密封件高週期磨耗評估

Abstract

斜圈彈簧致動聚四氟乙烯密封件係一裝配於往復作動之軸心抑或活塞之元件，聚四氟乙烯材料因較缺乏彈性，通常需將彈簧裝配於密封件溝槽以克服此問題。經過高週期循環運轉後，密封件與軸心之接觸壓力因磨耗增加而下降，最終可能導致密封失效。本研究以應用於半導體晶片封裝設備點膠機之密封件為檢視對象，針對環狀斜圈彈簧進行壓縮模擬，將其徑向力量-位移關係簡化為等效彈簧模型。採用Drucker-Prager組成律模型描述聚四氟乙烯材料行為，進行單軸拉伸模擬，擬合相對應實驗量測結果，獲致所需材料參數。建立密封件軸對稱模型，撰寫使用者副程式進行磨耗分析，採用改良之Archard磨耗模型，計算每一增量步之接觸壓力與滑移距離增量，並控制相對應節點位移。本研究透過自行提出之混合式滑移距離增量分析手法，搭配合理調整倍數因子，大幅提昇數值運算效率。數值分析可獲致與實驗相近之密封件幾何構形與密封唇部磨耗比例，密封面接觸壓力分佈則隨磨耗週期增加愈趨下降且均勻。進一步透過流體動力潤滑分析計算密封件之淨洩漏量，獲致經磨耗後之密封性能變化。

Canted coil spring energized polytetrafluoroethylene (PTFE) seals are typically used in areas where elastomeric seals cannot meet the frictional, temperature, pressure, or chemical-resistance requirements of the application. After relatively high cycle operations, the contact pressure between the seal and the associated component could decrease due to wear of the contact surface, which eventually leads to the loss of the sealing capability. Failure of the seals would result in damage of equipment, and the expense of repairing is essentially higher than simply replacing the damaged seals. Evaluation of the sealing performance is therefore rather important. However the experimental investigation of the wear behavior is generally time consuming and costly, wear simulation procedures based on the finite element analysis for the seal are proposed here. Experimental and numerical investigations of mechanical behaviors of the canted coil spring and PTFE material are first performed, and the wear analysis model of spring-energized PTFE seal used in semiconductor equipment is then constructed. The modified Archard model is implemented into a self-coded user subroutine of commercial finite element software to assess the wear amount of the seal. Simulation results show that the profile of the worn seal and the worn thickness of the seal lip as well are consistent with the corresponding experimental observations. Contact pressure distributions of the contact surface of the seal are examined during the period of the wear process. It is reported that the contact pressure declines gradually with respect to the increasing operation cycles, and the potential leakage caused by the wear could then occur.