複合式讀卡機之疲勞失效分析與可靠度評估

Abstract

本文目的在於研究複合式讀卡機的疲勞失效模式及其效應，推斷容易引起失效的零件，然後建立三種不同破壞準則探討零件疲勞壽命的可靠度。研究過程中，首先瞭解複合式讀卡機之作動要點、功能及機構特色，建立作動流程與可靠度方塊圖，藉由失效模式與效應分析探討複合式讀卡機的元件，分析低層次組件失效對較高層次系統的影響，並推斷容易引起疲勞失效的零件，再依據零件材料之疲勞應力，建構三種破壞準則即「疲勞應力小於工作應力振幅」、「安全因數小於1」、「工作應力點與Goodman失效面的距離小於0」，並藉此建立極限狀態方程式，再利用first order second moment方法計算可靠度指標β值，並研究各參數之變異程度對零件疲勞壽命之可靠度影響。文中說明如何計算各種破壞準則的可靠度，並分析何種破壞準則計算可得到較保守之可靠度指標β值，進一步分析零件各設計參數對可靠度之敏感度分析，於敏感度分析結果之中，可選擇高敏感度參數作為設計、製造、進料檢驗重點以生產高可靠度低成本之零件。

The purpose of this paper is to study the failure of the critical components of the hybrid card reader using the failure mode and effects analysis (FMEA). In the failure analysis, three different failure criteria are used to study the fatigue life reliability of the components. In the analysis process, after reviewing the operational conditions, functions and mechanism characteristics of the hybrid card reader, the operational procedure and reliability related diagrams are constructed. The FMEA is used to analyze the components’ failure effects to study how they can affect the reliability of the system and determine which components are easier to fail. The fatigue life reliabilities of the components are computed by using the three different failure criteria, namely, stress-strength criterion, safety factor, and Goodman failure criterion. The limit state equations derived from the corresponding failure criteria are used in the reliability analysis of the components. The first order second moment method is used to calculate the reliability index β and study how the component parameters’ variances affect the fatigue life reliability of the component. The results obtained in this study can identify the failure criterion which produces the lowest reliability. In the sensitivity analysis, the effects of the component’s design parameters on fatigue reliability are investigated. The results can help identify the key factors important to the design, manufacturing and inspection of components with higher reliability and lower cost.