非破壞評估可靠度之模型適合度探討

張紘睿(Horng-Ruey Chang)

指導教授 ： 吳文方

國立臺灣大學/工學院/機械工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00122

摘要

在航空、核能、鋼鐵業中，為了維護結構的安全性或產品的品質，人們常使用非破壞檢測(nondestructive testing, NDT)來尋找結構中可能存在的裂縫。從檢測結構後得到的訊號(signal)，我們可以判斷結構存在裂縫與否。但在許多因素的影響之下，有雜訊(noise)存在，也就是檢測裂縫得到的訊號存在不確定性。對此，我們可以線性迴歸模型解釋，裂縫長度與所得訊號成正比，各裂縫所得到的所有訊號是變異數相同的對數常態分佈，也就是說，雜訊總是相同的常態分佈。並可建立檢測機率(probability of detection, ) 曲線，以探討非破壞檢測儀器對不同長度裂縫的檢出機率。實際上，由於樣本數有限，不同裂縫所得的雜訊分佈未必分散程度相同，也未必來自常態分佈，因此我們可以統計學中的假設檢定來驗證，文中舉兩個例子分別驗證後，雜訊可視為來自常態分佈，但量測不同大小裂縫所得雜訊，其分佈的分散程度則不相等，亦即變異數不相等。

關鍵字

非破壞檢測 ； 檢測機率曲線

並列摘要

Non-Destructive Testing (NDT) plays an important role in the safety assessment of structures. Based on signal response of NDT detection, we can judge whether there are cracks or not in structures. However, The NDT result is influenced by many factors. Because of such uncertainty, the signal response data had better be analyzed with a linear regression model. The (Probability of Detection, ) curve as a function of crack length can be constructed from the data based on the model to reveal the ability of detection for a certain NDT apparatus. Since the thus evaluated is related to the probability distribution of the noise. A detailed statistical analysis of the noise is also provided in the present study. After testing of the probability distribution of noise, the assumed normal distribution is valid. But the variance of the probability distribution of noise from different crack length is not the same.

並列關鍵字

NDT ； POD

參考文獻

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