巨磁阻感測器於渦電流的非破壞性檢測之開發

Abstract

非破壞性檢測現今是一個相對成熟的領域，在交通運輸、製造和石化業中有著廣泛的應用。渦電流現象應用於非破壞性檢測已行之有年，然而，其檢測能力仍然存在著許多挑戰。隨著現代工業技術的不斷發展，對於缺陷檢測的要求也越來越嚴格，這使得渦電流技術和設計的發展向檢測深層缺陷、較小缺陷以及最小化激發電流幅度等方向的去邁進。能夠檢測到的缺陷的尺寸越小，診斷能力就越大。此外，在系統設計的方面也往自動化的檢測為主，以達到最高的檢測效率。渦電流檢測的系統經過幾十年的研究，已經有許多研究人員提出各種具有不同優勢的探針，在提高感測靈敏度、檢測極限方面都有著不少的進展。近年也有許多研究將感測元件加入渦電流系統中，其中較受關注的是巨磁阻電流感測元件。該元件可以在特定磁場範圍內有著出色的電壓變化，因此可以被做為渦電流檢測中接收線圈的角色，透過微弱的磁場變化即可獲得明顯的檢測結果，進而提高整體檢測效率。本研究在渦電流的非破壞性檢測上提出了一種雙線圈搭配巨磁阻感測器的組合，搭配自動化的檢測裝置及程式。在這個系統中，搭配了通過0.12 A的偏壓線圈，可以提高探針的量測靈敏度。在量測結果方面，對於1 mm至5 mm寬度的缺陷都有良好的響應結果，對於鋁片的不連續面也可以明顯的量測出來，對於激發頻率的部分也可以在100 Hz時請出的呈現出缺陷的存在。對於表面以下1毫米處的缺陷也可以在1000 Hz的激發頻率下明顯的表現在量測結果上。Non-destructive testing (NDT) is now a relatively mature field with widespread applications in transportation, manufacturing, and the petrochemical industry. Eddy current phenomena have been used in non-destructive testing for many years; however, their detection capabilities still face numerous challenges. With the continuous development of modern industrial technology, the requirements for defect detection have become increasingly stringent. This has propelled the advancement of eddy current technology and designs towards detecting deeper flaws, smaller defects, and minimizing excitation current amplitudes. The ability to detect smaller defects enhances diagnostic capabilities. Additionally, there is a trend towards automated inspection in system design to achieve the highest inspection efficiency.After decades of research on the eddy current detection system, many researchers have proposed various probes with different advantages, and there has been a lot of progress in improving the sensing sensitivity and detection limit. In recent years, many studies have added sensing elements to the eddy current system, among which the giant magnetoresistive current sensing element has received more attention. The element can have excellent voltage changes in a specific magnetic field range, so it can be used as a receiving coil in eddy current detection, and obvious detection results can be obtained through weak magnetic field changes, thereby improving the overall detection efficiency.This study proposes a combination of double coils setup with a GMR sensor for NDT of eddy currents, along with an automated testing apparatus and program. In this system, the incorporation of a bias coil with a current of 0.12 A enhances the sensitivity of the probe. In terms of measurement results, it demonstrates good response to defects ranging from 1 mm to 5 mm in width, and can also distinctly detect discontinuous surfaces in aluminum sheets. Defects can be clearly identified at an excitation frequency of 100 Hz. Additionally, defects situated up to 1 millimeter beneath the surface can be prominently manifested in the measurement results under an excitation frequency of 1000 Hz.