【摘要】：微觀和宏觀應(yīng)力集中區(qū)域是金屬構(gòu)件和機(jī)器部件發(fā)生損傷的主要部位。常規(guī)的無(wú)損檢測(cè)方法在管道及鐵磁性材料試件的缺陷檢測(cè)等方面具有重要意義，但無(wú)法切實(shí)有效的預(yù)防由于各種微觀應(yīng)力集中區(qū)域引起的突發(fā)性事故。近年來(lái)發(fā)展起來(lái)的金屬磁記憶檢測(cè)方法是通過對(duì)鐵磁性材料進(jìn)行早期診斷以達(dá)到預(yù)防的目的。但由于該技術(shù)理論尚不完善，影響因素眾多，在工程應(yīng)用中外界磁場(chǎng)對(duì)金屬磁記憶檢測(cè)的影響尚不能定量評(píng)估，故研究外界磁場(chǎng)對(duì)磁記憶檢測(cè)方法的影響十分必要。 本文研究能量平衡理論、電磁場(chǎng)理論及J-A磁機(jī)械效應(yīng)理論等，利用不同理論分析在磁記憶檢測(cè)過程中外界磁場(chǎng)對(duì)檢測(cè)結(jié)果的影響，從而證明外界磁場(chǎng)可能掩蓋磁記憶信號(hào)。通過以鋼筋及冷拔棒等具有代表性的鐵磁性材料做為實(shí)驗(yàn)試件，利用永磁鐵磁場(chǎng)模擬外界磁場(chǎng)，對(duì)存在應(yīng)力的鋼筋及冷拔棒在外界磁場(chǎng)環(huán)境下進(jìn)行金屬磁記憶檢測(cè)。檢測(cè)結(jié)果顯示在外界磁場(chǎng)影響下鐵磁性材料的彈性階段應(yīng)力集中區(qū)域磁記憶信號(hào)消失，，磁場(chǎng)環(huán)境下重復(fù)受力后磁記憶信號(hào)即可被重新識(shí)別；塑性階段應(yīng)力集中區(qū)域磁記憶信號(hào)不會(huì)因外界磁場(chǎng)出現(xiàn)明顯的變化。根據(jù)理論分析與實(shí)驗(yàn)檢測(cè)結(jié)果，結(jié)合金屬磁記憶磁疇壁聚合模型，鐵磁性材料在外界磁場(chǎng)的磁化作用下，內(nèi)部磁疇會(huì)發(fā)生偏轉(zhuǎn)或者位移形成殘余應(yīng)力，在彈性階段由于外加應(yīng)力相對(duì)殘余應(yīng)力較小，應(yīng)力集中區(qū)域磁記憶信號(hào)容易被外界磁場(chǎng)信號(hào)所掩蓋，導(dǎo)致磁記憶信號(hào)消失。磁場(chǎng)環(huán)境下重復(fù)受力會(huì)增加外加應(yīng)力抵消殘余應(yīng)力作用，磁記憶信號(hào)重新顯現(xiàn)。對(duì)于塑性階段由于外加應(yīng)力遠(yuǎn)大于外界磁場(chǎng)所致的殘余應(yīng)力，故會(huì)不產(chǎn)生明顯影響。 根據(jù)理論分析與實(shí)驗(yàn)檢測(cè)結(jié)果表明，在外界磁場(chǎng)環(huán)境下金屬磁記憶檢測(cè)方法在施加應(yīng)力較小時(shí)，彈性階段應(yīng)力集中區(qū)域磁記憶信號(hào)被抵消；當(dāng)外加應(yīng)力增加后，外界磁場(chǎng)影響效果減小。外界磁場(chǎng)不會(huì)對(duì)塑性階段金屬磁記憶信號(hào)產(chǎn)生明顯影響。因此，金屬磁記憶是一種有效可靠的早期診斷方法，具有普遍的適用性。
[Abstract]:Micro-and macro-stress concentration areas are the main damage areas of metal components and machine components. The conventional non-destructive testing (NDT) method is of great significance in the defect detection of pipes and ferromagnetic materials, but it can not effectively prevent the sudden accidents caused by various micro-stress concentration areas. The metal magnetic memory detection method developed in recent years is to achieve the purpose of prevention by early diagnosis of ferromagnetic materials. However, because the theory of this technique is not perfect and there are many influencing factors, the influence of external magnetic field on metal magnetic memory detection can not be quantitatively evaluated in engineering application, so it is necessary to study the influence of external magnetic field on magnetic memory testing method. In this paper, the theory of energy balance, the theory of electromagnetic field and the theory of JA magneto-mechanical effect are studied, and the influence of external magnetic field on the results of magnetic memory testing is analyzed by using different theories, so as to prove that the external magnetic field may cover up the magnetic memory signal. By using typical ferromagnetic materials such as steel bar and cold-drawn bar as experimental specimens and using permanent magnet magnetic field to simulate the external magnetic field, the metal magnetic memory of steel bars and cold-drawn bars with stress in the external magnetic field environment was tested. The results show that the magnetic memory signal in the elastic phase of ferromagnetic material disappears under the influence of external magnetic field, and the magnetic memory signal can be re-recognized after repeated stress in the magnetic field environment. In the plastic stage, the magnetic memory signal in the stress concentration region does not change obviously due to the external magnetic field. According to the theoretical analysis and experimental results, combined with the metal magnetic memory domain wall polymerization model, the internal magnetic domain deflection or displacement will occur in ferromagnetic materials under the magnetization of the external magnetic field to form residual stress. In the elastic stage, the magnetic memory signal in the stress concentration region is easily masked by the external magnetic field signal because the applied stress is relatively small relative to the residual stress, which leads to the disappearance of the magnetic memory signal. The repeated stress in the magnetic field will increase the applied stress to counteract the residual stress, and the magnetic memory signal will appear again. In plastic stage, the residual stress caused by external magnetic field is much larger than that caused by applied stress, so there is no obvious influence on the residual stress caused by external magnetic field. According to the theoretical analysis and experimental results, it is shown that the magnetic memory signal in the stress concentration region of the elastic phase is counteracted by the metal magnetic memory detection method in the environment of external magnetic field when the applied stress is small. When the applied stress increases, the effect of external magnetic field decreases. The external magnetic field has no obvious effect on the metal magnetic memory signal in plastic stage. Therefore, metal magnetic memory is an effective and reliable early diagnosis method, which has universal applicability.
【學(xué)位授予單位】：沈陽(yáng)工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG115.28

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