本文選題：金屬磁記憶檢測 + 力磁耦合�。� 參考：《南昌航空大學》2017年碩士論文

【摘要】：金屬磁記憶信號是弱磁信號,容易受很多因素的影響,以至于金屬磁記憶方法不能為工程實踐提供可靠的、準確的檢測。本論文主要從試驗研究和理論研究分析磁化狀態(tài)、環(huán)境磁場和熱處理工藝對金屬磁記憶信號變化規(guī)律的影響。對三種不同磁化狀態(tài)的Q235鋼平板工件進行靜載拉伸試驗,探討了磁化狀態(tài)對磁記憶信號和力磁耦合關系的影響。試驗結(jié)果表明:在彈性階段和塑性變形的初始階段,對于磁化的試件,應力是使初始磁化狀態(tài)不斷向無磁滯磁化狀態(tài)靠近的過程,而磁化狀態(tài)的改變量由初始磁化狀態(tài)與無磁滯磁化狀態(tài)之間的距離決定。磁化試件的表面所有采樣點的力磁變化趨勢整體呈“聚攏"的趨勢;而對于未磁化的工件,應力使試件磁化,所有點的力磁變化趨勢整體卻呈“張開"的趨勢;在塑性變形的穩(wěn)定階段,對于磁化和未磁化的工件,磁化強度變化量都較小,基本保持穩(wěn)定。對六種不同環(huán)境磁場作用下的45#鋼圓棒試件進行靜載拉伸試驗,探討環(huán)境磁場對磁記憶信號和力磁耦合關系的影響。試驗結(jié)果表明:外加磁場不能改變磁記憶信號曲線和力磁關系曲線的形狀,但可以改變它們值的大小;在一定的磁場范圍內(nèi),應力引起的磁記憶信號值隨環(huán)境磁場的增加而增加,但當環(huán)境磁場超過某一臨界值時,磁記憶信號值反而隨環(huán)境磁場的增加而減少;當環(huán)境磁場為零或完全被抵消時,應力卻不能產(chǎn)生磁化效應,力磁關系曲線為一條水平的直線。觀察五種不同熱處理工藝金相試樣40Cr鋼圓棒的顯微組織,并測量試樣表面點的磁記憶信號值。結(jié)果表明:試件經(jīng)標準淬火之后,隨回火溫度的升高,磁記憶信號值不斷增大,抗拉強度不斷減小,但塑性卻不斷增強。對五種不同熱處理工藝的拉伸試樣40Cr鋼圓棒進行靜載拉伸試驗,探討熱處理工藝對磁記憶信號的影響。試驗結(jié)果表明:對于原始退火、中溫回火和高溫回火的拉伸試樣,它們的磁記憶信號曲線和梯度曲線的變化規(guī)律近似相同;對于標準淬火和低溫回火的拉伸試樣,它們的磁記憶信號曲線和梯度曲線的變化規(guī)律近似相同。因此在金屬磁記憶檢測的實踐中,特別是在定量檢測的應用中必須考慮環(huán)境磁場的影響,且被檢測構件的初始磁化狀態(tài)和熱處理工藝不可忽略。
[Abstract]:Metal magnetic memory signal is a weak magnetic signal, which is easily affected by many factors, so that metal magnetic memory method can not provide reliable and accurate detection for engineering practice. In this paper, the effects of magnetization state, environmental magnetic field and heat treatment process on the variation of metal magnetic memory signal are analyzed in terms of experimental and theoretical studies. Static tensile tests were carried out on three Q235 steel plate workpieces in different magnetization states, and the effect of magnetization state on magnetic memory signal and magneto-magnetic coupling was discussed. The experimental results show that in the elastic stage and the initial stage of plastic deformation, the stress of the magnetized specimen is the process of making the initial magnetization state approach to the unhysteresis magnetization state continuously. The change of the magnetization state is determined by the distance between the initial magnetization state and the unhysteresis magnetization state. For the unmagnetized workpiece, the stress causes the magnetization of the specimen, but the trend of the change of the force and magnetism of all the points is "open" as a whole, and the trend of the change of the force and magnetism of all the sampling points on the surface of the magnetized specimen is "converging" as a whole, while for the unmagnetized workpiece, the stress makes the sample magnetized. For both magnetized and unmagnetized workpieces, the change of magnetization intensity is small and stable in the stable stage of plastic deformation. The static load tensile test of four steel round bar specimens under six different environmental magnetic fields was carried out to investigate the effect of environmental magnetic field on the coupling relationship between magnetic memory signal and force magnetic field. The experimental results show that the applied magnetic field can not change the shape of the magnetic memory signal curve and the magneto-magnetic relation curve, but can change the magnitude of their values, and in a certain magnetic field range, The magnetic memory signal caused by stress increases with the increase of the ambient magnetic field, but when the ambient magnetic field exceeds a certain critical value, the magnetic memory signal value decreases with the increase of the ambient magnetic field, and when the ambient magnetic field is zero or completely offset, However, the stress does not produce magnetization effect, and the magneto-force relation curve is a horizontal straight line. The microstructure of the 40Cr steel rod of five different heat treatment processes was observed, and the magnetic memory signal of the surface of the sample was measured. The results show that the magnetic memory signal value increases and the tensile strength decreases, but the plasticity increases with the tempering temperature rising after standard quenching. The static tensile test of 40Cr steel round bar with five different heat treatment processes was carried out, and the effect of heat treatment process on magnetic memory signal was discussed. The experimental results show that the variation of magnetic memory signal curve and gradient curve are approximately the same for the tensile specimens with original annealing, moderate tempering and high temperature tempering, and the tensile specimens with standard quenching and low temperature tempering, Their magnetic memory signal curves and gradient curves are approximately the same. Therefore, in the practice of metal magnetic memory testing, especially in the application of quantitative testing, the influence of environmental magnetic field must be considered, and the initial magnetization state and heat treatment process of the tested components should not be ignored.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG115.284

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