基于磁导率检测技术的铁磁试件检测试验研究

发布时间：2018-01-23 04:28

本文关键词： 无损检测磁导率检测应力集中疲劳损伤热处理工艺　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：磁导率检测技术是一种依据探头闭合磁路中感应电压与磁通量的变化率成正比的电磁感应原理来检测试件磁导率变化的评价方法。该检测技术不仅可高精度检测构件某区域与磁导率相关的各种变化,如应力集中、疲劳损伤、结构相变、老化蜕变等,还能够检测力学韧性和力学脆性的转变、检测铁磁材料的马氏体奥氏体相变、检测位错缺陷密度变化、检测晶粒晶界的变化等。本文首先介绍了磁导率检测技术的研究背景及国内外研究现状。基于电磁学、铁磁学、金属物理学、电磁检测、热处理等多个学科知识,阐述了磁导率检测技术的检测机理;从电磁感应原理和磁路欧姆定律出发,推导分析了磁导率检测技术的检测方法和检测原理。依据磁导率检测原理,针对棒状待检构件设计研制一高灵敏检测传感器,研究了检测线圈绕线线经、绕线线圈匝数、激励电压对最佳检测频率和检测分辨率的影响。研究发现,最佳激励频率随线径的增加而减少,信号分辨率随线径的增加而增加;绕线匝数与激励最佳频率无关,但与信号分辨率有关;激励电压对最佳频率无影响,但对信号分辨力有影响。试验中所用的传感器参数为:激励线圈和检测线圈的线经采用0.35mm,线圈缠绕采用激励线圈和检测线圈叠加的缠绕方式;选用交流电压源作为激励源,最佳激励电压为5V,最佳检测频率为250Hz,选取最佳激励线圈和检测线圈都为400匝。分别对Q235钢、45号钢进行了拉伸、疲劳试验研究,对40Cr钢进行了热处理试验研究。测量分析了磁导率参量随拉应力、残余应力和热处理组织之间的变化关系。在拉伸试验中,研究发现,Q235钢绝对信号变化量为0.33V,相对信号变化量可达到8%;对45号钢,绝对信号变化量为0.3V,相对信号变化量可达到7.6%。检测信号对拉力残余应力的反应非常灵敏,Q235钢绝对信号变化量为0.8V,相对信号变化量可达到20%;对45号钢,绝对信号变化量为1.0V,相对信号变化量可达到26%。对疲劳损伤的检测灵敏度较低,在整个疲劳损伤试验过程中,Q235钢绝对信号变化量为0.13V,相对信号变化量可达到3.3%;对45号钢,绝对信号变化量为0.035V,相对信号变化量可达到1%。在热处理试验中,磁导率信号随淬火温度的升高而减小;在相同淬火温度条件下,磁导率信号随回火温度的升高而增加。依据磁导率检测技术,可有效测量试件所处的应力状态和残余应力状态;依据应力作用后遗留的残余应力,可判断构件曾经受过的最大应力,测定构件的应力前历状况;依据磁导率信号值可有效地判断热处理工艺质量。
[Abstract]:The permeability measurement technique is a new method to measure the change of permeability of the sample according to the principle of the inductive voltage in the closed magnetic circuit of the probe is proportional to the change rate of magnetic flux. This technique can not only be used to detect the magnetic permeability of the specimen with high precision. A variety of changes related to permeability in an area of a component. Such as stress concentration, fatigue damage, structural transformation, aging transformation, can also be used to detect mechanical toughness and mechanical brittleness transformation, to detect martensite austenitic transformation of ferromagnetic materials, and to detect the change of dislocation defect density. Firstly, this paper introduces the research background of permeability measurement technology and the research status at home and abroad, based on electromagnetism, ferromagnetism, metal physics, electromagnetic detection. In this paper, the mechanism of permeability testing technology is expounded, based on the knowledge of heat treatment and many other disciplines. Based on the principle of electromagnetic induction and the Ohm law of magnetic circuit, the detection method and principle of permeability detection technology are deduced and analyzed. A highly sensitive detection sensor is designed and developed for rod-shaped components to be tested. The effects of coil winding, winding coil turns and excitation voltage on the optimal detection frequency and detection resolution are studied. The optimal excitation frequency decreases with the increase of the line diameter, and the signal resolution increases with the increase of the line diameter. The number of winding turns is independent of the optimal excitation frequency, but is related to the signal resolution. The excitation voltage has no effect on the optimum frequency, but has an effect on the signal resolution. The sensor parameters used in the test are as follows: the line of the exciting coil and the detecting coil is 0.35mm. Coil winding adopts the winding mode of excitation coil and detection coil superposition; The AC voltage source is selected as the excitation source, the optimal excitation voltage is 5 V, the optimal detection frequency is 250 Hz, and the optimum excitation coil and detection coil are 400 turns. The tensile and fatigue tests of 45 # steel and the heat treatment test of 40Cr steel were carried out. The magnetic permeability parameters with tensile stress were measured and analyzed. The relationship between residual stress and heat treatment structure. In the tensile test, it is found that the absolute signal of Q235 steel is 0.33 V, and the relative signal change can reach 8 parts. For 45 steel, the absolute signal variation is 0.3 V, and the relative signal variation can reach 7.6. The detection signal is very sensitive to the residual stress of tensile force. The absolute signal change of Q235 steel is 0.8V, and the relative signal variation can reach 20V. For 45 steel, the absolute signal change is 1.0 V, and the relative signal variation can reach 26%. The sensitivity of fatigue damage detection is low, and it is in the whole process of fatigue damage test. The absolute signal change of Q235 steel is 0.13V, and the relative signal variation can reach 3.3V; For 45 steel, the absolute signal variation is 0.035 V, and the relative signal variation can reach 1. In the heat treatment test, the permeability signal decreases with the increase of quenching temperature. At the same quenching temperature, the permeability signal increases with the tempering temperature. According to the permeability measurement technology, the stress state and the residual stress state of the specimen can be effectively measured. According to the residual stress left behind by the stress action, the maximum stress of the component can be judged, and the stress history of the component can be measured. According to the signal value of permeability, the quality of heat treatment process can be effectively judged.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115

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