磁记忆力磁效应及对热处理质量评价的研究
发布时间：2018-09-13 13:23
【摘要】：磁记忆检测技术是基于地磁场作用下铁磁材料的力磁效应,该技术不仅能够检测铁磁材料的宏观裂纹,而且还能对材料应力集中区域进行早期判断,能够预防突发性的灾难发生,是一种新型的无损检测方法。目前,磁记忆检测技术主要研究的是,对铁磁材料构件是否存在宏观裂纹或者应力集中而进行的试验研究和探索性应用上,而对于热处理方面的研究较少。本文首先结合金属磁记忆的相关理论,以有限元分析和拉伸试验为研究手段,探索铁磁材料的力磁效应,最后将金属磁记忆技术应用到对铁磁材料热处理后的质量及性能评价上,这对于推动金属磁记忆检测技术在工程上的应用具有重要的意义。以Q235钢为研究对象,通过对不同缺口特征(V形缺口,半圆形缺口,双关联缺口)的试件进行了静载拉伸试验,同时对双关联试件进行了有限元仿真分析,观察其应力分布,探讨在地磁场环境下试件内部应力对磁记忆信号的影响,并将试验结果与仿真结果进行了对比。结果表明:从拉伸曲线上可知,三种缺口试件均发生了缺口强化现象,V形缺口试件缺口强化现象比半圆形缺口试件明显,而双关联缺口试件的缺口强化现象最为明显。从磁记忆曲线上可知,随着载荷的增加,不同缺口试件的磁记忆信号曲线变化规律一致,均在应力集中处发生了非线性的变化,且V形缺口处的磁记忆信号变化幅度大于半圆形缺口。双关联缺口中心处的磁场值近似于相对称两固定点磁场值的叠加,也近似为单个缺口试件在对应位置处磁场值的叠加,试验结果与仿真结果具有一致性。仿真结果还表明,从应力分布云图上可以看出,V形缺口应力集中程度比半圆形缺口大,且在双关联缺口中心处也出现了应力集中现象,而在试件中间应力集中部位法向分量漏磁场Hp(y)梯度值k(y)并没有达到最大,此时用漏磁场法向分量的梯度值对其应力集中程度进行评价不再适用。以45钢为研究对象,分别将试件进行了不同淬火方式(淬火温度、冷却介质)和不同回火方式(回火温度)的热处理试验,继而进行了静载拉伸试验。结果表明:磁记忆信号(35)B值随淬火温度的增大而降低,随冷却速度的增大而减小,随回火温度的增大而增大,即可以根据磁记忆信号特征(35)B值的大小,对淬火参数(淬火温度和淬火冷却速度)以及回火参数(回火温度)进行评价。根据磁记忆信号特征(35)B值,建立了铁磁材料热处理后力学性能参数与磁记忆信号之间的关系,(35)B值越小,其抗拉强度越大,伸长率越小。根据拉伸过程中有序拉应力作用下磁记忆信号曲线梯度的变化特征,可以对经过不同淬火方式和不同回火方式热处理的试件进行热处理质量评价,也可以对其受力状态以及损伤程度进行有效评估。
[Abstract]:The magnetic memory detection technique is based on the magnetic effect of ferromagnetic material under the action of geomagnetic field. This technique can not only detect the macroscopic crack of ferromagnetic material, but also make early judgement on the stress concentration area of material. It is a new nondestructive testing method that can prevent sudden disaster. At present, the main research of magnetic memory detection technology is whether there are macroscopic cracks or stress concentration in ferromagnetic materials, but less on heat treatment. In this paper, based on the theory of metal magnetic memory, finite element analysis and tensile test are used to study the magnetic and mechanical effects of ferromagnetic materials. Finally, the metal magnetic memory technology is applied to evaluate the quality and performance of ferromagnetic materials after heat treatment, which is of great significance to promote the application of metal magnetic memory detection technology in engineering. Taking Q235 steel as the research object, the static load tensile tests were carried out on specimens with different notched characteristics (V-shaped notches, semi-circular notches, double-correlated notches). At the same time, the finite element simulation analysis was carried out to observe the stress distribution of the double-correlated specimens. The effect of internal stress on magnetic memory signal in geomagnetic field is discussed, and the experimental results are compared with the simulation results. The results show that: from the tensile curves, the three notched specimens have notched strengthening phenomenon. The notched strengthening phenomenon of V-shaped notched specimens is more obvious than that of semi-circular notched specimens, while the notched strengthening phenomenon of double-correlated notched specimens is the most obvious. From the magnetic memory curve, it can be seen that with the increase of load, the variation of magnetic memory signal curve of different notched specimens is the same, and the nonlinear changes have taken place at the stress concentration. The variation of magnetic memory signal at V-shaped notch is larger than that of semi-circular notch. The magnetic field value at the center of the double correlation notch is similar to the superposition of the magnetic field value of the two fixed points of phase symmetry and the magnetic field value of the single notched specimen at the corresponding position. The experimental results are consistent with the simulation results. The simulation results also show that the stress concentration of V-shaped notches is larger than that of semicircular notches, and the stress concentration is also observed at the center of double-correlated notches. However, the Hp (y) gradient value of the normal magnetic field of the normal component is not the maximum at the middle stress concentration part of the specimen, so it is no longer applicable to evaluate the degree of the stress concentration by using the gradient value of the normal component of the magnetic field leakage. Taking 45 steel as the research object, heat treatment tests of different quenching methods (quenching temperature, cooling medium) and different tempering methods (tempering temperature) were carried out respectively, and then static load tensile tests were carried out. The results show that the (35) B value of magnetic memory signal decreases with the increase of quenching temperature, decreases with the increase of cooling rate, and increases with the increase of tempering temperature. The quenching parameters (quenching temperature and quenching rate) and tempering parameters (tempering temperature) were evaluated. According to the characteristic of magnetic memory signal (35) B, the relationship between the mechanical properties of ferromagnetic material after heat treatment and the magnetic memory signal is established. The smaller the value of (35) B is, the greater the tensile strength is and the smaller the elongation is. According to the variation characteristics of magnetic memory signal curve gradient under the action of ordered tensile stress during the tensile process, the heat treatment quality of the specimen treated by different quenching and tempering methods can be evaluated. The stress state and damage degree can also be evaluated effectively.
【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】：TG142.15;TG161
本文编号：2241298
[Abstract]:The magnetic memory detection technique is based on the magnetic effect of ferromagnetic material under the action of geomagnetic field. This technique can not only detect the macroscopic crack of ferromagnetic material, but also make early judgement on the stress concentration area of material. It is a new nondestructive testing method that can prevent sudden disaster. At present, the main research of magnetic memory detection technology is whether there are macroscopic cracks or stress concentration in ferromagnetic materials, but less on heat treatment. In this paper, based on the theory of metal magnetic memory, finite element analysis and tensile test are used to study the magnetic and mechanical effects of ferromagnetic materials. Finally, the metal magnetic memory technology is applied to evaluate the quality and performance of ferromagnetic materials after heat treatment, which is of great significance to promote the application of metal magnetic memory detection technology in engineering. Taking Q235 steel as the research object, the static load tensile tests were carried out on specimens with different notched characteristics (V-shaped notches, semi-circular notches, double-correlated notches). At the same time, the finite element simulation analysis was carried out to observe the stress distribution of the double-correlated specimens. The effect of internal stress on magnetic memory signal in geomagnetic field is discussed, and the experimental results are compared with the simulation results. The results show that: from the tensile curves, the three notched specimens have notched strengthening phenomenon. The notched strengthening phenomenon of V-shaped notched specimens is more obvious than that of semi-circular notched specimens, while the notched strengthening phenomenon of double-correlated notched specimens is the most obvious. From the magnetic memory curve, it can be seen that with the increase of load, the variation of magnetic memory signal curve of different notched specimens is the same, and the nonlinear changes have taken place at the stress concentration. The variation of magnetic memory signal at V-shaped notch is larger than that of semi-circular notch. The magnetic field value at the center of the double correlation notch is similar to the superposition of the magnetic field value of the two fixed points of phase symmetry and the magnetic field value of the single notched specimen at the corresponding position. The experimental results are consistent with the simulation results. The simulation results also show that the stress concentration of V-shaped notches is larger than that of semicircular notches, and the stress concentration is also observed at the center of double-correlated notches. However, the Hp (y) gradient value of the normal magnetic field of the normal component is not the maximum at the middle stress concentration part of the specimen, so it is no longer applicable to evaluate the degree of the stress concentration by using the gradient value of the normal component of the magnetic field leakage. Taking 45 steel as the research object, heat treatment tests of different quenching methods (quenching temperature, cooling medium) and different tempering methods (tempering temperature) were carried out respectively, and then static load tensile tests were carried out. The results show that the (35) B value of magnetic memory signal decreases with the increase of quenching temperature, decreases with the increase of cooling rate, and increases with the increase of tempering temperature. The quenching parameters (quenching temperature and quenching rate) and tempering parameters (tempering temperature) were evaluated. According to the characteristic of magnetic memory signal (35) B, the relationship between the mechanical properties of ferromagnetic material after heat treatment and the magnetic memory signal is established. The smaller the value of (35) B is, the greater the tensile strength is and the smaller the elongation is. According to the variation characteristics of magnetic memory signal curve gradient under the action of ordered tensile stress during the tensile process, the heat treatment quality of the specimen treated by different quenching and tempering methods can be evaluated. The stress state and damage degree can also be evaluated effectively.
【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】：TG142.15;TG161
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