共查询到17条相似文献,搜索用时 31 毫秒
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金属磁记忆检测技术是一种可早期检测铁磁构件应力集中程度的新方法,但进一步定量评价和广泛应用的瓶颈问题是复杂的应力磁化反转特征.对40Cr钢圆棒试件在不同最大拉力下进行反复加载-卸载拉伸试验,测定试件表面某确定点处漏磁场与拉应力的关系.试验结果表明,当试件处于弹性变形阶段时,漏磁场强度与拉应力的变化规律为线性关系;当试件受力超过屈服强度时,漏磁场强度与拉应力的变化规律变为折线,表现为先减小后增大再减小的应力磁化反转现象.随着最大拉力的增大,应力磁化反转极值点位置向较高拉应力方向移动,漏磁场强度最大变化量△Bmax也逐渐增大. 相似文献
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以20钢含V型缺陷平板试样为研究对象,通过试验方法和ANSYS仿真方法对试样在拉伸载荷下的应力分布进行反复加载卸载分析,测量了试样表面规定路径的切向和法向的漏磁场分布;分析了V型缺陷对磁记忆信号的影响以及固定位置的磁场值随应力的变化关系;最后将试验结果与模拟结果进行对比,发现试验结果与模拟结果具有很好的一致性。在应力小于50MPa时磁场值随应力的增加而减小,在应力大于50MPa时磁场值随应力的增加而增加。变化关系表现出了明显的应力磁化反转现象,磁化反转位置在50MPa(约是最大应力的30%)。 相似文献
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观察了晶粒取向3%Si-Fe在横向磁化场及横向拉应力作用下,磁畴结构和磁声发射强度的变化。在横向拉应力下,横向条状畴形成并增长。应力增大,横向条状畴碎化形成点状畴结构。磁畴与磁声发射强度变化相对应,揭示了磁场发射强度受横向拉应力影响的实质。 相似文献
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磁化技术是指物质经过比地球大得多的磁场处理;来改变物质结构及物质与物质间的物理化学反应过程,达到需求的目的。不同的物质经过磁场处理后,表现出不同的磁性质,根据测定是物质的磁化率,把物质分成铁磁性,顺磁性、抗磁性。物质具有不同磁性质,是由于物质被磁化时,其微观结构发生的变化不同。 相似文献
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通过测量磁化曲线、电阻-温度关系和热分析等手段,研究了磁场对镍基铁磁合金试样Ni-Mn-Ga相变的影响.结果表明:在磁场作用下相变温度升高了约1.5 K,具有明显的磁场影响特征.利用马氏体相变热力学理论,研究了磁场对镍基铁磁合金化学自由能和非化学自由能与温度的变化关系,建立了其作用的数理模型,并与实验结果比较后基本吻合. 相似文献
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Duan Z.-X.Ren S.-K.Xi X.-W.Yuan L.-H. 《钢铁研究学报》2016,(1):77-80
Metal magnetic memory testing is a novel method which can early detect stress concentration level of ferromagnetic components, but the bottleneck problem of further quantitative evaluation and widely application is the complex stress-magnetism reversal characteristic. A repeated loading-unloading tensile test was applied to round bar specimens made of 40Cr steel under different maximum tensile and the relation between the leak magnetic field at certain point on the surface and tensile stress was measured. The results show that the law of the change between the surface leak magnetic field at certain point and tensile stress is a linear relation in elastic deformation stage. When tensile exceeds yield strength, the law of the change between the surface leak magnetic field at certain point and tensile stress is a polygonal line, appearing a stress-magnetism reversal phenomenon: decreasing firstly, then increasing and decreasing again. With the increase of the maximum tensile, the extreme point of stress-magnetism reversal moves to higher tensile stress and maximum variation ΔBmax of leak magnetic field increases as well. 相似文献
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磁记忆是力磁效应的一种表现,目前关于力磁效应的基本规律及机理研究还没有统一的定论。为了进一步对磁记忆效应的机理及不同材料不同应力状态下磁记忆信号特征进行试验性的研究,对不同铁磁材料(Q235,20号钢,45号钢)圆棒试件进行静载拉伸试验,分别测量某固定点处在线加载和在线卸载2种不同应力状态下的磁记忆信号。试验结果表明:3种不同材料在线加载时磁记忆信号各表现出了不同的力磁效应;在线卸载时测得的磁记忆信号更能有利地分析构件的应力阶段;弹性阶段时磁荷梯度GF变化幅度不大,接近屈服阶段时,磁荷梯度变化幅度变大,可以利用磁荷梯度对低碳钢材料应力定量评价。试验结果为磁记忆效应机理研究提供了一定的依据,也为金属磁记忆检测的定量检测提供了潜在可能性。 相似文献
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金属磁记忆检测技术由于其能够快速便捷的对铁磁性构件的损伤进行识别,且被认为具有识别隐性损伤的能力,而被广泛研究。为推进金属磁记忆检测技术在桥钢箱梁损伤检测方面的应用,对桥钢箱梁进行了静力受弯试验,提取其变形最严重的上翼缘磁信号分布,建立了损伤区域力与磁信号和磁信号梯度的关系曲线,并提出用磁场梯度指数来表征钢梁的受力和损伤状态。结果表明:上翼缘磁信号曲线与应力变化形态正好相反,磁信号曲线在进入塑性后发生反转变为负值,且随应力变化的速度增快,可以判断构件进入塑性状态,即将发生损伤;磁场梯度曲线在损伤最严重的区域出现最大值,且随着荷载的增大,磁梯度最大值点不断向钢梁中间移动,由此可以进行破坏状态的预警;磁场梯度与应力关系曲线可将构件整个受力过程明显的区分为初始、屈服、塑性、损伤4个状态;可以用磁场梯度指数来进行构件受力状态与损伤状态的表征。该研究可为金属磁记忆检测技术在桥钢箱梁损伤状态的定量评估和预警方面的应用提供依据和参考。 相似文献
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金属磁记忆检测技术是一种适用于铁磁材料的新兴的无损检测技术,主要优势在于无需外加激励磁场源,即在天然地磁场的激励作用下,通过测量材料表面的漏磁信号,就能够对铁磁构件的早期损伤进行检测,避免结构或构件发生突然的脆性破坏。针对近10余年金属磁记忆检测技术的研究现状,概述了该技术的理论基础,总结了该技术理论研究、试验研究以及工程应用新进展,探讨了磁记忆检测技术的损伤评判准则,分析了影响磁记忆检测信号的因素,基于此,提出了磁记忆检测技术目前存在的问题和未来的研究发展方向。 相似文献
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以于微合金高强度结构钢,抗腐蚀性能非常重要,前人的研究成果主要集中在应力腐蚀,氢致裂纹腐蚀和疲劳腐蚀等方面,关于磁场处理后微合金结构钢抗腐蚀性能的研究未见报道,在微合金钢由奥氏体向铁素转变的过程中施加稳恒磁场,将导致其室温组织发生变化,而组织的改变必然对微合金钢的抗腐蚀性能产生影响,作主要研究了磁场处理后试样的失重量和腐蚀率的变化规律,并提出了斯特方程的修正表达式。 相似文献
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Lu-Sha Zhang Xiao-Feng Zhang Bao Wang Qing Liu Zhi-Gang Hu 《Metallurgical and Materials Transactions B》2014,45(1):295-306
A three-dimensional mathematical model of the magnetic field, flow field, and temperature field in a 1500 mm × 90 mm CSP funnel-type mold is used to numerically study the effect of an electromagnetic brake (EMBr) on flow and heat transfer behavior of molten steel. A number of effects of EMBr on the flow pattern and temperature distribution of molten steel are simulated. The jet flow discharge from the submerged entry nozzle (SEN) is significantly suppressed. In addition, heat transfer in the upper part of the mold increases under the influence of EMBr, which can improve the mobility of liquid steel at the meniscus and achieve low superheat casting. The relations between casting speed and magnetic flux density, and between SEN submergence depth and the installation position of the EMBr device, are taken into account to study the effects of braking on molten steel. The results show that the braking effect is weakened with an increase in either the casting speed or the SEN submergence depth. In order to insure the efficient and stable operation of a continuous casting production, the magnetic flux density should be increased by approximately 0.1 T when the casting speed increases by 1 m/min. In addition, an optimal braking effect for molten steel can be obtained when the distance between the bottom of the nozzle and the upper surface of the EMBr device is 100 mm. 相似文献
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Lvjie Liang Shengyong Pang Xinyu Shao Chunming Wang Ping Jiang Xin Chen 《Metallurgical and Materials Transactions A》2018,49(1):198-209
For decades, post-welding magnetic treatment has been used to reduce residual stress of welds by improving the crystal structure of solid-state welds. In this paper, we propose a new magnetic treatment method, which can reduce the time-dependent thermal stress field in situ and reduce the final residual stress of welds by simply exerting an assisted weak magnetic field perpendicular to the welding direction and workpiece during laser welding. A new finite-element model is developed to understand the thermal–mechanical physical process of the magnetic-assisted laser welding. For the widely used 304 austenite stainless steel, we theoretically observed that this method can reduce around 10 pct of the time-dependent thermal stress field, and finally reduce approximately 20 MPa of residual stress near the heat-affected zone with a 415-mT magnetic field for typical welding process parameters. A new mechanism based on magneto-fluid dynamics is proposed to explain the theoretical predications by combining high-speed imaging experiments of the transient laser welding process. The developed method is very simple but surprisingly effective, which opens new avenues for thermal stress reduction in laser welding of metals, particularly heat-sensitive metallic materials. 相似文献