【作者】 王威；

【导师】 苏三庆； 王社良；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2005， 博士

【摘要】 本文从一个新的角度,即以铁磁材料的磁特性和应力耦合关系为核心,研究钢结构构件应力检测问题,目的在于解决钢结构磁力耦合应力检测所涉及的基本原理、理论依据、磁力学模型、应用技术、实现的关键技术等问题,从而把这种“磁”法检测技术应用到钢结构工程的应力检测中来。研究得到以下结论: (1) 依据铁磁学基础理论分析了应力对磁畴及磁畴壁的影响机理,指出了应力的存在改变了磁畴的结构,引起了畴壁的移动和磁畴磁矩的转动,使得畴壁能以及畴壁厚度发生了改变,从而使铁磁材料的磁特性发生了改变,其技术磁比曲线在不同应力下呈现出不同的特征。通过测试铁磁材料磁特性的变化,可以测出构件的应力。指明了实施土木建筑钢结构应力检测的关键在于解决应力对钢构件磁参量的影响关系,即建立钢结构材料磁力效应本构关系。 (2) 对钢结构材料磁力学模型进行研究,提出了钢结构拉压杆磁力耦合本构关系表达式,该本构关系揭示了钢结构受力构件的磁性变化与应力之间的函数关系,可反映磁力特性的传递函数关系。 (3) 在磁力耦合场隋况下提出了耦合参数A,该参数考虑了力磁耦合作用,并在试验的基础上,采用正交试验的数值回归分析方法,得到了耦合场参数经验公式。显著性分析表明,应力对耦合参数A的影响比外磁场大,这对钢结构拉压杆磁力耦合本构关系的简化与应用非常有意义。 (4) 针对建筑钢结构中常用的Q235钢拉压杆试件进行了磁力耦合试验研究,寻找出了应力对Q235钢磁滞回线影响的变化规律,建立了不同外磁场下Q235钢拉压杆应力与磁导率关系试验结果图。确定出了最佳的测试激励外磁场区间。Q235钢拉压杆的磁导率受应力和外磁场两个参数变化的影响,根据试验数据结果,采用正交试验的数值回归分析方法,得到了磁导率随应力和外磁场两个变量的双参数回归计算公式,由该回归公式的计算结果,建立了磁导率随应力和外磁场变化而变化的三维对应关系图。显著性分析表明,外磁场变化对磁导率的影响比应力大。计算结果与试验结果吻合较好。 (5) 使用理论建立的本构关系,代入耦合场参数,得到了不同外磁场和不同应力下的H-B关系模型,用ANSYS有限元程序进行计算。通过设定跑道型线圈,设定线圈匝数,由线圈通电流产生磁场,钢杆件置于感生磁场中被磁化加载的计算方法,得到了不同外磁场和不同应力条件下的磁导率计算结果。分析了不同的线圈匝数产生的外磁场的大小,计算表明在试件条件下线圈8000匝时的感生磁场已经容纳了最佳的测试外磁场区间。分析比较表明,理论计算、试验结果与有限元计算得到的应力对磁导率影响的变化规律一致,数据符合较好,说明采用这种有限元计算的方法是可行的。在确定本构关系的条件下,采用这种模拟计算方法,计算结果可更多还原

【Abstract】 From a new perspective, focusing on the relationship between the magnetic properties and stress of ferromagnetic material, the stress NDT&E for steel structure are researched in the thesis. This problem includes as follows: basic principle and theory, magneto-mechanical coupling model, application method, key realizing technology and so on. The dissertation research on NDT&E theory and application based on magnetic-mechanical coupling effect for steel structure is a daring explorations, which compensate the lack that there haven’t been application of magnetic NDT&E to test stress for steel structure in civil engineering in China. Compared with other non-destructive techniques, the magnetic NDT&E for steel structure is a new promising technique in the future. The summary is listed below:(1)According to the ferromagnetic basic theory, the basic principle of magnetic NDT E for steel structure is analyzed. Theoretical major analyzes the influence of stresses on movement and change modes of magnetic domains in ferromagnetic materials and points out that the main modes stress influence movement of domains is the movement of domain wall and rotation of magnetic torque of domain. So the magnetic characteristic will be changed, and magnetic hysteresis loops have different feature. It is key that how to solve the relationship between the magnetic properties of steel structure and stress, or how to deduce the constitutive relation.(2)The model for steel structure stress NDT&E is set up and a simply constitutive relation expression of magnetic-mechanical coupling effect according to much theory deduction and analysis is deduced in the paper. The formula reveals the function relationship between magnetic properties change and stress of steel structure & member under external force. The constitutive relation is foundation of theory for experiment research and can guide stress testing for practical steel structure.(3)In coupling situation, a coupling parameter is put forward, which thinks over magnetic-mechanical coupling effect. Based on experiment, an experience formula of the coupling parameter is gained by numerical regression analysis methods of orthogonal experiment calculation, which has important significance for revising the magnetic-mechanical coupling constitutive relation formula The stress has more influence than magnetic on the coupling parameter.(4)The magnetic-mechanical coupling experiment of Q235 steel rod in building structure is completed in the paper for the first time. Q235 steel is a ferromagnetic material and is most extensively used for structure engineering. But there is few research on the magnetic properties changes by applying external loads for this sort of low carbon steel. Experimental measurements of magnetization curve arepresented, and magnetic hysteresis loops have changes due to undergoing an external variable stress for Q235 Steel Rod. When in the stage of the level of magnetization saturation hasn’t been arrived, the experimental results showed that the permeability under 0 stress is smaller than under tensile stress and bigger than the permeability under compressive stress. While magnetization arrived at the level of saturation, the permeability under 0 stress is bigger than both under tensile stress and under compressive stress. If the tensile stress increase, the permeability of Q235 steel rod tends to decrease, if the compressive stresses increase, the permeability of Q235 steel rod tends to increase. This mutual influence relation provides an experimental foundation for the magnetic NDT&E of steel structure later. The theory analysis of the simplified constitutive relation expression is an agreement with the experimental results of magnetic hysteresis according to the qualitative analysis. Both of them are mutually confirmed. From quantitative analysis and contrast, in different external magnetic situation, the experimental result figure of Q235 steel rod magnetic-mechanical constitutive relation is set up for the first time. A best numerical range of exciting magnetic is determined. The permeability is a function of both external magnetic and stress. According to experiment results, an experience formula of the permeability is gained by regression analysis methods of orthogonal experiment numerical calculation, in which calculation error is very small. The change of magnetic field has more influence than stress on the permeability. A three dimension figure of permeability-stress corresponding relation is gained according to the result of numerical calculation. If there were many times reference of experimental results, and the experience formula of the permeability-stress corresponding relation will be made a demarcate according to these data, then a more exact testing result will be obtained.(5) In different external magnetic situation and different stress situation, the H-B constitutive relation model have been gained by the theoretical constitutive relation expression formula of magnetic-mechanical coupling effect and by the coupling parameter that is revised by the experiment The H-B constitutive relation model is numerical calculation by the commercial finite element program ANSYS, which is attempts to simulate die increasing part of the H-B curve of Q235 steel which is in uniaxial stress stage. By setting up the runway coil, an external magnetic can be induction by the runway coils. When the coil’s number is 8000, the induction external magnetic has included the best numerical range of measure external magnetic. The ANSYS numerical calculation results show that the H-B curve can be gained, and permeability-stress corresponding relation can be gained according to the result of numerical calculation. The change regularity of permeability influenced by stress can be reflected according to calculation results. According to the calculation analysis, the theory and experiment and ANSYS calculation are identical and are mutually confirmed. The numerical method by amending ANSYS program is available. The error is mainly corrected with the numerical of constitutive relationmodel. If the numerical value that is selected has more representation character, the calculation results are closer to real values.(6) How to measure magnetic is another key technology. Aim at magnetizing and measure magnetic, several concretized suggest that can be suitable for testing stress of building steel structure are posed according to section shape of steel structure member, which is Hie basement of how to develop testing equipments by magnetic-mechanical coupling for steel structure.(7)Several key technologies that how to realize stress NDT&E by magnetic-mechanical coupling for steel structure are discussed, and the accuracy of stress testing result is very depended on the magnetizing and magnetic signal measure and processing. A initial route of how to realize stress testing technology is put forward, whose most key problem is how to measure the value of magnetic characteristic parameter of steel structure member under coupling influenced by stress and magnetic. The magnetizing technology is the first key step, whose key problem is to determine the best numerical range of measure external magnetic. Magnetic signal measurement is the second key step, which includes how to produce magnetic signal and how to measure magnetic signal, and the transformation of magnetic signal is core, in which the key problem is how to define the magnetic-mechanical coupling constitutive relation. The processing technology is the third key step, which includes how to magnify and filter magnetic signal and other key segment. The anti-inference and demagnetization technology are of necessity.更多还原