电磁胀环高速变形过程多物理场耦合分析及其测量技术研究

发布时间：2018-09-13 13:30

【摘要】：电磁成形技术是目前突破传统轻质铝合金成形制造工艺缺陷的极具潜力的技术之一。但是,电磁成形过程是一个由电磁场、结构场、温度场等多物理场耦合作用下的物理过程,其成形过程复杂,材料在多场作用下,其变形性能也得到改变,其成形机理十分复杂。而电磁胀环是一种可视为处于环向单向拉伸状态的电磁成形过程,其结构高度对称,各物理场分布均匀,分析难度较小。因此,本研究基于电磁胀环实验,对电磁胀环过程当中各物理场的相互耦合进行分析,并建立电磁胀环有限元仿真模型,对电磁胀环过程当中的关键物理量——金属环工件涡流、金属环工件高速变形的径向位移搭建测量系统并进行测量。本文选用电磁胀环作为研究模型,对电磁成形过程中,电磁场、结构场、温度场等多物理场的耦合作用进行了分析。对电磁胀环实验平台的驱动电路进行了建模,对成形线圈和金属环工件的电磁过程进行了分析,对金属环工件的受力过程和运动状态进行了简化分析,对电磁成形过程的热能来源以及温度变化对材料的影响进行了探讨。然后利用COMSOL Multiphysics多物理场建模与仿真软件对电磁胀环模型进行了2D轴对称建模,对电磁胀环过程进行了数值模拟分析。在电磁胀环过程中,由于成形线圈中的电流变化而在金属环工件中产生了感应电流,从而使得金属环工件受到了相应的电磁力作用。对该感应电流的测量对于分析金属环工件在高速变形中的受力和应力应变十分重要。由于任何物理接触都会对金属环工件中感应电流的产生影响,而罗科线圈又是一种良好的非接触式电流传感器,因此,本文提出了一种基于罗科线圈的间接测量法对金属环工件中的感应电流进行测量,并分析了其测量原理,设计了一套基于该原理的的涡流测量系统,使用间接测量法所需要的罗科线圈进行了电磁胀环涡流测量实验,并将实验结果与有限元仿真结果进行了对比。针对电磁成形过程中,金属工件高速变形行为研究中的位移测量难题,本文提出了一种基于电磁探针的电磁胀环高速位移测量方法,并分析了其测量原理,设计了一套基于电磁探针的高速位移测量系统。通过测量金属环工件中的感应涡流在电磁探针中产生的磁通量,获得了金属环工件感应涡流的磁场分布。利用金属环工件在膨胀过程中,当工件通过同轴心分布的电磁探针时,其相应电磁探针中磁通量为零的特点,搭建了有多个电磁探针的测量板,测量得到了金属环工件的实时位移曲线,并同时使用了高速摄像机测量以验证该方案的有效性,结果得出两者测量结果趋于一致。该高速位移测量方案为电磁成形过程中金属工件高速变形行为的研究提供了一种有效、简洁的测量手段。
[Abstract]:Electromagnetic forming technology is one of the most potential technologies to break through the defects of traditional light aluminum alloy forming process. However, the electromagnetic forming process is a physical process under the coupling of electromagnetic field, structure field, temperature field and other physical fields. The forming process is complex, and the deformation property of the material is changed under the action of many fields. The forming mechanism is very complex. The electromagnetic expansion ring is a kind of electromagnetic forming process which can be regarded as being in the state of circumferential uniaxial tension. Its structure is highly symmetrical, the distribution of physical fields is uniform, and it is less difficult to analyze. Therefore, based on the experiment of electromagnetic expansion ring, the coupling of each physical field in the process of electromagnetic expansion is analyzed, and the finite element simulation model of electromagnetic expansion ring is established. The measurement system for the radial displacement of the metal ring workpiece and the metal ring workpiece with high speed deformation is built and measured, which is the key physical quantity in the process of electromagnetic expansion. In this paper, the coupling of electromagnetic field, structure field, temperature field and other multi-physical fields in electromagnetic forming process is analyzed by using the electromagnetic expansion ring as the research model. The driving circuit of the electromagnetic expansion ring experimental platform is modeled, the electromagnetic process of the forming coil and the metal ring workpiece is analyzed, and the stress process and motion state of the metal ring workpiece are simplified. The source of heat energy in electromagnetic forming process and the influence of temperature change on material are discussed. Then the 2D axisymmetric model of the electromagnetic expansion ring model is modeled by using COMSOL Multiphysics multi-physical field modeling and simulation software, and the numerical simulation of the electromagnetic expansion ring process is carried out. In the process of electromagnetic expansion the inductive current is produced in the metal ring workpiece because of the change of the current in the forming coil which makes the metal ring workpiece subjected to the corresponding electromagnetic force. The measurement of the inductive current is very important to analyze the stress and strain of metal ring workpiece in high speed deformation. Because any physical contact affects the inductive current in the metal ring workpiece and the Rocco coil is a good non-contact current sensor, In this paper, an indirect measurement method based on Rocco coil is proposed to measure the inductive current in metal ring workpiece, and its measuring principle is analyzed, and a eddy current measuring system based on this principle is designed. The eddy current measurement experiment of electromagnetic expansion ring is carried out by using the Rocco coil, which is needed by indirect measurement method, and the experimental results are compared with the results of finite element simulation. In view of the difficult problem of measuring the high speed deformation behavior of metal workpiece during electromagnetic forming, this paper presents a method of measuring high speed displacement of electromagnetic expansion ring based on electromagnetic probe, and analyzes its measuring principle. A high speed displacement measurement system based on electromagnetic probe is designed. By measuring the magnetic flux of the induced eddy current in the metal ring workpiece in the electromagnetic probe, the magnetic field distribution of the induced eddy current in the metal ring workpiece is obtained. Taking advantage of the fact that the magnetic flux of the metal ring workpiece is zero in the process of expansion, when the workpiece passes through the coaxial electromagnetic probe, a measuring plate with multiple electromagnetic probes is built. The real-time displacement curve of metal ring workpiece is obtained, and the high speed camera measurement is used to verify the effectiveness of the scheme. The results show that the two measurements tend to be consistent. The high speed displacement measurement scheme provides an effective and simple method for the study of high speed deformation behavior of metal workpieces during electromagnetic forming.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG391

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