The long-life driving coil is the prerequisite for electromagnetic forming industrial application. Up to date, the temperature rise is one of the major factors that restrain its working life. For the purpose of reducing the temperature rise of the driving coil, this paper proposes a new coupled cooling method, in which an extra cooling coil is placed on one side of the driving coil, then the Joule heating is coupledly transferred by delaying the breakover control of the driving coil. To achieve this purpose, a finite element simulation model of Electrical Circuit- Electromagnetic Field-Thermal Coupling in the plates setting of the electromagnetic forming is established, after which the influence rules of coil turns, cross-sectional area and materials of cooling coil on temperature rise are analyzed. Then, this paper also establishes a coupled cooling circuit model, in which the influence of cooling coil structure parameters on the Joule heating of driving coil is analyzed. Furthermore, Simulation results show that effective Joule heating transfer can be reached by the best optimization scheme of the cooling driving coil. Specifically, the average temperature rise reduces by 13 degrees, namely 22.8% by using this new method.

Electromagnetic tube expansion has been extensively studied for its obvious advantages in lightweight alloy processing.Due to the reduction of wall thickness and the non-uniform deformation in axial direction, the development of the existing electromagnetic tube expansion has been restricted.In this paper, the method of electromagnetic tube expansion with axial compression is proposed, with which both the radial and the axial electromagnetic force are applied to decrease the reduction of wall thickness.The simulation results show that the reduction of wall thickness is reduced from 15.05％ to 9.65％.Furthermore, the method of electromagnetic tube expansion with concave coil to weaken the electromagnetic force in the middle part is proposed to improve the tube forming performance.In the simulation, the maximum deformation is 36 mm, and it is obvious that the radial electromagnetic force produced by "concave" coil can effectively solve the problem of non-uniform tube deformation.The improvement of electromagnetism force loading can effectively solve problems in electromagnetic tube expansion and promote its industrial application.

三线圈轴向压缩式管件电磁胀形能够实现工件的轴向流动,解决传统管件电磁胀形存在的壁厚减薄问题,但其工装结构复杂、线圈配合困难,导致其实际成形效果并不理想.为了更加简单有效地实现轴向电磁力与径向电磁力双向加载,本文首次提出双线圈轴向压缩式管件电磁胀形方法.该方法仅在管件顶部与底部对称设置驱动线圈,通过分析优化驱动线圈的几何参数及线圈与管件的相对位置,为管件提供合理的电磁力分布.此外,建立管件电磁胀形过程的电磁-结构耦合有限元模型,对比分析单线圈、三线圈和双线圈管件电磁胀形电磁力分布规律与管件成形性能,进一步研究驱动线圈几何参数对电磁力分布和管件壁厚的影响规律.分析结果显示,管件内壁胀形量相同时,因双线圈加载能够产生更大的轴向电磁力,壁厚减薄量较单线圈减小28.2％.显然,双线圈轴向压缩式管件电磁胀形亦能解决管件壁厚减薄的问题,且其工装结构简单、线圈配合容易,具有更加明显的技术优势与应用前景.

To improve the heating efficiency of the induction cooker system, this paper adopts the method of introducing an adiabatic layer between the pot bottom and the coil. By using COMSOL software, the electromagnetic - thermal coupling model of the induction cooker is established to analyze the effect of the adiabatic layer on the food temperature and coil temperature, and finally the heating efficiency is explored. The obtained simulation results show good agreements with the experimental results, and then the effectiveness of the proposed method is verified.

电磁成形是一种高速率脉冲成形技术,因其能大幅改善金属材料成形性能而得到广泛关注,其研究主要涉及材料科学与电磁技术两大问题.纵观其发展历史,电磁成形材料科学问题得到大力发展而电磁技术问题相对滞后.该文在阐述电磁成形基本原理与电磁力分布的基础上,将目前涌现的新技术划分为改善电磁力分布的电磁成形技术、改变电磁力施加方式的电磁成形技术、与传统机械加工相结合的电磁成形技术三大类别.针对每一类技术,分别阐述了其解决的技术问题、实现方案及成形效果,并进一步指出其存在的技术难点与研究方向.此外,介绍了目前解决驱动线圈结构强度与温升问题的方法,指出长寿命驱动线圈是电磁成形实现工业化应用的前提.电磁技术问题的深入研究带动了电磁成形技术的快速发展,未来仍需攻克"柔性电磁力加载"和"驱动线圈温升"两大难题,推动电磁成形工业化应用进程.

In conventional electromagnetic tube expansion (EMTE), the wall thickness of the tube decreases significantly because the electromagnetic force is mainly in the radial direction. To solve this problem, this paper proposes a new method named electromagnetic tube expansion with axial compression (EMTEAC). Besides the driving coil, we introduce a coil at each end of the tube to generate axial electromagnetic force on the tube. We use the finite element method to analyze the distribution of the magnetic flux density and the electromagnetic force generated by the three coils in series. The simulation results show that the axial electromagnetic force generated by EMTEAC is about 7 times that generated by conventional electromagnetic tube expansion, which enhances material flow when the tube is expanding. The effectiveness of the method is verified by a series of experiments. The experimental results show that EMTEAC reduces the decrease in wall thickness from 27 to 19%.

In the conventional electromagnetic tube expansion, the end effects generated by the conventional helix coil may lead to inhomogeneous tube deformation in the axial direction. This paper is aimed at overcoming this issue by proposing a new concave coil structure to replace the helix coil currently used by the industry practice to generate a radial electromagnetic force on the tube. The proposed concave coil is expected to reinforce the electromagnetic force distribution profile and, hence, improving the axial inhomogeneous deformation of the tube. In this context, a new R-L criterion of deformation uniformity is first proposed. Second, an electromagnetic-structural coupling finite element model is established to investigate the relationship between the distribution of electromagnetic force generated by the concave coil and the uniformity of the tube under various voltage levels. The effectiveness of the proposed method is validated through a series of experimental and simulation analyses. Furthermore, based on the characteristics of the electromagnetic tube expansion, a modified multilayer concave coil structure is proposed to overcome the axial inhomogeneous deformation of long tubes.

An accurate soil resistivity horizontal hierarchical model (SRHHM) is critical to selecting the site of the DC ground electrode. In order to build an relatively accurate model, current inflow test is carried out to test the accuracy of the initial SRHHM. However, there is no existing unified method to guide how to amend the initial model through current inflow test. Therefore, based on practical cases, this paper establishes a two-dimensional axisymmetric finite element model for current inflow test by using the ANSYS software, and studies the effect of each layer soil resistivity on the Earth surface potential (ESP) distribution. Based on these studies, some basic rules of amendment for SRHHM are proposed. Furthermore, the proposed rules are applied to the current inflow test of the actual project in Yi’an Chong, Hunan. The results show that the amended soil resistivity horizontal hierarchical model is better in fitting the ESP distribution obtained from the current inflow test.

As a high-speed forming technology, electromagnetic forming has been more and more widely used because it can improve the material forming performance greatly. In electromagnetic forming process, the pulsed electromagnetic force generated by the coils is the load of the workpiece, hence its distrib ution characteristics have a great influence on the workpiece forming performance. Based on the basic principle of electromagnetic forming, this paper introduces and analyzes some latest electromagnetic forming technologies with different coil systems, including electromagnetic incremental forming, space-time-controlled multi-stage pulsed magnetic field forming, and electromagnetic tube expansion with axial compression. Aim at each forming method, the following contents are mainly studied: 1) The key technical problems solved by this method. 2) The structure of the coil system. 3) The distribution of magnetic flux density and electromagnetic force. 4) The advantages and disadvantages of the method. Through above analysis, it is hoped that the basic idea of technological innovation in electromagnetic forming is clarified in this paper, which can provide guidance for the future innovation direction of electromagnetic forming.

In this paper, the existing technology of live crossing was analyzed, the classification and comparison of the commonly used live across technology were carried out. Structure of the proposed mechanical live crossing protection equipment is described and the main parts are built parameterized. Combining the practical scenarios of 1000 kV UHV AC transmission demonstration project which across the ChengChi motorway, model of the device is established. Stress of the main part of the model is verified by computer numerical simulation. The simulation results show that the strength of the key structure of the device is in the range of safety factor. The research shows that the device is reasonable. It provides a new solution for the construction of live crossing.