Research On Temperature Field Of Plasma Arc Controlled By Magnetic Field

Flexible forming using plasma arc controlled by magnetic field is a new no mould processing technique which has very wide application prospect on large plates in multiple varieties and low batch production. The quality of plasma arc controlled by magnetic field affects forming quality and efficiency during the flexible forming process. So it appears to be particularly important to diagnose the thermodynamic parameters of plasma arc controlled by magnetic field.Under the financial aid of National Natural Science Foundation (50775019), the thesis has completed the following works:This thesis used spectral diagnostics to diagnose the thermodynamic parameters of plasma arc controlled by magnetic field. First of all, Experimental device of plasma arc controlled by magnetic field was designed and constructed. The device is composed of generating system of plasma arc controlled by magnetic field, optical system, and control and display components. Image of plasma arc controlled by magnetic field was acquainted using charge coupled device of CCD, the data was converted using image acquisition card and its control, display and storage using computer.The digital image of plasma arc controlled by magnetic field was made pretreatment such as removing background noise, filtering processing and enhancing morphological features using MATLAB in order to obtain good visual effects and detection effect. Then the plasma arc before and after being in a magnetic field was made comparative analysis and obtained the characteristics of plasma arc controlled by magnetic field. A typical trip data of the plasma arc controlled by magnetic field is made smoothing and correction treatment, then the edge of arc column was determined using straight-line intersection method. The thesis discussed the order of data curve using least square fitting method need to satisfy two actual conditions of the given error range and minimizing the wave shock phenomenon. Furthermore, the method of best fitting order was determined.The thesis described the numerical methods of the non-symmetric Abel inverse transform and verified the effective of the method using detection function. Under the assumptions of local thermodynamic equilibrium (LTE), optically thin and non-uniformity of plasma arc controlled by magnetic field, the non-symmetric Abel inverse transform was solved using variable separation approach and the least square fitting method and obtained the relationship between spatial emission coefficient of plasma arc controlled by magnetic field and the arc column radius. Then the functional relationship between spatial emission coefficient of arc column and temperature was obtained through calculating the particle density and partition function of plasma arc based on Saha equation and state equation. The radial temperature field distribution of 17 rows of data covering the arc column was obtained using the method of standard temperature; Furthermore, two-dimensional temperature distribution of axial cross section of plasma arc controlled by magnetic field was finally obtained.The result shows that two-dimensional temperature distribution of axial cross section obtained in this thesis verifies the characteristics of plasma arc controlled by magnetic field. Furthermore, it provides reference for parameters controlled on flexible forming using plasma arc controlled by magnetic field, as well as creates favorable conditions for solving the actual heat source model of plasma arc controlled by magnetic field.