Aviation titanium alloy pipe fitting port electromagnetic alignment principle
The electromagnetic calibration of pipe fitting port can be divided into two ways: from outside to inside reducing and from inside to outside expanding. In this paper, the shape is calibrated from the inside out, so as to ensure that the roundness of the outer surface of the pipe fitting port meets the requirements. The electromagnetic alignment principle of titanium alloy pipe fitting port is shown in Figure 1. At the beginning of electromagnetic alignment, the high voltage switch K is closed, and the energy storage capacitor C releases pulse current to the solenoid coil and forms a strong pulse magnetic field B around the coil.
Titanium alloy pipe manufacturers said: due to the rapid change of magnetic flux near the driver plate, the driver plate generates an induced current J in the direction opposite to the coil current, and forms an induced magnetic field B 'in the direction opposite to the original magnetic field B, the generation of B' prevents the original magnetic flux from passing through the driver plate, forcing the magnetic induction line to be dense in the gap between the coil and the driver plate. Therefore, the axial component of the primary magnetic field B and the induced magnetic field B 'in the gap is superimposed, so that the axial electromagnetic force Pz is subjected to the driver. The superimposed radial component will generate the radial electromagnetic force Pr, which is the key to electromagnetic alignment. The driving plate is subjected to a huge radial electromagnetic force, which immediately produces high-speed movement and deformation and pushes the TC4 pipe fitting to the external mold to complete the whole process of calibration.
Through the combination of finite element simulation and experiment, the influence of small diameter coil turns and iron core on electromagnetic alignment is obtained, which has guiding significance and practical value for the development of electromagnetic alignment of aviation pipe fittings.
The experimental results show that: 1) With the increase of coil turns, the peak current of discharge loop decreases significantly, and the oscillation frequency slows down. Choosing a reasonable number of coil turns is beneficial to increase the forming efficiency and improve the calibration effect. 2) With the increase of coil turns, the large radial electromagnetic force decreases, and the large deformation after calibration decreases. At the same time, the radial electromagnetic force scope increases along the axial direction, and the deformation of the pipe fitting port becomes more uniform. 3) The increase of the iron core increases the self-inductance coefficient of the coil, resulting in the decrease of the peak current of the discharge loop and the extension of the discharge period. When the saturation magnetic flux of the iron core is not reached, the increase of the iron core increases the magnetic induction intensity and the induced eddy current density, and then enhances the electromagnetic force received by the drive sheet. Although the iron core itself has a certain energy consumption, the shape correction effect of the coil with iron core is obviously better than that without iron core.