No abstract

Lorentz force particle analyzer (LFPA) is a non-contact electromagnetic measurement technique for the cleanliness inspection of liquid metal. Based on its principle, an optimized prototype of micro-particle measurement device is designed and built. Inclusion particles of different sizes in millimeter and submillimeter in liquid metal are inspected by this device at room temperature. The characteristics and formation mechanisms of typical inclusion particles pulse signal and laser path signal are compared and discussed. The wavelet decomposition method is used to denoise the original signal, and the desired signal is extracted and sorted out. Results show that LFPA is suitable for the measurement of inclusion particles in liquid metal.

In the process of production or use, micro defects (micro particles or pores) will be produced in the thin metal plate. The number and size of these micro defects determine the quality of the thin metal plate, affecting its service life and factor of safety.Therefore, quantitative and accurate characterization of micro defects is a necessary condition to ensure the quality and safety of thin metal plate products.This article studies the application of motion induced eddy current magnetic field testing in electromagnetic testing to detect defects in conductive and non magnetic materials.The simulation results show that when the lift off distance and the surface remanence of the permanent magnet are determined, the size of the permanent magnet is positively correlated with the amplitude of the defect detection signal.The main reason is that the amplitude of the defect detection signal is linearly related to the current density mode at various points on the defect motion path in the motion induced electric field without defects. Increasing the size of the permanent magnet can effectively improve the current density mode.As a continuation of the above results, an optimization method for excitation magnetic field in motion induced eddy current magnetic field detection has been proposed.The two types of permanent magnet arrays generated by this method generate larger amplitude defect detection signals compared to simple permanent magnets with the same volume and surface residual magnetism. The experimental results show that the excitation magnetic field arrangement designed by the above optimization method increases the signal amplitude by 80-90% compared to traditional methods.This optimization method helps to improve the sensitivity of motion induced eddy current magnetic field detection methods.