Research On Environmental Adaptability Test Method Of Electromagnetic Materials

The shielding performance of electromagnetic materials is an important factor affecting the electromagnetic compatibility of equipment.With the increasingly extensive application fields of electromagnetic materials,they face more and more extreme environments.At present,there is a lack of unified,perfect and scientific standards for the adaptability evaluation methods of electromagnetic materials in various environments in China.The traditional simulation and theoretical calculation methods are difficult to characterize the environmental characteristics of various electromagnetic materials.Therefore,it is of great significance to study the shielding performance test methods of electromagnetic materials in different environments to evaluate their environmental adaptability for the reliability of equipment.The main research and work of this paper are as follows:1.A magnetic shielding effectiveness test system suitable for high and low temperature environment is established for magnetic materials.The Helmholtz coil is made and its performance is measured.The matching circuit is made for the Helmholtz coil by using the simple real frequency method,which reduces the standing wave ratio(SWR)of the coil at high frequency.An active magnetic field probe with amplification circuit structure is designed and fabricated.The temperature stability of coaxial cables with different media is tested and compared,and the calibration coefficient of magnetic field probe at different temperatures is measured.The test result shows that the temperature adaptability of different magnetic materials is different.The actual scene and demand should be considered in application.2.Research is carried out on the electromagnetic pulse adaptation test method for the shielding performance of conductive gaskets.A conductive liner electromagnetic pulse test system was established using a ringing wave pulse current generator already available in the laboratory,and the calculation formula of pulse current waveform was derived.Electromagnetic pulse adaptation tests were conducted on different kinds of conductive gaskets to study the effect of pulse current intensity on the volumetric resistivity of the liners,normalized pulse current peak to peak values were used as indicators to quantitatively evaluate the adaptation ability of various types of gaskets to electromagnetic pulses,and the test results showed that the volumetric resistances of the tested gaskets exhibited the first decreasing,then stabilizing,and finally rising trends with the increasing pulse current.3.Research is carried out on the salt spray environmental test method for the shielding performance of conductive gaskets.Nine different fixtures with different materials and surface treatment processes were processed to simulate the matching scene of conductive rubber with different overlapping surfaces in order to solve the problem that actual assembly was not considered in the traditional test methods.The salt spray test chamber was used to simulate the salt spray environment,and the tests were carried out according to GJB 150 A.The corrosion was initially judged by comparing the surface state of fixture before and after the salt spray test,the quality of conductive rubber and the contact resistance of DC surface.The electromagnetic shielding performance of conductive rubber before and after the salt spray test was tested by the transfer impedance test device.The test results show that the salt mist adaptability of conductive rubber is changed when it is assembled with different joints.In addition,based on the theory and test results,some engineering suggestions for improving the environmental suitability of conductive rubber salt mist are put forward.4.Research is carried out on the vibrational environmental adaptation testing methods for the shielding performance of conductive gaskets.A test system was established by using a vibration table to simulate the vibration environment,and the change of volume resistivity of the conductive gasket before,during,and after vibration was compared,in order to investigate the selection of the parameters of the vibrational mode and the effect of the assembly method of the conductive gaskets on the test results.