Research On Evaluation Method Of Electrical Contact Degradation State Of Aviation Electrical Connectors

Aviation electrical connector is the basic and main component of the aircraft electrical wiring interconnection systems.The degradation and failure of electrical contact has become a crucial factor which can affect the reliability of electrical connectors.At present,most researches on evaluation methods of electrical contact degradation of electrical connectors focus on contact resistance,which can’t fully reveals the law of electrical contact degradation yet.This article starts with the analysis of the failure mechanism of the high frequency electrical contact of the connector.The relationship between the microscopic physical features and the macroscopic electrical contact characteristics is also studied.In addition,the measurement method of the high frequency contact impedance of the connector is studied and the contact impedance under the circumstances of different degradation factors is measured.On this basis,the equivalent electrical parameters in the contact impedance model are identified,and the changes of electrical parameters with the degradation of electrical contacts are studied.First of all,on the basis of the microscopic characteristics of the contact surface,a high-frequency contact impedance model of electrical contact is established.The effects of electrical contact surface features including contact material,contact surface roughness and failure surface features on high frequency contact impedance are analyzed.The contact resistance and contact impedance of the connector are simulated by electromagnetic simulation software.The effects of roughness and corrosion on electrical contact characteristics are studied.And the impact of connector electrical contact degradation on signal integrity was studied from two perspectives of time domain and frequency domain.With the deterioration of the connector,the contact impedance increases gradually at low frequency and decreases at the high frequency.In addition,electrical contact degradation will cause signal reflection and attenuation,which will affect the signal integrity.Secondly,the accelerated degradation test of the electrical connector according to the corresponding environmental test standard is designed included the acid salt spray corrosion test and the cyclic plug degradation test.For the connector samples before and after the degradation,the surface morphology observation and energy dispersive spectrum analysis of the contact surface are carried out through the scanning electron microscope.The surface smoothness of the connector deteriorates after accelerated degradation.Micro-holes and corrosions appear on the surface,the type and content of elements have also changed accordingly.Then,the electrical contact characteristics of the connector is measured and studied.The DC contact resistance of the connectors with different degradation levels under different environmental stresses are measured by milliohm meter.The contact resistance increases as the degree of degradation increases.The S parameters of the connector are measured with a vector network analyzer and the equivalent transmission line model is established to realize the measurement of the contact impedance.As the frequency increases,the contact impedance changes from inductive to capacitive,and the maximum value and transition frequency will change accordingly with the degree of degradation.Finally,the electrical parameters in the model are identified based on the LevenbergMarquardt algorithm to study the relationship between electrical parameters and electrical contact degradation.The accuracy of parameter identification is verified through regression analysis.Based on performance degradation test data and parameter identification results,the relationship between electrical parameters and the degree of electrical contact degradation is studied.As the degree of degradation increases,the increase in contact inductance is the main factor causing the change of contact impedance.The research results of this paper can provide new ideas for the evaluation of the electrical contact degradation state of electrical connector,which is meaningful for the fault diagnosis and the reliability prediction of the degradation of the connectors.