Research On Mechanical Deformation Characteristics Of Disk Type Suspension Insulator In Extremely Cold Region

In recent years,there have been many accidents of insulator failure and fracture caused by stress shrinkage of metal accessories and long-term freezing of cement in the extremely cold regions with the minimum temperature of-58℃ in winter in north China,northeast China and northwest China in winter.In the existing researches,the mechanical deformation of porcelain and glass insulators and the physical parameters of the interface between pin and cement are still in the blank by combining the structural characteristics and mechanical operation characteristics of porcelain and glass insulators.Therefore,it is of great significance to analyze and test the deformation characteristics of disk-type suspension insulators.This thesis makes an in-depth study of the deformation rules and deformation positions of disc type suspension insulators based on the theory of energy balance fracture mechanics of Griffith.An experimental study is made on the characteristics of insulator deformation and its failure mode under extreme environment.And an experimental research method is proposed to provide the direction for insulator optimization.The main research results are as follows:(1)The mechanical strength of each component of the disk-type suspension insulator was tested and analyzed in the extreme low temperature environment.The test results show that the metal accessories,insulator parts and cement adhesive of the insulator increased with the decrease of temperature to different degrees.At the same time,the size of the metal accessories and insulation parts did not change significantly with the decrease of temperature,while the volume of cement adhesive decreased with the decrease of temperature.It is found that the mechanical strength of single insulator can be increased by 15%~30% through the glaze on a piece of porcelain.(2)A mathematical model is established for the fracture of cement during the mechanical deformation of insulators.Through finite element static simulation analysis of insulator,the stress of insulator components is observed.Based on the mechanical damage experiment and the analysis of the deformation of disk-type suspension insulators under static load,the causes of fluctuations on the force-deformation curve and the stress-strain curve are analyzed by combining the fracture model of cement,and then the mechanical deformation characteristics and distribution rules of disk-type suspension insulators are determined by the fracture theory and test results.The research results provide a direction for the optimization of insulator’s pins.(3)A method based on the classical central drawing test is proposed to measure the physical parameters of the bonding interface between the pin and the cement.In view of the buffer layer materials and the coating process commonly used in the manufacturing of insulators,the test of the bonding strength of the interface is carried out,including the shear bonding strength and the static and dynamic friction coefficient tests.Through analysis of the experimental phenomena and data,it was found that interface normal pressure had a great influence on the shear strength of the interface between steel feet and cement cement.Interface normal pressure has great influence on the shear strength of the pin and cement.With the increase of normal pressure P at the bonding interface,the interface shear and adhesive strength increases.The corresponding relationship was = 0.959 + 2.153 through fitting.The results provide guidance for the optimization of insulator buffer layer.