Experimental Study On Transverse Magnetic Fretting Wear Of Large Transformer Flange Bolts

With the continuous improvement of people's quality of life,electricity has become one of the indispensable resources of today's society.Therefore,the power industry has become an important development target that cannot be ignored by various countries.The construction of the“Belt and Road”not only drives the economic development of African countries,but also the construction of ecological power plants and power stations,alleviating the situation of local power supply shortages.Power supply capability provides a strong guarantee.The transformer is the core component of each power transmission and transformation system,and its reliability in operation plays a vital role in the safety of the entire power transmission and transformation system.Based on the research results at home and abroad,this paper analyzes the loosening process of large transformer flange bolts under lateral vibration.The relationship between transverse alternating load and frequency and fretting wear of bolts is further studied through experiments.The main research contents of the paper are And the conclusion is as follows:In this paper,the emergence and development of the theory of thread and fretting wear are introduced in detail,and the research status of the loosening of threaded joint under transverse alternating load is introduced.Secondly,the working principle of the transformer and the stability test experiment on the transformer are introduced.After that,based on the slip characteristics of the bolt joint contact surface under the vibration of general transverse alternating load,the radial magnetic force generated by electromagnetic induction in the transformer is analyzed.The bolt loosening process under the vibration of such alternating magnetic force is analyzed.In order to study the loosening process of bolts under the condition of transverse magnetic excitation radiation generated by large transformers during opening,closing and sudden change of current,the lateral vibration test of simulated bolt connection is carried out by MTS landmark37025 hydraulic pressure,and then the bolt connection is observed.The preload force and preload torque decay process under different lateral loads and frequencies,and the wear amount and surface damage are measured.The experimental results show that the bolt pre-tightening force is divided into two stages: the deformation stage in which the pre-tightening force decreases rapidly at the initial stage of the experiment and the fretting wear stage in which the pre-tightening force decreases slowly.The pre-tightening torque drop is divided into three stages: the first stage is not obvious due to the high local contact stress;the second stage is rapidly declining due to the deformation expansion;the third stage bolt enters the fretting wear stage.The pre-tightening torque begins to slowly decrease.Under low frequency vibration of the bolt,the amount of mass change is not sensitive to small changes in frequency.The surface wear of the bolt in contact with the clamp increases as the alternating amplitude load increases;it decreases as the frequency increases.