Study On Stress Behavior And Cylinder Corrosion Characteristics Of Double Expansion Column Under Impact Load

Hydraulic support is the most important supporting equipment of fully mechanized working face in coal mine.Years of practical experience shows that the corrosion of column cylinder in coal mine is very prominent.Corrosion is the main form of column damage and an important incentive for column failure.Therefore,it is of great significance to study the corrosion initiation mechanism of column in coal mine and explore the correlation between working conditions and column corrosion for improving the corrosion resistance of column.In the process of coal mining,instantaneous rock burst is an important factor leading to column failure.Based on the national standard of column impact test,the stress response characteristics of φ500 double telescopic column under impact load were studied by using the finite element method combined with fluid-solid coupling technology.The results show that the maximum deformation of the column is in the middle cylinder,the maximum value is 1.62 mm.The maximum stress of the live column is 759 MPa at the top of the live column.The stress of the bottom cylinder is concentrated in the middle area of the bottom cylinder,and the maximum stress is 326 MPa.The stress of the guide sleeve is small and mainly concentrated at the bottom of the guide sleeve.The maximum stress of the guide sleeve of the bottom cylinder is greater than that of the middle cylinder.Previous research results show that the corrosion characteristics of metals are closely related to the stress state.Based on the stress analysis results of φ500 double telescopic column under impact load,the mechanical characteristics of the composite coating structure on the cylinder surface of the column were studied by using the finite element method,and the coupling relationship between the structural parameters of the composite coating and the stress distribution and corrosion characteristics was explored.The results show that the stress of tin bronze layer in the composite coating on the surface of column cylinder is the largest.With the increase of elastic modulus of tin bronze,the interface stress and stress of tin bronze gradually decrease.Therefore,the corrosion resistance of column surface can be effectively improved by increasing the elastic modulus of tin bronze.The Poisson ’ s ratio of tin bronze,tin bronze layer thickness and chromium layer thickness have little effect on the stress of the coating.For the column cylinder,the corrosion is often manifested as local flake spalling.According to the electrochemical environment characteristics of the cylinder,the electrochemical finite element analysis model of the inner wall corrosion of the cylinder was established.The effects of emulsion pressure,emulsion ratio and initial defect form on the formation and development of corrosion were studied.The results show that the emulsion pressure,initial defect depth and width have little effect on the corrosion development of cylinder inner wall,while the initial defect morphology,especially the crack defect type,has a great influence on the evolution of corrosion morphology,but the crack propagation direction has no obvious effect on corrosion.The increase of emulsion concentration can reduce the incidence of cylinder corrosion,but when the emulsion solubility exceeds 5 %,this effect will be weakened rapidly.Salt spray corrosion is an important experimental method to study the corrosion properties of metals.The corrosion behavior of 27 Si Mn coating samples of column cylinder under stress state was studied by salt spray corrosion method,and the influence of stress,corrosion environment and temperature on the corrosion of samples was explored.The results show that the increase of stress makes the corrosion of the sample more serious.Under the same conditions,the corrosion degree of the sample increases with the decrease of p H value or the increase of temperature in the corrosion environment.