Theoretical And Experimental Studies On Contact Damage Of Elastic Force Joint Sleeve Of Oil Film Bearing In Rolling Mill

The up to date assembly method of the sleeve and roll neck of oil film bearing, used on large-scale 4-h strip rolling mill, is Elastic force joint. This technology is a patent of Mitsubishi heavy industries Ltd.. And its outstanding virtue is the minimal fluctuation of the rolling force produced by the rolling mill structure.Bearing used on 1580 PC mill of Baoshan Steel Co. is Mesta oil film bearing and elastic force joint sleeve product by Mitsubishi heavy industries Ltd.. Equal interference is designed along the axis of sleeve and its assembly and disassembly depends on hydroforming. In recent years, Mitsubishi heavy industries Ltd. in Japan has presented analysis reports about the serious damages of the sleeve and shell, including sleeve felt, fracture occurring on the ends of sleeve etc., and believed that the low hardness of sleeve caused by the improper quencher is the only cause of damages. But the damage problems of sleeve have not been resolved yet. To solve the scratching and sticking damage problems of sleeve, based on the contact mechanics and the damage theory, this paper presents theoretical and experimental studies on damage mechanisms occurring in assembly, disassembly and milling process of elastic force joint sleeve of oil-film bearing in large-scale rolling mill. This paper provides a theoretical and experimental basis for producing new elastic force joint sleeve of oil film bearing.For solving nonlinear elastic contact problem with friction, this paper proposes node-surface discriminatory mode, mathematical programming model of contact nonlinear equations and the optimum generalized minimal residual algorithm. The renewed computing structure of 3-D node-surface elastic frictional contact problems presented in this paper has widened the extent of application for complicated elastic frictional contact problems. Using parallel computing method, the 3-D deformation and stress fields of sleeve and roll neck of oil film bearing under elastic force joint is calculated. And it is showed that the singular stress fields occurring in the rims of two ends of sleeve dominate the damages of the sleeve and roll neck caused by wear, roughen and stick etc..We use the revised iteration method to get the analytic solution of the sleeve displacement. The stress and displacement fields of the assembly process are determined on the basis of coupling relation between the oil pressure of hydroforming and sleeve deformation. It is noticed that the oil pressure of hydroforming provides convenience for assembly and disassembly of sleeve, but it also leads the hoop stress reaches to the yield limit and creates residual plastic deformation. Subsequently it causes the abnormity of oil film thickness distribution and damage of the shell.Experimental simulation of the wear mechanisms occurring in the assembly process of the sleeve and roll neck reveals the wearing process of sleeve, such as pitting corrosion, forming of plastic deformation particulates and scratching and roughening. By introducing spectrum analysis method and fractal geometric theory, this paper studies the damage state of contact surface and demonstrates the relation of surface topography and frequency spectrum corresponding to different stress states. The statistical fractal model of contact surfaces is presented, and the influence of contact stresses on damage states under different load condition is analyzed.Based on Reynolds equations of elasticity and hydrodynamics theory, this paper determined the distribution of oil film pressure and its influence factors. According to the contact deformation and contact stress analyses for sleeve with rolling force, the conditions of contact fatigue and fretting damage caused by micro-slip and stress concentration on the rims of the sleeve are revealed. Based on a equivalence of the local stress and strain fields derived from the classical analysis for the edge of the contact surface and the crack tip fields obtained according to the fracture mechanics methods, we explained the mechanical mech...