Research On Steady State Creep Of Thick Walled Cylinder Under Complicated Loads

Thick-walled cylinder is an important structure in engineering, creep has negative effect on thick-walled cylinder machines at high temperature and under complex load. In this study, by combining creep mechanics theory with stress function method of elastic mechanics, formula of steady state creep stress of thick wall cylinder is derived. According to the formula, steady-state creep stress of oil-film bearing bushing which is subjected to a type of non-uniform oil film pressure is analyzed. Based on the tensile test of the Babbitt of oil film bearing, creep property and mechanical property are analyzed. And according to the creep characteristic of Babbitt, creep process of oil film bearing bushing is simulated by using the method of finite element analysis, analytical solution is compared with simulated result, and main job description is as follows:Firstly, stress function method in elastic mechanics is combined originally with relevant theories of creep mechanics, a new computing method of creep stress of thick-walled cylinder is proposed under complicated load. Analysis of the characteristics of calculation formula, relationship between radius and creep stress is obtained at different ratio of external diameter and internal diameter of thick-walled cylinder. It is confirmed that the maximum creep stress is occurred in the thick-walled cylinder boundary. Maximum creep stress of thick wall cylinder increases after then reduces with the increase of wall thickness. When ratio of external diameter and internal diameter of thick-walled cylinder K is 1.58, creep stress of thick-walled cylinder is the largest, which can provide the theoretical reference to structure design of thick-walled cylinder.Secondly, based on actual size of oil film bearing bushing, creep process is simulated. According to results of simulation, rules of creep stress distribution are obtained. Results of analytical method is agree well to the results of ANSYS by analyzing contrast figure of analytical results and simulation results, which show that method of this study is correct and precision can meet the demand of practical engineering.And then, creep process of three-dimensional oil film bearing bushing is simulated by using finite element software ANSYS, of which parameters come from tensile test of Babbitt and test on lubricating performance of oil-film bearing oil. Results show that creep of oil film bearing bushing is occurred in actual working condition, the oil film pressure has a great influence on the oil film bearing bushing. Maximum creep stress is occurred in the region in which the oil film pressure and temperature are the largest, which decrease with the increase of radius.Finally, based on the creep test, steady-state creep equation in Norton form and exponential form are obtained, formula of the stress relaxation in Norton form and exponential form are obtained by using the creep coefficient which come from three groups of experimental data. Results of theoretical analysis are compared with finite element analysis and the theoretical calculation results are agree well to the results of finite element methods, which show that method of this study is right. Results show that in the process of relaxation, creep rate of Norton form is smaller than creep rate in the form of index. Form of Norton the formula of stress relaxation of higher precision than the exponential form.