| The crane equipment,as one of the special equipment of modern material handling,promotes the development of the national economy.It is widely used in factory,freight terminal,rail transportation and construction industry.As a special crane for metallurgical forging industry,the main structure of the casting crane is the main bearing structure.Its service life determines the service life of the whole crane.With the high speed,heavy load and frequent occurrence of the casting crane,the fatigue performance of the main beam structure should be focused on at the same time of strength,stiffness and stability.The casting crane bears the function of variable amplitude load for a long time,and fatigue fracture is the main form of failure.In this paper,100/40t-28.5m four beam eccentric rail casting crane as the research object.The following study is carried out.(1)The theory of metal structure is applied to calculate the static strength of the casting crane,and the dangerous points on the dangerous section of the main beam are determined under the condition that the static strength is satisfied.By analyzing and investigating the working process of the casting crane.With MATLAB,the operation process of lifting car on main girder structure is simulated,and the stress time history of dangerous point is determined.The stress spectrum of the corresponding dangerous point was obtained by the statistics and counting by the rain flow counting method.(2)The method of crack growth and fatigue life prediction for metal structure of the casting crane is proposed,and the corresponding mathematical model is derived.According to the nondestructive testing technology,the results of the casting crane detection are divided into the case of crack and no crack.For the second stage of crack growth with crack mechanics and equivalent stress method,a fatigue life prediction model based on crack growth for metal structure of the casting crane is established.Based on the nominal stress and cumulative damage theory,combined with the mean stress correction method,a two parameter stress life surface model including stress mean and stress amplitude is derived for no crack cases.(3)Finite element simulation analysis of fatigue life: simplifying the casting crane,establishing its finite element analysis model,and carrying out the statics analysis of the finite element.On this basis,based on the fatigue analysis module Msc.Fatigue in the finite element software Msc.Patran,the fatigue crack growth and fatigue residual life of the casting crane are analyzed based on the Growth method,and the whole life of the metal structure of the casting crane is discussed by combining the stress fatigue analysis(S-N curve method).The simulation results are compared with the theoretical calculation results,the range of the relative error is analyzed,and the reliability of the finite element simulation results is determined.It provides theoretical and finite element analysis technology support for the design and life evaluation of cast cranes. |
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