| Tower crane,which covers a large construction space,is a large lifting equipment commonly used in engineering.The number of tower cranes in the market has increased year by year since 2008.In 2019,the number of tower cranes in China has reached821,000 units.The rapid growth of market ownership is bound to bring the corresponding safety risks,in recent years the tower crane accidents are increasing,and according to statistics,in these tower crane breakage accidents,there are 50%-90% of the reasons are due to the long-term use of tower cranes lead to fatigue damage.In this context on the tower crane such large lifting equipment fatigue life analysis methods of research is increasingly urgent.This paper takes QTZ250 as the research object,according to the structural characteristics of tower crane and working form of tower crane fatigue life research method,tower crane cyclic load spectrum acquisition and carry out software analysis to verify the theoretical analysis.And these points as the main work of this paper to study.For the study of fatigue life of large lifting equipment first to determine the theoretical method of fatigue life assessment,and then to determine the fatigue characteristics of the entire body material,and then to obtain the working load spectrum that can reflect the load characteristics,and finally after calculation can get the service life of the tower crane.The specific research work is as follows.(1)This paper refers to the previous research in China and abroad,summarizes the characteristics of the previous research on the fatigue life of cranes,and makes a reference for the fatigue life analysis of tower cranes afterwards.The research difficulties in the calculation of the fatigue life of tower cranes are proposed according to the previous studies,and the research contents and research methods of this paper are planned for the proposed research difficulties.(2)according to the actual work of the tower crane and the use of the tower crane grade,determine the type of fatigue of the tower crane for high circumference fatigue,the fatigue life of this form of research is more appropriate to choose the nominal stress method.The method has experienced considerable research time and accumulated a considerable amount of experimental data and relevant experience.Considering the complexity of tower crane load loading,the diversity of tower crane structure,the calculation of parameters and the accumulated experience of the existing fatigue accumulation theory,this paper selects the linear fatigue accumulation damage theory to calculate the damage to the tower crane and then find out the fatigue life of the tower crane.(3)In this paper,the tower crane is modeled according to the "Tower Crane Design Standard",and the finite element static analysis is carried out jointly with ANSYS Workbench.The typical working conditions of the tower crane are selected according to the field experience and the lifting characteristic curve of this model of tower crane,and the static analysis is carried out to pave the way for the acquisition of load spectrum and the analysis of fatigue life.(4)Using the two-way data transfer interface of ADAMS and ANSYS software for joint operation of the flexible parts of the tower crane for flexible body modeling and model replacement,combined with the ADAMS/Cable module to establish the tower crane wire rope model,completed the tower crane rigid-flexible coupling virtual prototype model.Five typical working conditions of the tower crane were selected,and the dynamics simulation was carried out after validating the model,and a series of data reflecting the mechanical properties of the tower crane were obtained,which provided the necessary conditions for the subsequent fatigue life calculation of the tower crane.(5)Based on the finite element results and the load characteristics of the tower crane in each working condition obtained from the simulation of the tower crane rigidflexible coupling virtual prototype dynamics,the dangerous working conditions and dangerous nodes of the tower crane were deduced,and the fatigue life of the tower crane in this condition was obtained by the nominal stress method;after that,the pinhole connection structure in the dangerous working condition was selected as the analysis object according to the special characteristics of different structures of the tower crane.After that,the fatigue life of the tower crane was obtained by the stress severity factor method.Finally,ANSYS ncode Designlife fatigue analysis software was used to analyze the life of the tower crane in each working condition,and compared with the theoretical calculation results,the results of the two calculation methods are more consistent.Combined with the actual day work of the tower crane in the proportion of each working condition,the use of Miner fatigue accumulation damage theory to obtain a relatively accurate overall fatigue life of the tower crane.For the tower crane and other large lifting machinery fatigue life analysis and maintenance of key components replacement provides a certain reference. |
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