Research On Fatigue Life Of Steel Structures

As the backbone of mechanical equipment,the steel structure is one of the key components in mechanical equipment,which bears most of the load of the mechanical equipment in the working state.The steel structure forms a loadbearing structure by welding,riveting,bolting and other suitable connection methods of the steel or steel plate.It is used in a high proportion in the manufacturing industry and has made a great contribution to the rapid development of the social economy.In the case of equipment failure failure damage,the steel structure "accumulates into a disease" and fatigue fracture occurs frequently,accounting for 50%-90% of all mechanical damage.Fatigue failure damage is most likely to occur at the original defects(cracks)of the steel structure.In engineering practice,this form of damage is the most common.Therefore,it is very necessary to study the fatigue life of the steel structure,which will have certain guiding significance for the use,detection and repair of the steel structure.Aiming at the problem of fatigue damage of steel structures,welded steel structures are taken as research objects,respectively from the aspects of basic fatigue theory,fatigue test and related equipment development,static load analysis and test of steel structures,software for evaluating fatigue life of steel structures and fatigue test programs,etc.The research on the fatigue life of the steel structure is as follows:1)Aiming at the problem that steel structures are prone to fatigue damage,based on the basic theory of steel structure fatigue,the fatigue damage history of steel structures and several major factors affecting fatigue damage are analyzed,and the commonly used fatigue cumulative damage theory and fatigue life assessment methods are summarized,Find out the fatigue life assessment method that is more suitable for steel structures,namely the fracture mechanics method.Due to the advantages and disadvantages of fatigue research methods,the feasibility and necessity of fatigue testing of steel structures are analyzed,and the laboratory fatigue test methods and fatigue test equipment are summarized and summarized.And mechanical structure performance test and analysis system performs fatigue-related test performance indicators on steel structure test pieces.2)The steel structure static load analysis process is divided into three stages.In the first stage,a set of steel structure static load test plan was formulated according to the actual test situation.In the second stage,according to the support form and stress position of the test bench,the theoretical stress analysis and static analysis of the test piece are carried out,and on the basis of the static analysis,the fatigue safety factor analysis is carried out,and the pre-test piece may show fatigue damage s position.In the third stage,the test bench is built according to the static load test plan,and the static load test is carried out on the test piece.The measured stress data is compared with the static analysis result to understand the overall stress state of the test piece and lay the foundation for the later fatigue test basis.3)With the help of MATLAB/GUI graphical interface development platform,the software interface of steel structure fracture fatigue life assessment can be realized,which can quickly and conveniently evaluate the steel structure fracture fatigue life.The fatigue life of steel structure specimens is predicted from the fracture mechanics method and the steel structure design specifications,respectively,highlighting the rationality and safety of using the fracture mechanics method to evaluate the fatigue life of steel structures.According to the steel structure test piece,the fatigue test plan is prepared and loaded on the fatigue test bench to verify the stability of the fatigue test system and the rationality of the test plan,and at the same time predict the location and cause of the fatigue failure of the test piece.