Fatigue Life Evaluation For Boom Structure Of Wheel Crane

With the continuous improvement of China’s modernization construction,the demand for wheeled cranes in the infrastructure construction market is increasing.Wheel crane is widely used in manufacturing,industry,mining,urban construction,warehousing,marine development,aerospace and other fields due to their excellent mobility.It plays a vital role in air,sea,land,military and civilian areas,and assists and improves the work of all walks of life.As the main bearing structure,the boom structure’s strength and fatigue life directly determine the performance,safety and reliability of the wheel crane.With large tonnage becoming the mainstream of wheel crane development,engineering accidents caused by fatigue damage occur from time to time,posing a major threat to the life and property of the country and the people.To study the fatigue failure of the jib structure of the wheel crane and evaluate its remaining life scientifically and accurately has very important social value and research significance for improving the safety,stability and reliability of the wheel crane.The research methods of fatigue failure of wheel crane boom structure mainly include theoretical analysis,experimental analysis and numerical analysis.Theoretical analysis focuses on the basic theoretical research.There are differences between the life assessment results and the actual work situation.The accuracy and engineering practicability of theoretical analysis need to be improved.Test analysis is limited by the test cycle,test conditions and test costs,and only the dangerous points determined by experience can be tested,and the fatigue life of the whole structure cannot be obtained.Numerical analysis has become a necessary means to solve such problems.Finite element method is the most mature numerical analysis method at present,and is widely used in the fatigue life analysis of mechanical structures.Aiming at the fatigue life of the boom structure of the wheel crane,the stress is calculated based on the finite element method,and the fatigue life of the wheel crane is evaluated based on the fatigue failure theory.The main research work of this paper includes:(1)By studying the load type of the jib structure of the wheel crane,the load is simplified and combined according to the length of the load action time,the actual working conditions and working characteristics of the crane,and the reasonable load is selected based on the dangerous working conditions,and the stress analysis of the jib structure of the crane is carried out.(2)Through the study of the structural characteristics,working load and weld structure of the wheel crane boom,a simplified finite element calculation model of the wheel crane boom structure is established,its strength is analyzed,and the hot points of the wheel crane boom structure are determined.(3)Based on the patch test of the boom structure of wheel crane under typical working conditions,the correctness and validity of the simplified finite element calculation model are verified by comparing the test stress results with the calculated stress results;Combined with fatigue test,S-N curve and weld fatigue curve of main material of boom structure are obtained.(4)Based on the finite element analysis results of the boom structure of the wheel crane,combined with the S-N curve of the boom structure material and the nominal stress method,the damage value caused by a single load cycle is calculated;The fatigue life of the boom structure is analyzed by using the fatigue cumulative damage theory,and the calculation method suitable for evaluating the fatigue life of the boom structure is obtained.