Crack Initiation Life Analysis Of Boom Of Wk-75 Excavator

According to data released by the National Bureau of Statistics,China’s total energy consumption in 2016 was 4.36 billion tons of standard coal.Coal consumption accounts for 62% of total energy consumption.For a long period of time now and in the future,coal is still the main source of energy in our country.The National Energy Administration also emphasized once again that the dominant energy status of coal has remained unchanged for a long period of time.This development situation puts forward higher requirements for the performance of coal mining equipment.This article takes the WK-75 excavator boom,developed by Taiyuan Heavy Machinery Group Co.,Ltd.,as the research object.It studies the crack initiation life of the boom,in other words,it studies the fatigue strength of the boom.This paper further ensures the strength of the boom、reliability,make up for the lack of strength research of the boom only using the strength theory to ensure the strength of boom,provide a certain theoretical basis for the design of the boom and ensure the safety of the staff.The main contents of the article include the following aspects:1)First,the crack initiation life calculation method is introduced.In most cases,structural fatigue belongs to stress fatigue.However,if the geometry of the structure is relatively complex,even if the external load of the structure is small,stress concentration is likely to occur in a certain part of the structure,and strain fatigue will occur at that location.In this paper,the calculation methods of stress fatigue crack initiation life and strain fatigue crack initiation life are introduced,which lays a foundation for the study of boom fatigue strength.2)A rigid-flexible coupling model of WK-75 mining excavator was established,and the dynamics simulation was performed based on this model.In the simulation load spectrum of the boom in the thrust shaft hole and the shaft axis borehole was obtained,which provided the required load spectrum for fatigue analysis.Because the connection between the tension rope and the boom is an ultra-static structure,rigid body dynamics cannot solve the statically indeterminate problem.Therefore,it is necessary to make the flexible of the rope and establish the rigid-flexible coupling model of the excavator to ensure the accuracy of the load spectrum.3)Dynamic static finite element analysis of the boom.Due to the fact that the boom has a certain speed during the turning process,according to the D’Alembert’s principle,the inertial force is applied to the boom to make the boom stand still.Then,the finite element analysis of the boom is used to calculate the maximum equivalent stress of the boom,and the result is used to determine the fatigue form of the boom.4)Estimate the boom initiation life of the boom.Since the fatigue of the boom belongs to stress fatigue,the S-N curve was used to estimate the crack initiation life of the boom.In this paper,fe-safe software is used to estimate the crack initiation life of the boom and the crack initiation life of the boom is 425 days.Based on the crack initiation life of the boom obtained in this paper,the company can periodically detect cracks on the boom and dispose them.Then the fatigue life of the boom will be extended,and the safety of the workers will be ensured.