Crack Growth Life Prediction And Analysis Of Boomof WK-75 Mechanical Excavator

Owing to poor working environment, complex operation objects and diversified working attitudes, the structural units of heavy mechanical excavators may inevitably bear alternate loads of various degrees and operating modes. Boom, an important part of a mechanical excavator, has a relatively high load fluctuation, which then easily brings its elements microscopic and further expanded macroscopic cracks under actions of alternating stress, resulting in fatigue failure. Thus it’s necessary to precisely and reasonably predict the operational life span of excavator booms.The main research contents include:(1) Put forward a set of new boom evaluation methods by combing the complex structure and large size features of heavy excavator boom WK-75, and applying the numerical calculation theory of fracture mechanics and crack propagation theory.(2) Import the boom model established by UG software into ANSYS workbench, and use finite element analysis software to analyze the finite element static strength under dangerous conditions.present a method to determine the stress time course in the dangerous area, providing stress spectrum data for boom life calculation. The method bases the dynamic simulation analysis in ADAMS on the dangerous area of the boom generated from formal finite element static strength.(3) Determine the crack models according to structures and loads in different dangerous areas. Set up the model of finite element for cracked boomswith finite element analysis software. The fracture mechanics analysis on boom model has completed after an eventual finite element calculation of stress-intensity factors of crack borders in various points and various crack scales. In accordance with the stress-intensity factor amplitudes in various crack scales, a function expression ΔK= f(a) is generated for crack lengths and the amplitudes in various dangerous points. Use the Paris formula of crack propagation rate to predict the propagation life of fatigue crack in dangerous boom points.This main research is of great importance not only to the precise operational life prediction and a more reasonable design of mining excavator booms, and construction safety guarantee, but also to corresponding maintenance and scrap basis for the safety use of excavators.