Extreme Prediction And Fatigue Life Anlysis Of Hydraulic Disc Brakes Of Bridge Erecting Machines

In recent years,the construction of high-speed railways in China has developed rapidly,forming a crisscross high-speed railway network.In the construction process of high-speed railway lines,bridge building machines play an important role as essential mechanical equipment.The research on their stability and safety has developed quickly.As an important part of maintaining the stable operation of bridge building machines,the research on the brake system of bridge building machines has gradually developed.During the development and testing phase of bridge building machine brake systems,comprehensive dynamic performance calculations and tests are carried out,but the dynamic response is generally considered using equivalent static loads.However,such large mechanical equipment often faces harsh operating environments and variable forces,which makes equivalent static loads less accurate.Therefore,monitoring and simulation analysis of the working state of such equipment using virtual prototyping technology is particularly important.In this thesis,the ST3SH-A hydraulic disc brake of the SLJ900/32 mobile bridge building machine was studied,and static analysis and dynamic simulation of the main structure were carried out to study the dynamic response of the brake system in the dangerous area during service,and a complete analysis process was established.The research content focuses on the structural dynamic performance and internal mechanism of the brake system under specific working conditions.Stress extreme value prediction and fatigue life analysis of the structural danger area were carried out based on the obtained time-domain data,providing a reference for the design and application of bridge building machine brake systems.The main research contents are as follows:(1)Taking the ST3SH-A hydraulic disc brake as the research object,the typical working conditions were analyzed by static analysis using the finite element software ANSYS Workbench,and the dangerous areas of the main structure were determined.(2)A rigid-flexible coupling model of the brake system was established using ABAQUS and ADAMS joint simulation.A G-grade random road was established using harmonic superposition method.The process of the bridge building machine traveling on an uneven road surface while hoisting a beam was simulated,and the load timehistory curve was extracted as input to analyze the stress response of the dangerous area of the brake system.The stress time-history data of the dangerous area were extracted.(3)The extreme value prediction theory and the operation process of the average conditional exceedance rate(ACER)function are elaborated,and the extreme value of stress at the danger point of the brake at 95% confidence interval is predicted based on the average condition exceedance rate function(ACER)and the dynamic simulation data of the brake,and the applicability of the average condition exceedance rate method in large engineering machinery and equipment is verified by comparing with the measured data.(4)The fatigue life of brakes under specific operating conditions is calculated using the nominal stress method combined with fatigue cumulative damage theory and verified using the ANSYS n Code Designlife module to evaluate the fatigue life of brakes and provide a reference for brake design and application.