Dynamic Simulation Of Telescopic Boom System Under Composite Motion And Optimization Design Of Luffing Mechanism

With the vigorous development of infrastructure industry,driven by the demands of municipal,transportation,water conservancy and hydropower projects,Chinese construction cranes have entered a period of rapid development and gained deep attention.The telescopic boom is the core part of the truck crane to bear the load,and its stiffness,strength and stability determine the lifting performance of the equipment.The luffing mechanism is an important part of the truck crane to realize the luffing operation,and the selection of hinge point location directly affects the stability of the luffing process.Therefore,the structural characteristics analysis and dynamic simulation are carried out for the telescopic boom system of the truck crane,and the multi-objective optimization design of its luffing mechanism is carried out.The research results have important theoretical significance and engineering reference value for improving the work stability of the truck crane.The main research contents of this thesis are as follows:(1)Referring to GB/T3811-2008 "Design Specification for Cranes",starting from the cross-sectional shape,expansion and contraction method,and load bearing capacity of truck cranes,the calculation formula for the critical force of load instability of the telescopic boom in the variable amplitude plane and the recursive formula for the bending internal force of the n-section telescopic boom considering the self weight of the boom are derived,and the mechanical analysis of the telescopic boom structure is carried out.(2)By using ANSYS and Hypermesh software,the structural characteristics of the telescopic boom of a truck crane are analyzed to obtain the maximum stress,maximum deformation,and corresponding dangerous positions of the telescopic boom under two typical working conditions: fully retracted and fully extended.The first six modal vibration modes of the telescopic boom under these two working conditions are extracted to avoid the occurrence of boom resonance phenomenon.(3)The rigid-flexible coupling dynamics model of the truck crane was established by using ANSYS and ADAMS co-simulation software,and the pure lifting motion and the combination of lifting and rotating motion were selected as parameters for the dynamic simulation,and the displacement curve,stress curve,boom stress nephogram and maximum stress node curve of the telescopic boom were obtained.The influence mechanism of rotary speed,lifting weight and other factors on the working performance of truck crane is revealed,which provides a certain theoretical basis for improving the working efficiency of crane and ensuring the construction safety.(4)The optimization model of crane luffing mechanism is established.With the minimum force,minimum total length change rate and minimum stroke of luffing hydraulic cylinder as optimization objectives,the multi-objective optimization is carried out on the hinge point position of the luffing mechanism.The satisfaction function is constructed by combining the robust design method and analytic hierarchy process,and the relative optimal solution is selected from the optimal solution.In order to improve the stability of the truck crane luffing mechanism under the working state,improve the service life of the luffing mechanism.