| Designing the lifting truck is to solve the problem of transporting certain cargoes over short distances.It is therefore necessary to meet the requirements of self-propelled walking,compact structure and easy operation.The lifting truck studied in this paper is based on a forklift by removing the weight of the original vehicle,and installing booms,columns,beams,and outrigger structures.The mechanical properties of the outrigger structures have a crucial influence on the lifting and handling.Therefore,the lifting trucks must be studied as the research object and analyze the key technologies of the support structure under the lifting operation,such as static,dynamic response,lightweight design and contact stress.Thus,hopefully providing some references for the similar structure design and analysis.According to the design requirements,the overall plan for the lifting truck was designed firstly in this thesis.Referring to the GB/T 3811-2008,the outrigger reaction force of the lifting truck was calculated corecctly based on the rigid frame hypothesis.Applying the theory of classical mechanics,the structural parameters of the outrigger structures were preliminarily selected,and then calculated and analyzed the strength and stability of the components of the outrigger structure;the hydraulic cylinders with corresponding motions of the support outriggers were designed and selected.Taking into account the constraints of cargo handling conditions,the maximum supporting capacity of the legs,and the stability of the entire vehicle against overturning,the most reasonable installation position for the outrigger structures is determined.Before establishing the finite element model,the geometric model of the outrigger structures needed to be simplified on the premise of satisfying the analysis accuracy.Then the finite element model of the outrigger structures represented by the leg device was established in the software ANSYS Workbench.The static analysis was completed under five operating conditions and the stress cloud diagram was drawn.The maximum stress under the most unfavorable conditions was 111.270 MPa.Then modal analysis was performed to determine the modal frequency and mode shape of the first 10 stages and used it as a precondition for determining whether the structures will be resonant in the harmonic response analysis.After the harmonic response analysis,the maximum displacement amplitude was known,the frequency appeared around 117 Hz.Linear buckling analysis determined its critical buckling load and compared it with the actual load bearing,thus clarifying the corresponding safety margin.From the static analysis,it was obvious that the strength of outrigger structures and needed to optimize.The finite element parametric model of support structure was established and design of experiment was completed to obtain sample data.ISIGHT and MATLAB softwares were integrated to establish an LM-BP neural network approximation model to complete design parameter sensitivity analysis.After theoretical calculation and simulation analysis,the strength of the outrigger structure was the main condition.The lightweight design was completed by using multi-island genetic algorithm and combining with MATLAB through regarding the strength as the constraint condition and the structural weight as the optimization goal.Finally the weight decreased by 8.409%.The Software ABAQUS/CAE was used to establish the finite element model of the above outrigger structure,set the corresponding contact conditions and completed the nonlinear contact analysis to solve the slider contact problem.Through changing the slider’s structural dimensions,material properties,friction coefficient,and the number of sliders,the contact stress of sliders was studied and the conclusion was drawn: The contact stress is significantly lower when the cast bronze material was used than the Q235 steel.When the friction coefficient f was 0.15,the contact stress was minimized. |
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