| Due to the increasing of slenderness ratio and the usage of lightweight,high strength material,the flexible characteristics of crane with large boom become more remarkable.The combined effects of flexible large overall motion and the flexible deformation of boom lead to the crane boom has obvious nonlinear characteristics.In the current design rules for cranes,there is no formal calculation method for the characteristics of the flexible boom.Therefore the design of large flexible boom is referenced by the foreign products of same type for single product design in domestic,which causes the low efficiency of design and the insufficient design accuracy.In order to break the above mentioned limitations,improve the accuracy of flexible boom design,shorten the design period,it need finally form a theory for seriation design based on excellent design products.The flexible boom of crane crawler crane is chosen as the research object in this paper,which is the most typical structure form of the truss boom.Based on the kinetics equations of flexible boom and the similitude method,the dissertation has derived the dynamic characteristics similarity relations of flexible truss boom.The main research contents are as follows:(1)The summary about development status of flexible multi-body system dynamics and the applications of similarity theory in the field of structural dynamics are presented.According to the working conditions of crawler crane,the main boom is selected for modeling analysis.In the process of modeling,the finite element method is use to discrete flexible boom model,floating frame method is used to describe the flexible deformation of boom with a large overall motions,finally the dynamic equations of flexible crawler crane boom is established based on the Lagrange equation.(2)Based on the assumption that the lateral displacement of the truss boom equals to the solid-web boom,this paper derived the truss boom equivalent conversion coefficient of moment of inertia,which can take the effect of web members into consideration.By using the coefficient,it can enable the dynamics equations of flexible boom to solve the truss structure.Therefore,the numerical simulation model by using the Simulink is presented based on the equivalent conversion coefficient.The specific parameters of QUY750 crawler crane boom is used to solve dynamic equations of flexible boom and the related results are analyzed.(3)The two basic methods commonly used in the similarity design are expounded.Specific to the completely geometric similar truss boom,similarity relations of natural frequency and other parameters are deduced.By given the calculation of natural frequency and vibration mode of flexible boom prototype and model,the correctness of the similar relations can be verified.The method for calculating the approximate natural frequency of flexible boom under a large overall motion is derived by combining perturbation theory and vibration analysis.At last the similarity relations of flexible boom dynamic characteristics are derived and verified by numerical simulation.(4)With the purpose of validating similarity relations of the flexible boom dynamic characteristics,the paper designed two sets of scale model for experiments by taking the slenderness ratio of actual boom as the standard.By compared the dynamic characteristics of flexible boom which has different section size and length,the correctness of the similarity relations derived by similitude method can be verified.The experiment results show that the correctness of using similitude method. |
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