Nonlinear Similar Design Of Large Slenderness Ratio Truss Boom

For the large lifting machinery boom system that has large slenderness ratio and nonlinear characteristics in the engineering field, stand-alone design and manufacture use analogy and imitation, which lacks specific design methods and theoretical basis in domestic. Crane design enters a new stage with the development of computers and finite element numerical methods, such as optimization design, finite element design, modular design and other modern design methods. But these methods belong to a kind of "post-design" approach, which checking improvement or numerical optimization is carried out on the basis of the product having an initial structural parameters. These methods still don't solve the problem above.To reduce design costs, improve design efficiency, strengthen inheritance of the optimized benchmarking product and accomplish rapid design, nonlinear similarity design method of target product is derived under large deformation based on prototype product. This thesis is based on the project "Research on Nonlinear Similarity Design Mechanism and Similarity Dynamics Analysis Method of the Large Slenderness Ratio Lifting Boom" which is funded by the National Natural Science Foundation (approve number:51475068). The main methods are as follows:(1) The main boom that is widely used in large slenderness ratio structures is as the research object in this paper. By analyzing the load features, force model is established in luffing plane and rotary plane by the load combination ? when the lifting mechanism and the rotating mechanism simultaneously works.(2) Under the assumption of each demand parameters of prototyping products being known, FEM basic equations are expressed in the form of potential function by introducing displacement potential function based on the similarity theory. Unit similarity criterion is established in the local coordinate system by non-dimensional treatment for FEM basic equations are expressed in the form of displacement potential function. Nonlinear similarity criterion in the global coordinate system is obtained by using coordinate transformation method to conversion parameters from the local coordinate system to the global coordinate system.(3) Similar Design of the design goals chord member cross-sectional area is derived by nonlinear similarity criterion and stability principle. The width and height of the boom is derived based on rigidity principle. The layout of web member is discussed. Weld crosswise W structure is selected and the angle between web member and chord member and the length of web member is designed similarly.Adopting existing and ripe QUY750 crawler crane as a prototype product, each of the required parameters is obtained by eigenvalue buckling analysis and nonlinear buckling analysis. Boom parameters of 1100t crawler crane are designed from the parameters obtained of QUY750 crawler crane by using the methods of nonlinear similarity criterion and boom nonlinear design method that are derived above. Comparing with boom structure parameters of LR11350 crawler crane, the differences of working range, hoist, the angle between web and chord in rotary plane, length of web member in rotary plane of boom that is obtained by similar design are little. The model of chord and web is smaller than LR11350's. The differences of the angle between web and chord in luffing plane, length of web member in luffing plane of boom is larger compared with LR11350's. The reason may be first-order theory that is adopting, the lower limit that width and height of design structure takes or sufficient safety factor of prototype product and LR11350 crawler crane.