Dynamic Modeling And Analysis Method Of Flexible Beam Systems Of Crane

In dynamics of machinery and engineering mechanics yields, more and more attention is paid to kinetic-elastic dynamic analysis of flexible bodies. Crane with flexible booms is a typical heavy-load flexible machinery. Crane bears combined action of axial and transverse loads, so accurate dynamic analysis is the major means to ensuring its safe operation. The elastic dynamic analysis method of mobile flexible beam system with the second-order effect considered is researched on basis of the geometric nonlinear finite element and flexible multibody system dynamic method, and the typical mobile case of crane is analyzed. The method provides an important theoretical basis for analysis and designs of great flexible booms of crane.The traditional interpolation method, assumption of displacement and shape function are abandoned. The relations of forces and displacements in the end are deduced with vertical and horizontal bending theory considering the second-order effect. The relation is expressed as the form of element equilibrium equation, which is accurate finite element equation of planar beam with the second-order effect considered. Therefore accurate stiffness matrix can be obtained. The former equation is deduced without assumption and omitting according to the second-order theory. Several classical examples in the stability and second-order effect of beam structures are analyzed with the accurate finite element method. The results are compared to accurate analytic solutions and it is proved that the method is effective and exact in geometric nonlinear analysis of beam structures.Crane structures work in the scope of elasticity. Using concomitant coordinate method, the paper extended the small distortion finite element of beam and truss system based on the theory of second-order to geometry nonlinear finite element of beam and truss system in the condition of large displacement and small distortion. The expressions of geometric nonlinear large displacement are obtained by high accurate descriptions of equilibrium equations of elastic beam in local coordinate system and accurate coordinte transitions between displacement and distortion in global and concomitant coordinate system. So the high precision total and tangent equilibrium equations on frame system of large displacement are deduced. Strong support is provided for geometric nonlinear analysis of great flexible crane structures. In elastic dynamic analysis for flexible beam system of crane, the method that distortions are described in concomitant local coordinate system and rigid motions and large displacements are described in global coordinate system is applied to mobile beam system. The kinetic equations of beam and link element in the local coordinate system are derived through accurate description for mobile status of flexible body. Because other dynamic characteristic matrices like the mass matrix directly correlate with the shape function, these matrices are derived by using the shape function of the traditional method. The stiffness matrix is derived by high accurate finite element method. With the mobile coordinate method, the dynamic equations in the global coordinate system are obtained using the relation of nodes' displacement, velocity and acceleration in mobile and global coordinate system. The dynamic equations include all inertial coupled matrices, and the interrelationship and couple of rigid motion and elastic deformation are considered entirely. The integration method of system dynamic equations and method of processing lump parameters are introduced, and the solution method and program organization are discussed. The program flow charts are described and the corresponding finite element program is generated. Some typical machines are analyzed and it is proved that the modeling theory and program are correct.The elastokinetic analysis of horizontal jib tower crane in case of braking the slew and boom system of the port crane in case of modifying amplitude are made.The results show that the displacement and internal force of crane increase when the second-order effect is considered. So the heavy-load crane with high flexibility should be analyzed considering second-order effect.