Dynamic Contact Analysis of Flexible Telescopic Boom Systems with Moving Boundary

A flexible telescopic boom is a multi-body system composed of several hollow booms nestled into each other. For this kind of system, due to the limitation of the elemental size being fixed, it is necessary to divide it into many small-sized elements and judge which two elements are in a contact state in real time using the traditional finite element methods. This complex operation often requires calculations on enormous scales and can even result in simulation failure. In view of the above difficulties, an efficient dynamic contact analysis model of flexible telescopic boom systems with a moving boundary is proposed in this study. Firstly, on the deformable axis of the boom, some crucial points are defined as inner and outer contact points, and spatial points are selected as nodes for describing the motion of the system. Secondly, in contrast to the traditional solid finite element method, the assumption that elemental nodes are fixed with the material points is removed, and on this basis, a geometrical nonlinear dynamic element with moving nodes is constructed, which can describe the moving boundary problem effectively and is used to model each boom. Thirdly, to better cooperate with the moving boundary conditions, a contact model and its corresponding discretization method are developed on the premise of not removing the sliding joint constraints, which are used for dynamic contact analysis considering the friction effect between adjacent booms. Finally, experiments were conducted to evaluate the accuracy of the modeling, wherein the dynamic response properties of the supported beam under the action of a moving load and the dynamic behavior of the telescopic boom being extracted were analyzed.