Study On Mechanics Modeling For Super-lift System Of All Terrain Cranes

The super-lift system is a guyed system for all terrain cranes to improve the state of forces of the telescopic booms. The lifting capacity is enhanced notably with the existence of it. With the increasing of the load and height, the mass and length of the telescopic boom of all terrain cranes become larger and larger. When operating in medium or long radius, the deformation of the boom is very large, which restricts its lifting capacity seriously. Therefore the super-lift system is added to telescopic boom to change the form and the state of forces. Between the super-lift system and the telescopic boom a stable bi-triangle shape is formed, which enhances the stability, reduces the deformation and increases the lifting capacity of the telescopic boom. However the technology of the super-lift system is complicated and has a late start of domestic development. The super-lift system is few and not in depth according to domestic researches.This paper studies the super-lift system, finds out the variation of telescopic boom with the super-lift system or not and the effect of super-lift system parameters on the telescopic boom and verifies the analytical results with finite element method, from the perspective of mechanics,taking the QAY350 all terrain cranes designed by some company for example. The primary work of this paper is as follows:(1) The mechanical model of the telescopic boom with super-lift system is Simplified and developed. Based on the mechanical model, analytical calculation is carried out with the force method in classical mechanics, deriving the analytical formulae of the force of root linkage point of the telescopic boom, luffing cylinder, flexural moment, and axial force of each section of the telescopic boom, and maximum stress analytical formulae of weak section under the lifting load, dignity weight and the side load.(2) Taking QAY350 for example, the paper calculates the force of root linkage point of the telescopic boom, luffing cylinder, and maximum stress analytical formulae of weak section if with super-lift system or not. With the finite element method, the paper also verifies maximum stress analytical formulae of weak section in three working conditions when the boom is fully stretched.(3) Curves of maximum stress analytical formulae of weak section are drawn changing with super-lift system parameters in three working conditions when the boom is fully stretched. Based on the curves, the optimal values of parameters can be found, providing a theoretical basis for the designed value of the super-lift system parameters when comparing with the actual value.The results show that the mechanical model of the telescopic boom with the super-lift system are internal forces statically indeterminate structure of secondary; Forces of the telescopic boom decreases obviously and more when the telescopic boom is fully stretched when the super-lift system is added; The optimal values of a, a2,l1,,θare same with the actual value. The results illustrate the effect of super-lift system on the telescopic boom theoretically, providing a theoretical basis for the designed value of the super-lift system parameters.