Research On Slewing Plane Stability Of Booms For Crawler Crane

With the expansion of national infrastructures, the mass, size and lift height of related equipments are getting bigger. Due to its superiority, crawler crane highlights more importance in the lifting industry. As the main load-bearing part of crawler crane, boom system’s performances determine the lifting capacity of the crane largely. Besides considerations of strength and stiffness, stability has received widespread attention for its characteristic of sudden. In past design cases, the boom is regarded as a simply supported beam in its luffing plane, whereas the slewing plane as a cantilever beam. Obviously, the stability in slewing plane is worse than in luffing plane. Howerver, in case of the boom’s slewing plane instability, the directions of the tractions, dragged by the traction system consists of wire ropes and pulling plates, will change. In other words, the tractions have non-orienting force effect on the boom system, which has positive effects on the stability in slewing plane of the boom.Focus on the problem, the working condition of main boom system, main boom system with auxiliary bracing, single brace rod system and double brace rod system are researched to solve the critical load in slewing plane in this paper. It is difficult to do analytic analysis directly due to the space latticed structure. Thus, equivalent inertia moment calculation formula is deduced from the principle of the equality of critical load. In this way, latticed structures can be simplified to solid-webbed structures. Then, by force analysis and establishing the differential equations for each working condition, the characteristic equation related to the critical load is derived. The reliability of the algorithm is verified by examples. Finally, in consideration of various boom systems’features, the influences of the components’ structure parameters are analyzed to provide references for practical engineering design. At the same time, batch computing system for stability is established using MATLAB. The system can settle the matter of various working condition and large volume of work. The main research work is as follows:(1) Based on the principle of equality of critical load, the equivalent method for latticed simplified to solid-webbed structure is researched. Its rationality is obtained through examples.(2) According to Timoshenko elastic stability theory, the critical load of the beam, which is forced by non-orienting force is discussed. The approach to solve instability critical load in slewing plane for the main boom, which is forced by pulling plate solely, is analyzed.(3) Boom system with auxiliary bracing, single brace rod and double brace rod boom system are respectively discussed. The correspondent mechanics simplified models are given, and each component’s axial force is got. On the assumption that each component’s slewing plane buckling curve occurs, every axial and lateral component force of the non-orienting forces are provided. And then, on condition of force analysis, deflection differential equation is established respectively. The characteristic equation of slewing plane instability critical load is solved through boundary conditions and deformation compatibility conditions. Further, the specific load is obtained by numerical approaching method. Moreover, based on those methods, analyzing characteristics of the boom’s structure, batch computing system for critical loads of boom system’s slewing plane instability is established.(4) From the perspective of boom system’s slewing plane stability, the impact of auxiliary bracing’s length, fixed angle and locating are analyzed, to provide reference for its design. And the influence of each component’s structure parameters are also researched, thus recommended values for sub-boom’s and brace rod’s inertia moments are given, and so is the length selection for the brace rods. These can also provide reference for products’design.