The Strength Analysis And Optimization Design Of Type QY25Motocrane Structure

With the rapid development of all industries in our country, motocrane has become an essential hoisting machinery in the construction of civil engineering, transportation engineering and national defense engineering. Since users’requirements of security and stability for motocranes are becoming increasingly higher, it is necessary to perform delicate and precise analyses on the structure of motocranes, in order for their optimal design and ensuring their good working performance.Taking the motocrane QY25U as the main research object, its static and fatigue strength, modal and harmonic response are analyzed by using the finite element analysis software ANSYS Workbench. Considering that the lazy arm is the most important load-carrying component and whether its structure is reasonable will affect the performance and cost of motocrane, QY25C is also studied as an auxiliary research object with the whole analyses on QY25U. Under the circumstances of different rotary positions and working conditions, lifting performances of the two types of motocranes are compared and analyzed. Through that, the change rules of stress and strain are obtained when lazy arm of motocranes use different section shapes and lie in different positions, and some advices for its optimization design are also put forward.The researches show that the finite element analytical model of motocranes corresponds to their working reality, the calculation results of strength and stiffness are relatively reasonable. Under the circumstances of same load, the maximum stress of lazy arm when it is working in the right back of motocrane is greater than in the side position, but its maximum deformation is less than in the side position; since the maximum stress and strain of the U-shaped lazy arm are less than those of the hexagonal one, the lifespan and lifting performance of U-shaped lazy arm are better than those of the hexagonal one. Through the modal analysis, the inherent frequency and vibration shape of motocranes are obtained, the result shows that the vibration is mainly performance in lazy arm because of its long size, while the amplitude of the base is very small. By optimization, the size of the lazy arm section is obtained which can sufficiently improve the lifting performance and reduce the mass of motocranes.By use of the method of comparing the results of type QY25U and type QY25C, the lifting performance and mechanical properties of motocranes are studied, which provide a referential theoretical basis for the structural optimization of motocranes.