Parameter analysis and optimization of tubular transitional layer damping structure for agricultural machinery

Abstract: To solve the violent vibration and impact problem of agricultural machinery together with considering that there are many tubular structures on it, the concept of transitional layer is introduced based on the traditional constrained damping structure, and a new kind of tubular damping structure with transitional layer is proposed. It is worth mentioning that the elastic modulus of the transitional layer must be situated between those of metal material and viscoelastic damping material. Thus, when the structure vibrates under the action of external force, the transition layer can work similar to a lever, and shear deformation of the damping layer will be increased so as to improve the effect of the energy consumption of the whole structure. At the same time, with respect to the thickness increase of the damping layer to improve the structure's energy consumption, the proposed transitional layer damping structure can also enhance the use stiffness of the original structure. Structural loss factor is an important index to evaluate the vibration reduction performance of a mechanical damping structure, and its mathematical model is established based on the strain energy method. The influence of transition layer parameters on the structural loss factor is studied. The results show that the selection of the transition layer's elastic modulus and thickness is more important than that of density in practical application. What's more, with the increase of the transition layer's elastic modulus, the structural loss factor does not always increase, but changes similar to the shape of inverted bell, which indicates that the optimum design value of transition layer's elastic modulus exists. In general, when the material elastic modulus of the transition layer is more than 100 times bigger than that of the damping layer, it will get the ideal vibration damping effect. In addition, with the increase of the thickness of the transition layer, the loss factors of the tubular transition layer damping structure are enhanced, too. In practice, the relationship between the increase of the transition layer's thickness and the installation space constraints should be considered. However, when the density of transition layer increases, the loss factor of the structure decreases, but it is not obvious. Using ANSYS's sub-problem approximation method, the parameters of the tubular transitional layer damping structure are optimized. Through optimization, the mode loss factors of structure of the first 4 orders are respectively increased, in which the first-order loss factor is increased by 34.19%, the second order is enhanced by 12.11%, the third order improves by 22.39%, and the fourth order is also increased by 12.70%. To further verify the optimization results, harmonic response analysis is done among the un-damped tube, the tubular transition layer damping structure before optimization and the optimized structure. The analysis results show that the transition damping treatment can effectively reduce the vibration amplitude of the structure and the optimized structure has better damping effect. The research results of this project are helpful to the further development of high-performance tubular damping structures in construction machinery. At the same time, it can also provide methods and theoretical basis for the design of other vehicles and vibration-isolating structures in many engineering applications.