Stability analysis of large slenderness ratio horizontal hydraulic cylinder

Abstract

Abstract. An improved two sections pressure bar method (ITSPBM) was presented to analyze the stability of the large slenderness ratio horizontal hydraulic cylinder. The friction moments, the bearing reactions at the two hinge joints as well as the clearances between the piston and the inner wall of the cylinder were taken into consideration. The result shows that the stability safety factor is 6.20. Meanwhile, in the finite element model of the horizontal hydraulic cylinder, the nonlinear friction force and clearances were involved. The result reveals that the stability safety factor is 9.24. Through comparing the results of the ITSPBM, the traditional two sections pressure bar method (TTSPBM), the finite element method (FEM) and the method in NB/T 35020-2013, it suggests that the stability of the large slenderness ratio horizontal hydraulic cylinder meet the actual engineering requirements and the friction moments at the two hinge joints can extremely enhance the stability. IntroductionUnder the condition of large axial load, the stability problem of large slenderness ratio horizontal cylinder is critical for the safety and reliability of the whole structure design. As for the large slenderness ratio horizontal hydraulic cylinder, it is simplified as equal section mechanical model in engineering design to analyze the stability according to the Euler formula. In this algorithm, the hydraulic cylinder and the piston rod are fixedly connected. The clearance between the piston rod and the guide sleeve, the friction moments at the two hinge joints and the bearing reactions are not considered. The calculation results cannot fully reflect the deflection and buckling characteristics of the large slenderness ratio horizontal hydraulic cylinder. GUO Ying-long et al [1] put forward two sections pressure bar mechanical model and the calculation formula of the buckling critical load is derived taking into account the reactions between the piston rod and the hydraulic cylinder and the stiffness of the hydraulic cylinder. Considering the initial deflection of the hydraulic cylinder and the piston rod, self-weight, and the friction moments at the two hinge joints, P J Gamez -Montero et al [2][3] derived the calculation formula of the buckling critical load and verified the variation law of the buckling critical load with the initial deflection. The results of the tests show that the influence of the friction moments cannot be ignored when the clearance between the pivot and sleeve is enough small. Under the actual working conditions of the hydraulic cylinder system, the axial pressure exerted by the oil in the hydraulic cylinder applies on both ends of the piston rod. Based on the mechanical model, WU Ting-ping [4] considered the bearing reactions existing at both ends of the hydraulic cylinder and calculated the stability of the