Effect of wear rings on buckling load capacity of Two-Stage hydraulic cylinder

Abstract

In a two-stage hydraulic cylinder, the rod is a critical component for stability against buckling failure. A small disturbance in the rod may increase the instability that may lead to catastrophic failure. A small support against the instability may increase the system's flexural strength to make it more stable. The wear rings provide an elastic support against the rod and cylinder's instability and increase the flexural strength of the connections. In this paper, a theoretical model for the buckling load of a pin-pin-mounted two-stage hydraulic cylinder is proposed. The buckling load calculation by the proposed approach is in close match (6.96% deviation) with the experimental results reported in the literature for the case of single-stage hydraulic cylinders. The effect of bending stiffness on stability is considered by considering the stiffness of the rod and cylinder along with the wear rings. A hyperelastic model is used to determine the bending stiffness of wear rings in three different cases: first when all wear rings are present, second when three wear rings are present, and third when only two wear rings are present. The stiffness of the rod and piston head is determined with the help of the conjugate beam method. Eigenvalue buckling analysis (finite element method) is carried out to verify the buckling load of a two-stage hydraulic cylinder with two, three, and four wear rings. Theoretical results are observed to be in good agreement with the numerical simulations (FEA) results, with a percentage deviation of 0.22 % − 9.22 % for different cases of wear rings positions. It is observed that when all four wear rings are present, the buckling load capacity increases by 1.14 times, whereas the removal of wear rings on the gland side decreases it by 0.96 times.