Abstract
Hydraulic actuators are commonly adopted in machines and structures to provide translating forces with significant magnitudes. Although their application dates back to the industrial revolution, their bending behavior under compression is typically addressed by simple Euler’s instability analysis on the rod, neglecting effects such as the cylinder inertia and stiffness, the presence of contact elements in the cylinder-rod junction and on the piston, geometrical misalignments and imperfections, and friction moments at the support. Such simplifications lead to unjustified reduced critical load calculations on the component. In the present paper, a complete mathematical formulation, which accounts for such effects, is presented and validated against experimental data. A numerical sensitivity analysis is conducted, to assess the contributions of initial rectilinear imperfections, wear rings stiffness and dimension, and supports friction on the actuator’s limit buckling load and bending behavior under compression. Results are presented, including the effect of the cited parameters on the buckling load, providing a reliable tool for the mechanical designer. In particular, an optimum position for the wear ring distance is found. Moreover, increased wear ring stiffness and reduced imperfections increase the buckling load and reduce the bending stresses before the critical load.
Highlights
Hydraulic actuators have been widely adopted to apply and multiply translating forces in mechanical systems
The results found in classic literature, related to the definition of the actuator critical buckling load, have been demonstrated to be overconservative, as in the single-beam Euler model [3], or overestimating, as the instability model with infinite stiffness hollow cylinder [4]
The test settings are corresponding to the base values adopted for the numerical model in the sensitivity analysis
Summary
Hydraulic actuators have been widely adopted to apply and multiply translating forces in mechanical systems. The results found in classic literature, related to the definition of the actuator critical buckling load, have been demonstrated to be overconservative, as in the single-beam Euler model [3], or overestimating, as the instability model with infinite stiffness hollow cylinder [4]. The limitation of such classical models is the lack of correlation to actual buckling limit load found on working examples, leading often to component oversizing in the best situation, or to unreliable buckling load values, higher than the experimental ones. The stresses induced by the bending behavior under compression loads were not matching experimental values
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