Numerical investigation of a mono-tube damper with a shim stack

Abstract

The objective of this paper is to investigate the operation of a mono-tube damper through the application of Computational Fluid Dynamics analysis to the piston and flows through a series of flexible shims which cover exits of the piston orifices. The shims and orifices combine to form a system of variable area flow paths of the damper in parallel with the permanent bleed orifices. Shim stack stiffness characteristics were obtained using experimental and Finite Element techniques. The deflection characteristics were non-linear and were highly dependent upon small gaps present between shims and the restraining bodies. With the nature of the shim deflection being highly complex the computational fluid dynamics models investigated the shim deflection using a global uniform displacement method and also a more representative displacement based upon the finite element shim modelling. It was observed that the global displacement models allowed radially inward flow to establish and also overpredicted pressure drops. Finite element analysis of the shims allowed accurate representation of flow paths to be simulated which closely matched experimental and mathematical predictions. The computational fluid dynamics analyses showed that the discharge velocity for the global shim offset is greater than that from a variable shim deflection calculation. The damper pressure drop is highly dependent upon the shape of the flow path formed by the shim deflection. The presence of sharp direction changes through the piston and valve assembly leads to increased damping rates and piston pressure drops.

Validation of Fatigue Model of a Hydraulic Shock Absorber Equipped with Shim Stack Valves

“…The former fatigue prediction methods were based on Roark's stress and strain formulas stated in the form of pre-derived and parameterized equations [5]. Nowadays the finite element modeling approach is being implemented to support development of more advanced models [1][6] [7][8] [2][4] [9][10] [11]. The latest research deals with development of FDI (Fluid Structure Interaction) models including morphing of the fluid cavity [7], CFD (Fluid Structure Dynamics) models [12], and experimental techniques as PIV (Particle Image Velocity) [13] [14].…”

“…Nowadays the finite element modeling approach is being implemented to support development of more advanced models [1][6] [7][8] [2][4] [9][10] [11]. The latest research deals with development of FDI (Fluid Structure Interaction) models including morphing of the fluid cavity [7], CFD (Fluid Structure Dynamics) models [12], and experimental techniques as PIV (Particle Image Velocity) [13] [14]. There are also other methods applicable in fatigue testing to increase test accuracy and confidence.…”

Transient numerical investigation of a large-scale hydro-pneumatic suspension considering variations in check valve parameters and operational conditions

“…A fluid-structure interaction model was constructed to determine the flow characteristics of a damper with a shim stack in it, (Czop et al, 2012). Inspiringly, all of these scenarios and others were fleshed out in a new article (Bell and Beale, 2017) finished at Oxford Brookes University. The authors concluded HFF 30,4 that the use of CFD techniques allows the damper operational movement to be modelled more realistically and that the use of the Reynolds averaged Navier-Stokes (RANS) k-« model is appropriate to develop the turbulent flow in a shock absorber.…”

Influence rules of geometric parameters on deformation of valve slices in valve-controlled adjustable damping shock absorber

“…Kulkarni et al (2014) studied valve slice’s deformation and its damping force under different pressure drops, and analyzed the influences of the port size, port position, fixed radius, and other-related parameters on the nonlinear velocity. Bell and Beale (2015) worked on the deformation of valve slices in the single-tube shock absorber, and figured out the damping change trend under different number of valve slices. Zhou and Xu (2010) established the corresponding physical model of valve slices using the small deflection question based on elastic mechanics, and derived an accurate calculation method to solve the warping question of slices, and a comparison has been done between the calculation and simulation by finite element method (FEM).…”