Investigation of damper valve fluid-structure interaction through the application of experimental visualisation techniques

Automotive dampers (or shock absorbers) improve tyre contact with the road and provide ride comfort and/or tyre grip. They do this by resisting transient wheel motion during vehicle manoeuvring through shearing of hydraulic fluid and dissipating energy in the form of heat. The damper performance is almost entirely governed by the damper valve. Damper valves are complex hydraulic systems, where the valve pressure differential and flow relationship are dictated by the coupling of the elastic response of the deformable valve structure and the fluid flowing through the valve. Therefore, the overall objectives of this research are to development and/or apply experimental technique(s) that observe the damper valve fluid flow and deflection and then comment on these observations. This research uses a novel application of non-intrusive experimental techniques to visualise the flow field and deflection of the valve to study their interaction with one another and the surrounding valve structure. The 25mm Kinetic (Pty Ltd) damper valve studied in this research restricts the damper fluid from exiting the main flow orifices by deflection of both a shim stack and a blow-off disc. A review of the literature demonstrated that traditional experiments highlight the overall damper response and omit the complex fluid-structure interaction within the valve. No evidence of experimental investigations of the fluid-structure interaction within damper valves was located, possibly due to the difficulty associated with their small, complex geometry. Flow visualisation techniques and PIV reliably captured the flow field within the valve once an appropriate experimental setup had been developed. Post-processing of the velocity fields offered additional data that was used to analyse specific components of the valve performance, and optical correction improved the accuracy of the results.