An optimization-based design approach for a novel self-adjuster using shear thickening fluid

Abstract

Recently, the increasingly strict safety and emission regulations in the automotive industry drove the interest towards automatic length compensating devices, e.g., hydraulic lash adjusters (lower emission) and slack adjuster in brake systems (faster brake response). These devices have two crucial requirements: (a) be stiff during high load, while (b) be flexible in the released state to compensate for environmental effects such as wear and temperature difference. This study aims to use the advantageous properties of shear thickening fluids to develop a less complicated, cost-efficient design. The proposed design is modeled by a system of ordinary differential equations in which the effect of the non-Newtonian fluid flow is taken into account with a novel, simplified, semi-analytical flow rate-pressure drop relationship suitable for handling arbitrary rheology. The adjuster’s dimensions are determined with a multi-objective genetic algorithm based on the coupled solid-fluid mechanical model for six different shear thickening rheologies. The accuracy of the simplified flow model is verified by means of steady-state and transient CFD simulations for the optimal candidates. We have found that the dominating parameters of such devices are (a) the shear thickening region of the fluid rheology and (b) the gap sizes, while the piston diameters and the zero viscosity or the critical shear rate of the fluid have less effect. Based on the results, we give guidelines to design similar-length compensating devices.

Mechanical behavior of a torsional shear thickening fluid damper

“…This method allows accurate prediction of the hysteretic performance of STF dampers without the need for complex constitutive models of STF. Building upon this foundation, Nagy-György et al [20] employed a differential equation model to optimize the damping performance of STF dampers. Their approach involved capitalizing on the fluid compressibility properties of STF at low shear rates and the incompressibility properties of solid-like materials at high shear rates.…”