Shock Absorber Mathematical Modeling

Abstract

The objective of this work is to provide the engineering department with a simple and useful tool to predict the valve pieces to be used in a shock absorber during the design phase, in order to diminish the experimental work to be done during the vehicle ride test and prototype manufacturing. This tool is a group of equations that can predict the force behavior of the shock absorber and the corresponding valves according to the preliminary shock absorber force x velocity curve defined by the vehicle suspension engineers. INTRODUCTION This project about Shock Absorber Mathematical Modeling is concerned with equations that lead us to know shock absorber force related only to valve code, through measurements and experiments. Such model will support new valve codes creation. At first, we worked with 35-mm diameter piston but it is possible to extend that model for others, for example with P.T.F.E. piston ring. We tried to isolate and to simplify the shock absorber real effects through boundary conditions in order to measure each effect separately and to compare real with theoretical behavior. The shock absorber with traditional design consists in three sets of valves. One group is in the piston assembly and another similar in concept in the base valve. The piston valves control mainly the rebound phase and the base valve the compression phase. (Fig.1). As the bleeds, springs and blow-off present different energy dissipation, each one must be modeled separately and total effect in the shock absorbers shall be obtained by the “blending “ of the curves in the transition of the valve operation. Fig.1 – Shock absorber components