Influence of shock absorber wearing on vehicle brake performance

Abstract

In order to safely maintain a vehicle, it is necessary to verify the most important systems that affect safety during Periodic Motor Vehicle Inspections (PMVIs). In a previous paper, a test method and validation criteria were suggested by the authors to verify shock absorber status during PMVIs, as they are a fundamental component that may wear out during a vehicle's life. In this paper, variations of the performance of the vehicle's brakes resulting from shock absorber wearing have been analyzed, in order to confirm whether the suggested criteria is valid for taking into account longitudinal forces and pitch movement on the vehicle. A simulation-based study was conducted with several configurations of a worn damper on a vehicle driving on two virtual roads: smooth and undulating. The results confirmed that the damping coefficient established as an acceptable value to verify the shock absorber status in PMVIs is also valid considering the forces involved in a braking maneuver.

Development and verification of a shock absorber and its shim valve model based on the force method principles

“…However, the problems dealt with by the author are not related to the structure of the valves [18,19], and discrepancies, which were explained by the ignorance of physical properties of the oil (Oil Bulk modulus), were noticed during the model validation. The influence of the technical condition of structural elements of the shock absorber on its exploitation and damping characteristics is examined in literature [2,3,4,11,13,28] as well. It can be seen from the provided examples that various research works, where the influence of the structure of a shock absorber on its damping characteristics is discussed, are published; however, in such works, including the reviewed ones, seeking to simplify the process of modelling, various simplifications are made and they predetermine inexact results of modelling or the models becomes too complicated and not ready for practical application.…”

Influence of a shock absorber model on vehicle dynamic simulation

“…Figure 17 shows the damper speed during testing and shows that it was extremely low. Because of this low speed, the dissipated energy on the damper was very low and it had little influence on the sprung mass pitch movement and none on the brake performance [18]. Table 4 summarizes the results on a rough road.…”

Diagnostics of the On-Vehicle Shock Absorber Testing

“…It has been shown as well that the shock absorbers wear may affect the process of braking a car with the ABS when moving on uneven ground, which has been highlighted by e.g. the authors of [5].…”

“…Since the literature data (e.g. those provided in [5]) show a marked impact of the shock absorber condition on the course of the vehicle braking process, a decision was made to re-verify this information. With this end in view, 16 experimental tests were carried out on an Opel Agila 1.2 Twinport car provided with ABS (car mass ca.…”

“…As one of the peculiarities of such a method, the stroke of the tester vibration plate is to be constant, equal to e.g. 6 mm, as it is in the case of the EUSAMA machines [1][2][3][4][5][6][7]. Unfortunately, such testers, which are the most popular, suffer from a major drawback: the final test result strongly depends on the tire inflation pressure, sprung mass, sliding friction in the suspension system, test conditions, and tester characteristics [1-2, 4, 6-8].…”