Physical 1-D System Simulation Model for Monotube Shock Absorbers for Simulation with Excitation up to 70Hz 2015-01-2353

In an automotive suspension, the shock absorber plays a significant role to enable the vehicle performances, especially in ride, handling and Noise-Vibration-Harshness (NVH). Understanding its physical characteristics is of great importance, as it has a main influence on the overall vehicle performance.

Within this research project simulation models for different passive monotube shock absorber systems have been created in a 1-D system simulation software. The simulation models are designed and parameterized physically.

To validate the simulation models measurements on different hydropulse-shaker with specially designed control signals to investigate the response during high frequency excitation, have been done. A detailed discussion of the several models and results of a simulation to measurement comparison is given. After detailed investigation the shock absorber simulation models are now adaptable to the multi body simulation.

As a result nearly equal experimental and simulated response of the different shocks was found. Some deviations are remaining during high frequency (>30Hz) operation of the damper. Dominant parameters to influence the damper response have been found. A sensitivity analysis shows the influences of these parameters. An analytical model to approach the shim stack stiffness was designed. For a validation detailed Finite-Element-Method (FEM) models of the shim stack have been developed and compared with load cases up to 100 bar hydraulic pressure. Additionally an FEM-model of the shock absorber and detailed modal analysis have been made to calculate and validate the natural frequencies of the shock. Limitations of this current study are the investigated monotube shock absorber systems, not including and including stroke-dependent-damping.

The presented novelty is the method of the configuration of the shock absorber simulation models only with geometric data. The shim stack models to calculate its stiffness instead of fatigue calculation are new as well. The new configuration approach increases the possibility to design automotive shock absorbers in advance of having a prototype. With the multi-body simulations of the chassis forecasts of the cars behaviour are possible at earlier stages during the development cycle. As OEM it is possible to simulate the behavior of the shock absorber in detailed car models.