Design of electrorheological dampers by means of finite element analysis: theory and applications

The mechanical behaviour of parts containing ER fluid can be derived, once the constitutive equation for characterising the fluid is known. An elastic-plastic material model with kinematic strain-hardening was selected, its parameters having been determined from a test with uniaxial loading. Four different damper designs were analysed by the finite element program nisa. This material model displays no frequency dependence but, if required, the model may be modified to account for frequency dependence by introducing strain-rate sensitive friction. The paper describes how this is done. The application of an ER damper to a Laval rotor system was studied. The system response to stationary as well as to some transient loads was derived by a time-integration technique in Matlab. The results agree well with those obtained from a small Laval rotor test rig. One concludes that the force-displacement hysteresis loop can be predicted by FE calculation for any damper design. The loop may then be simplified so as to be described by only two parameters for ensuing transient response analysis.