A lumped mass thermo-mechanical model for the dynamics of a damper filled with a magnetorheological fluid is described, analyzed, and numerically simulated. The model includes friction and temperature effects, and consists of a differential inclusion for the piston displacements coupled with the energy balance equation for the temperature. The fluid viscosity is assumed to be a function the temperature and electrical current, which in practice may be used as the control variable. Numerical simulations of the system behavior are presented. In particular, the simulations of an initial impact show how the subsequent oscillations can be effectively damped. (C) 2013 Elsevier Inc. All rights reserved.