Experimental investigation and theoretical modelling of an impact damper

Impact damping is a method for improving damping of a dynamic system by means of energy dissipation due to repeated collisions of a free mass on the base structure. This paper deals with the theoretical and experimental investigations carried out to study and characterize damping with respect to the level of base excitation. The mathematical model consists of a two degree of freedom system (in which the main system is modelled as single degree of freedom system (sdof)) which undergoes momentum transfer between main mass and impact mass. The velocity response obtained from the mathematical model for the main mass and impact mass clearly indicates that the damping of the system depends on the number of effective impacts and not on the total number of impacts. Here the effect of impact damping is studied for low frequency and high amplitude excitation. Optimum parameters are determined for design of impact damper based on the mathematical model. Experiments are conducted on a cantilever beam for various excitation levels. The damping characteristics obtained from test data are compared with the predictions made from mathematical model. A good match is obtained between theoretical and experimental results. It is also observed that the energy gets re-distributed to higher modes due to the high shock that occurs during collision of the impact mass with main mass.