Cyclic bending and the damping behaviour of short fibre-reinforced magnesium alloy AZ91

The influence of cyclic bending on the damping behaviour of AZ91 magnesium alloy-based composite was determined at room temperature. The logarithmic decrement of free decaying vibrations of bending beams as a function of the number of cycles exhibits four regions. In the first region, damping increases due to an increase of the dislocation density. Then steady state, a constant logarithmic decrement follows. The third region is characterised by a rapid decrease of the logarithmic decrement. Cracks nucleation in the matrix was manifested by a rapid increase of damping with increasing number of cycles and finally by failure of the sample – the fourth region.