Experimental research of the damping characteristics of the fatigue stand caused by changes in material properties

Abstract The paper presents the results of research on changes in the damping characteristics of the MZGS100 fatigue test stand. The work of the stand is influenced by the type of material of the tested samples, where different properties affect the dynamic characteristics of the stand. It is important to assess the impact of changes in properties during the test on the work of the test stand. Fatigue tests were carried out for three materials: S355J0 steel 2017A-T4 aluminium alloy and CuZn40Pb2 brass. The tests were carried out under fatigue bending loads for the number of failure cycles in the low-cycle range. During the investigation, the test was interrupted and the impulse response of the stand at various stages was recorded and the change in system response was assessed. It was observed that in the case of brass, the damping curve of the system changed continuously, and the damping factor of the system increased by 23%. In the case of steel, practically no changes were noticed, while the aluminium alloy showed changes of 9%. In the final stage of the test for steel and aluminium alloy, a change in the frequency of natural vibrations was observed, which indicates a decrease in the system stiffness caused by the weakening of the specimen's cross-section. This effect was not noticed for brass samples, which together with the change of the damping coefficient indicates a cyclical change of the material properties.