3.2 Influence of temperature on the dynamic behavior

The influence of temperature on the dynamic behavior was measured through dynamic stiffness tests at low frequency. The test consists in applying 1000 load cycles of a sinusoidal nature between 20 and 95 kN at a frequency of 5 Hz, determining the stiffness as the average obtained in the last 10 cycles. The dynamic stiffness was analyzed at different temperatures: 20, 40, 60, and 80°C. In Figure 12, the evolution of the shortening of the rail pad during the last cycle is represented. The differences with respect to the previous static behavior are appreciated. Thus, the rail pad only shortens by 0.64 mm at 80°C under dynamic conditions, having reached a 31.2% higher static strain. This decrease in the strains also reflects a decrease in the dynamic energy dissipated (Edd); thus, the material under dynamic conditions resembles an elastic body that does not dissipate energy (Figure 13).

Figure 12. Dynamic behavior at different temperatures (cycle 1000).

Figure 13. Energy dissipated under static conditions (Ede) and dynamic (Edd).
