The stability of the energy-dissipation characteristics of various materials subject to cyclical (fatigue) loadings

Conclusions

• 1. The alloy G75D25 possesses highly stable damping properties, the level of these not changing in the presence of cyclic overloadings (in the stress range σ=0.3–0.8 σ_0.2).

• 2. The brief cyclic overloading of steel 20 greatly increases its damping capacity, so that the energydissipation characteristics are comparable in magnitude with those of the highly damping alloy G75D25. The acquisition of considerable energy-dissipation capacity under vibration conditions by this steel is quite stable, and continues to hold on subsequent cyclical loading, even for stresses much smaller than the fatigue limit. This is an extremely valuable property from the practical point of view. since it increases the reliability of parts subject to chance or planned brief cyclical overloadings.

• 3. The cyclical overloading (σ=0.8 σ_0.2) of titanium alloy OT4 does not produce any marked increase in its original small damping capacity. At the same time there is a certain critical stress (σ=0.83 σ_0.2) such that any cyclical overloads exceeding it are extremely dangerous, since they lead to such an intense heat evolution and self-heating of the sample that even for relatively low loading frequencies (200 cycles/min) premature fracture may occur, with partial fusion of the sample at the edges.