NONLINEAR ELASTIC BEHAVIOR OF THE ROLLER BEARING STEEL SAE 52100 DURING CYCLIC LOADING

When subjected to uniaxial symmetrical push-pull tests, the hardened roller bearing steel SAE 52100 (100Cr6) exhibits unusual sickle-shaped hysteresis loops. This observation can be attributed to the fact that the elastic modulus is stress-dependent as a consequence of non-linear elastic effects. Elastic unloading experiments performed in tension and in compression during a cycle permitted the stress dependence of the elastic modulus to be determined quantitatively. The experimental observations can be described in good approximation by a quadratic extension of Hooke's law in accord with an anharmonic lattice potential. Applying this concept, the originally bent hysteresis loops can be converted into hysteresis loops of the usual shape in the representation of stress vs plastic strain. A comparison of the results with measurements on alpha-iron whiskers reported in the literature indicated that the departures from linear elasticity observed in high-strength steels are in the same order of magnitude as in the case of pure iron.