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2 International Journal of Applied Mechanics and Engineering

2 2010

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Internal damping of ferritic : pearlitic steel in dependence on temperature

Blazek D., Palcek P., Mintach R.

International Journal of Applied Mechanics and Engineering

2010

Vol. 15, no 2

383-388

The topic of this paper is an analysis of ultrasonic internal dumping of low carbon steel in dependence on temperature. The damping measurements were performed in range from 20 to 350 C measured data are presented in the form of dependence of internal damping on temperature. Two internal damping maximums were measured at the temperature of 170 and 210 C. The precipitation process running in material from about 200 C was measured. This leads to increated hardening and Young's modulus.

Influence of loading type on the shape of fatigue lifetime curve

Bokuvka O., Novy F., Mintach R., Cincala M.

International Journal of Applied Mechanics and Engineering

2010

Vol. 15, no 2

321-328

The paper is devoted to an experimental examination of the influence of loading type on the shape of fatigue lifetime curve of the high-carbon-chromium bearing steel (100Cr6). The push-pull and rotating bending loading tests (R=-1) were used with the aim to obtain experimental data in the region from [...] cycles to [...] cycles. The shape of fatigue lifetime curve of 100Cr6 bearing steel depends on the loading type. The S-N curve obtained using rotating bending consists of two parts corresponding to surface and subsurface fatigue crack initiation, resulting in a stepwise S-N curve. In this case, the typical stepwise S-N relationship clearly indicates that the mechanism of fatigue crack initiation transfers from the surface to subsurface with decreasing the applied stress level. On the other hand, the S-N curves obtained at push-pull loading revealed a continuous downward slope without any indication for a plateau region and subsurface fatigue crack initiation occurs in the whole range of amplitudes. This fact has to be taken in consideration while selecting a structural material.