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This paper presents an assessment of the performance of a set of multi-axial high-cycle fatigue criteria on the basis of a series of fretting fatigue experiments. We carried out tests on a creep-resistant chromium steel material used for steam-turbine blades. The first type of experiment employed the classical cylinder-on-flat geometry with flat dog-bone specimens. The second set of experiments adopted dovetail geometry. Various loads were applied in order to capture a wide range of contact slip amplitudes. A set of eight plain multi-axial fatigue criteria was applied to the numerically simulated stress response in the contacts during a single load cycle. Methods, which originated in the so-called theory of critical distances, were used for correcting the results in order to take the stress gradient effect into account. A simple factor based on slip amplitudes is introduced in order to consider the surface damage and is calibrated for the McDiarmid method. This criterion provided the best estimates of the most probable cracking sites. [ABSTRACT FROM AUTHOR]

The paper deals with an approximate method for calculating elastic-plastic stresses and strains on the surface of notched samples. The method is based on the Abdel-Karim-Ohno cyclic plasticity model. The plane stress condition is considered within the evaluation. The output of the approximation on several multiaxial axial-torsion load paths is compared to our own experimental results. Experiments were carried out on samples of two notch types manufactured from the 2124-T851 aluminum alloy. Strain distribution in the notch area was measured by digital image correlation. The comparison between computational solution and measured response shows that the new method allows for obtaining reasonably good approximation, even for relatively complicated multiaxial load cases.

The purpose of this article is to compare two predictive methods of J integral assessments for center-cracked plates, single-edge cracked plates and double-edge cracked plates produced from X52 and X70 steels, and a longitudinally cracked pipe produced from X70 steel. The two methods examined are: the GSM method and the J s procedure of the French RCC-MR construction code, designated here as the FC method. The accuracy of J integral predictions by these methods is visualized by comparing the results obtained with the "reference" values calculated by the EPRI method. The main results showed that both methods yielded similar J integral values, although in most cases, the GSM predictions were slightly more conservative than the FC predictions. In comparison with the "reference" values of the J integral, both methods provided conservative results for most crack configurations, although the estimates for cracks of a relative length smaller than 1/8 were not found to be so conservative. The prediction of burst pressures for external longitudinal semielliptical part-through cracks in X70 steel pipe showed that the magnitudes of predicted burst pressures came very close to each other, and were conservative compared to FEM (finite element method) calculations and experimentally determined burst pressures.