ABSTRACT: The purpose of this paper is determining the rate of fatigue damage due to applying rotating bending fatigue test on standard specimens and the effect of rotating bending fatigue on the yield and ultimate strength, elongation and area reduction. The existence of scatter in fatigue test results is common. With regard to the testing apparatus, the least amount of scatter is produced by rotating bending machines, since mis-alignment is less critical than in axial loading machines. The specimens are made of CK45 steel. The test specimens are prepared on the basis of the instruction of fatigue testing instrument in accordance with the prescribed standard (DIN 50113).Based on S-N diagram the number of failure is determined in a special fa-tigue load. Different fatigue loads are applied to the specimens on which fatigue test is done in such a way that no specimen reaches to its fracture cycle. Then tensile test is done on the specimens and the yield strength, ulti-mate strength, percentage of area reduction and the percentage of elongation is determined for any specimen. The results are then compared with the data obtained for a virgin specimen (the specimen on which no fatigue test is done and the tensile test is carried out in it directly). Among these mechanical property, Ultimate Stress and Area reduction are more sensitive to rotating bending fatigue in which can be used as a criterion for fa-tigue damage due to rotating bending.

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