A simple criterion for multiaxial fatigue failure of specimens with a small surface defect is proposed. The purpose of this paper is to present a unified prediction method of fatigue limit of defect specimens using this criterion and the (area)~(1/2) parameter model. No fatigue test is necessary for prediction. Combined loading fatigue tests were carried out using smooth specimens and specimens with an artificial hole, whose diameter ranges from 40 to 500μm. The tests were performed under the in- phase fully-reversed loading condition. Materials investigated are an annealed 0.37% carbon steel, a quenched and tempered Cr-Mo steel, a high strength brass and a nodular cast iron. The fatigue limit was determined by the threshold condition for propagation of a mode Ⅰ crack emanating from a defect. Good agreement is found between predicted and experimental results. The relation between smooth and defect specimen is also discussed with respect to non-detrimental defect.
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