ESTIMATION OF FATIGUE-STRENGTH OF NITRIDE D SAMPLES BY MEANS OF STANDARDIZED WOHLER DIAGRAM

Based on results of rotation bending tests of the annealed and nitride d steel 31CrMoV9 statistic verified S-N-curves were estimated. The loc ation of the failure initiation point, surface or subsurface, has an i mportened influence on the parameters of the S-N-curve. The origin of failure mainly depends of the specimen geometry, the structure of the nitrided case and the load conditions. For smooth and notched specimen s with subsurface Failure the fatigue strength can be calculated by Ko gaev and Serensen and the standardized Wohler diagram can be used for fatigue limit calculation independently of the structure of nitrided c ore.