causes-of-cracks-below-th-surfaceCauses of crack initiation and growth belowthe part surface: The crack breaks through to the surfaceat this size, and initially grows rapidlyin the relativelybrittle coating. Here,it often reaches adangerous size.FlawShaft under circumferential flexural loadsSurface with increasedfatigue resistance- tempered (steel)- coated- Oberfläche mit erhöhter0Pressure TensionCompression residualstress in the surface area0Pressure Tension Temperature SrengthCooled zonePart with thermalstressTension Evenly stressed cross-sectionwith volume flaws