Without consistent surface preparation, it becomes harder to know whether a result reflects the material or the specimen condition. How Surface Marks Create Stress ConcentrationsA tensile specimen is designed around controlled geometry. Why Fatigue Specimens React More Strongly To Surface DefectsA tensile test loads the specimen once until fracture. That is why fatigue specimen preparation typically specifies polishing direction, not only roughness. Surface Finish Targets Depend On The Test ProgramSurface finish requirements should follow the test method, not a universal number.