Abstract
Fatig e tests were made on 12 kinds of variously finished surfaces, worked out on the Si-Mn-Cr steel with a tensile strength of 100kg/mm2 The surface treated by sand blast was strongest for repeated load. The surface, polished by emery-paper or cloth longi_??_udinally, was next in rank, having a strength corresponding to 94% of the former. The surface, worked by lathe or grinding machine was the weakest, its strength corresponding to only 83% of the first. The polished surface, on which Vieker's hardness was inspected or numerals were stamped, has a fatigue streng h as high as that worked by the lathe or grinding machine. The suriaee on which numerals were wri_??_en by eleetric pencil had irregular strength and lacked reliability. The fatigue strength of the holed surface decreased to below 45% of the non-holed bar, by the notch effect of the hole, and could be raised no more even by polishing of its surface.
