抄録
I succeeded in extending Woodvine's fatigue theory over the tensile properties of case hardened steel (mild carburized), technical cohesion strength was induced. I concluded that case hardened layer prevented the inner layer to slip (or to yield), and made three stages of tensile properties with case depth; 1 st; true breaking strengthe's lowering, 2 nd; the technical cohesion strength of inner layer, 3 rd; the tensile strength increase only by the case hardened layer. (Carbon and chrom steels were used).
The value of technical cohesion strength by this method is lower than that of the notch method by Kuntze, this depends on the residual stress. Why case hardened layer in my calculation has an assumed higher tensile strength than solid high carbon steel depends on the residual stress. Then, I measured the residual stress of the test pieces and made clear that these were founded on the tension residual stress in the inner layer and the compression residual stress in the case hardened laver.
Next, I tried to extend the Woodvine's fatigue theory to the tensile test pieces with various notch radius. Without the case hardened layer it coincided with the experimental results of low carbon steal by Kuntze, while with case hardened layer it approached the value of the calculated result by Neuber, but their case depths are sufficiently deep to increase their tensile strength only by the case hardened layer.
