The Time-strength of Steel and Cast Iron under Repeated Tension

Abstract

In designing machine parts and structures, the time-strength often comes into question. The authors made many fatigue tests on specimens of steel and cast iron under repeated tension, and obtained their S-N diagrams. Then the authors came to the conclusion, that (1) the S-N diagram of cast iron, both in logarithmic scale, consists of the two straight lines, i.e., a horizontal line which represents the endurance limit and a straight line, the value of which at N=1 is equal to the tensile strength, (2) the S-N diagram of steel, both in lograrithmic scale, consists of three straight lines, i.e., a horizontal line which represents the endurance limit, another straight line which represents the tensile strength, and a sloped straight line, the extent of which at N=1 is equal to the true breaking strength.