FCP Report No. 49

Effects of Fatigue in the Elastic Regime on the Mechanical Properties of Low-Carbon Steels

by

Alexander W. Riedy and James F. Stubbins
Nuclear Engineering Program

Abstract

Three low-carbon steels, one ferritic (SAE 1018) and two bainitic (A33B C1 I and C1 II) all with similar compositions, were fatigued in the elastic regime at a stress amplitude of 207 MPa to 104 and 106 cycles at 7.5 Hz at temperatures of 25° C and 300° C (only bainitic steels). Following fatigue, changes in tensile, notch-tensile, micro-hardness, and microstructural properties were determined. The data obtained indicates that elastic fatigue causes SAE 1018 to soften, and increases notch-tensile ductility in all three steels. Transmission electron micrographs show an increase in dislocation density and the generation of subgrains with fatigue at 106 cycles and from incremental over-strain tests to 1% strain.

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