Abstract
The fatigue characteristics of a Cu-bearing high-strength low-alloy (HSLA) steel were investigated in air, relative humidity ≈50 pct, as a function of microstructure, which was altered by heat treatments and welding. Small fatigue cracks (≈30-Μm long) were naturally initiated from smooth specimens and grown past the transition length (≈200 Μm), where they exhibited the characteristics of large fatigue cracks. The number of cycles to crack initiation depended on stress magnitude but not on microstructure, although the site of initiation was microstructurally dependent. Small cracks in all microstructures grew at δK values below the large crack threshold. The as-received (polygonal ferrite) microstructure and one of the lath microstructures that resulted from heat treatment exhibited the same growth rate correlation as large cracks in the linear (Paris) region, and could be considered as an extension of the large crack growth region down to the point of initiation. Small cracks grew at rates faster than expected through one of the heat-treated and the weld microstructures; therefore, the number of cycles required for growth from initiation to the transition to large crack growth decreased about threefold, which is a potentially important factor in predicting lifetimes of structures made from this steel.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call