Abstract
Recently, a technique for rapidly determining a material’s fatigue limit by measuring energy dissipation using infrared thermography has received increasing interest. Measuring the energy dissipation of a material under fatigue loading allows the rapid determination of a stress level that empirically coincides with its fatigue limit. To clarify the physical implications of the rapid fatigue limit determination, the relationship between energy dissipation and fatigue damage initiation process was investigated. To discuss the fatigue damage initiation process at grain size scale, we performed high-spatial-resolution dissipated energy measurements on type 316L austenitic stainless steel, and observed the slip bands on the same side of the specimen. The preprocessing of dissipated energy measurement such as motion compensation and a smoothing filter was applied. It was found that the distribution of dissipated energy obtained by improved spatial resolution measurement pinpointed the location of fatigue crack initiation. Owing to the positive correlation between the magnitude of dissipated energy and number of slip bands, it was suggested that the dissipated energy was associated with the behavior of slip bands, with regions of high dissipated energy predicting the location of fatigue crack initiation.
Highlights
Knowing the fatigue limit of a material is indispensable in structural design; its determination by conventional fatigue testing is a time-consuming and costly process
Limitations of the utilized measurement systems meant that these researchers investigated the behavior of slip bands and dissipated energy in different spatial resolutions, in addition to on different sides of the specimen
In this study, dissipated energy measurements with high spatial resolution were performed alongside slip bands observations for type 316L austenitic stainless steel under fatigue loading
Summary
Knowing the fatigue limit of a material is indispensable in structural design; its determination by conventional fatigue testing is a time-consuming and costly process For this reason, studies on the rapid determination of fatigue limit by observing temperature changes have been conducted since the beginning of the 20th century for various materials, structures, and fatigue types [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. In the work of Cugy et al [36], the number of slip bands observed on the specimen surface was found to correlate with the average temperature increase caused by energy dissipation for a low carbon steel. Limitations of the utilized measurement systems meant that these researchers investigated the behavior of slip bands and dissipated energy in different spatial resolutions, in addition to on different sides of the specimen (e.g., the temperature increase was averaged over the entire specimen, and/or the growth of slip bands was investigated on the reverse side to dissipated energy measurements)
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