A Comparison of Fatigue Design Methods
AKRON UNIV OH
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There are two basic fatigue-testing methods fatigue using a maximum cyclic force, the stress-life method, and fatigue using a maximum cyclic strain, the strain-life method. Wohler first tests to establish a S-N diagram were based on a rotating beam with a constant maximum force loading. Subsequently, the R. R. Moore test that used four-point loading with a constant load was developed and became one of the standard tests. Most machine design textbooks teach fatigue design methods based on these basic tests. Because of research and development activities in the l960s, cyclic strain methods were developed Low-cycle fatigue analyses based on these new methods have been found to be more accurate in this low-cycle regime. Of course endurance limits of both methods do not change differences are in predicting low-cycle fatigue life. This paper presents a short comparison of these two fatigue design methods.