Fatigue limit

About: Fatigue limit is a research topic. Over the lifetime, 20489 publications have been published within this topic receiving 305744 citations. The topic is also known as: endurance limit & fatigue strength.

strengthening and fracture in fatigue (approaches for achieving high fatigue strength)

Abstract: Three approaches to the problem of fatigue-resistant materials are reviewed and discussed. The macroparametric approach, which utilizes semiempirical equations to predict the effects of fracture stress, fracture ductility, and the cyclic strain-hardening exponent on fatigue, is useful for screening and selecting fatigue-resistant materials. The microstructural approach, which relates microstructure to the various stages of fatigue, is useful for designing new alloys and thermomechanical treatments to achieve fatigue resistance. The third approach utilizes fundamental deformation characteristics of materials to form a unifying rationale with which to describe fatigue behavior. Such concepts as slip-mode, stacking fault energy, and slip homogenization are discussed. Examples from the literature are cited to illustrate the degree of success which has been achieved with each approach. Some of the more promising future directions for developing fatigue resistance are also discussed.

Steel bridge members under variable amplitude, long life fatigue loading

Abstract: The research described in this report is intended to provide information on evaluating the fatigue resistance of welded attachments subjected to variable amplitude fatigue loading. The research consisted of laboratory studies of welded attachments under random variable amplitude load spectra defined by a Rayleigh-type distribution with most stress-cycles below the constant amplitude fatigue limit. (Some stress cycles exceeded this limit.) Eight full-size beams with web attachments and cover plates were tested during the program. Fatigue crack growth data were generated using random block variable amplitude stress spectra defined by a Rayleigh-type distribution. Also, nonload-carrying fillet-welded cruciform-type specimens were tested under simple bending using a random variable amplitude block loading to supplement the existing shorter life studies carried out on stiffener details. The results obtained from these variable amplitude tests are consistent with the previously reported constant amplitude test. However, the existence of a fatigue limit below which no fatigue cracks propagate is assured only if none of the stress range cycles exceed this constant amplitude fatigue limit. If any of the stress range cycles (as few as one per thousand cycles) exceed the limit, fatigue crack propagation will likely occur. The random variable test data from the beam specimens generally fell between the upper and lower confidence limits projected from constant cycle data. The smaller simulated details generally resulted in the random variable test data falling near the upper confidence limit of constant amplitude test results.