Vibration fatigue

About: Vibration fatigue is a research topic. Over the lifetime, 3460 publications have been published within this topic receiving 46297 citations.

Probabilistic constitutive relationships for cyclic material strength models

Abstract: A methodology is developed that provides a probabilistic treatment for the lifetime of structural components of aerospace propulsion systems subjected to fatigue. Material strength degradation models include both a heuristic fatigue strength reduction model and a fatigue crack growth model. Probabilistic analysis is based on simulation, and both maximum entropy and maximum penalized likelihood methods are used for the generation of probability density functions. The resulting constitutive relationships are included in several computer programs. The programs determine the random time for a nickel-base superalloy engine component to reach a given fatigue strength or a given crack size. Results are presented in the form of probability density functions and cumulative distribution functions of the log of mechanical fatigue cycles.

Prediction of residual fatigue life using nonlinear ultrasound

Abstract: Prediction of fatigue life of components during service is an on-going and unsolved challenge for the NDT and structural health monitoring community. It has been demonstrated by a number of researchers that nonlinear guided waves or the acoustic nonlinear signature of fatigued cracked material provides clear signs of the progressive fatigue damage in the material, unlike linear guided waves. However, even with nonlinear acoustic-ultrasound methods there is a necessity to compare the current nonlinear feature to a previously measured cracked material state to assess the absolute residual fatigue life. In this paper, a new procedure based on the measurement of the second-order acoustic nonlinearity is presented which is able to assess the fatigue life of a metallic component without the need of a baseline. The Nazarov–Sutin crack nonlinearity equation and the Paris law are combined in order to obtain an analytical solution able to evaluate the theoretical second-order quadratic nonlinear parameters as a function of the crack growth and fatigue life that evolve during cyclic loading in metals. The model makes the assumption that the crack surface topology has variable geometrical parameters. The method was tested on aluminum alloy specimens AA2024-T351, containing fatigue fracture of different sizes, and excellent correlation was obtained between the theoretical and measured second-order nonlinear parameter. Then, it was demonstrated clearly that by measuring the nonlinear parameters it is possible to estimate crack size and fatigue life. Finally, advantages and limitations of the procedure are discussed.

Multiaxial fatigue life prediction of composite bolted joint under constant amplitude cycle loading

Abstract: In this paper, a fatigue model of composite is established to predict multiaxial fatigue life of composite bolted joint under constant amplitude cycle loading. Firstly, finite element model is adopted to investigate stress state of composite bolted joint under constant amplitude cycle loading. Secondly, Tsai–Hill criterion is used to calculate equivalent stress of joint. At last, modified S–N fatigue life curve fitted by unidirectional laminate S–N curve which takes ply angle and stress ratio into consideration is adopted to determine fatigue life of composite. Calculation results of equivalent stress model show excellent agreement with experiments of composite bolted joint.