Unified criterion for fatigue endurance modelling under combined loading: Static and vibratory

Abstract : The damage tolerance design community is concerned with a need to understand mechanically short cracks propagation regimes. The prospects for propagation of such cracks are heavily influenced by the stress gradient and multiaxiality around the crack initiation site. Moreover, geometrically complex mechanical components can present local zones with high stress gradient and extreme multiaxiality when submitted to non-proportional loading. Much efforts have been spent on fatigue endurance models by both local and non-local approaches. On the other hand damage tolerance models for short cracks regime is not yet mature. Nevertheless, it is concurred that the current state of the art cannot be applied in the aforementioned loading cases due to unsatisfactory corroboration with experimental results. Hence, there is no robust unified model considering the multiaxial stress states with a high stress gradient in non-proportional loading. This paper proposes a new approach for modelling endurance based on Linear Elastic Fracture Mechanics (LEFM) parameters extended to the short crack propagation regime. A Von Mises based Distortional Elastic Energy (DEE) is computed from these LEFM parameters around a conservatively parametrized mechanically short crack tip. The DEE which is integrated from a set of predefined spatial reference stress fields, is scaled by an intensity factor followed by a temporal basis obtained by the Karhunen-Loève Procedure (KLP). This allows the DEE to be fitted to the dynamic stress fields at the most probable crack initiation zone. As far as the path of the DEE remains under the short crack non propagation threshold, endurance limit of the mechanical structure will be equal to that of an unflawed standard fatigue specimen as represented in a Kitagawa-Takahashi diagram. The material considered in this work is TA6V.
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https://hal.archives-ouvertes.fr/hal-01903882
Contributor : Yoann Guilhem <>
Submitted on : Wednesday, October 24, 2018 - 4:45:46 PM
Last modification on : Friday, May 24, 2019 - 5:27:58 PM

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  • HAL Id : hal-01903882, version 1

Citation

Bhimal Bholah, Yoann Guilhem, Julien Jaravel, Sylvie Pommier. Unified criterion for fatigue endurance modelling under combined loading: Static and vibratory. International Conference on Fatigue Damage of Structural Materials XII (FATDXII), Sep 2018, Hyannis, United States. ⟨hal-01903882⟩

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