Delayed failure under static fatigue of Hi-Nicalon bundles: The role of stress dispersion on scale effect

Mazerat, S.; Pailler, R.

doi:10.1016/j.matlet.2021.129806

Cited by 7 publications

(15 citation statements)

References 11 publications

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“…This leads to a bias on the stress exponent, referred to as the scale effect in Refs. [8, 10]: n f = 12.6 17 and n t = 8.4 5 for Hi–Ni type. As a consequence, the ratio τ f / τ t decreases as the stress increases.…”

Section: Resultsmentioning

confidence: 99%

“…The explanation behind the m τt value is less straightforward because it is affected by multiple parameters. Nonetheless it is globally ruled by the stress and the strength of the critical filament ( α t ‐related) weighted again by the stress exponent 8,10 . The following ranking of m τt values can be done according to Figure 3: TS > NL207 = ZMI > ZMI Cl > Hi–Ni > Hi–Ni–S.…”

Section: Resultsmentioning

confidence: 99%

“…Although several models were proposed to relate the failure time to the applied stress, 13,14 the Paris–Erdogan power law is here employed. This model, admitted to be strictly empirical, was selected to maintain continuity with previous works 5,8,11,15,16 . The temperature dependence of the stress exponent ( n ) 14 was hence not considered in this work.…”

Section: Methodsmentioning

confidence: 99%

“…f ( Pp ) , respectively, the strength (with probability P q ) of the critical fiber and the stress applied to it (with probability P p ). These parameters depend on the stress and strength of each fiber of the tow (unique configuration for each specimen), ruled by a weakest link approach 8 :

\begin{equation}{\tau }_t = \frac{{2K_{IC}^{2 - {n}_f}}}{{({n}_f - 2){A}_{1.f}{Y}^2\sigma _{app.f({P}_p)}^{{n}_f}}}\left[ {\sigma _{r.f({P}_q)}^{{n}_f - 2} - \sigma _{app.f\left( {{P}_p} \right)}^{{n}_f - 2}} \right]\end{equation}

where K IC is the toughness and A 1. f an environmental constant. Y is the crack geometry factor and is assumed to be constant along the whole filament lifetime to simplify the model.…”

Section: Methodsmentioning

confidence: 99%

“…A dedicated Monte Carlo simulation tool was developed defining randomly ς , γ and, for each filament, a strength and a stress among established distributions (in practice, random numbers sampled with uniform distribution between 0 and 1). The lifetime of each filament was calculated and sorted to define the tow failure ( α t fraction) for a given applied stress 8,10 . In this work, no load sharing was considered 16 .…”

Section: Methodsmentioning

confidence: 99%

See 4 more Smart Citations

Failure by slow crack growth of SiC fibers: Comparing the lifetime scatter for single filaments and multifilament tows

Mazerat¹,

Pailler²

2022

J Am Ceram Soc.

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SiC‐based fibers are subjected to slow crack growth, a crack growth mechanism activated by stresses and the chemical environment, as identified by static fatigue testing. Such tests can be performed on filaments or bundles. Although both types of specimens show a similar lifetime variation, testing of bundles is often preferred. This work compares the scatter of lifetimes predicted for filaments and for tows using a dedicated Monte Carlo simulation tool relying on the following hypotheses: The stress applied to a single filament can be defined, whereas the size of its most critical flaw cannot; on a bundle, neither the applied stress nor the strength of the critical filament (which triggers the cascade failure and the tow failure) can be defined. Depending on the parallelism of fibers inside the bundle and their strength dispersion, the lifetime scatter can be narrower for filaments compared to tows or vice versa.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

\begin{equation}{\tau }_t = \frac{{2K_{IC}^{2 - {n}_f}}}{{({n}_f - 2){A}_{1.f}{Y}^2\sigma _{app.f({P}_p)}^{{n}_f}}}\left[ {\sigma _{r.f({P}_q)}^{{n}_f - 2} - \sigma _{app.f\left( {{P}_p} \right)}^{{n}_f - 2}} \right]\end{equation}

where K IC is the toughness and A 1. f an environmental constant. Y is the crack geometry factor and is assumed to be constant along the whole filament lifetime to simplify the model.…”