Studying the Crack Growth Rate Variability by Applying the Willenborg’s Model to the Markov’s Simulated Trials

A large number of factors influencing the fatigue crack rate are traditionally studied separately. In this case, their interactions are not taken into account, and the experiment does not possess the property of optimality. The article describes the authors’ vision of the problem, how it would be possible to approach the solution of the research problem from the point of view of the theory of optimal experiment planning. Initially, it is proposed to consider three basic factors, namely: the influence of loading asymmetry, loading frequency and sequence of overloads. A full factorial experiment with varying factors at extreme levels is considered. The formalization of the factors describing the sequence of overloads is proposed.

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Numerical study of the crack growth variability under irregular loading

Gadolina

Voronkov

2021

Zavod. lab., Diagn. mater.

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Estimation of the scatter of the durability at the second stage of fatigue, namely at the stage of crack propagation is a problem of scientific and obvious practical importance: machines operate according to their technical condition, which means monitoring of the actual crack length during their service life. The limits of the spread of the strength values at the stage of crack propagation in aluminum samples are studied using published data and a previously developed model. In view of the great importance of this problem, a special simulation model was used to generate the extrema of a random sequence based on target Markov matrices. On the one hand, this simulation method guarantees the characteristic traits of real sequence in exploitation (TWIST standard in this example). On the other hand, it contains reasonable randomness — these two parts together provide an opportunity to study the variability of the crack growth rate. For the simulation experiment, literature data on aluminum and steel samples were used along with popular fatigue crack growth models (Paris, Foreman and Willenborg models). In addition, the Miner’s summation rule was quantitatively tested to estimate the crack growth resistance coefficient under various loads. The agreement with the literature experimental data is shown. Preliminary data on the effect of the type of loading (random or block) on the durability are given on the basis of scientific literature data. The proposed simulation method can be useful for testing various models. It is also intended to develop an experimental design for laboratory testing in the future.

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Studying the Crack Growth Rate Variability by Applying the Willenborg’s Model to the Markov’s Simulated Trials

Cited by 3 publications

References 16 publications

Irregular Process Type Effect on Fatigue Crack Propagation Rate

Irregular Process Type Effect on Fatigue Crack Propagation Rate

An optimal experiment planning in the problem of longevity evaluation at crack propagation stage

Numerical study of the crack growth variability under irregular loading

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