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Comparison of bayesian and other approaches to the estimation of fatigue crack growth rate from 2D textural features

Mojzeš M., Kukal J., Lauschmann H.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1269--1278

EN

The fatigue crack growth rate can be explained using features of the surface of a structure. Among other methods, linear regression can be used to explain crack growth velocity. Nonlinear transformations of fracture surface texture features may be useful as explanatory variables. Nonetheless, the number of derived explanatory variables increases very quickly, and it is very important to select only few of the best performing ones and prevent overfitting at the same time. To perform selection of the explanatory variables, it is necessary to assess quality of the given sub-model. We use fractographic data to study performance of different information criteria and statistical tests as means of the sub-model quality measurement. Furthermore, to address overfitting, we provide recommendations based on a cross-validation analysis. Among other conclusions, we suggest the Bayesian Information Criterion, which favours sub-models fitting the data considerably well and does not lose the capability to generalize at the same time.

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Recent Progress in Full Scale Fatigue Test of PZL-130 "Orlik" TC-II Structure

Reymer P., Leski A., Dragan K.

Fatigue of Aircraft Structures

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2012

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Iss. 4

76--81

EN

This article presents preparation of the Full Scale Fatigue Test of the PZL-130 "Orlik" TC-II. After completing the flight load acquisition stage [1] a load block representing 200 Simulated Flight Hours in 194 flights was developed. This load block was further modified in order to introduce fatigue markers on the crack surface [2] visible during Quantitative Fractography, planned to take place during the Teardown Inspection of the structure after completion of the test. Meanwhile, the test rig along with the loading system and the test specimen were prepared at Výzkumný a Zkušební Letecký Ústav (VZLU, Prague, Czech Republic). The test specimen, consisting of the overhauled fuselage, modernized wings and the landing gear, was instrumented with the identical strain gauge measuring system as presented in [3], which was calibrated before the commencement of fatigue testing. Finally, some preliminary issues encountered during the fatigue test startup were highlighted and the outline for future work was described.

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ZL-130TCII Fracture Markers Solution for Full-Scale Fatigue Test

Kłysz S., Lisiecki J., Zasada D., Gmurczyk G., Leski A.

Fatigue of Aircraft Structures

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2011

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Iss. 3

22--27

EN

In the context of PZL-130TC-II full-scale fatigue test, several strategies of fatigue loadings that create fracture surface markings were considered. One block of spectrum is made of 200 flights. By reordering those flights, a block which should create a fracture marker, was developed. It was very important that reordering the load spectrum or adding overloads or underloads did not change spectrum severity. Pilot tests of aluminium alloys specimens were carried out to finalise appropriate marker intervals before commencing full-scale tests. The experiment was conducted with the MTS machine with 810.23 system. The results and conclusions are presented within this paper.

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Struktura geometryczna warstwy wierzchniej w ujęciu fraktalnym

Przerada I., Bochenek A., Iwaszko J.

Inżynieria Materiałowa

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2003

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R. XXIV, nr 6

551-553

PL

Efektywną drogą podwyższania własności użytkowych elementów maszyn jest kształtowanie struktury i właściwości warstw wierzchnich. Z ich opisem wiążą się m.in. pojęcia: morfologii, topografii i kształtu powierzchni. Dostępna literatura dowodzi, że istnieją związki pomiędzy morfologią warstw powierzchniowych a technologią ich wytwarzania. Z drugiej strony, morfologia powierzchni ma wpływ na istotne właściwości (twardość, odporność na zużycie, odporność korozyjna, współczynnik tarcia). Problem ilościowego opisu geometrycznych cech powierzchni warstwy wierzchniej jest więc ważnym zagadnieniem, które należy rozpatrywać wykorzystując najnowsze osiągnięcia takich dziedzin, jak: stereologia, analiza obrazów, fraktografia ilościowa. Do badań wykorzystano powłoki natryskiwane plazmowo na podłożu ze stali. Warstwy o zróżnicowanej morfologii oceniono metodą klasyczną za pomocą profilometru oraz wykorzystano jedną z metod analizy fraktalnej - metodę cięciwy. Uzyskane wartości wymiarów fraktalnych mogą stanowić dodatkowy parametr ilościowej oceny geometrycznych cech powierzchni.

EN

The effective way to improve the properties of machine elements is the forming of structure and properties of superficial layers. Their description is related to the following notions: morphology, topography and surface shape. The available literature proves that there are relationships between the morphology of superficial layers and the technology of their production. The morphology of superficial layers has a significant effect on their properties, including also service properties, such as hardness, wear resistance, corrosion resistance, friction coefficient. Thus, the problem of the quantitative description of the superficial layer surface features is an important problem of surface engineering, therefore it should be considered using the most up to date achievements in such fields, as: stereology, image analysis and quantitative fractography. The specimens of steel 45 with different layers sprayed on by two methods were subjected to examination. The layers with morfological diversity on their surfaces were investigated by classic method (profilometer) and fractal method (chord method). The values of fractal dimensions may be an addition parameter of the quantitative analysis of the geometrical features of superficial layers.