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1

Methodical approach to the analysis of experimental data associated with the fatigue cracks propagation under overload conditions

Kłysz S., Szabracki P.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2009

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nr 25

171-183

EN

The paper presents an analysis how overloads affect of fatigue cracks propagation rate where the analysis is carried out with use of the retardation model. The completed analysis covered the results of experimental examination of RCT-type samples made of the WT3-1 titanium alloy and was intended to determine interrelationships between individual parame-ters of the applied model. Comparison between theoretical calculations and experimental data was carried out for two options: with the analysis of samples for the entire range of lifetime until the sample was destroyed, and with a separate analysis of data for time inter-vals between the overload moments, whereby the values of C, m and n coefficients were determined each time for the retardation model. Finally, the dependence of coefficient values on the stress intensity factor during overload cycles is developed.

2

Peculiarities of fatigue crack growth and modifications of the Wheeler retardation model

Kłysz S.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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Vol. 269, z. 67

85-104

EN

In this paper some peculiarities of fatigue crack growth are considered, ones referred to curves of a crack length vs. a number of cycles or the rate of propagation vs. the range of stress intensity factor, i.e. curves typical of tests with overloads applied in cycles. Difficulties with the model-based description (based on the Wheeler retardation model) of fatigue crack growth have been shown. The modifications of the Wheeler retardation model have been presented, ones that improve capabilities of describing data which result from investigation into fatigue crack growth phenomena.

3

Analiza rozwoju pęknięć zmęczeniowych w stali 18G2A i jego opis modelowy.

Kłysz S.

Zagadnienia Eksploatacji Maszyn

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1999

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Vol. 34, nr 2

223-234

PL

Omówiono własności rozwoju pęknięć zmęczeniowych dotyczące przebiegu krzywych a=f(N) (długość pęknięcia w funkcji liczby cykli) lub da/dN=f( delta K) (prędkość propagacji w funkcji zakresu współczynnika intensywności naprężeń), właściwych dla badań z cyklicznie zadawanymi przciążeniami na stali 18G2A. Wskazano na trudności w opisie rozwoju pęknięć w oparciu o model opóźnień Wheelera w związku z ww. własnościami. Przedstawiono modyfikacje modelu Wheelera poprawiające możliwości opisu modelowego danych uzyskanych z badań rozwoju pęknięć zmęczeniowych i zastosowano zmodyfikowany model do takiego opisu.

EN

The properties of development of fatigue cracks has been discussed that concern curves a=f(N) (length of the crack as a function of cycle number) or da/dN=f(delta K) (propagation velocity as a function of stress intensity coefficient) characteristic for tests with cyclic overloading for the steel 18G2A. Difficulties of model description of cracks development based on the Wheeler model were out, which emerge from the a/m. properties. The modified Wheeler model with delays has been applied that improves the possibilities of description of data obtained from tests of fatigue cracks development.