THE KINETICS AND MECHANISM OF THE FATIGUE FRACTURE OF SAMPLES OF 40H AND 38H2N2MA STEELS
It is known that the most of breakdown fractures of the structures or machine parts are related either to the fatigue fracture or brittle fracture caused by the fatigue crack. For this reason, to reduce the possibility of the fatigue crack initiation and development, the expensive medium and highly alloyed steels are often used. This paper presents the comparative analysis of the parameters of the fatigue fracture of samples of low alloyed 40H steel and medium alloyed 38H2N2MA steel.
The fatigue tests of 10×15×80 mm prism samples made of 40H steel with the U- and V-shaped stress concentrators and of 38H2N2MA steel samples with the U-shaped stress concentrator were carried out on the Instron 8802 installation at the temperature of 20 °C according to the three-point bending scheme with ⱱ=10 Hz, R=0.1 and various ΔР values. Steels were tested after the quenching in oil and the subsequent heating to 300 °C. The microrelief of fractures was studied using the SIGMA scanning electron microscope of the ZEISS Company.It is identified that the stress concentrator shape in the samples influences significantly the time to the fatigue crack initiation. The straight-line section of the kinetic diagrams of the fatigue fracture of 40H and 38H2N2MA steels almost completely coincide, although the coefficient n in the Paris’s equation for the 38H2N2MA steel is slightly higher than for the 40H steel. The microfractografic studies have shown that the propagation of a fatigue crack in the 38H2N2MA steel was associated with the more ductile fracture mechanism than in the 40H steel. Thus, it is determined that the low alloyed 40H steel is equal to the medium alloyed 38H2N2MA steel in its fatigue characteristics.
McEvily A.J. Metal Failures: Mechanisms, Analysis, Prevention. Hoboken, Wiley & Sons Publ., 2002. 324 р.
Klevtsov G.V., Botvina L.R., Klevtsova N.A., Limar L.V. Fraktodiagnostika razrusheniya metallicheskikh materialov i konstruktsiy [Fractodiagnostics of fracture of metal materials and constructions]. Moscow, MISiS Publ., 2007. 264 p.
Shtremel M.A. Razrushenie. V 2-kh kn. Kn. 2. Razrushenie struktur [Fracture. books. Structural fracture]. Moscow, MISiS Publ., 2015. Kn. 2, 976 p.
Makhutov N.A., ed. Nauchnye osnovy povysheniya malotsiklovoy ustalosti [Scientific foundations of increasing low-cycle fatigue]. Moscow, Nauka Publ., 2006. 624 p.
Shkolnik L.M. Skorost rosta treshchin i zhivuchest metalla [Cracks growth rate and metal durability]. Moscow, Metallurgiya Publ., 1973. 215 p.
Terentev V.F. Ustalost metallov [Fatigue of metals]. Moscow, Nauka Publ., 2015. 312 p.
Pakhmurskiy V.I., Levitskiy M.O., Mikitishin S.I. Life duration to the fatigue crack initiation and the rate of its growth in the 80kp and U8 steels. Fiziko-khimicheskaya mekhanika materialov, 1975, vol. II, no. 4, pp. 41–44.
Cherepanov G.P. Mekhanika razrusheniya [Mechanics of brittle fracture]. Izhevsk, IKI Publ., 2012. 872 p.
Kotsanda S. Ustalostnoe rastreskivanie metallov [Fatigue cracking of metals]. Moscow, Metallurgiya Publ., 1990. 622 p.
Lin W. Nano Mechanics and Materials. Theory: Multiscale Methods and Applications. Hoboken, John Wiley & Sons Publ., 2006. 368 p.
Ilyushchenko A.F., Markova L.V., Chekan V.A., Fomikhina I.V., Koleda V.V. Atlas proizvodstvennykh razrusheniy razlichnykh konstruktsiy [Atlas of industrial destructions of various structures]. Minsk, Belaruskaya navuka Publ., 2017. 313 p.
Estrin Y., Vinogradov A. Fatigue behaviour of light alloys with ultrafine grain structure produced by severe plastic deformation: An overview. International Journal of Fatigue, 2010, vol. 32, no. 6, pp. 898–907.
Klevtsov G.V., Bobruk E.V., Semenova I.P., Klevtsova N.A., Valiev R.Z. Prochnost i mekhanizmy razrusheniya obemnykh nanostrukturirovannykh metallicheskikh materialov [Durability and fracture mechanisms of three-dimensional nanostructured metallic materials]. Ufa, RIK UGATU Publ., 2016. 240 p.
Shtremel M.A. Razrushenie. V 2-kh kn. Kn. 1. Razrushenie materialov [Fracture. The destruction of materials]. Moscow, MISiS Publ., 2014. Kn. 1, 670 p.
RD 50-345-82. Metodicheskie ukazaniya. Raschety i ispytaniya na prochnost. Metody mekhanicheskikh ispytaniy metallov. Opredelenie kharakteristik treshchinostoykosti (vyazkosti razrusheniy) pri tsiklicheskom nagruzhenii [RD 50-345-82: Methodical Instructions. Calculations and Strength Tests. Methods of Mechanical Testing of Metals. The Definition of Characteristics of Crack Resistance (Fracture Toughness) under Cyclic Loading]. Moscow, Izdatelstvo standartov Publ., 1983. 96 p.
Paris P.А., Erdogan F.A. Сritical analysis of crack propagation laws. Trans ASME, 1963, no. 4, pp. 582–594.
Yarema S.Ya. The study of the fatigue crack growth and kinetic diagrams of the fatigue fracture. Fiziko-khimicheskaya mekhanika materialov, 1977, vol. 13, no. 4, pp. 3–19.
Klevtsov G.V., Valiev R.Z., Klevtsova N.A. Strength and fracture mechanism of nanostructured light materials under cyclic loading. Vestnik Tambovskogo universiteta. Seriya: Estestvennye i tekhnicheskie nauki, 2015, vol. 20, no. 1, pp. 85–91.
Botvina L.R. Razrushenie: kinetika, mekhanizmy, obshchie zakonomernosti [Destruction: kinetics, mechanisms, and general regularities]. Moscow, Nauka Publ., 2008. 334 p.
Klevtsov G.V., Valiev R.Z., Islamgaliev R.K., Klevtsova N.A., Khafizova E.D., Merson E.D., Pigaleva I.N. The kinetics and fatigue fracture mechanism of the AK4-1 aluminum alloy in the sub-microcrystalline state. Deformatsiya i razrushenie materialov, 2014, no. 1, pp. 22–26.
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