Molokov K., Vasilchenko N.
KONSTANTIN MOLOKOV, Candidate of Engineering Sciences, Associate Professor, Department of Welding Engineering, School of Engineering, e-mail: spektrum011277@gmail.com
NATALYA VASILCHENKO, Associate Professor, Department of Mechanics and Mathematical Modeling, School of Engineering, e-mail: sopromama@mail.ru
Far Eastern Federal University
8 Sukhanova St., Vladivostok, Russia, 690950
Calculated lifetime estimation
under the low-cycle loading of ferrite-perlite steels
Abstract: The article presents the author’s individual technique and model enabling one to determine the number of cycles, which the material withstands under low-cycle load and make it possible to obtain fatigue curves under low-cycle loading for various ferrite-pearlite steels. The procedure has been developed on the base of existing facture criteria and it is applicable for quasi-brittle, quasi-static fracture of steels. Calculation method of evaluating a low-cycle fatigue has been developed based on the semiempiracal structural-mechanical model of determining the endurance limit for ferrite-pearlite steels.
The mathematic model offered by the authors enables one to apply Wöhler curves to the low-cycle failure area of ferrite-pearlite steels. The results of the numerical experiment attest to the fact that the failure of the material may be partly expressed by steady component under loads exceeding the limits of fluidity or fatigue resistance of the material. It has been demonstrated that the damage increases as the plastic prestrain ratio increases and results in the decline in the number of cycles down to failure under low-cycle fatigue. Under high deformations of materials considerably far exceeding the flowing deformation, the damage increases sharply and disproportionately provided that the material undergoes cyclic loading. Basing on the consideration of the damage caused by the plastic prestrain deformation it has been suggested that there be specified a reduction of the number of cycles under the loads beyond the flowing.
Key words: low-cycle fatigue, ferrite-pearlite steel, soft loading, endurance limit stress, damage, Goodman diagram, fatigue curve.
2. Collins J. Metal damage in structures, M., Mir, 1984, 694 p.
3. Maksimadzhi A.I., Novikov O.A., Sokolov L.G. The low alloy steel in shipbuilding. L., Shipbuilding, 1964, 302 p.
4. Matokhin G.V. The rating life of welded structures made of ferrite-pearlite steels. Vladivostok: FESTU-Press, 2001. 202 p.
5. Matokhin G.V., Gorbachev K.P. Fundamentals of computational methods of linear fracture mechanics. Vestnik FEB RAS. 2005;6:116–122.
6. Matokhin G.V., Molokov K.A. The estimated effective concentration coefficients. Research on improving the efficiency of shipbuilding and ship repair. Vladivostok, FESTU, 2006, pp. 184–192.
7. Molokov K.A., Slavgorodskaya A.V. Damage assessment ferrite-pearlite steels with overload. Marine Intelligent Technology. 2013;2 (special issue):56–58.
8. Muratov R.H., Kornilov M.A. Asymmetry of accounting method in the calculation of the loading cycle cyclic durability. Part 2. Experimental verification of the adjusted equation with versatile exponents. Heavy Engineering. 2013;10:46–49.
9. The strength of welded joints under variable loads. Ed. V.I. Trufyakov, Institute of electric welding, Ukrainian Academy of Sciences. Kiev, Naukova Dumka, 1990, 256 p.
10. Calculations and tests of strength in mechanical engineering. Methods of mechanical testing of metals. Test methods for fatigue. GOST 25.502-79. M., Standards Publishing, 1979.
11. Serensen S.V. Fatigue of materials and structures. Fav. tr. 3 vols, vol. 2. Kiev, Naukova Dumka, 1985. 256 p.
12. Serensen S.V., Makhutov N.A. The resistance of welded joints of mild steel low-cycle loading, depending on the properties of the individual zones. Problems of strength. 1970;12:25–33.
13. Serensen S.V. Strength of materials fatigue and brittle fracture. M., Atomizdat, 1975, 191 p.
14. Matohin G.V., Molokov K.A. Computational method of endurance limit determination for different loading cycle parameters. The Seventh International Symposium on Marine Engineering. October, 24-28. Tokyo, The Japan Instit. of Marine Engineering, 2005, p. 192–193.
15. Negoda E.N. Account of centicycle fatigue strength of welding joints. Materials of a conference. The Eighteenths Asian Technical Exchange And Advisory Meeting on Marine Structures (TEAM ’2004), Russia, 2004, p. 179–185.