PSI - Issue 18

Prokhorov A. et al. / Procedia Structural Integrity 18 (2019) 802–808 Author name / Structural Integrity Procedia 00 (2019) 000–000

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time (25 million cycles and 46 million cycles, respectively). It should be noted that in this sample on the micro relief in the area of accelerated crack growth, plastic fatigue grooves are more pronounced compared with samples tested under normal conditions. 6. Conclusion As part of an experimental study of the characteristics of the fracture of AISI 420 steel samples after heat treatment, under very high cyclic fatigue regime, carried out on an ultrasonic resonant testing machine with a loading frequency of 20 kHz. The work was carried out to prepare the test facility and the material for ultrasonic tests material, including the assessment of the fatigue limit. The specimens were tested under normal conditions and under the influence of an external magnetic field. The structural analysis of specimens was carried out after each tested. The test program includes preliminary parts devoted to the assessment of the fatigue limit based on Risitano techniques a loading frequency of 10 Hz. The main part of the part of the work was devoted to the study very high cyclic fatigue regime. In order to eliminate the overheating effect during the very high cyclic fatigue test we assembled an original control system based on a non contact infrared pyrometer. The specimens made of AISI 420 were tested under normal conditions and under the influence of an external alternating magnetic field. As a results we have obtained three stages of temperature evolution during very high cyclic fatigue test: initial stage, stable process and rapid increasing. Those stages accompanying by increasing main frequency and second harmonic of alternating magnetic field. The fracture surfaces of the tested samples were investigated. Fatigue cracks in the form of a “fish eye” are observed on the fracture surfaces. Fracture surfaces can be divided into several zones: the zone of the center of destruction or slow crack growth, the zone of accelerated crack growth, and the dam zone. In the zone of slow crack growth, an unstructured macro relief is observed. In the zone of accelerated crack growth, pronounced fatigue grooves are observed, which corresponds to the movement of crack growth in the Paris mode. In the final zone, a relief of a fragile quasi-cleat is observed, with detachment crests observed on the facets of the quasi-cleat. An important observation in this work is the significantly smaller size of the zone of slow crack growth in a specimen located in an alternating magnetic field. Acknowledgements The reported study was funded by RFBR according to the research project № 16-51-48003 References Wang C, Wagner D, Wang Q and Bathias C (2012) International Journal of Fatigue 45(12) 91–97 Bathias C and Paris P (2005) Gigacycle fatigue in mechanical practice (New York: Marcel Dekker Publisher Co.) ISBN 0-8247-2313-9 Zhu X, Shyam A, Jones JW, Mayer H, Lasecki JV (2006) Allison JE Effects of microstructure and temperature on fatigue behavior of E319-T7 cast aluminum alloy in very long life cycles. Int. J. Fatigue 28:1566-1571. Botvina L (2005) Gigaciklovaya ystalost – novaya problema fiziki I mehaniki razrysheniya. Plants laboratory. Materials diagnostic. 70(4):41-51. Sakai T (2009) Review and prospects for current studies on very high cyclic fatigue of metallic materials for machine structural use. Journal of solid mechanics and materials engineering. 3(3):425-439. Plekhov O., Saintier N., Palin-Luc T., Uvarov S., Naimark O. (2007), Theoretical analysis, infrared and structural investigation of energy dissipation in metals under quasi-static and cyclic loading. Material Science and Engineering, vol. 462, no. 1, pp. 367-370. Naimark O., Davydova M., Plekhov O., Uvarov S. (2000), Nonlinear and structural aspects of transitions from damage to fracture in composites and structures. Computers & Structures, vol. 76, no. 1, pp. 67-75. Luong, M., Dang-Van K., (1993), Metal fatigue limit evaluation using infrared thermography. Proceedings of workshop advanced infrared technology and applications, Capri, 20–21, pp. 245–253 Risitano A., Risitano G., Clienti C. (2011) Determination of Fatigue Limit by Mono-Axial Tensile Specimens Using Thermal Analysis Key Engineering Materials 452 pp. 361-364 Soultan M., Kleber X., Chicois J., Vincent A., (2006), Mechanical Barkhausen noise during fatigue of iron. NDT & E International. vol. 39, № 6. pp. 493-498,