PSI - Issue 59

Viktor Kovalov et al. / Procedia Structural Integrity 59 (2024) 771–778

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V. Kovalov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

After every 10 min of operation, the lateral surface of the specimen in the zone of the presumed brittle crack trajectory was examined with a MB- 2 microscope (Brinnell magnifier) (×24) (Fig . 2). After the crack appeared, its length was measured at regular intervals (5...10 min.) using the same microscope with an accuracy of 0.01 mm. After the crack increased, the loading was reduced. The tests were continued until the crack length of 3.0...4.0 mm was obtained, after which the tests were stopped and the specimen was removed from the testing machine (Fig.3).

Fig. 2. Fatigue crack length measurement during loading process.

Fig. 3. General view of the crack in the model specimen.

For the purpose of the comparative study of fatigue resistance of specimens processed according to different technological schemes, the specimens were loaded according to the principle of constancy of the specified value of loading of the specimen during the entire time of testing. In this case, the mode of loading change in the tested specimen occurred according to a symmetrical cycle. The tests were carried out on the basis of 106 cycles. The test base, i.e. the number of cycles at which the endurance limit is determined, was calculated by the formula:

The endurance limit of the specimen was determined by the formula: ∑ , where .