PSI - Issue 81

Bezhenov Sergiy et al. / Procedia Structural Integrity 81 (2026) 260–263

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related to the study of the dependence of material strength characteristics on the types and modes of surface plastic processing of materials Yasniy et al. (2017); Tsyban’ov et al. (2020); Iasnii et al. (2020); Samara et al. (2024). There are clearly not enough studies that reveal the mechanism of the influence of hardening parameters on the mechanical properties of materials. Fundamentally new possibilities for studying strengthening mechanisms appear when using acoustic emission (AE) in fracture mechanics, since the AE method is based on the study of elastic waves in a solid that arise as a result of local internal dynamic restructuring of its structure Skalskiy and Andreykiv (2006); Evans (2006); Hudramovich et al. (2017). The AE method has high productivity, can be used under exploitation conditions and is capable to register the kinetics of structural changes (damages accumulation) in the material loaded. However, information about the investigation of the fatigue via AE method is fragmentary and insufficient for the determination of the criterions for estimating the work ability of the elements of constructions. The purpose of the work is to propose a method for predicting damage of materials with different technological heredity under high-cycle fatigue (HCF) conditions using non-destructive testing data. 2. Materials and methods The custom-designed model samples of different classes of materials made of medium carbon steel (C – 0.46 %,) low-alloy steel (C – 0.38 %, Cr – 1.0 %, Mn – 0.55 %), heat-resistant Ni-based alloy (Cr – 20.89 %, Ti – 2.6 %, Al – 0.6 %, Fe – 0.46%, Cu – 0.37%, Si – 0.31 %, Mn – 0.29 %), deformable Ti-based alloy (Al – 6.4 %, Mo – 3.3 %) were investigated. The investigation included, first of all, examination of the samples after standard technological processing (S). Secondly, the samples subjected to superficial ultrasonic hardening (SH) have been studied. The following research methods were used in the work: test for high-cycle fatigue; continuous control by the acoustic-emission method under cyclic loads; correlation analysis. The high-cycle fatigue tests were carried out according to the cantilever bending scheme with a symmetrical load cycle in the cycle stress range from the endurance limit σ w to the critical stress σ cr , which corresponds to the critical number of cycles N cr which restricts the high-cycle fatigue (HCF) zone. Acoustic emission monitoring was carried out using a wideband transducer with simultaneous analysis in three frequency bands: low (0. 2 … 0 .5 MHz), middle (0. 5 … 1 .0 MHz), and high (1. 0 … 2 .0 MHz). The acoustic emission count rate was taken as the informative parameter of AE signals. 3. Results and discussions The results of fatigue tests were presented in accordance with hypothesis Bezhenov (2013) about the existence of a pole of HCF curves for materials of the same class with different technological heredity, according to which the traditional two-parameter equation of the fatigue curve (Wöhler’ line) is transformed into an equation where, in addition to the values of number of cy cles before failure and amplitude of cycle stresses, the variable is also the slope of the fatigue curve. Fig. 1 schematically shows the interpretation of the HCF curve equation using a pole and taking into account the domain of existence of the function. With this approach, the construction of fatigue curves for structural metal materials with different technological heredity is significantly simplified, and, consequently, the costs of time, material and labor resources for testing are significantly reduced.

Fig. 1. Generalized scheme for constructing a high-cycle fatigue curve taking into account the pole.

The main problem with this approach is determining the coordinates of the pole of the fatigue diagram. The ordinate of the pole is the ultimate stress at which the predominant action of elastic deformation of microvolumes of material during cycling is still