PSI - Issue 51

Kamila Kozáková et al. / Procedia Structural Integrity 51 (2023) 145–151 K. Kozáková et al. / Structural Integrity Procedia 00 (2022) 000–000

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2014; Tridello et al., 2021). Risk volume can be considered as the region of the specimen subjected to applied stress amplitudes above certain percentage of the maximum applied stress amplitude (Paolino et al., 2014). The present paper compares the fatigue behavior of two types of stainless steels with different risk volumes during high-frequency loading. Specimens were specially designed for ultrasonic fatigue tests. The present paper summarizes the whole process of fatigue measurement including the design of specimens with different risk volumes, the description of experimental materials, and fracture surface analysis.

Nomenclature R

stress factor RV risk volume �� stress in risk volume region ���� LM light microscope scanning electron microscope backscattered electron image EBSD electron backscatter diffraction maximum applied stress amplitude SEM BSE

2. Comparison of risk volumes of different specimens Risk volume is a volume, where a crack is most likely to initiate. A specimen for low-frequency tests with a typical cylindric body (marked as specimen 1), and two specimens for the ultrasonic tests (marked as specimens 2 and 3), were modeled. The specimens for ultrasonic tests differ in the diameter of the central part of the glass hour shape, see Fig. 1. The stress distribution along the axes of specimens is determined by finite element analysis, see Figs. 2 and 3. Specimen no. 1 was loaded with tension and solved by static analysis, the specimens 2 and 3 were solved by the harmonic analysis. In our case, the risk-volume is considered as a region subjected to applied stress amplitudes above the 90% of the maximum applied axial stress amplitude, ���� , see eq. 1. �� ∈ 〈0.9 ∙ ���� ; ���� 〉 (1) The corresponding elements loaded with stress �� were selected (see Fig. 4) and the risk volumes of specimens are listed in Table 1. Table 1. Risk volumes of specimens. Specimen no. 1 2 3 RV [mm 3 ] 460.22 87.07 21.02 The specimen for low-frequency tests, specimen no. 1 has the largest risk volume, the second largest risk volume has the specimen for ultrasonic tests with the diameter of 5 mm (no. 2), and the smallest risk volume has an ultrasonic frequency loaded specimen with the diameter of 3 mm (no. 3).