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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3.2. Design of specimens Experimental specimens (no. 2 and 3 from Fig. 1) differ in diameters. They were designed for ultrasonic fatigue tests so that their intrinsic frequencies of longitudinal oscillations are close to 20 kHz. In Fig. 7, you can see several mode shapes and natural frequencies of specimen no. 2. Specimens were modeled so that their first mode shape has a modal frequency close to 20 kHz and the specimen is deformed in the axis. Specimens were modeled using axisymmetry. After machining, the central parts of specimens were electropolished to get a very fine surface.

Fig. 7. Mode shapes.

3.3. Experimental data All fatigue tests were carried out under uniaxial symmetric tension/compression loading ( ���1 ) at room temperature at the frequency of 20 kHz. Specimens were cooled with running distilled water. Fatigue data were

Fig. 8. Fatigue data (a) 1.4306, (b) 1.4307, empty points are runout specimens (not broken until 10 �� cycles ).