Issue 68

L. M. Torres Durante et alii, Frattura ed Integrità Strutturale, 68 (2024) 175-185; DOI: 10.3221/IGF-ESIS.68.11

to the fact that in some specimens immersed in water, corrosive effects were observed due to water contact and the high operational frequency of the machine. Stress (MPa) Voltage (v) Test time (s) Number of cycles 187.8 20 594000 1.19×10 10 197.2 21 135 2.70×10 6 206.5 22 1860 3.72×10 7 206.5 22 661.8 1.32×10 7 206.5 22 1411.8 2.82×10 7 215.9 23 828.6 1.66×10 7 215.9 23 210 4.20×10 6 215.9 23 702.6 1.40×10 7 225.3 24 948 1.90×10 7 225.3 24 826.8 1.65×10 7 234.7 25 255.6 5.11×10 6 234.7 25 927.6 1.86×10 7 244.1 26 300 6.00×10 6 253.5 27 175.2 3.51×10 6 253.5 27 210 4.2×10 6 253.5 27 310.02 6.20×10 6 262.9 28 375 7.50×10 6 262.9 28 350.4 7.00×10 6 Table 7: Ultrasonic fatigue experimental data obtained for 316 stainless steel specimens immersed in water.

Figure 7: Stress-number of cycles graph of 316 stainless steel immersed in water, with representative marks of the used voltages. In Tab. 8 are listed the experimental tests performed on stainless steel 304 immersed in antifreeze. At the lowest working load of 169 MPa, specimens exhibited a fatigue life exceeding 3.44×10 9 cycles; while tests conducted at the highest load (263 MPa) demonstrated a fracture for 3.62×10 6 cycles. Fig. 8 displays the stress-number of cycles graph illustrating the ultrasonic fatigue behavior of stainless steel 304 immersed in antifreeze.

181