PSI - Issue 13

Junji Sakamoto et al. / Procedia Structural Integrity 13 (2018) 529–534 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 4. SEM image of fracture surface of the specimen vibrated at a gravitational acceleration of 70 G rms .

4. Discussion

In this section, we examined the predictability of the time to failure of the material subjected to vibration. The time to failure of a material can be predicted using the stress and/or strain and their number of cycles or by using the power spectral density (PSD) of the stress, as reported by Dirlik (1985) and Tovo (2002). In this study, we calculated the stress and frequency of the load using a finite element method and verified whether the time to failure could be easily predicted. First, a modal analysis was carried out to specify the mode of the specimen, which was fixed at the bottom surface similar to the experiment. Figure 5 shows the natural frequencies and mode shapes of the six modes obtained using ANSYS modal analysis. Mode 1 and mode 2 are bending modes with a natural frequency of 30 Hz. Mode 3 is a torsional mode with a natural frequency of 38 Hz. Mode 4 and mode 5 are different types of bending modes compared to mode 1 and mode 2, and the natural frequency is 510 Hz. Mode 6 is a tension – compression mode with a natural frequency of 921 Hz.

Fig. 5. ANSYS modal analysis.