PSI - Issue 68
1322 4
Junji Sakamoto et al. / Procedia Structural Integrity 68 (2025) 1319–1323 Junji Sakamoto et al. / Structural Integrity Procedia 00 (2025) 000–000
Fig. 5. Relationship between the vibration frequency and bending displacement amplitude.
Fig. 6. Relationship between D d a and S ·d d a /d f v .
2.2.2 Procedure for predicting crack area Using the two basic datasets described in Section 2.2.1 (Figs. 5 and 6), the following procedure was used to predict the crack area. • Step 1: Calculate d d a /d f v at the loaded vibration frequency, as shown in Fig. 5. • Step 2: Monitor d a during the vibration test and calculate D d a . • Step 3: Predict S by substituting d d a /d f v and D d a into Eq. (2), which is the approximate straight line shown in Fig. 6. 3. Results and discussion In this section, the S is predicted using the aforementioned method for a new test at f v = 25.3 Hz. Following Step 1 in Section 2.2.2, d d a /d f v at f v = 25.3 Hz was calculated to be -25.1. In Step 2, d a was monitored during the test, and D d a was calculated. Figure 7 shows the results of calculating D d a . According to Step 3, by substituting the values of d d a /d f v and D d a into Eq. (2), the S was predicted. Fig. 8 shows a comparison of the predicted and experimental results. In the actual experimental results, fatigue cracks were first observed at 30,000 cycles, followed by a gradual increase in S . On the other hand, the predicted values of S were not zero even before the actual crack was observed. This is because the amplitude of the bending displacement during vibration changes slightly from cycle to cycle, as shown in Fig. 7. However, after 30,000 cycles, when cracks were observed, the predicted values of S agreed well with the experimental value. Although the accuracy and coverage of prediction must be verified at other vibration frequencies, the results suggest that the crack area can be predicted using the change in the bending displacement amplitude. This may be because the change in vibration depends approximately on the crack area and the degree of change can be estimated from the introduced slope.
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