PSI - Issue 78

Yangwen Zhang et al. / Procedia Structural Integrity 78 (2026) 1008–1015

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The predicted initiation of the first fatigue crack during the 100% d bd loading phase can be estimated using the following expression: n c = 1 − n 2 N 2 − n 3 N 3 · N 1 (4) where n c is the estimated number of cycles to crack initiation at 100% d bd , accounting for the prior damage accu mulated during the 25% and 50% d bd loading phases. Based on this equation and the simulation results, the estimated number of cycles to crack initiation during the 100% d bd phase is calculated to be approximately 85. This life predic tion has been further experimentally validated.

3. Experiment validation

The simulated SHARK ® hysteretic damper was further tested under quasi-static loading, following the defined loading sequence, at an independent, certified testing facility. The test setup is shown in Fig.5. Displacement control mode was employed throughout the tests, with both the applied displacement and the reaction force continuously recorded. Additionally, visual inspections were conducted to monitor crack initiation and progression.

Fig. 5. Test-Setup.

The first crack became visible to the naked eye after approximately 90 cycles at 10% d bd , having a deviation of only 5.6% from the predicted 85 cycles based on simulation. The initiation of the crack was observed in the vicinity of the region exhibiting the maximum strain amplitude, as depicted in Fig.6. The simulation accurately predicted the fatigue failure location, which corresponds exactly to the intended failure zone in our design. The measured hysteresis loop (100% d bd ) is plotted in Fig.7. Since cycle 90 corresponds to the onset of cracking, the loops are grouped into two stages: cycles 1–90 (pre-crack) and cycles 91–100 (post-crack). In the post-crack stage, the reaction force showed a little faster rate of reduction. A more detailed discussion of the experimental results is presented in the next section.