Experimental investigation of crack opening loads in an aircraft load spectrum

Fatigue Crack Growth Rates and Crack Tip Opening Loads in CT Specimens Made of SDSS and Manufactured Using WAAM

“…The latter is known to be error-prone for pin loaded specimens, such as the CT specimens used in the present study. The details of the compliance-based methods are not presented here since these are standardised in ASTM E647 [30] and reviewed extensively in past studies [31][32][33][34][35][36].…”

“…Various noise filtering techniques have been proposed in the past, such as moving average filter, lowpass filter, etc. Guided by previous in-depth studies on crack closure measurement [33][34][35][36], we applied a third order lowpass Butterworth filter to the raw load and strain signals. A sufficiently high cut-off frequency equal to 10 times the loading frequency was selected to filter out high-frequency electrical noise without altering the nonlinear response generated by crack closure.…”

“…Due to hysteresis, the experimentally measured compliance offset at or near the maximum load is non-zero. Hence, the 2% compliance offset is taken relative to the mean compliance offset in the upper portion of the loading cycle [35]. Representative compliance offset curves for a "single" load cycle are shown at two different normalised crack lengths (a/W = 0.25, a/W = 0.6) in Figures 4 and 5, respectively.…”

Fastener fatigue fracture analysis and life prediction of composite connection structure

“…Li et al [10] studied the wear mechanism of bolted joints, including fatigue wear, oxidation wear and abrasive wear, and their fracture morphology showed the characteristics of fatigue cracks and depressions. Wallbrink C et al [11] showed through experimental research that crack opening load levels can change significantly from cycle-to-cycle, and these levels are typically larger than for constant amplitude loading at the same R-ratio. Therefore, in the current fatigue analysis framework, both in modeling and experimental data processing, crack initiation and crack propagation are treated as two batch-independent processes.…”