Detection of small surface-breaking fatigue cracks in steel using scattering of Rayleigh waves

2010

Exp Mech

The synchronized ultrasonic measurement with the surface acoustic wave (SAW) was carried out during the fatigue testing of bolted specimens of the aluminum alloy in synchronization with a fatigue cycle. The stationary SAW measurement was also carried out in the fatigue testing under pausing the fatigue tester at the mean load. In both measurements, the intensity of the scattered wave gradually increased with the number of fatigue cycles in the fretted region ahead of a bolt hole due to surface roughness, and the steep increment occurred following appearance and propagation of the fatigue crack. The steep increment was detected earlier in the synchronized measurement than that in the in-process measurement. In the synchronized SAW measurement, the intensity of the reflection from the fatigue crack increased with increasing stress level in the fatigue cycle. Then, the crack length was estimated with the intensity change of the reflection from the crack in the fatigue cycle following the Elber's model modified by Suresh on the crack opening and closure following the stress intensity factor. The method developed in the present work shows the potential of the synchronized surface acoustic wave measurement as a tool for the early detectability of the fatigue crack as well as for the evaluation of crack opening/closure behavior in the bolted joint.

Section: Evaluation Of Crack Size From Change In Peak Intensity In a mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Size Estimation of Fatigue Crack Appearing at Bolt Joints of Aluminum Alloy Plates by Synchronized SAW Measurement

2010

Exp Mech

“…The expected SAW velocity was 3030 m·s ¹1 with a wavelength of 150 µm at 20 MHz, 1) and hence the depth of penetration was assumed to be 150220 µm. 4,18) In Fig. 2, the experimental setup for the synchronized SAW measurement carried out during the fatigue testing with the bolted specimen is also shown.…”

Section: Ultrasonic Measurementmentioning

confidence: 99%

Depth Evaluation of Fretting Fatigue Crack Appearing at Bolt Joints of Aluminum Alloy Plates by Synchronized Surface Acoustic Wave Measurement

2012

Mater. Trans.

The surface acoustic wave (SAW) measurement was carried out for the bolted specimen of aluminum alloy by synchronizing the ultrasonic pulsation with a fatigue cycle in the fatigue testing. The reflection from the crack increased in the loading stage of the fatigue cycle, reached maximum and then decreased in the unloading stage of the fatigue cycle. The sigmoidal intensity change of the reflection from the fatigue crack in a fatigue cycle occurred following opening/closing behavior of the crack, and the intensity took the maximum value when the crack was fully opened. The SAW intensity distribution between the crack and the bolt hole edge was also analyzed to evaluate the depth of the crack: the SAW intensity distribution after the crack root was subjected to the band-pass filtering to recognize the creeping wave (the longitudinal wave) reflected from the crack tip, and then the crack depth was estimated from the propagation time of the creeping wave from the crack root to the crack tip, which was in good agreement with the value measured in the cross section of the specimen and evaluated through the scanning acoustic analysis.

“…The nondestructive methods such as ultrasonic detection techniques [1][2][3][4][5][6][7][8][9] have been developed for characterization and detection of the surface crack. The authors [10,11] carried out the surface acoustic wave (the SAW) measurement during the fatigue testing of the bolted joints to detect the initiation and propagation of the fatigue crack at the bolted region.…”

Section: Introductionmentioning

confidence: 99%

Real-time Measurement of Ultrasonic Waves at Bolted Joints under Fatigue Testing

2011

Exp Mech

The real-time measurement of the surface acoustic wave (SAW) was carried out during the fatigue testing of the bolted joints of aluminum alloy plates with a frequency of 0.001 Hz. SAW distributions in the bolted region were compared with those obtained by the synchronized measurement, in which the ultrasonic wave was generated in synchronization with a loading cycle in the fatigue testing with a frequency of 10 Hz. At different numbers of fatigue cycles, the intensity of the reflection from the fatigue crack obtained by the real-time measurement was in good agreement with that obtained by the synchronized measurement. In the real-time measurement, the reflection intensity and profile changed with the stress level in a loading cycle, which were in good agreement with those obtained by the synchronized SAW measurement. From these results, it was confirmed that the SAW distributions obtained by the synchronized measurement is coincident with ones obtained by the real-time measurement in one loading cycle, and is not influenced by the measurement conditions.