Ultrasonic detection of fatigue damage

✍ Scribed by Narayan R. Joshi; Robert E. Green Jr

• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 607 KB
• Volume: 4
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(72)90067-7

✦ Synopsis

4bstract-Results are reported of recent experiments which used change in ultrasonic attenuation measurements as a continuous monitor of fatigue damage during cyclic testing of polycrystalline aluminum and steel specimens. Ultrasonic pulses were generated by an x-cut quartz transducer firmly attached to the clamped end of a specimen rod using Eastman 910 cement. The frequencies of these ultrasonic pulses were IO MHz for polycrystalline aluminum and 5 MHz for cold rolled steel. The specimen shape, transducer size, and frequency used insured that the entire specimen was completely filled with ultrasound in a guided wave mode. The specimen was fatigued as a cantilever beam in reverse bending at 1800 cycles per minute with vertical amplitude peak-to-peak set at a fixed value in the range 7.5-15 mm. In a typical test the ultrasonic attenuation initially remained constant, increased slowly, and then increased catastropically just prior to fracture of the test specimen. All experiments performed on both aluminum and steel specimens at various vibrational amplitudes yielded similar results in that ultrasonic attenuatton served as a very sensitive indicator of fatigue damage and in every case indicated that failure was eminent several hours before conventional ultrasonic testing could detect an additional echo caused by energy reflected from a crack. These results strongly suggest that ultrasonic attenuation measurements can be exploited successfully to predict earlier fatigue damage and perhaps fatigue life in practical applications.