TY - GEN
T1 - A possible mechanism causing subharmonics in ultrasonic testing of a closedcrack
AU - Naito, Keiichi
AU - Sugiura, Toshihiko
PY - 2010/12/1
Y1 - 2010/12/1
N2 - Nowadays nondestructive testing is noted due to the need of maintenance instructures, such as nuclear energy plants and aircrafts. However, detection andsizing of a closed crack are difficult by the conventional ultrasonic testing,because ultrasonic waves penetrate the contact area of the closed crack. Nownonlinear ultrasonic testing is attracting attention. Though there have beenexperimental reports on superharmonics or subharmonics and some theoreticalresearches accounting the superharmonics, so far there have yet been few reportsthat clarify the mechanism causing the subharmonics. Generation ofsuperharmonics at a closed crack was theoretically explained by modeling thecontact of the crack surfaces as a nonlinear spring. This modeling is based onthe fact that, when the gap between the crack surfaces decreases, the contactpressure increases nonlinearly due to the asperity of the crack surfaces. Inthis study a closed crack was regarded as a nonlinear spring with up to thethird order terms, and nonlinear analysis and numerical simulation were carriedout. In experiment, two aluminum specimens strongly pressed were used in placeof a metal block with a closed crack. Numerical simulation predicts generationof the subharmonics. They can appear if the input frequency close to twice thenatural frequency. Conditions for the subharmonics can also be foundanalytically with respect to the input frequency and the input amplitude.Subharmonics were also confirmed by experiment. In conclusion, a possiblemechanism causing the subharmonics at a closed crack was explained by regardinga closed crack as a nonlinear spring with up to the third order terms.
AB - Nowadays nondestructive testing is noted due to the need of maintenance instructures, such as nuclear energy plants and aircrafts. However, detection andsizing of a closed crack are difficult by the conventional ultrasonic testing,because ultrasonic waves penetrate the contact area of the closed crack. Nownonlinear ultrasonic testing is attracting attention. Though there have beenexperimental reports on superharmonics or subharmonics and some theoreticalresearches accounting the superharmonics, so far there have yet been few reportsthat clarify the mechanism causing the subharmonics. Generation ofsuperharmonics at a closed crack was theoretically explained by modeling thecontact of the crack surfaces as a nonlinear spring. This modeling is based onthe fact that, when the gap between the crack surfaces decreases, the contactpressure increases nonlinearly due to the asperity of the crack surfaces. Inthis study a closed crack was regarded as a nonlinear spring with up to thethird order terms, and nonlinear analysis and numerical simulation were carriedout. In experiment, two aluminum specimens strongly pressed were used in placeof a metal block with a closed crack. Numerical simulation predicts generationof the subharmonics. They can appear if the input frequency close to twice thenatural frequency. Conditions for the subharmonics can also be foundanalytically with respect to the input frequency and the input amplitude.Subharmonics were also confirmed by experiment. In conclusion, a possiblemechanism causing the subharmonics at a closed crack was explained by regardinga closed crack as a nonlinear spring with up to the third order terms.
KW - Nondestructive Testing
KW - Nonlinear Acoustics
KW - UT
UR - http://www.scopus.com/inward/record.url?scp=80054083729&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=80054083729&partnerID=8YFLogxK
U2 - 10.1109/ULTSYM.2010.5935556
DO - 10.1109/ULTSYM.2010.5935556
M3 - Conference contribution
AN - SCOPUS:80054083729
SN - 9781457703829
T3 - Proceedings - IEEE Ultrasonics Symposium
SP - 2392
EP - 2395
BT - 2010 IEEE International Ultrasonics Symposium, IUS 2010
T2 - 2010 IEEE International Ultrasonics Symposium, IUS 2010
Y2 - 11 October 2010 through 14 October 2010
ER -