A new transducer holder mechanism for efficient generation and reception of Lamb modes in large plates

Das

Jata

2009

Smart Mater. Struct.

Self Cite

The applicability of guided waves to predict the point of impact in a stiffened plate is investigated. The conventional triangulation technique cannot predict the point of impact in a stiffened plate because the triangulation technique assumes that the wave speed is independent of the direction of propagation, which is not true for stiffened plates. An alternative method based on the optimization scheme was proposed by Kundu et al (2007 J. Acoust. Soc. Am. 122 2057-66) to locate the point of impact in plates by analyzing the time of arrival of the ultrasonic signals received by passive sensors attached to the plate. After successful extension of this technique to predict the point of impact in anisotropic but homogeneous composite plates (Kundu et al 2008 Ultrasonics 48 193-201) it is investigated in this paper whether this technique works well for predicting the point of impact in an inhomogeneous plate where the stiffeners make the structure inhomogeneous. Experiments are carried out by dropping ping pong and metal balls on the plate to simulate the impact phenomenon and recording acoustic signals by passive transducers adhesively bonded to the plate at three different locations. The impact points are predicted and compared with the actual locations of impact.

Section: Experimental Investigationmentioning

confidence: 99%

“…For over a decade Lamb waves have been used for material characterization and defect detection in composite coupons [3][4][5][6][7][8][9][10], large metal plates [11][12][13] and interfaces [14,15]. However, the Lamb wave technology for inspecting stiffened plates has not been fully developed yet.…”

Section: Introductionmentioning

confidence: 99%

Detection of the point of impact on a stiffened plate by the acoustic emission technique

Das

Jata

2009

Smart Mater. Struct.

Self Cite

“…Use of Lamb waves for material characterization and defect detection in composite coupons [2][3][4][5][6][7][8][9], large metal plates [10][11][12], and interfaces [13,14] is a technology that is more than a decade old. However, the technology related to the use of guided waves for inspecting tiled structures has not been fully developed yet.…”

Section: Introductionmentioning

confidence: 99%

Health Monitoring of a Thermal Protection System using Lamb Waves

Structural Health Monitoring

Das

Jata

2008

Self Cite

The applicability of guided waves as a structural health monitoring (SHM) tool to predict the point of impact and detect delamination in a thermal protection system (TPS) is studied. A model TPS was designed by bonding ceramic porous tiles to a 2.2 mm thick 2124-T351 aluminum alloy plate. The delamination defect may be caused by the impact phenomenon or due to other reasons such as manufacturing defect, thermal, or mechanical fatigue, etc. Impact phenomenon is simulated by dropping a ping pong ball on the tiled structure. The delamination at the interface between the ceramic tile and the aluminum plate is simulated by removing the adhesive bond at the selected interface regions during the specimen fabrication process. The conventional triangulation technique cannot predict the point of impact in a tiled plate structure because the triangulation technique assumes that the wave speed is independent of the direction of propagation which is not the case for ceramic tile mounted plates. An alternative method based on the optimization scheme was proposed by Kundu et al. [1] to locate the point of impact in plates by analyzing the time of arrival of the ultrasonic signals received by passive sensors attached to the plate. This objective function based method is used to locate the impact point on the tiled plate. Experiments are carried out by dropping a ping pong ball on the tiled structure and recording acoustic signals by passive transducers adhesively bonded to the plate at three different locations. The impact point is predicted and compared with the actual location of impact. Delamination detection studies were conducted in the pitch-catch mode, by changing the angle of strike and the frequency of the transducer excitation to generate the appropriate guided wave mode. The delamination defect could be detected and the impact point could be identified underlining the importance of the use of guided waves as an SHM tool for TPS.

“…The inconsistency problem arising from the diverging beam and the water surface disturbance could be avoided by this conical water container design. Ghosh and Kundu 12 have discussed in detail the advantages of conical water containers for large plate inspections.…”

Section: Evolution Of the Coupling Mechanism Designmentioning

confidence: 99%

A new transducer holder mechanism for pipe inspection

Guo

The Journal of the Acoustical Society of America

2001

Self Cite

A new transducer holder mechanism has been designed and fabricated for pipe inspection by cylindrical guided waves. Commercially available ultrasonic transducers have been used to generate compressional ultrasonic waves in the coupling medium. Those waves are converted to cylindrical guided waves in the pipe by the new coupling mechanism. A number of advanced coupling mechanisms developed recently for large plate and pipe inspection require the presence of a coupling fluid between the ultrasonic transducer and the pipe or plate specimen. These mechanisms can be used for inspecting horizontal pipes and plates. The new coupling mechanism presented in this article uses solid material as the coupler and can be used equally well for inspecting horizontal as well as inclined or vertical pipes. The new coupling mechanism has been designed to generate efficiently different Lamb modes in the pipe. The new design has been used to inspect different kinds of anomalies in copper and aluminum pipes. The preliminary results show that a number of Lamb modes, when generated properly by the new coupling mechanism, are very sensitive to the pipe defects. These experimental results along with the new design of the coupling mechanism are presented in this article.