Ultrasonic methods are well known as powerful and reliable tool for defect detection. Conventional ultrasonic techniques rely generally on piezoelectric transducers where transmission of energy to the material is achieved with contact. In the last decades focus and interest have been directed to non-contact sensors and methods, showing many advantages over contact techniques where inspection depends on contact conditions (pressure, coupling medium, contact area). The growing interest is also due to the further development of air-coupled probes, thanks to new materials for acoustic devices and manufacturing technologies. The use of laser as tool for ultrasonic defect detection is also an emerging approach in the industry and holds substantial promise as inspection is remote, feasible in hostile environment, can be automated and also performed with the test object in motion. Moreover, thanks to its ability of producing frequencies in the MHz range, laser-generated ultrasound enables fine spatial resolution of defects. The non-contact hybrid ultrasonic method described here is of interest for many applications, requiring periodic in service inspection or after manufacturing. Despite the potential impact of laser-generated ultrasound in many areas of industry, robust tools for studying the phenomenon are lacking and thus limit the design and optimization of non-destructive testing and evaluation techniques. Ultrasonic waves propagate through the structure interacting with defects, corners and curved surfaces, causing reflection and mode conversion. Moreover, interference between waves can produce a more complex pattern. This makes the laser-generated ultrasound propagation in complex structures an intricate phenomenon extremely hard to analyze. Only simple geometries can be studied analytically. Numerical techniques found in literature have proved to be limited in their applicability by the frequencies in the MHz range and very short wavelengths. The acoustic field in complex structures should be well understood for each application to optimize sensitivity toward a particular type of defect. A specific numerical method is presented in this chapter to efficiently and accurately solve ultrasound wave propagation problems with frequencies in the MHz range traveling in relatively large bodies and through air. Tests simulated with numerical analysis are replicated experimentally for validation. The numerical technique provides a valuable tool for studying the laser-generated ultrasound propagation and for designing and optimizing non-destructive testing and evaluation techniques. The information that can be acquired can be very valuable for choosing the right setup and configuration when performing non-contact hybrid ultrasonic inspection.

Pantano, A., & Cerniglia, D. (2010). Experimental and Numerical Method for Nondestructive Ultrasonic Defect Detection. In Earl N. Mallory (a cura di), Nondestructive Testing: Methods, Analyses and Applications (pp. 63-95). Hauppauge NY : Nova Science Publishers, Inc..

Experimental and Numerical Method for Nondestructive Ultrasonic Defect Detection

PANTANO, Antonio;CERNIGLIA, Donatella
2010

Abstract

Ultrasonic methods are well known as powerful and reliable tool for defect detection. Conventional ultrasonic techniques rely generally on piezoelectric transducers where transmission of energy to the material is achieved with contact. In the last decades focus and interest have been directed to non-contact sensors and methods, showing many advantages over contact techniques where inspection depends on contact conditions (pressure, coupling medium, contact area). The growing interest is also due to the further development of air-coupled probes, thanks to new materials for acoustic devices and manufacturing technologies. The use of laser as tool for ultrasonic defect detection is also an emerging approach in the industry and holds substantial promise as inspection is remote, feasible in hostile environment, can be automated and also performed with the test object in motion. Moreover, thanks to its ability of producing frequencies in the MHz range, laser-generated ultrasound enables fine spatial resolution of defects. The non-contact hybrid ultrasonic method described here is of interest for many applications, requiring periodic in service inspection or after manufacturing. Despite the potential impact of laser-generated ultrasound in many areas of industry, robust tools for studying the phenomenon are lacking and thus limit the design and optimization of non-destructive testing and evaluation techniques. Ultrasonic waves propagate through the structure interacting with defects, corners and curved surfaces, causing reflection and mode conversion. Moreover, interference between waves can produce a more complex pattern. This makes the laser-generated ultrasound propagation in complex structures an intricate phenomenon extremely hard to analyze. Only simple geometries can be studied analytically. Numerical techniques found in literature have proved to be limited in their applicability by the frequencies in the MHz range and very short wavelengths. The acoustic field in complex structures should be well understood for each application to optimize sensitivity toward a particular type of defect. A specific numerical method is presented in this chapter to efficiently and accurately solve ultrasound wave propagation problems with frequencies in the MHz range traveling in relatively large bodies and through air. Tests simulated with numerical analysis are replicated experimentally for validation. The numerical technique provides a valuable tool for studying the laser-generated ultrasound propagation and for designing and optimizing non-destructive testing and evaluation techniques. The information that can be acquired can be very valuable for choosing the right setup and configuration when performing non-contact hybrid ultrasonic inspection.
Settore ING-IND/14 - Progettazione Meccanica E Costruzione Di Macchine
Pantano, A., & Cerniglia, D. (2010). Experimental and Numerical Method for Nondestructive Ultrasonic Defect Detection. In Earl N. Mallory (a cura di), Nondestructive Testing: Methods, Analyses and Applications (pp. 63-95). Hauppauge NY : Nova Science Publishers, Inc..
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10447/52566
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