Modelling of waves propagation on irregular surfaces using ray tracing and GTD approaches: Application to head waves simulation in TOFD inspections for NDT

Abstract

Edge Diffraction Coefficients around Critical Rays L Fradkin, M Harmer and M Darmon-Towards semi-automated non-destructive evaluation L Fradkin, V Zernov, G Elston et al.-Elastodynamic models for extending GTD to penumbra and finite size flaws A Kamta Djakou, M Darmon and C Potel-Recent citations Frequency control of sol-gel composite films fabricated by stencil printing for nondestructive testing applications Tsukasa Kaneko et al-Curie temperature and high temperature behavior of Pb(Zr,Ti)O 3 /Pb(Zr,Ti)O 3 sol-gel composites Shota Fujimoto et al-This content was downloaded from IP address 34.218.44.141 on 11/05 Abstract. The Time of Flight Diffraction (TOFD) technique is a classical ultrasonic method used in ultrasonic non-destructive evaluation, which allows a precise positioning and a quantitative size evaluation of cracks in the inspected material. Among the typical phenomena arising in the current TOFD inspection, the so-called "head wave" is the first contribution reaching the receiver. The head wave propagation on a planar interface is well known and identified as a critical refraction taking place on the material surface. On irregular surfaces, it has been shown that the head wave results from the melting of surface and bulk waves mechanisms and that surface irregularities are responsible for numerous diffractions of the incident head wave. To simulate such behaviour, a model has been developed using a ray tracing technique based on time of flight minimization (generalized Fermat's principle). It enables the calculation of the ray path and the corresponding time of flight of all waves propagating in the material, including the head wave. To obtain a complete propagation model for these waves (both trajectory and amplitude), the integration of Geometrical Theory of Diffraction (GTD) models is currently performed by coupling them with the ray-based approach discussed above. 1. Introduction Among the various NDE inspections techniques, the Time of Flight Diffraction (TOFD) technique allows a precise and quantitative evaluation of surface breaking or embedded cracks. This technique uses two ultrasonic probes which are mechanically associated and remote from each other. In a contact inspection, the two probes are positioned on the surface of the inspected specimen using a wedge to ensure the impedance adaptation between the probes and the specimen. The first probe emits an ultrasonic pulse in the specimen, and the second probe receives the diffracted signals arising from the specimen. In Fig. 1, a schematic example of a TOFD inspection on a specimen with a planar surface is provided.

Frequency control of sol–gel composite films fabricated by stencil printing for nondestructive testing applications

“…Ultrasonic nondestructive testing (NDT) is used in various industries such as power plants because of its subsurface detect=flaw detection capability and cost effectiveness. [1][2][3][4][5][6][7][8][9] Piezoelectric ultrasonic transducers with high-temperature durability have been desired because of system simplicity. 10) However, the development of piezoelectric ultrasonic transducers for high-temperature NDT applications is difficult, owing to not only the Curie temperature of piezoelectric materials but also the need for couplant and backing materials.…”

Curie temperature and high temperature behavior of Pb(Zr,Ti)O3/Pb(Zr,Ti)O3sol–gel composites

“…Ultrasound has been widely used for nondestructive testing (NDT) because of its cost-effective subsurface inspection capability. [1][2][3] Recently, ultrasonic NDT at high temperatures has attracted industrial interest for the construction of safety infrastructures. 4,5) Even though there are other methods suitable for the NDT of high-temperature applications, such as laser ultrasound [6][7][8][9][10] and electromagnetic transducer (EMAT), [11][12][13] high temperature ultrasonic transducers using piezoelectric materials have been desired because of the system simplicity.…”