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RESEARCH PAPERS

# Ray Based Model for the Ultrasonic Time-of-Flight Diffraction Simulation of Thin Walled Structure Inspection

[+] Author and Article Information

Department of Applied Mechanics and Centre for Nondestructive Evaluation,  Indian Institute of Technology Madras, Chennai 600 036, India

K. Balasubramaniam

Department of Mechanical Engineering and Centre for Nondestructive Evaluation,  Indian Institute of Technology Madras, Chennai 600 036, Indiabalas@iitm.ac.in

C. V. Krishnamurthy

Department of Mechanical Engineering and Centre for Nondestructive Evaluation,  Indian Institute of Technology Madras, Chennai 600 036, India

J. Pressure Vessel Technol 127(3), 262-268 (Feb 21, 2005) (7 pages) doi:10.1115/1.1989353 History: Received February 09, 2005; Revised February 21, 2005

## Abstract

It is necessary to size the cracklike defects accurately in order to extend the life of thin-walled $(<10mm)$ components (such as pressure vessels) particularly for aerospace applications. This paper discusses the successful application of ray techniques to simulate the ultrasonic time-of-flight diffraction experiments for platelike structures. For the simulation, the diffraction coefficients are computed using the geometric diffraction theory. The A and B scans are simulated in near real time and the different experimental parameters can be interactively controlled due to the computational efficiency of the ray technique. The simulated results are applied to (1) defect signal identification for vertical defects, (2) inspection of inclined defects, and (3) study the effect of pulse width or probe frequency on experimental results. The simulated results are compared with laboratory scale experimental results.

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## Figures

Figure 4

GUI for simulating TOFD B scan. (a), (b), (c), and (d) are the lateral wave, top tip diffracted signal, bottom tip diffracted signal, and backwall reflected signal, respectively

Figure 1

Principle of TOFD technique and expected A-scan signals

Figure 2

B-scan simulation using ray method for a different position of a vertical embedded crack in the (a) right half, (b) middle, and (c) left half of the probe, as well as the corresponding (d) B-scan simulation. Here 1, 2, 3, and 4 correspond to lateral, defect echo from the top, defect echo from the bottom, and backwall echo, respectively.

Figure 3

Reference input pulse used for simulation. The pulse width and number of cycles are related to the probe frequency.

Figure 5

Comparison of experimental and simulated B-scan images using 5 MHz probe frequency. Figures (a), (b), (c), and (d) are experimental B scans over the defects of sizes 6.5, 3.25, 1.6, and 0.8 mm, respectively and (e), (f), (g), and (h) are simulated B scans over the same defects.

Figure 6

Superposed experimental (dotted) and simulated A-scan (solid) singles over the defects of sizes (a) 6.5 mm, (b) 3.25 mm, (c) 1.6 mm, and (d) 0.8 mm, respectively

Figure 7

Comparison of experimental and simulated B-scan images using 10 MHz probe frequency. Figures (a), (b), (c), and (d) are experimental B scans over the defects of sizes 6.5, 3.25, 1.6, and 0.8 mm, respectively, and (e), (f), (g), and (h) are simulated B scans over the same defects.

Figure 8

Superposed experimental (dotted) and simulated A-scan (solid) singles over the defects of sizes (a) 6.5 mm, (b) 3.25 mm, (c) 1.6 mm, and (d) 0.8 mm, respectively

Figure 9

Measuring the defect size (L) and the angle of inclination (θ) for an inclined defect

Figure 10

Comparison of experimental B scans with simulated B scans on a 10 mm thick aluminium sample, with 60° inclined (θ) defects of sizes (L), (a) 6.5 mm and (b) 3.25 mm

Figure 11

Variation of defect curve shape for different angle of inclination (θ), from horizontal defect (a) to vertical defect (j), for a 6 mm defect in a 10 mm thick aluminum plate

Figure 12

Comparison of experimental B scans with simulated B scans on a 10 mm thick aluminum sample, with vertical defects of sizes (a) 6.5 mm and (b) 1.6 mm

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