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The ultrasonic characterisation of solid-state bonds

Som, Amit Kumar; (1991) The ultrasonic characterisation of solid-state bonds. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The ultrasonic characterisation of solid-state bonds, in particular diffusion bonds has been considered in this thesis. The study has concentrated on titanium sheet material diffusion bonded with similar materials on either side of the bond-line. A review of diffusion bonding, ultrasonic diffusion-bond non-destructive evaluation (NDE) and acoustic microscopy is presented. A broadband Pulsed Digital Reflection Acoustic Microscope (PDRAM) with a centre frequency of 50 MHz has been designed and built as part of this study. The system is capable of imaging small flaws about 100 µm in diameter on the diffusion bond-line between two titanium plates typically 2 to 3mm thick. Calibration of the system has been conducted through the use of the optical concept of the Modulation Transfer Function (MTF) and evaluation of its various imaging modes have been presented. Images and data in the form of reflection (CR) and transmission (CT) coefficients from the diffusion bond-line are obtained using two different techniques: C-scan and Leaky Rayleigh wave scans. The variation of Cr and with impedance contrast ratio (Z1/Z2) has been discussed by considering plane incidence on a perfect interface. Cr and values have been obtained using the C-scan technique. Metallographic sections that provide the bond-line normal to the free surface are used for a qualitative optical classification of bond quality. Quantitative CR and CT values and images are obtained by scanning these samples using leaky Rayleigh waves. The results are compared with a Finite Difference (FD) model developed within the Ultrasonics Group at UCL. This considers Rayleigh wave interaction on welded quarter spaces. Both FD model and experimental CR and CT values are found to be in good agreement at values of Z1/Z2 close to or equal to 1 (valid for specimens in this study). Reasons for any differences observed are discussed.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The ultrasonic characterisation of solid-state bonds
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Diffusion bonds
URI: https://discovery.ucl.ac.uk/id/eprint/10107875
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