ISSN:
1573-4862
Keywords:
Adhesive joints
;
diffusion bonded joints
;
Lamb waves
;
interface waves
Source:
Springer Online Journal Archives 1860-2000
Topics:
Electrical Engineering, Measurement and Control Technology
,
Mathematics
Notes:
Abstract The role of plate waves in the inspection of adhesive and diffusion bonded joints is examined. This involves a review of the modal techniques which have been proposed for the measurement of the adhesion and cohesion properties of adhesive joints and the presentation of some of our own studies on the detection and characterization of an unwanted layer of brittle alpha case in diffusion bonded titanium. It is concluded that Lamb waves, which occupy the whole joint, are viable in principle but are limited in both applications by their strong sensitivity to the material properties and the thicknesses of the adherends and their relative insensitivity to those of the bondline layer. On the other hand, embedded modes, which propagate along an embedded layer, are largely insensitive to the adherends, the dispersion curves showing a major improvement in sensitivity to the properties of the layer and to the boundary conditions between the layer and the adherends. The drawback is that their exploitation is limited in practice because it is difficult to excite and detect them. True modes offer good potential but require access to the ends of the joints. In attempting to excite leaky modes, minima of the reflection coefficient, commonly used to measure Lamb wave dispersion curves in immersion coupled plates, do not correspond to the dispersion curves because the acoustic impedance of the adherends is too large. Therefore, although measurement of the minima offers good potential for inspection, this is a response technique and cannot be associated directly with the plate modes. In neither of the examples studied could an interface wave exist at a single interface between the bondline layer and an adherend. However, in general such modes could be rather attractive for inspection, provided that their wavelengths are much smaller than the layer thickness, because they are sensitive to the interface region but not to the thicknesses of the layers, and they are relatively simple to measure.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00742584
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