Index of content:
Volume 134, Issue 6, December 2013
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
134(2013); http://dx.doi.org/10.1121/1.4826177View Description Hide Description
Interface waves traveling along the boundary between two solids have been studied for nearly a century. However, little attention has been given to the case where interface waves travel at the boundary between a soft and stiff solid and when the soft material is relatively light and viscoelastic. In this paper, the characteristics of interface waves that propagate along a soft-stiff boundary are described. These waves are similar to a leaky Rayleigh-like wave on the stiff solid in terms of the wave velocity and displacement wave structure. Analytical and finite element models are used to model and simulate wave propagation. An example problem of bond evaluation for coatings on metal structures is considered. Experiments on 2.5 cm thick steel plate with 2.5 cm viscoelastic coatings show good agreement to models. Additionally, the results of models and experiments show several promising features that may be used to evaluate bonds in a non-destructive evaluation approach.
Characterization of micrometric and superficial residual stresses using high frequency surface acoustic waves generated by interdigital transducers134(2013); http://dx.doi.org/10.1121/1.4826176View Description Hide Description
Controlling thin film deposition of materials and property gradients is a major challenge for the implementation of applications in microelectronics or glassmaking. It is essential to control the level of residual stress and thus important to have the right tools to characterize this stress in terms of scale and nature of the deposits. In this context, dispersion of ultrasound surface waves caused by the presence of a residual micrometric surface stress was studied in an amorphous medium for different superficial fields of residual stress. The design and implementation of SAW-IDT MEMS sensors enabled quasi-monochromatic Rayleigh-type surface waves to be generated and the dispersion phenomenon to be studied over a wide range of frequencies. The thicknesses of the stressed cortical zones as well as the level of stress were estimated with good accuracy using an inverse method.