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A finite element model that calculates the energy dissipation to be expected in a crack during sonic infrared (SIR) imaging is described. The finite element model calculations presented, verify the experimental conclusion that chaotic sound excitation produces more heating in cracks than does nonchaotic sound at comparable sound excitation power levels.

Thermal wave reflections from a plane boundary were studied.

The plastic yield and fracture of rubber-modified polystyrene specimens under tensile load have been investigated at room temperature. The experimental procedure consisted of rapidly alternating measurements of transmitted and emitted infrared (IR) radiation from samples under tensile stress. The load-displacement data were simultaneously recorded. Both single-edge-notched and dog-bone-shaped test coupons were studied. In each tensile test run, we observed a significant decrease of material transparency in the IR which occurred near the low yield point. A further increase in material deformation was accompanied by a substantial temperature increase. After material failure, the surface morphology of the test specimens in the vicinity of the crack was examined using atomic force microscopy (AFM). Our results are explained in the context of existing models of material crazing., The toughening properties of rubber added to a glassy polymer in form of small particles, and the ability of such two-component systems to endure large strains, have long been established [...]

The experimental thermal wave images of planar subsurface defects are inverted to determine an enhanced representation of the shape and size of planar subsurface defects. The inversion is effected by an algorithm. The inversion algorithm can also be used in the improvement of the spatial resolution of such defects. The calculations are performed on Macintosh IIfx computers for 128 by 128 pixel images. The inversion time is 1 minute or less.

The technique of sonic infrared imaging (SIR) consists of the excitation of an object with a short pulse of 15 to 40 kHz sound, in combination with IR imaging of the object’s surface temperature as a function of time. Sonic infrared imaging is effective for detecting surface and subsurface cracks. The recent discovery of acoustic chaos has provided a means of greatly enhancing the effectiveness of SIR. We describe the properties of chaotic sound in the context of SIR crack detection, and show examples of the enhancement of the detectability of cracks through the use of chaotic sound. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A second, finite-element-based, computational model that contains the essential features of an actual laboratory sonic infrared imaging (SIR) experiment is described. The chaos results from the combination of the 20-kHz vibration and the bouncing of the transducer from the sample surface.

Provides information on research carried out which examined the plastic yield and fracture of rubber-modified polystyrene specimens under tensile load. What the experimental procedure consisted of; Analysis of single-edge-notched and dog-bone-shaped test coupons; Results of the research carried out.