Influence of surface breaking crack properties on ultrasound diffusion

Yogesh Kane - M.S. Thesis Defense
Advisor:  Dr. Joseph Turner

Date:  Monday, December 1, 2003
Time:  2:40 p.m.
Place:  W129 Nebraska Hall

Surface breaking cracks are a common occurrence in concrete, a single major cause for the failure of many structures. A numerical model was developed to replicate the ultrasonic diffusion process in concrete experiments to study the influence of these surface-breaking cracks. The model also incorporates dissipation, a mechanism of energy loss during the diffusion process.

The heterogeneous composition of concrete under the influence of a variety of loading parameters result in cracks that are not always straight. These cracks also exist with different types of contact conditions. Hence, to determine the applicability of the ultrasound diffusion technique to these problems, the influence of crack depth and crack properties was investigated.

Experiments were performed on cast slabs with uncracked, normal surface cracks, fluid-filled surface cracks and oriented cracks. Experimental data were analyzed using different means during these investigations such that the analysis methods could be contrasted. The experimental results were then compared with numerical outcomes for application of diffusion theory to various practical problems encountered during non-destructive testing (NDT) of concrete. It is shown that the diffusion model is effective for the analysis of fluid-filled cracks as well as empty cracks of arbitrary orientation.