Phase Steering and Focusing Behavior of Ultrasound in Cementitious Materials

Deterioration of civil infrastructure system (CIS) raises not only safety issues but also socio-economic concerns. In order to meet the high demand of structural condition assessment and health monitoring, development of quick, reliable and accurate NDE methods became critical issues recently. Compared to metal structures, NDE for cement-based materials is still premature and requires further development

Self-Focusing of Rayleigh Waves: Simulation and Experiment

In earlier work [1,2] a simple idea for self-focusing of a linear array has been used for Rayleigh and Lamb waves. The self-focusing procedure automatically moves the focal region of the array towards the defect that produces the largest backscattered signal by adjusting the excitation times of the elements of the array. Experimental results demonstrate the ability to self-focus Rayleigh waves and Lamb waves on defects in thick slabs and thin sheets. The aim of this paper is to supplement the experimental results with a measurement model of the self-focusing of surface waves. A model for the surface wave generated by a single element of the linear array has been developed. The field generated by the entire array has been simulated by using superposition

Work-unit and Commodity Neighborhoods: Evaluating the Residents' Preference

Small cracks inside a solid are difficult to detect using a conventional ultrasonic focused transducer because its focal point and radiation direction are fixed. Using a self-focusing array can enhance the ability of crack detection and characterization because the beam steers itself inside a specimen and focuses the ultrasound on the crack, thereby increasing the ultrasonic signal/noise ratio