Advances in Ultrasonic Imaging for Internal Flaws in Structures

Abstract


 
 
 In the field of non-destructive testing of structures, 3D imag- ing of internal flaws is a critical task. Defect imaging allows the engineer to make informed follow-up decisions based on the morphology of the flaw.
 This paper will present advances in ultrasonic tomography for the 3D visualization of internal flaws in solids. In particular, improvements to the conventional tomographic imaging algorithms have been made by utilizing a mode-selective im- age reconstruction scheme that exploits the specific displacement field, respectively, of the longitudinal wave modes and the shear wave modes, both propagating simultaneously in the test volume. The specific mode structure is exploited by an adaptive weight assignment to the ultrasonic tomographic array. Such adaptive weighting forces the imaging array to look at a specific scan direction and better focus the imaging onto the actual flaw (ultrasound reflector).
 This study shows that the adaptive weighing based on mode structure improves image contrast and resolution compared to a conventional ultrasonic imaging technique based on delay- and-sum. Results will be shown from simulations and imaging experiments of simulated flaws in an aluminum block.