Ultrasonic array imaging through an anisotropic austenitic steel weld using an efficient ray-tracing algorithm

Abstract

Ultrasonic inspection of austenitic welds is challenging due to their highly anisotropic and heterogeneous microstructure. The weld anisotropy causes a steering of the ultrasonic beam leading to a number of adverse effects upon ultrasonic array imagery, including defect mislocation and aberration of the defect response. A semi-analytical model to simulate degraded ultrasonic images due to propagation through an anisotropic austenitic weld is developed. Ray-tracing is performed using the A* path-finding algorithm and integrated into a semi-analytical beam-simulation and imaging routine to observe the impact of weld anisotropy on ultrasonic imaging. Representative anisotropy weld-maps are supplied by the MINA model of the welding process. A number of parametric studies are considered, including the magnitude and behaviour of defect mislocation and amplitude as the position of a fusion-face defect and the anisotropy distribution of a weld is varied, respectively. Furthermore, the use of the model to efficiently simulate and evaluate ultrasonic image degradation due to anisotropic austenitic welds during an inspection development process is discussed.

Analytic Approach for 2D Phased Array Delay Law Calculation in Case of Inspection of Objects with Complex Geometry

“…Beamforming of focusing problem is performed by exciting transducer elements with different time delays. Delay from source S (phased array element) to target T (defect) was calculated using conventional methods and trigonometric functions with respect to angles or by Fermat principle to express as the shortest path problem [8]. Proposed method focusing is expressed by semi analitical fashion with coordinate transformation.…”

“…Otherwise, optimization formula, which includes basis function, needs to be derived. It is not worth to derive it and for optimization of (7) and (8) iterative root finding method can be used from sage software [11]. The example below is calculated using iterative root finding algorithm method with the grid in the same way for line and B-splines.…”

“…The focus point is behind complex surface at T(45,35) from S(80,60). In order to calculate point on Figure 4 with conventional methods the shortest path algorithms could be employed [8], [12] results depend on the node size, using iterative algorithm and probing all pixels on boundary give same results, but computational price of lasting considerable time is high if pixels count is large.…”

Weld map tomography for determining local grain orientations from ultrasound

“…This principle can be effectively used with efficient shortest path-finding algorithms popular from the origins of computer science. Zhang et al [11] suggested using various incarnations of the Dijkstra method to model ultrasound in welds, which was further studied in more detail in [19,20]. The present model draws from those contributions but with some modifications to improve efficiency.…”

Multiple Wavemode Scanning for Near and Far-Side Defect Characterisation

“…For defects on the far-side of the sample from the transducer, bulk ultrasound waves can be used for inspection. Where only one side of the sample is accessible, standard inspection may use time of flight diffraction, or phased array techniques [14,15]. For a simple inspection procedure, a modified version of through-transmission using an angle beam probe can be used, where a wave is transmitted into a sample and the blocking of the wave by a far-side defect is imaged [16][17][18][19].…”