Abstract
Plane wave imaging (PWI) is attracting more attention in industrial nondestructive testing and evaluation (NDT&E). To further improve imaging quality and reduce reconstruction time in ultrasonic imaging with a limited active aperture, an optimized PWI algorithm was proposed for rapid ultrasonic inspection, with the comparison of the total focusing method (TFM). The effective area of plane waves and the space weighting factor were defined in order to balance the amplitude of the imaging area. Experiments were carried out to contrast the image quality, with great agreement to the simulation results. Compared with TFM imaging, the space-optimized PWI algorithm demonstrated a wider dynamic detection range and a higher defects amplitude, where the maximum defect amplitude attenuation declined by 6.7 dB and average attenuation on 12 defects decreased by 3.1 dB. In addition, the effects of plane wave numbers on attenuation and reconstruction time were focused on, achieving more than 10 times reduction of reconstruction times over TFM.
Highlights
Ultrasonic phased arrays have attracted more and more attention in nondestructive testing and evaluation (NDT&E), due to its ability for achieving high-sensitivity dynamic focus scanning in a wide range without moving the transducer, compared with conventional ultrasonic testing [1,2,3,4,5,6]
In regard to the two methods, the defects in the middle of Figure 5 are at similar levels, but at the position farthest from the array, the plane wave imaging (PWI) provides a lower amplitude attenuation than that of the total focusing method (TFM), which indicates the PWI owing a higher detection range and capability
32-element phased array, and the defects area was was taining 12 defects was inspected by a 32-element phased array, and the defects area subsequently imaged
Summary
In PWI, a specific time delay is set to emit plane waves at different angles in the medium, and PWI imaging at a certain angle is formed by delay-and-sum methods in all array elements. The PWI method has been applied in industry and realized an equal or higher image quality, with obvious reduction of computation time compared to the TFM method. The quality of TFM imaging and PWI imaging with a 128 elements array was tested, and three to ten times less transmissions than with the TFM method were achieved [20]. As a typical and widely used industrial probe, the 32-element linear array was applied to analyze the imaging quality and reconstruction time of the proposed method.
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