Abstract
The ultrasonic annular array transducer usually has a stronger focusing acoustic field than the linear array and matrix transducer with the same number of array elements, and is more suitable for the detection of large thickness and high attenuation components. However, due to the special arrangement of array elements, the focusing beam cannot be deflected and has a large near field, which limits its application in practical detection. The element parameters of annular array transducer are often designed and analyzed according to the 2-D acoustic field model of a linear array transducer. Therefore, the 3-D acoustic field distribution model of the annular array transducer is established, and the influence of the element parameters on its spatial acoustic field focusing characteristics is analyzed. The design criteria of the array element division mode and element size are proposed, which can avoid the generation of high-energy side lobe and grating lobe, and have good axial acoustic field. Then, the influence of excitation aperture on the energy and size of focal spot at different depths is discussed. The dynamic focusing method with variable aperture of annular array is established, and the C-scan detection experiment is carried out on the addictive manufacturing titanium alloy specimen. The detection results show that the variable aperture method has better central amplitude consistency and imaging accuracy for different depth defects, and has better near surface detection ability than the fixed aperture method.
Highlights
Ultrasonic array technology is a kind of multichannel ultrasonic testing technology which arranges several piezoelectric wafers into an array according to a certain combination mode
For different depth focusing points, the fixed Fixed aperture Variable aperture (F/D) variable aperture method has the best performance in the consistency of focal spot size, and the fixed F/Nf variable aperture method is more excellent in the consistency of focusing energy intensity and detection sensitivity
Since the variable aperture method is more consistent in the focal spot size at different depths, the size difference between defects in Figure 10(c) is smaller than that of the C-scan results of fixed aperture
Summary
Ultrasonic array technology is a kind of multichannel ultrasonic testing technology which arranges several piezoelectric wafers into an array according to a certain combination mode. Ultrasonic the linear array transducer and ultrasonic matrix transducer are the most widely used in theoretical research and industrial application. The influence of focusing depth and excitation aperture size on the focal spot size and acoustic energy of annular array transducer is analyzed, and a variable aperture dynamic focusing method of annular array is established. The C-scan experimental results of additive titanium alloy show that the variable aperture dynamic focusing method can improve the detection ability and sensitivity of different depth defects. It provides theoretical guidance for the application of ultrasonic annular array transducer in the detection of large thickness and high attenuation components
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