The Research On Ultrasonic Phased Array Testing And Imaging Technology

Ultrasonic phased array technology is gradually applied to the field of industrial testing.Traditional ultrasonic phased array imaging methods are mainly based on the line-scanning or the sector-scanning mode.In order to obtain higher resolution of the ultrasonic images and deeply characterize the information of material defects,in recent years,synthetic aperture focusing technology and total focusing method are also being gradually applied to the field of ultrasonic image processing.The traditional line-scanning imaging method usually used in the ultrasonic phased array inspection are introduced firstly.The effects of focus aperture and focus depth on the results of line-scanning imaging were illustrated by phased array experiments.It shows that the resolution of the image is insufficient when the aperture is too small and the defect is far away from the focus.In order to overcome the insufficient of traditional scanning imaging,the synthetic aperture focusing imaging algorithm and total focusing imaging algorithm are developed and compared with the traditional imaging method.Here a simplified total focusing imaging algorithm is proposed based on the reciprocity of ultrasonic propagation to enhance the calculation efficiency.The results of the experiment show that this proposed algorithm is no loss of image quality and can significantly improve the calculation efficiency.The focusing experiments show that transverse resolution of synthetic aperture focusing is clearly improved comparing to the traditional line-scan imaging.Both of the amplitude and lateral resolution of the near surface defects in the total focusing method become better than those of synthetic aperture focusing imaging.Finally,the synthetic aperture focusing imaging algorithm and total focusing imaging algorithm in the isotropic materials are used in the heterogeneous and anisotropic weldment.By combing the ray tracing and dichotomy,it is possible to calculate the acoustic path between an arbitrary array point and an internal imaging point of incidence in an anisotropic weld.The travel time of the array source to the imaging point can be calculated accurately using this curve ray tracing path.Then synthetic aperture focusing and total focusing imaging for the heterogeneous and anisotropic weldment are developed and some numerical simulation results are given.The provided model can be used as an efficient tool for the evaluation of nickel-based alloy welds by the ultrasonic phased array.