Research On Ultrasonic Total Focus Method Based On Phase Weighting And Correction Compensation

Ultrasonic total focus method is an ultrasonic phased array imaging method.Compared with the traditional phased array imaging method,the total focus method has a larger imaging range and higher detection accuracy,but at the same time,there is a lot of noise in the image,and the algorithm has a weak imaging ability for near-surface defects.In order to improve the imaging quality of total focus method,this paper proposes a sign coherence weighting factor,which is combined with the instantaneous phase coherence factor to form an aggregate weighting factor,which can suppress ultrasonic side lobe and improve image signal-to-noise ratio.The experimental results show that the aggregation weighting factor greatly improves the signal-to-noise ratio and defect resolution of the total focused image,and its effect is much better than that of the total focused image when the instantaneous phase coherence weighting factor is used alone.Since the value of the directivity compensation factor in the traditional correction compensation factor may be 0,which will lead to image distortion,this paper proposes an improved calculation formula of the directivity compensation factor,which makes the whole directivity compensation factor greater than 0,so as to avoid image distortion.In this paper,it is named offset directivity compensation factor,Proposed in this paper is proved by experiment and the offset directivity compensation factor can effectively improve the surface defect of nearly all focusing algorithm ability of imaging and diffusion attenuation factor combined into the new compensation correction factor,the image quality of imaging has great improvement,can imaging the near surface defects,also can make the image of defect signal amplitude is more uniform.After combining the aggregate weighting factor and the correction compensation factor to form the final combined weighting factor,the B-type phased array test block and self processed steel test block are detected and imaged in this paper.Experimental results show that the signalto-noise ratio(SNR)and resolution of fully focused images are greatly improved by using final combined weighting factor,and the image quality is much higher than that of images only using IPCF.On this basis,the imaging ability of near-surface defects is also greatly improved.It can detect side drilled holes(SDHs)with a diameter of 0.5 mm at a distance of 2 mm from the detection surface and SDHs with a diameter of 1 mm at a distance of 1.74 mm from the detection surface...