Ultrasonic Control of Welded Joints in a Du800-Type Pipeline. Part II: Improving Image Quality and Comparison with X-Ray Testing Results

It has been shown in the first part of the article that the DFA method in its version intended for ultrasound propagating in a homogeneous isotropic medium does not suffice for reconstructing high-quality images of reflectors in the welded joint of a Du800-type pipeline. To improve the image quality further while using the DFA method, it is necessary to determine the elastic properties of a Du800 pipeline buildup and allow for its anisotropy with respect to the propagation of ultrasound as well as the surface profile. The DFA-Y and maximum-entropy (ME) methods have been applied to increase the resolving ability and reduce the noise level. Comparing the results of ultrasonic and X-ray testing has made it possible to draw a conclusion that the former is more informative for revealing crack-like reflectors.