Optimization of image synthesis for complex geometry objects in the robotic ultrasonic system
This paper is devoted to the optimization of image synthesis for complex shape objects in the robotic system of ultrasonic testing. The basis of this process is a preliminary analysis of the object with complex geometry to ensure reproducibility and accuracy of the tests in the specified range. It includes such stages as digital model creation, geometric surface analysis, creating of control points and vectors, searching for optimal model location, model verification on reachability, collisions and singularity.
Ultrasonic Sampling Phased Array Testing as a Replacement for X-ray Testing of Weld Joints in Ship Construction
According to European Standard EN 1712 ultrasonic testing of thin-walled welded joints is mandatory for wall thicknesses of more than 8 mm only. Any thinner components do have to undergo X-ray inspection. Besides various advantages of X-ray testing viz. high sensitivity to smallest inclusions, high acceptance in the ship building sector and 'automatic' documentation of inspection results, there are also several deficiencies (like radiation protection issues, inspection time expenditure etc.) creating a reasonable request for more cost-effective alternatives. Sampling Phased Array technology introduced by Fraunhofer-IZFP provides significant improvement of flaw detectability also in thin-walled welded joints due to its tomographic approach in processing of signals obtained by ultrasonic phased array transducers. It allows high-quality imaging of welded joints and detection of relevant material flaws. Real-time ultrasonic imaging with tomographic quality offers a great alternative to X-ray testing with respect to inspection speed and modern documentation of inspection results. The basic principles of Sampling Phased Array are presented in the paper and several application results obtained on welded joints of marine objects are presented.
Ultrasonic inspectability of austenitic stainless steel and dissimilar metal weld joints
Since their invention in 1912, austenitic stainless steel materials are widely used in a variety of industry sectors. In particular, austenitic stainless steel material is qualified to meet the design criteria of high quality, safety related applications, for example, the primary loop of the most of the nuclear power plants in the world, due to high durability and corrosion resistance. Certain operating conditions may cause a range of changes in the integrity of the component, and therefore require nondestructive testing at reasonable intervals. These in-service inspections are often performed using ultrasonic techniques, in particular when cracking is of specific concern. However, the coarse, dendritic grain structure of the weld material, formed during the welding process, is extreme and unpredictably anisotropic. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of ultrasonic Phased Array techniques becomes desirable. The “Sampling Phased Array” technique, invented and developed by Fraunhofer IZFP, allows the acquisition of time signals (A-scans) for each individual transducer element of the array along with image reconstruction techniques using “SynFoc” algorithms. The reconstruction considers the sound propagation from each image pixel to the individual sensor element. For anisotropic media, where the sound beam is deflected and the sound path is not known a-priory, we implement a new phase adjustment called “Reverse Phase Matching” technique. This algorithm permits the acquisition of phase-corrected A-scans that represent the actual sound propagation in the anisotropic structure; this technique can be utilized for image reconstruction.