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2450 views Articles & News Ali NDT Inspector, Iran, Joined Mar 2013, 82 Ali NDT Inspector, Iran, Joined Mar 2013 82 08:24 Jan-03-2015 Photoelastic Visualisation of Phased Array Sound Fields: Part 19 – Formation of grating lobes Overall                  Reply  Translate  Close   Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998, 1246 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1246 19:40 Jan-03-2015 Re: Photoelastic Visualisation of Phased Array Sound Fields: Part 19 – Formation of grating lobes In Reply to Ali at 08:24 Jan-03-2015 (Opening). An explanation of grating lobes is presented in the Jan 2015 edition of NDT.net. http://www.ndt.net/article/ndtnet/2015/2_Ginzel.pdf Several people deserve special thanks. First I would like to thank Rolf Diederichs for publishing the material. By means of the combined formats of written word and video imaging, Rolf has managed to make the NDT.net noticeably superior to the traditional hard-copy journals available to readers. The idea to produce an explanation of grating lobes is thanks to Ali Golshani. Ali asked me if it would be possible to see grating lobes using photoelastic visualisation. For many years, PAUT instructors have simply stated the sort of explanation provided in the official definitions, i.e. "parasitic replications of the main beam caused by spatial under sampling (pitch between elements compared to wavelength)". This has not been very helpful for students to understand their origin. At the time Ali asked me I was not sure it could be done...I hope the explanation has met his expectations. As with so many of my projects, I again resorted to Civa to help with my explanation and personal understanding of acoustic phenomena. Using Civa, I was able to configure a delay law that would produce a pronounced grating lobe with the limited selection of phased-array probes I have. I would like to thank the good people of the CEA and EXTENDE for their ongoing help with my use of Civa. Finally, the video of a simple 74° beam in transverse mode is in itself not a great illustration of the lobes that form. In order to illustrate how constructive interference causes the lobes I used a technique of image addition first developed by Dr. Till Schmitte. I would like to thank Till for pointing out this very useful tool of image processing. 1                 Reply  Translate  Close   Product Spotlight Ultrasonic Testing Immersion Tanks with Unmatched Scanning Features StandTecScan Systems TecScan’s non-destructive testing Ultrasonic Immersion Tanks & scanners are designed for high pe ... rformance and demanding NDT testing applications. Our Scan3D™ line of High Precision Immersion Tanks are specifically designed for automated ultrasonic testing of complex composites parts used in aerospace and industrial applications. > 5 Showcases4 Videos Webinar: Improving Heat Exchanger Inspection Analysis StandZETEC, Inc. Zetec will host a webinar on automated analysis software for more effective heat exchanger inspectio ... ns in power generation, oil & gas, pharmaceutical manufacturing & other applications. Register now. We will demonstrate how to reduce inefficiencies from legacy acquisition techniques so analysts can focus on identifying signals of interest, evaluating them & making confident decisions. > 5 Showcases5 Videos NEW - TD Focus-ScanRX StandTechnology Design Ltd The NEW Next Generation Advanced UT platform, TD Focus ScanRX - Also available as a card stack solut ... ion. Key Improvements 1. Data acquisition is significantly faster than current design 2. Better aesthetic – closely aligns with HandyScan RX 3. Improved IP rating (Target IP66) 4. Ruggedized housing 5. Connectors are protected from impact and ingress 6. Integrated stand and separate retractable handle easy to keep clean) 7. Touchscreen with ruggedized display glass 8. 3-Axis encoder input > 4 Showcases4 Videos NEOS III StandLogos Imaging NEOS III is Logos Imagings lightest DR system. With a built-in battery and internal wireless commu ... nication, the NEOS III is perfect for users that want to quickly assess an item. > 5 Showcases more Showcases Share... Home Exhibition Archive Forum Jobs Members Events Directory NDT A-Z Advertise Privacy Policy Contact About © NDT.net - Where expertise comes together. The Largest Open Access Portal of Nondestructive Testing (NDT)- since 1996 We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info Accept top this is debug window