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2593 views Articles & News Ali NDT Inspector, Iran, Joined Mar 2013, 93 Ali NDT Inspector, Iran, Joined Mar 2013 93 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, 1254 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1254 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 Wireless TOFD scanner StandOKOndt GROUP Quick, accurate and highly reproducible welds testing. The System operates wirelessly and is compat ... ible with any type of Windows based Laptop, Desktop or Tablet. > 6 Showcases6 Videos Immersion systems StandScanMaster Systems (IRT) Ltd. ScanMaster ultrasonic immersion systems are designed for high throughput, multi shift operation in a ... n industrial or lab environment. These fully integrated systems provide various scanning configurations and incorporate conventional and phased arrays technologies to support diverse applications, such as inspection of disks, bars, shafts, billets and plates. All of ScanMaster immersion systems are built from high accuracy scanning frames allowing for scanning of complex parts and include a multi-channel ultrasonic instrument with exceptional performance. The systems are approved by all major manufacturers for C-scan inspection of jet engine forged discs. Together with a comprehensive set of software modules these flexible series of systems provide the customer with the best price performance solutions. > 5 Showcases5 Videos Research and Applications Development For NDT StandECLIPSE SCIENTIFIC The Research and Applications Development (RAD) group is a newly formed team within Acuren dedicat ... ed to tackling challenging inspection problems. Our focus is the development of novel, field deployable, advanced inspection techniques for use in cases where standard NDT methods are ineffective. We don't wait for new innovations, we engineer them. From concept to commissioning. > 3 Showcases5 Videos Cygnus 6+ PRO Multi-Mode Ultrasonic Thickness Gauge StandCygnus Instruments Ltd The Cygnus 6+ PRO thickness gauge is the most advance gauge within the Cygnus range with key featu ... res including: comprehensive data logging; A-scan and B-scan display; manual gain control; Bluetooth connectivity; and much more. With its unique dual display and three measuring modes (Multiple-Echo, Echo-Echo and Single-Echo), this surface thickness gauge offers maximum versatility for inspections. > 5 Showcases5 Videos 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