where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
2813 views
Articles & News
Ali
NDT Inspector,
Iran, Joined Mar 2013, 117

Ali

NDT Inspector,
Iran,
Joined Mar 2013
117
08:24 Jan-03-2015
Photoelastic Visualisation of Phased Array Sound Fields: Part 19 – Formation of grating lobes
Overall

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
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 
 

Product Spotlight

Eddy Current inspection : RotoETscan Rotating Head

The rotating head RotoETscan detects the presence of longitudinal surface or sub surface defects a
...
t high speed. The rotating head is often installed directly on the production line. It is generally dedicated to the control of long products such as tubes, bars and wires, made of ferrous or non-ferrous material. It can also be used for inspection of small parts (billets).
>

AIS229 - Multipurpose Real Time System

Latest standard & automatic real time system developed by Balteau. The AIS229 has been designed to
...
do series inspection in a wide variety of industry. Composed of a shielded cabinet, 5 axis manipulator, x-ray generator and tubehead from 160kV to 225kV, a fl at panel & much more, the AIS229 is most certainly one of the most multipurpose RTR system available on the market.
>

CIVA 2020 UT Module

CIVA NDE Simulation Software is the world leader of NDT Simulation. The UT simulation Module incl
...
udes: - "Beam computation": Beam propagation simulation - "Inspection Simulation": Beam interaction with flaws or specimens The user can simulate a whole inspection process (pulse echo, tandem or TOFD) with a wide range of probes (conventional, Phased- arrays or EMAT), components, and flaws.
>

FD800 Bench Top Flaw Detectors

The bench-top FD800 flaw detector range combines state-of-the-art flaw detection with advanced mater
...
ial thickness capabilities. Designed for use in the laboratory these gauges are the tool you need for all your flaw detecting needs.
>

Share...
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