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 -

386 views
Technical Discussions
John Brunk
Engineering, NDT Level III
Self employed, part-time, USA, Joined Oct 1999, 158

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
158
05:55 Oct-11-2000
temperature effects on plastic wedges

When performing angle beam testing of metals, there is a change in beam angle with temperature. This happens because the velocity change in plastic wedge materials for a given temperature change is larger than the change in the metal.
Beam angle increases with increasing temperature. The effect is most likely to be noticed when testing at high temperatures with a 70 degree wedge. Surface waves can drive you crazy. It has to be almost too cold to work to get
longitudinal waves with a 45 degree wedge. The more common problem is to be wrong about the location of the reflector because of the change in beam angle. I don't have the data with me and won't trust my memory for the numbers; but
I wrote an article about this for Materials Evaluation about 1987. I noticed this problem a couple of years earlier working outside in Wyoming in the winter. Different plastics used for wedges have different temperature coefficients.
If you keep your angle beam calibration reference at the same temperature as the test object, and keep track of the actual angle and attenuation as the temperature changes, that should take care of most problems unless you really have
to have a specific beam angle for a good reason. Attenuation changes can also be due to effects on the couplants.


    
 
 
William Friedman
R & D,
Lockheed Martin, USA, Joined Nov 1998, 6

William Friedman

R & D,
Lockheed Martin,
USA,
Joined Nov 1998
6
05:12 Oct-12-2000
Re: temperature effects on plastic wedges
: When performing angle beam testing of metals, there is a change in beam angle with temperature. This happens because the velocity change in plastic wedge materials for a given temperature change is larger than the change in the metal.
:
The problem I described in attenuation change occurs just as much when angle beams are not used so I don't think we are seeing an effect that occurs because of a change in angle. The difficulty is that even with a straight beam you might undercall the size of a flaw due when the temperature of the acrylic holder used to couple the transducer to the part.

William Friedman


    
 
 

Product Spotlight

TVC awarded UKAS accreditation

TVC are delighted to finally announce we have been awarded UKAS accreditation for our calibration
...
laboratory. Laboratory accreditation to ISO/IEC 17025:2005 enables us to conduct the Electrical Verification of Ultrasonic Flaw Detection Equipment to BS EN 12668-1:2010. It has taken many months of hard work and we want to thank our staff for all their efforts during this massive undertaking.
>

Semi-Automated Phased Array Immersion System for Small Composite Parts

Turn-key semi-automated system as an improved and affordable solution for inspection of small comp
...
osite parts. Includes support table, immersion tank, scanner, PA instrument, PC, Analysis software, database, wedge management and other options.
>

Echomac® PA Rail Wheel Tester

MAC introduces two versions of Rail Wheel Testers using ECHOMAC® PA platform based on customer requ
...
irements.
>

Lyft™: Pulsed Eddy Current Reinvented

PEC Reinvented—CUI Programs Redefined Corrosion under insulation (CUI) is possibly the greatest u
...
nresolved asset integrity problem in the industry. Current methods for measuring wall thickness with liftoff, without removing insulation, all have severe limitations. Eddyfi introduces Lyft — a reinvented, high-performance pulsed eddy current (PEC) solution. The patent- pending system features a state-of-the-art portable instrument, real- time C-scan imaging, fast data acquisition with grid-mapping and dynamic scanning modes, and flexibility with long cables. It can also scan through thick metal and insulation, as well as aluminum, stainless steel, and galvanized steel weather jackets. Who else but Eddyfi to reinvent an eddy current technique and redefine CUI programs. Got Lyft?
>

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