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 -
791 views
Technical Discussions
LANRE ALAPINI
NDT Inspector,
NDT TRAINING AND TESTING CENTRE HOUSTON TEXAS USA, Nigeria, Joined Nov 2008, 3

LANRE ALAPINI

NDT Inspector,
NDT TRAINING AND TESTING CENTRE HOUSTON TEXAS USA,
Nigeria,
Joined Nov 2008
3
06:27 Dec-09-2008
flaw checking

can any body explain the term lack of back wall reflection


 
 Reply 
 
James Boaden
Sales,
Midas NDT Systems Ltd., United Kingdom, Joined Jun 2002, 6

James Boaden

Sales,
Midas NDT Systems Ltd.,
United Kingdom,
Joined Jun 2002
6
07:00 Dec-09-2008
Re: flaw checking
----------- Start Original Message -----------
: can any body explain the term lack of back wall reflection
------------ End Original Message ------------

Using ultrasonics, a signal is generated that reflects back from the back surface of a component (when generated outside the component some sound reflects off the front surface and some penetrates, this then reflects off the back surface).

You should always get reflections from the back surface unless something stops the sound reaching it. Lack of back wall reflection dictates that a defect has stopped the sound reaching the back surface and the area of lack of back surface will be the same as the planar area of the defect.


 
 Reply 
 
S.V.Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 787

S.V.Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
787
07:36 Dec-09-2008
Re: flaw checking
----------- Start Original Message -----------
: can any body explain the term lack of back wall reflection
------------ End Original Message ------------

Lack of back wall reflection or echo means that the transducer is not receiving the ultrasound signal reflected from the back surface (opposite side of the test object). This can happen due to one or more of the following reasons:

It is assumed that the instrument and the probe are working and that the range has been calibrated properly.

Very rough surface resulting in poor coupling

Highly curved surface resulting in sound not entering the test object

Lack of parallelism between the test surface and the back surface, for example a wedge

Sintered material with lot of porosity.

We had some interesting experiences while testing hot rolled austenitic stainless steel plates and tungsten-copper blocks. If any one is interested, I will share. Or I may submit a short case study like paper.

Swamy
NDT Guru





 
 Reply 
 

Product Spotlight

Ultrasonic Squirter/Gantry System

TecScan’s NDT Ultrasonic Gantry Systems are industrial Squirter scanners designed for non-destru
...
ctive quality testing and raster scanning of large structures and parts. The Gantry Systems are usually composed of an Industrial Mechanical Scanner and a Control Room with System Workstation.
>

Conformable wedge transducer

The conformability is obtained with a flexible membrane filled with water between the transducer and
...
the inspected component. The coupling between the membrane and the component requires a small quantity of water or couplant. The conformable wedge combines the acoustic performance of immersion technique with good coupling and low attenuation.
>

Wireless TOFD scanner

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.
>

ISONIC 3510

Very Powerful Superior Performance Extremely Portable Smart Phased Array Ultrasonic Flaw Detector an
...
d Recorder with 2 Conventional UT and TOFD Channels uniquely combines PA, single- and multi-channel conventional UT, and TOFD modalities providing 100% raw data recording and imaging. Suitable for all kinds of every-day ultrasonic inspections
>

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