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 -

861 views
Technical Discussions
Mario Belo
NDT Inspection
Trenes Buenos Aires, Argentina, Joined Jan 2000, 7

Mario Belo

NDT Inspection
Trenes Buenos Aires,
Argentina,
Joined Jan 2000
7
00:16 Nov-02-2000
Corrections calculation

Dear experts:

Is it possible, to determine the transference corrections (surface and attenuation) from a reference block with endless wall (V1/5) to an unknown flaw (smaller than the beam) in a certain piece with different acoustic characteristics and a different surface, which does not present backwall, through the correspondent AVG (DGS) diagram?
An example would be welcome.

Best regards,

Mario Belo



 
 Reply 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 183

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
183
09:35 Nov-14-2000
Re: Corrections calculation
reply by Udo Schlengermann

If you calibrate on a block which has different material and surface than the test object, this is not possible, for the following reasons:
Four different losses determine the signal amplitude:
1. divergence - depending on the frequency, the roughness and the size of the contact area.
2. attenuation - in reference block and test object.
3. transmission losses - if the materials are different for both objects (acoustical impedances).
4. reflectivity of reflectors - calibration reflector and detected discontinuity.

The DGS diagram is designed for a full size contact (effective transducer diameter) and a material without attenuation.
Most standards therefore allow DGS method only if the curvature compared to transducer size is below a limit.
Transfer losses on curved, rough objects therefore are only valid for a given contour and roughness, and a defined distance of reflectors, i.e. they change with distance, if attenuation is not comparably equal on both objects.
Before using transfer losses, they have to be determined on a test block having the same curvature and the same roughness as the test object, containing the same reflector (e.g. backwall) at the same distance than your calibration block. Then losses no 4. and 3. are constant in both cases and the remaining difference to the DGS-curve is the transfer loss (attenutation and transmission losses).
It is therefore necessary to have at least one reflector of known size and distance in the test object. You cannot determine transfer losses using an unknown reflector.

Kind regards

Udo Schlengermann
++++++
: Dear experts:

: Is it possible, to determine the transference corrections (surface and attenuation) from a reference block with endless wall (V1/5) to an unknown flaw (smaller than the beam) in a certain piece with different acoustic characteristics and a different surface, which does not present backwall, through the correspondent AVG (DGS) diagram?
: An example would be welcome.

: Best regards,

: Mario Belo




 
 Reply 
 

Product Spotlight

NDT.net launches mobile-friendly design

NDT.net has revamped its website providing a mobile-friendly design.The front page received a comp
...
letely new design and all other sections are now reacting responsively on mobile devices. This has been a major step to make our website more user- friendly.
>

Cygnus 6+ PRO Multi-Mode Ultrasonic Thickness Gauge

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.
>

Varex Imaging Large Field of View (FOV) Digital Detector Arrays (DDAs)

A larger FOV DDA can reduce the space and volume of the X-ray inspection system on the factory floor
...
, enable faster scanning times, better throughput and better resolution images at a lower dose. Customers can also save time and money. With these benefits in mind, Varex Imaging has designed a family of large FOV detectors (4343HE, XRD 1611, 4343DX-I, 4343CT) for our industrial imaging customers.
>

MUSE Mobile Ultrasonic Equipment

The MUSE, a portable ultrasonic imaging system, was developed for in-field inspections of light-weig
...
ht structures. The MUSE consists of a motor-driven manipulator, a water circulation system for the acoustic coupling and a portable ultrasonic flaw detector (USPC 3010). The MUSE provides images of internal defects (A-, B-,C- and D-scan).
>

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