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 -

864 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

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.
>

NOVO Armor 15 & NOVO Armor 22

The Armor Kit Contains the NOVO Armor, which provides additional mechanical protection to the NOVO 1
...
5WN & NOVO 22WN Detectors, the Armor Stand and a traveling soft cover. - Newest shock absorbent technology case - Water resistant design - Supports wired & wireless communication - Multiple positioning options - Tripod connection using the Built-in 1/4” threads - Simple Detector battery replacement
>

Portable Ground Penetrating Radar - Proceq GP8000

The Proceq GP8000 portable ground penetrating radar instrument is the beginning of a new era in ND
...
T. The outstanding, patented ultra- wideband technology combined with a compact wireless probe delivers unmatched industry performance. Proceq GP8000 is the world’s first large-scale inspection solution that utilizes Augmented Reality in industrial applications.
>

On Demand Webinar: Using Eddy Current Array for Large Areas in Place of Magnetic Particle and Liquid Penetrant Testing

New on-demand webinar on the use of eddy current array (ECA) technology in lieu of liquid penetrant
...
testing (PT) and magnetic particle testing (MT) for large area screenings. The webinar includes an introduction to the technologies with advantages and disadvantages of each. Side by side examples are discussed including aircraft stringers, engine blades, forgings, weld plates & more. View it today.
>

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