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 -

1757 views
Technical Discussions
Todd Torrence
Todd Torrence
03:15 Oct-04-2000
Snells Law

My co-workers and I were talking about angle beam ultrasonics during break one day. Im not sure how, but started talking about what type of ultrasonic wave would be produced, using contact UT, if the wedge was made out of the same material as the test peice. For example, a steel wedge and a steel plate. There were two opinions, one was the sound wave would refract just as it would if it was a plastic wedge. The second opinion was that the sound wave would not change since the material velocity was the same in both materials. Any thoughts, or votes, on this subject would help settle the bet.



 
 Reply 
 
Massimo Carminati
Consultant
procontrol, Italy, Joined Jul 2000, 6

Massimo Carminati

Consultant
procontrol,
Italy,
Joined Jul 2000
6
06:31 Oct-04-2000
Re: Snells Law
Snell's Law clearly states that same sound velocity means same angle. In other words, a 45° steel wedge would generate a 45° Long beam in steel. Now I have another question for you: what would be the energy transmission coefficient?




 
 Reply 
 
Paul A. Meyer
R & D,
GE Inspection Technologies, USA, Joined Nov 1998, 47

Paul A. Meyer

R & D,
GE Inspection Technologies,
USA,
Joined Nov 1998
47
02:27 Oct-04-2000
Re: Snells Law
: Snell's Law clearly states that same sound velocity means same angle. In other words, a 45° steel wedge would generate a 45° Long beam in steel. Now I have another question for you: what would be the energy transmission coefficient?

The equations for calculating energy partitioning at an interface can be found in textbooks. "Ultrasonic Testing of Materials" by Krautkramer and Krautkramer demonstrates results of solid also "sliding" boundary contact between two solid materials. "Ultrasonic Waves in Solid Media" by Rose gives a more detailed description of the derivation.
Paul


 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1307

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1307
03:06 Oct-04-2000
Re: Snells Law
: : Snell's Law clearly states that same sound velocity means same angle. In other words, a 45° steel wedge would generate a 45° Long beam in steel. Now I have another question for you: what would be the energy transmission coefficient?

: The equations for calculating energy partitioning at an interface can be found in textbooks. "Ultrasonic Testing of Materials" by Krautkramer and Krautkramer demonstrates results of solid also "sliding" boundary contact between two solid materials. "Ultrasonic Waves in Solid Media" by Rose gives a more detailed description of the derivation.
: Paul

The idea for a metal wedge is, on the surface, quite simple; however, most elements used in NDT are operated in the dilational mode. That would mean that a compression mode would be impinging on the metal to metal interface. If you made the wedge 45 degrees you would introduce a bimodal effect. The compression mode would pass into the test piece at 45 degress but for steel there would also be an SV shear mode at about23 degrees.
For steel to steel with an incident compression mode at 45 degrees, the Transmission coefficient for the Long wave would be 0.77 and for the transverse it would be 0.32. These are determined from the equations in Krautkramer as noted by Paul Meyer.



 
 Reply 
 
Rainer Meier
R & D
retired from intelligeNDT Systems & Services, Germany, Joined Nov 1998, 15

Rainer Meier

R & D
retired from intelligeNDT Systems & Services,
Germany,
Joined Nov 1998
15
07:37 Oct-04-2000
Re: Snells Law
: : : Snell's Law clearly states that same sound velocity means same angle. In other words, a 45° steel wedge would generate a 45° Long beam in steel. Now I have another question for you: what would be the energy transmission coefficient?

: : The equations for calculating energy partitioning at an interface can be found in textbooks. "Ultrasonic Testing of Materials" by Krautkramer and Krautkramer demonstrates results of solid also "sliding" boundary contact between two solid materials. "Ultrasonic Waves in Solid Media" by Rose gives a more detailed description of the derivation.
: : Paul

: The idea for a metal wedge is, on the surface, quite simple; however, most elements used in NDT are operated in the dilational mode. That would mean that a compression mode would be impinging on the metal to metal interface. If you made the wedge 45 degrees you would introduce a bimodal effect. The compression mode would pass into the test piece at 45 degress but for steel there would also be an SV shear mode at about 23 degrees.
: For steel to steel with an incident compression mode at 45 degrees, the Transmission coefficient for the Long wave would be 0.77 and for the transverse it would be 0.32. These are determined from the equations in Krautkramer as noted by Paul Meyer.

I agree with Ed: Using a steel wedge you would also normally get two wave modes in your steel-testpiece: a compression mode and a shear mode. (But I didn't douplecheck the transmission coefficients, Ed mentioned).
The reason, because nobody uses steel wedges is the big impedance missmatch bedween steel and the coupling media. This whould cause a strong dependence of the transmitted energy on the width of the coupling gap!
The echo of a reflector could change from 100% (o dB) at a coupling gap of zero to appr. - 14 dB at a coupling gap of a quarter of the wavelength!

Rainer


 
 Reply 
 

Product Spotlight

NDTkit RT

NDTkit RT, TESTIA's Digital Radiography software The NDTkit product line software for X-ray analysi
...
s. NDTkit RT is a software benefiting from the Ultis kernel which is dedicated to radiographic image analysis. It offers a set of tools and filtering processes to assist RT operators in finding relevant flaws.
>

Combination of Digital Image Correlation and Thermographic Measurements

The combination of measuring results from the digital image correlation (ARAMIS, DIC) and temperat
...
ure measuring data from infrared cameras permits the simultaneous analysis of the thermal and mechanical behavior of test specimens in the materials and components testing field.
>

FMC/TFM

Next generation for Phased Array UT is here now with FMC/TFM! Have higher resolution imaging, impr
...
oved signal to noise ratio, characterize, size and analyze defects better with access to several wave mode views and save raw FMC data for higher quality analysis.  Some of the benefits are:
  • Beautiful Image! Easier to understand what you're looking at
  • Completely focused in entire image or volume
  • Much easier to define setups before inspection
  • Easier to decipher geometry echoes from real defects
  • Oriented defects (e.g. cracks) are imaged better
  • See image from different wave modes from one FMC inspection
  • FMC data can be reprocessed/analyzed without going back to the field
>

ISAFE3 Intrinsically Safe Sensor System

ISAFE3 intrinsically safe sensor system of Vallen Systeme is especially targeted at the petrochemica
...
l - as well as oil and gas transportation industry. The sensor system is designed for permanent monitoring or periodic inspection tasks. Sensors are available for different AE-frequency ranges optimized for corrosion and fatigue crack detection and other applications. The ISAFE 3 sensor system consists of an AE-sensor (model ISAS3) certified according to ATEX/IEC for installation in zone 0, gas group IIC, IP68, 20 to +60 °C, and a signal isolator (model SISO3) certified for installation in zone 2. An ISAS3 sensor can be mounted in atmosphere or submerged, e.g. in water or crude oil. It is supported by mounting tools for temporary (magnets) or permanent (welded) installation. ISAFE3 supports automatic sensor coupling test and can be used with any AE signal processor supporting 28V supply at 90 mA peak, e.g. Vallen Systeme ASIP-2/A.
>

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