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Technical Discussions
Philip
Philip
07:58 Jul-20-2005
Lateral Wave vs. Longitudinal Wave

How would it be possible to demonstrate that the ratio between lateral wave velocity and longitudinal wave velocity is the same for all kind of materials?
Is there some theoritical principles developed concerning this topic?


    
 
 
Godfrey Hands
Engineering,
PRI Nadcap, United Kingdom, Joined Nov 1998, 288

Godfrey Hands

Engineering,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
288
07:52 Jul-21-2005
Re: Lateral Wave vs. Longitudinal Wave
----------- Start Original Message -----------
: How would it be possible to demonstrate that the ratio between lateral wave velocity and longitudinal wave velocity is the same for all kind of materials?
: Is there some theoritical principles developed concerning this topic?
------------ End Original Message ------------

Philip,
They are not always in the same ratio.
Let me give you some examples:
Aluminium Long. 6320; Transv. 3130, i.e. 2:1
Gold Long. 3240; Transv. 1200, i.e. 2.7:1
Hardmetal Long. 6800; Transv. 4000, i.e.1.7:1
Steel Long. 5940; Transv. 3250, i.e. 1.8:1
Lead Long. 2160; Transv. 700, i.e. 3.1:1

Regards,

Godfrey Hands


    
 
 
Philip
Philip
08:55 Jul-21-2005
Re: Lateral Wave vs. Longitudinal Wave
I am not talking about shear wave, but LATERAL wave (or creeping, surface wave) vs LONGITUDINAL wave (compression)

----------- Start Original Message -----------
: : How would it be possible to demonstrate that the ratio between lateral wave velocity and longitudinal wave velocity is the same for all kind of materials?
: : Is there some theoritical principles developed concerning this topic?
: Philip,
: They are not always in the same ratio.
: Let me give you some examples:
: Aluminium Long. 6320; Transv. 3130, i.e. 2:1
: Gold Long. 3240; Transv. 1200, i.e. 2.7:1
: Hardmetal Long. 6800; Transv. 4000, i.e.1.7:1
: Steel Long. 5940; Transv. 3250, i.e. 1.8:1
: Lead Long. 2160; Transv. 700, i.e. 3.1:1
: Regards,
: Godfrey Hands
------------ End Original Message ------------





    
 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1228

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1228
04:03 Jul-22-2005
Re: Lateral Wave vs. Longitudinal Wave
Philip:
This is an interesting question in that it ties together some of the controversial aspects of nomenclature in ultrasonics.
The book "Engineering Applications of Ultrasonic Time-of-Flight Diffraction" by Charlesworth and Temple (second edition) discusses the wave modes and terminology used in TOFD. They define the compression wave travelling parallel to a flat surface as a "lateral wave". They also note that this is referred to by some authors as the "creeping wave". In their book, Charlesworth and Temple reserve the term "creeping wave" for those waves which follow curved surfaces.

The most comprehensive coverage on the topic I have read is by Langenberg "On the Nature of the So-Called Subsurface Longitudinal Wave and/or the Surface Longitudinal "Creeping" Wave", K.J.Langenberg, P. Fellinger, R. Marklein, Research in Nondestructive Evaluation, Springer-Verlag, 1990, pp 61-81
(This paper disproves the existance of a separate wave being identified as a "creeping wave").

The "lateral wave" in TOFD can be considered the shortest path between the transmitter and reciever in the inspection medium. (Charlesworth and Temple refer to it as the "direct subsurface signal").

Photoelastic imaging of waves verifies the postulation that 2 separate waves (compression and creeping) do not exist. Further evidence for this is in the formation of the headwave off the free boundary. Only a single headwave is seen and its shape is that of the boundary (i.e. the headwave is flat on a flat surface and curved on a curved surface). If two separate waves existed at separate velocities then the glancing incidence of the two would generate 2 headwaves with slightly different angles. This is definitely not the case so the lateral wave (creeping wave) is not separate from the longitudinal (compression) wave.

Regards
Ed

----------- Start Original Message -----------
: How would it be possible to demonstrate that the ratio between lateral wave velocity and longitudinal wave velocity is the same for all kind of materials?
: Is there some theoritical principles developed concerning this topic?
------------ End Original Message ------------




    
 
 
Philip Ducharme
Philip Ducharme
06:48 Jul-26-2005
Re: Lateral Wave vs. Longitudinal Wave
Ed,
This is very interresting!

If my understanding is right, you're telling that Lateral wave is nothing else than longitudinal wave. This would mean a velocity ratio Lateral/Longitudinal equal to one (1) (velocity should be the same for Lateral wave than for Longitudinal wave).

But from my own tests in lab, I have got a ratio of 0.87 ±0.02 on four (4) different materials. If the theorie you are talking about is correct this would mean that my set up was wrong...

AT least, now I can deduce that the velocity ratio is the same for every single material.

Regards,

Philip

----------- Start Original Message -----------
: Philip:
: This is an interesting question in that it ties together some of the controversial aspects of nomenclature in ultrasonics.
: The book "Engineering Applications of Ultrasonic Time-of-Flight Diffraction" by Charlesworth and Temple (second edition) discusses the wave modes and terminology used in TOFD. They define the compression wave travelling parallel to a flat surface as a "lateral wave". They also note that this is referred to by some authors as the "creeping wave". In their book, Charlesworth and Temple reserve the term "creeping wave" for those waves which follow curved surfaces.
: The most comprehensive coverage on the topic I have read is by Langenberg "On the Nature of the So-Called Subsurface Longitudinal Wave and/or the Surface Longitudinal "Creeping" Wave", K.J.Langenberg, P. Fellinger, R. Marklein, Research in Nondestructive Evaluation, Springer-Verlag, 1990, pp 61-81
: (This paper disproves the existance of a separate wave being identified as a "creeping wave").
: The "lateral wave" in TOFD can be considered the shortest path between the transmitter and reciever in the inspection medium. (Charlesworth and Temple refer to it as the "direct subsurface signal").
: Photoelastic imaging of waves verifies the postulation that 2 separate waves (compression and creeping) do not exist. Further evidence for this is in the formation of the headwave off the free boundary. Only a single headwave is seen and its shape is that of the boundary (i.e. the headwave is flat on a flat surface and curved on a curved surface). If two separate waves existed at separate velocities then the glancing incidence of the two would generate 2 headwaves with slightly different angles. This is definitely not the case so the lateral wave (creeping wave) is not separate from the longitudinal (compression) wave.
: Regards
: Ed
: : How would it be possible to demonstrate that the ratio between lateral wave velocity and longitudinal wave velocity is the same for all kind of materials?
: : Is there some theoritical principles developed concerning this topic?
------------ End Original Message ------------




    
 
 
M. Kim Johnson
M. Kim Johnson
09:48 Jul-26-2005
Re: Lateral Wave vs. Longitudinal Wave
Please be careful of terminology. It sounds as if you may be using the term *lateral wave* when you mean *shear wave*. There are two velocities of transmission for a material - the longitudinal wave (picture sound waves with compression fronts such as sound in air) and the shear wave (picture ocean waves). They are different. I have seen ratios from less that 0.5 to close 1.0, with some exceptions. I do not know why you would be getting measurements as close as you are for different materials, unless you are measuring very similar materials such as different alloy mixtures using the same base (iron, Al, etc.). I would suggest a trip to Google for some basic definitions and drawings on this topic before you procede further!

Good luck!

Kim

----------- Start Original Message -----------
: Ed,
: This is very interresting!
: If my understanding is right, you're telling that Lateral wave is nothing else than longitudinal wave. This would mean a velocity ratio Lateral/Longitudinal equal to one (1) (velocity should be the same for Lateral wave than for Longitudinal wave).
: But from my own tests in lab, I have got a ratio of 0.87 ±0.02 on four (4) different materials. If the theorie you are talking about is correct this would mean that my set up was wrong...
: AT least, now I can deduce that the velocity ratio is the same for every single material.
: Regards,
: Philip
: : Philip:
: : This is an interesting question in that it ties together some of the controversial aspects of nomenclature in ultrasonics.
: : The book "Engineering Applications of Ultrasonic Time-of-Flight Diffraction" by Charlesworth and Temple (second edition) discusses the wave modes and terminology used in TOFD. They define the compression wave travelling parallel to a flat surface as a "lateral wave". They also note that this is referred to by some authors as the "creeping wave". In their book, Charlesworth and Temple reserve the term "creeping wave" for those waves which follow curved surfaces.
:: The most comprehensive coverage on the topic I have read is by Langenberg "On the Nature of the So-Called Subsurface Longitudinal Wave and/or the Surface Longitudinal "Creeping" Wave", K.J.Langenberg, P. Fellinger, R. Marklein, Research in Nondestructive Evaluation, Springer-Verlag, 1990, pp 61-81
: : (This paper disproves the existance of a separate wave being identified as a "creeping wave").
: : The "lateral wave" in TOFD can be considered the shortest path between the transmitter and reciever in the inspection medium. (Charlesworth and Temple refer to it as the "direct subsurface signal").
: : Photoelastic imaging of waves verifies the postulation that 2 separate waves (compression and creeping) do not exist. Further evidence for this is in the formation of the headwave off the free boundary. Only a single headwave is seen and its shape is that of the boundary (i.e. the headwave is flat on a flat surface and curved on a curved surface). If two separate waves existed at separate velocities then the glancing incidence of the two would generate 2 headwaves with slightly different angles. This is definitely not the case so the lateral wave (creeping wave) is not separate from the longitudinal (compression) wave.
: : Regards
: : Ed
: : : How would it be possible to demonstrate that the ratio between lateral wave velocity and longitudinal wave velocity is the same for all kind of materials?
: : : Is there some theoritical principles developed concerning this topic?
------------ End Original Message ------------





    
 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1228

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1228
00:13 Jul-26-2005
Re: Lateral Wave vs. Longitudinal Wave

Philippe:
A picture is worth a thousand words.
Here is an actual TOFD probe on glass. The probe is 6mm diameter 5MHz (KB Benchmark series). The wedge is a nominal 60°L but because the glass has a velocity of 5970m/s L and 3700m/s S, the L wave is about 62°. All the main waves are seen and no creeping wave or lateral wave is made that is 87% of the L wave. But all these waves are predicted from finite element modelling. One of the authors in the paper I quoted is Dr. Langenberg in Germany. He had an article on the NDT.net:
http://www.ndt.net/article/ecndt02/195/195.htm

In that article he illustrated the same effects that I have imaged above! I pasted them below.

The importance of a small diameter probe for TOFD is evident because of the strong arc signals that can cause annoying late arrival signals. Usually these are weak enough that the flaw indications do not provide a large indication from them.

Fig 3: Time-domain EFIT ultrasonic transducer modelling in the 2-D pressureshear vertical (P-SV) case: a) longitudinal 0° wave transducer; b) longitudinal 30° wave transducer; c) longitudinal 70° wave transducer; d) subsurface longitudinal wave transducer; e) shear 45° wave transducer; f) Rayleigh wave transducer.

Salut
Ed



    
 
 
Vito Massarelli
Vito Massarelli
01:00 Apr-10-2012
Re: Lateral Wave vs. Longitudinal Wave
In Reply to M. Kim Johnson at 09:48 Jul-26-2005 .

Thanks a lot.
The info that everybody release in the forum was a lot helpfull.

You are gret people

    
 
 

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