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Technical Discussions
A U Rehman
R & D
Quaid-e-Azam University, Islamabad, Pakistan, Joined Apr 2001, 11

A U Rehman

R & D
Quaid-e-Azam University, Islamabad,
Pakistan,
Joined Apr 2001
11
05:16 Mar-18-2002
Angular Dependence of Shear Wave Velocities,

Dear Sir ,

Can any one of you have an idea or an equation to calculated the Shear Wave Velocity in Steel for different refracted angles, (e.g. we have 3174 m/s for 51 deg. Refracted Shear in some kind of steel and 3295 m/s for 72 deg. Refracted Shear for the same steel).

Can any one of you have an idea that how this velocity behaves ?
wheter it have a linear relation ?
or some sort of polynomial ?

Please Reply.


 
 Reply 
 
ILYA ETINGEN
ILYA ETINGEN
02:06 Mar-18-2002
Re: Angular Dependence of Shear Wave Velocities,
: Dear Sir ,
.
: Can any one of you have an idea or an equation to calculated the Shear Wave Velocity in Steel for different refracted angles, (e.g. we have 3174 m/s for 51 deg. Refracted Shear in some kind of steel and 3295 m/s for 72 deg. Refracted Shear for the same steel).
.
: Can any one of you have an idea that how this velocity behaves ?
: wheter it have a linear relation ?
: or some sort of polynomial ?
.
: Please Reply.

Shear Wave Velocity in
Steel must be equal for different refracted angles

I.Etingen



 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1304

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1304
03:50 Mar-18-2002
Re: Angular Dependence of Shear Wave Velocities,
Aziz:
The acoustic velocity of shear waves is not always equal in all directions. This special condition only occurs for isotropic materials.
Metals (including steels) are often anisotropic. You can easily see this from the preferred orientation of acicular crystals in a rolled plate.
This will result in acoustic birefringence. A definition for acoustic birefringence would be:
A material property in which anisotropy of shear velocity occurs. It is seen as the velocity difference of two horizontally polarized (SH) shear waves polarized in the principal stress directions, which propagate in the direction perpendicular to the principle stress directions. Velocities along the principle axes of stress are equal only if the principle stresses are equal.

This is in fact why we make effort to assess velocities in pipeline inspections. If the velocity in one plane and angle is significantly higher than for another, the higher refracted angles used in the slower direction could result in totalinternal reflection when used in the fast direction.

Ed


: : Dear Sir ,
: .
: : Can any one of you have an idea or an equation to calculated the Shear Wave Velocity in Steel for different refracted angles, (e.g. we have 3174 m/s for 51 deg. Refracted Shear in some kind of steel and 3295 m/s for 72 deg. Refracted Shear for the same steel).
: .
: : Can any one of you have an idea that how this velocity behaves ?
: : wheter it have a linear relation ?
: : or some sort of polynomial ?
: .
: : Please Reply.
.
: Shear Wave Velocity in
: Steel must be equal for different refracted angles
.
: I.Etingen
.



 
 Reply 
 
A U Rehman
R & D
Quaid-e-Azam University, Islamabad, Pakistan, Joined Apr 2001, 11

A U Rehman

R & D
Quaid-e-Azam University, Islamabad,
Pakistan,
Joined Apr 2001
11
07:05 Mar-18-2002
Re: Angular Dependence of Shear Wave Velocities,
Dear Ed.

But is this relationship is linear, i.e. if We have a shear wave velocity at 51 deg. refracted as 3174 m/s, and the shear wave velocity at 71 deg. refracted as 3294 m/s (i.e. around 6m/s /deg. deviation in refracted angle), then is it correct to say that we might hae the shear wave velocity for 61 deg. refracted as (3174 + 6(61-51)= 3234 m/s), and if it is correct then what about the wave velocities at the angles close to normal, were they follow the same linear pattern ?

Please Clearify,
This would be a great help.

Aziz

: Aziz:
: The acoustic velocity of shear waves is not always equal in all directions. This special condition only occurs for isotropic materials.
: Metals (including steels) are often anisotropic. You can easily see this from the preferred orientation of acicular crystals in a rolled plate.
: This will result in acoustic birefringence. A definition for acoustic birefringence would be:
: A material property in which anisotropy of shear velocity occurs. It is seen as the velocity difference of two horizontally polarized (SH) shear waves polarized in the principal stress directions, which propagate in the direction perpendicular to the principle stress directions. Velocities along the principle axes of stress are equal only if the principle stresses are equal.
.
: This is in fact why we make effort to assess velocities in pipeline inspections. If the velocity in one plane and angle is significantly higher than for another, the higher refracted angles used in the slower direction could result in total internal reflection when used in the fast direction.
.
: Ed
.
:
: : : Dear Sir ,
: : .
: : : Can any one of you have an idea or an equation to calculated the Shear Wave Velocity in Steel for different refracted angles, (e.g. we have 3174 m/s for 51 deg. Refracted Shear in some kind of steel and 3295 m/s for 72 deg. Refracted Shear for the same steel).
: : .
: : : Can any one of you have an idea that how this velocity behaves ?
: : : wheter it have a linear relation ?
: : : or some sort of polynomial ?
: : .
: : : Please Reply.
: .
: : Shear Wave Velocity in
: : Steel must be equal for different refracted angles
: .
: : I.Etingen
: .
.



 
 Reply 
 
Uli Mletzko
R & D, Retired
Germany, Joined Nov 1998, 89

Uli Mletzko

R & D, Retired
Germany,
Joined Nov 1998
89
07:23 Mar-18-2002
Re: Angular Dependence of Shear Wave Velocities,

The mean shear wave velocity of low alloy carbon steels is about 3250 m/s.
Therefore, the values mentioned by Aziz are within a deviation of _only_ one or two percent!

This is within the measuring accuracy of a standard UT instrument, calibrated manually using a standard control block, having average environment conditions (temperature, coupling, wedges of different probes etc.).
IMHO we can say that we have no reasons to assume _anisotropic_ conditions, and from a practical point of view for this _isotropic_ condition we have no angular dependence of shear wave velocity.

Regards
Uli Mletzko
MPA, NDT Group,
University of Stuttgart, Germany


 
 Reply 
 
Shaik Khaja Mohiuddin
Engineering
ST AVIATIONS SERVICES COMPANY LTD, Singapore, Joined Jan 2002, 6

Shaik Khaja Mohiuddin

Engineering
ST AVIATIONS SERVICES COMPANY LTD,
Singapore,
Joined Jan 2002
6
01:49 Mar-19-2002
Re: Angular Dependence of Shear Wave Velocities,
It is tru that the velocity varies with angle, however, the measured velocities(std we are using)are based on stand. atm. condition and the material property w r t the type of ultrasonic wave. As far as practical is concerned the so called difference would be very small or negligible in most of the std sizes of parts we examine. In addition to this we have reference standards, which nullifies the variation, if existing between the part being examined and the reference std.
Anyway, its a good topic to reasearch..we should look into it...at least academically.

Khaja

: Dear Sir ,
.
: Can any one of you have an idea or an equation to calculated the Shear Wave Velocity in Steel for different refracted angles, (e.g. we have 3174 m/s for 51 deg. Refracted Shear in some kind of steel and 3295 m/s for 72 deg. Refracted Shear for the same steel).
.
: Can any one of you have an idea that how this velocity behaves ?
: wheter it have a linear relation ?
: or some sort of polynomial ?
.
: Please Reply.
.



 
 Reply 
 
N.T.Azarov
Engineering
GosNIIGA, Russia, Joined Jan 2000, 12

N.T.Azarov

Engineering
GosNIIGA,
Russia,
Joined Jan 2000
12
04:49 Mar-19-2002
Re: Angular Dependence of Shear Wave Velocities,
: Dear Sir ,
.
: Can any one of you have an idea or an equation to calculated the Shear Wave Velocity in Steel for different refracted angles, (e.g. we have 3174 m/s for 51 deg. Refracted Shear in some kind of steel and 3295 m/s for 72 deg. Refracted Shear for the same steel).
.
: Can any one of you have an idea that how this velocity behaves ?
: wheter it have a linear relation ?
: or some sort of polynomial ?
.
: Please Reply.


Aziz:
For the answer to a question of the author it is necessary to have additional data about measurements, executed by him:
1. Circuit (scheme) of measurements.
2. Materials of a sample and transduser.
3. Condition of realization of measurements - temperature, humidity and others.
4. Evaluation by author of accuracy it of measurements. In this connection to indicated values of speed the author should add an error of measurements, for example,
3174 + _ 300m/s.
5. The values, indicated by the author, of speeds differ on 4 % and, apparently, are connected to errors of experiment.
N.T.Azarov.

.



 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1304

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1304
01:32 Mar-19-2002
Re: Angular Dependence of Shear Wave Velocities,

Aziz:

The anisotropy in rolled steel (and other anisotropic metals) does not permit a simple equation to be applied to make a prediction for the general case of changing refracted angle.
I had to determine values emperically for the work we did on line pipe steels. There some of the differences varied up to 8% in a single sample in the same plane.

The plane across which you sample will result in different changes and not always the same direction of change (e.g. the value may first go down then up again).


Attached are two graphs (forum site)I made some years ago on two different pipe steels. The upper is a spiral seam and the lower a long seam pipe (48 inch diameter submerged arc welded pipe). I was interested in testing the welds that join the pipes so I wanted to know the velocities in the steel along the pipe long axis. In the case of a spiral seamed pipe that means you are passing sound at an angle to the rolling direction (somewhere between 30-40 degrees) but for a long-seam pipe the weld seam and rolling direction are the same so the plane of interest was parallel to the rolling direction.

You see from the graphs that when the refracted angle cuts across the rolling direction at some angle then the fast and slow velocities appear to cross. But when the refracted angles sweep through a plane parallel to rolling the fast and slow velocities do not cross.


Ed



 
 Reply 
 

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