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Technical Discussions
Nathan
Nathan
14:29 Jan-27-2009
ULTRASONICS: Shear/Longitudinal Velocity Calculation...

Think I posted the last reply wrong

Ok. does it change from material to material then? or is there a proper formula?

I was testing Duplex Steel the other day with a measured velocity of .5815
which is between 'Steel, 4150, Rc64' of .582 and Magnesium (O-1) .580.
but the shear velocity has a big jump between the two materials...
We are unable to get a V1 block made out of this kind of steel...

    
 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 847

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
847
17:50 Jan-27-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Nathan at 14:29 Jan-27-2009 (Opening).

Nathan,

I'm a little curious, so I hope you won't mind if I ask a few questions? Is this Duplex Steel a material that you have to inspect on a regular basis? And why can't you get a block made? The reason I'm asking is because has you know, we should use a Calibration Block of similar material properties to what we are inspecting. ASTM E 164 gives you all the dimensions with tolerances for both a U.S. and Metric block.

I often come across similar situation with one of my client and when this arise, we ask him to make a Calibration Block that will suit our inspection requierement. In our case, it may be a little easier because they also have a very large machine shop that will accomodate our needs.

I hope you get your problem resolve.
Cheerio's

    
 
 Reply 
 
Nathan
Nathan
09:20 Jan-28-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Michel Couture at 17:50 Jan-27-2009 .

It was more of a theoretical question really.
I got sent to an offshore platform to get some wall thickness readings on some new carbon steel pipework,when I arrived, I noticed it was Duplex Steel D3N450. So I measured a pipework flange with a micrometer, then used this measurment for the velocity calibration on my Epoch LT.

We will only really be checking this piping for internal erosion, so the exact wall thickness is not 'that' important, however, the amount of loss (if there is going to be any) has to be logged. So, as we'll always use the same velocity, we should be able to calculate the loss.

The reason we can't get a V1 block made is that our supplier can only supply in aluminum, carbon steel or duplex.

    
 
 Reply 
 
TJ
TJ
20:55 Jan-28-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Nathan at 14:29 Jan-27-2009 (Opening).

There is a proper formula......This one is for determination of longitudinal velocity.

Lonigtudinal velocity= the square route of E(1-B)
__________
p(1+B)(1-2B)
where

E = Young's modulus of elasticity
B = the Poisson ratio
p = material density

Have Fun!

TJ

    
 
 Reply 
 
TJ
TJ
20:59 Jan-28-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to TJ at 20:55 Jan-28-2009 .

Longitudinal velocity= the square route of E(1-B) / p(1+B)(1-2B).

Sorry, post got jacked up!
TJ

    
 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 847

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
847
17:26 Jan-29-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Nathan at 09:20 Jan-28-2009 .

Hi Nathan,
I know where you're coming from. At some occasions, I was in the same situation. I relsove my problem by finding a good reliable machine shop and contracted them to do my calibration pieces. It's true that I didn't really have to deal with exotic metals. At the time, being in the aircraft industry, 2024T3, 7075T6 Al and Ti are readily available in my area.

Cheerio's
Michel

    
 
 Reply 
 
Nathan
Nathan
14:56 Feb-04-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Michel Couture at 17:26 Jan-29-2009 .

Tell me about it. it's starting to annoy me a bit.

    
 
 Reply 
 

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