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mansoor ali
India, Joined Jan 2015, 5

mansoor ali

India,
Joined Jan 2015
5
11:15 Apr-02-2016
Mode conversion in UT

Due to mode convertion the longitudinal wave produce shear wave at some angle.
Is there any possible the shear wave produce longitudinal wave inside the material due to angular backwall .Please explain about the above doubt.

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 815

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
815
13:12 Apr-02-2016
Re: Mode conversion in UT
In Reply to mansoor ali at 11:15 Apr-02-2016 (Opening).

Good Question.
45 degree refracted Longitudinal wave when incident on ID notches mode convert to shear wave at every reflection and lose 16 dB
45 degree refracted shear wave result in full reflection from ID notches. The mode conversion of shear waves occurs for angles less than 32.6 degrees. So there is some loss of energy due to mode conversion at 60 degree (90-60 = 30) and 70 degrees (90-70 = 20 degrees).

 
 Reply 
 
Mark
NDT Inspector
USA, Joined Oct 2009, 52

Mark

NDT Inspector
USA,
Joined Oct 2009
52
18:19 Mar-21-2019
Re: Mode conversion in UT
In Reply to Anmol Birring at 13:12 Apr-02-2016 .

Anmol,

Are you saying that the mode conversation happens off the back side of the plate or off of the vertical ID notch?

 
 Reply 
 
Darryl Carnall
Darryl Carnall
15:23 Apr-04-2019
Re: Mode conversion in UT
In Reply to Mark at 18:19 Mar-21-2019 .




TO 33B-1-1 NONDESTRUCTIVE INSPECTION METHODS, BASIC THEORY
Page 477 Section 5.5.3.5 Internal Mode Conversion
A frequently misinterpreted form of mode conversion found in the field is shear wave converted to longitudinal. For example, on an H-3 sleeve and spindle inspection using a 45° transducer to inspect a large radius or bore, a non-relevant indication occurs in the area of interest as a result of this conversion (Figure 5-62). At a certain transducer position, part of the shear wave will convert to longitudinal as it reflects from the bore. This longitudinal wave (paragraph 5.2.3.1) will travel at double the velocity of the shear wave and will be reflected to the surface, then back to the bore. It then returns to the transducer to cause a non-relevant indication similar to a crack indication. In this case, finger damping the part surface where the longitudinal wave reflects off of the part surface in front of the transducer will identify the indication as non-relevant.

 
 Reply 
 

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