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 -

840 views
Technical Discussions
Timothy MacInnis
Senior NDT Engineer
SAIC/Ultra Iamge International, USA, Joined Dec 1999, 10

Timothy MacInnis

Senior NDT Engineer
SAIC/Ultra Iamge International,
USA,
Joined Dec 1999
10
07:21 Dec-10-1999
Piezo-Composite UT Elements

I am currently using a piezo-composite element with a positive going square wave pulser. The units have been failing in a slowly, within hours, deteriorating fashion. I have spoke with various xdcr manufacturers and found that the polarization of the element requires a negative going pulse. I have always been able to just pick up a transducer and not worry about pulse polarity. Questions I have: can the elements be selectively polarized upon manufacture? Is there an industry standard stating all pulsers be negative going? Is their an industry standard for the polarization of elements?
Any response will be greatly appreciated.


    
 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1246

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1246
08:49 Dec-10-1999
Re: Piezo-Composite UT Elements
A positive going spike for a pulser is a bit non-standard but it is still
odd that it should cause a depolarisation (especialy so fast).
Is the voltage of the pulse especially high?
Is the duration of the pulse very long?
Are there a lot of cycles in the pulse?
Usually a fairly high temperature would need to be associated with a "depolarising voltage".
Are you running the experiment in a heat experiment?

Ed
: I am currently using a piezo-composite element with a positive going square wave pulser. The units have been failing in a slowly, within hours, deteriorating fashion. I have spoke with various xdcr manufacturers and found that the polarization of the element requires a negative going pulse. I have always been able to just pick up a transducer and not worry about pulse polarity. Questions I have: can the elements be selectively polarized upon manufacture? Is there an industry standard stating all pulsers be negative going? Is their an industry standard for the polarization of elements?
: Any response will be greatly appreciated.




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

Paul Meyer

R & D,
GE Inspection Technologies,
USA,
Joined Nov 1998
47
09:16 Dec-10-1999
Re: Piezo-Composite UT Elements
Hi Tim,
The factors causing dpolarization of a piezoelectric material are electric field, temperature, and time. There are many different piezoelectric materials used in transducer construction and some are more capable of tolerating reverse fields than others. As Ed points out high reverse fields at high temperatures are especially damaging. It's also possible that high rep rates can increase the internal temperature of the probe even though the environment isn't hot. Higher frequency probes use thinner piezoelectric elements which increase the field for the same pulse voltage.
If you can't reverse the pulsed field, you can probably have your probe supplier reverse the piezoelectric element to avoid this effect.
Regards,
Paul

: I am currently using a piezo-composite element with a positive going square wave pulser. The units have been failing in a slowly, within hours, deteriorating fashion. I have spoke with various xdcr manufacturers and found that the polarization of the element requiresa negative going pulse. I have always been able to just pick up a transducer and not worry about pulse polarity. Questions I have: can the elements be selectively polarized upon manufacture? Is there an industry standard stating all pulsers be negative going? Is their an industry standard for the polarization of elements?
: Any response will be greatly appreciated.




    
 
 

Product Spotlight

X-ray CT aids research into defect formation in AM parts

X-ray CT is used to research how additive manufacturing process parameters influence defect format
...
ion in AM parts.
>

High-performance Linear Phased Array Probes

Available to order from stock in a range of 5MHz – 7.5MHz and from 16 to 64 elements. Designed w
...
ith piezo-composite elements, Phoenix phased array probes provide high-resolution imaging to maximise sensitivity; accurate ultrasonic detection and sizing of defects in welds; and effective corrosion mapping. Housed in a rugged stainless steel case for on-site industrial NDT applications.
>

IRIS 9000Plus - Introducing the next generation of heat exchanger inspection.

Representing the seventh generation of the IRIS system, the IRIS 9000 Plus has nearly 200 years of c
...
ombined field inspection experience incorporated in its design. This experience combined with a strong commitment to quality and a history of innovation has made Iris Inspection Services® the undisputed leader in IRIS technology.
>

High-end Ultrasonic Flaw Detector with 32:128PR PAUT and 2-ch TOFD: SyncScan 2

SIUI’s newly launched SyncScan 2, is a high-end ultrasonic flaw detector with 32:128PR PAUT and
...
2-ch TOFD, which can maximize your efficiency for PA and TOFD. ● Support PA/TOFD/UT ● 32-ch PA is more suitable for inspection on extra-thick wall and high-attenuation material. ● 32-ch PA and 2-ch TOFD work simultaneously. ● Support PR mode for corrosion inspection.
>

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