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 -

NDTSS - Non Destructive Testing Society of Singapore
Come & join the membership of NDTSS, Gain access to international developments.
569 views
Technical Discussions
Terry White
Terry White
04:29 Dec-17-2002
U/T rep rate

We test nickel alloy billet material using basic pulse echo techniques. our method spec calls for a minimum pulse repetition rate of 500PPS. We often experience "wraparound" at this rate and have to lower the rep rate to eliminate the unwanted signals. My question is, why is it so important to maintain that rep rate? What harm could dropping it to 450 - 400 PPS do? Max surface scanning speed is 10 lin. inches per/sec. Transducer is 10 or 5MHz. Beamwidth as measured at .150" metal travel on a #1 FBH cal block is @ .040".


 
 Reply 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 182

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
182
06:46 Dec-17-2002
Re: U/T rep rate
reply:
Hello Terry,

If your scanning speed v is 10"/s and your beam width b is only 0.040", i.e. per shot you cover only 0,040", you need a pulse repetition rate for complete coverage of
frep = v/b.
For your example that means frep = (10"/0.04"s)=250Hz at least.
If you want a factor n for redundancy, i.e. n pulses per beam diameter b, the equation goes to
frep = n v/b.
In your case n=2 means frep = 2 10"/.040"s) = 500 Hz.

You are correct, that this repetition frequency may be too high for low attenuating materials as nickel based alloys are.
The only solution then is to look for the maximum repetition rate fmax you can work with (static), and for scanning to lower the scanning speed until you get full coverage including a safety factor n:
vmax = (b fmax/n)
If you get fmax = 50 Hz, with n = 2 you will get the maximum allowable scanning speed vmax = (0.04" 50/2s)= = 1"/s only.
May be, for lower repetition rates you need a digital ultrasonic instrument, because they have separate screen refreshing rates independent from pulse repetion frequency, whereas with analog instruments the screen refreshing rate is the same as the pulse repetition frequency and for low rates you will not see a constant screen display.

Kind regards
Udo Schlengermann
Agfa NDT GmbH, Huerth, Germany
+++

: We test nickel alloy billet material using basic pulse echo techniques. our method spec calls for a minimum pulse repetition rate of 500PPS. We often experience "wraparound" at this rate and have to lower the rep rate to eliminate the unwanted signals. My question is, why is it so important to maintain that rep rate? What harm could dropping it to 450 - 400 PPS do? Max surface scanning speed is 10 lin. inches per/sec. Transducer is 10 or 5MHz. Beamwidth as measured at .150" metal travel on a #1 FBH cal block is @ .040".
.



 
 Reply 
 

Product Spotlight

YXLON Cougar EVO

Scalable small footprint X-ray inspection systems for assembly and laboratory applications. The
...
YXLON Cougar EVO series was designed to provide the "best-in- class" inspection solutions for SMT, semiconductor, and laboratory assembly applications, while maintaining a small system footprint for maximum convenience. With optimized software and hardware, these systems produce higher quality and more consistent results than other electronics inspection systems currently on the market.
>

Robotic laser shearography enables 100% inspection of complex, flight-critical composite structures

An article in “Composites World Magazine” showcases Non Destructive Testing of aero-structures
...
with Laser Shearography. Over the years Dantec Dynamics has supplied many solutions for the aerospace industry. Referring to specific customer projects several of these cases are examined to outline the advantages of using Laser Shearography for automated defect detection.
>

Immersion systems

ScanMaster ultrasonic immersion systems are designed for high throughput, multi shift operation in a
...
n industrial or lab environment. These fully integrated systems provide various scanning configurations and incorporate conventional and phased arrays technologies to support diverse applications, such as inspection of disks, bars, shafts, billets and plates. All of ScanMaster immersion systems are built from high accuracy scanning frames allowing for scanning of complex parts and include a multi-channel ultrasonic instrument with exceptional performance. The systems are approved by all major manufacturers for C-scan inspection of jet engine forged discs. Together with a comprehensive set of software modules these flexible series of systems provide the customer with the best price performance solutions.
>

HD-CR 35 NDT Computed Radiography System

Portable high-resolution CR scanner for all radiography applications - weld testing, profile images
...
and aerospace. No matter what type of radiographic testing you are performing, the unique TreFoc Technology of the HD-CR 35 NDT imaging plate scanner always guarantees the highest image quality.
>

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