Laser welding 1

[Ndtmetal]

I have to create on purpose very small defects (>4mm) on Al stainless steel and 304L welds (by laser welding).The reason for doing that is to check a if a new NDT system can detect them.
The thickness of the samples will be 2, 5 and 10cm.
Do you think that I will be able to creat very small cracks by rapid water cooling after the welding or is there any other way?

 

[metengr]

Ndtmetal;
Your process for introducing weld defects will not be controlled. I would suggest you EDM notches and small flat bottom holes to simulate defects.

 

[Ndtmetal]

I have never heard about EDM notches can you please be more specific? What exacly are they?

 

[TVP]

Ndtmetal,

What metengr is suggesting is a standard industry technique using Electrical Discharge Machining (EDM) to introduce a linear defect of a certain known width for calibrating NDT equipment. It is the de facto standard for calibrating eddy current detectors used in the welding of tubes. Machining holes into a surface is another commonly used technique, but I will let others comment specifically on how to create them. The following link is a Google search using EDM + notch + eddy current:

http://www.google.com/search?hl=en&q=EDM+notch+eddy+current

 

[metengr]

You can search the Internet. Here is some information for starters;

http://www.phtool.com/pages/edm.asp

 

[Flesh]

There may not be enough heat input during your laser welding, but you could try a weld-restraint crack test. Such as the varestraint test, transvarestraint test, or circular-patch test. All of these are intended to create cracking in or adjacent to the weld and then indexed.

 

[EdStainless]

Where are you located? There is a company in the eastern US called P.H. Tool that is one of the best at making these EDM reference notches.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Robertmet]

Back in the late '60s I was involved in making standards for ultrasonic testing .This was in the early days of EDM and even UT.We used copper wire about .005" dia to drill EDM holes .This had never been done before as I remember so we had to be creative !! Much better than trying to create uncontrolled cracks in welds !!

 

[arunmrao]

Ndt metal.

It appears that you are not familiar with the engineering of developing calibration blocks. You might consider sourcing them for now,till you learn the different aspects of machining etc.

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[Ndtmetal]

Thank you all for your replies,
you have been really helpful.
I have to say that I work in Geneva,Cern and the NDT method we want to check is digital radiography.
Not ultrasonic nor eddy.

Thanks again!

 

[CoryPad]

Regardless of the NDT method, they all can use similar test blocks. EDM is the preferred method for manufacturing these. If you are ignorant of this method, you can find a lot of information from a simple Google search.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[arunmrao]

For radiography,reference standards are available from ASTM. You need some professional advice to guide you and this forum might not be the right place.

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)