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Technical Discussions
Yasu Ohgi
Yasu Ohgi
04:24 Feb-13-2000
Very Tight Cracks

Dear Sir.
I am an NDT engineer for machanical parts occupied Japanese company.
My problem is the method of detecting very tight and small cracks occured at the non ferrous casted parts edge.
The cracks are too tight to detect by PT, and it is hard to apply ET because of its lift-off characterization.
Someone who has a good idea, please imform me.
Regards.



    
 
 
Robert (Rocky) A. Day
Engineering
Milky Way Jewels, USA, Joined Nov 1998, 40

Robert (Rocky) A. Day

Engineering
Milky Way Jewels,
USA,
Joined Nov 1998
40
06:38 Feb-13-2000
Re: Very Tight Cracks
There are several things you can try. Tightly closed cracks are often a challenge for most NDT methods.

- Use a more sensitive penetrant, e.g. fluorescent.
- Not knowing your geometry I do not know if eddy current could be adapted but you might send samples for evaluation. I would be happy to look at them if you wish.
- Ultrasonics should be considered as well. Same geometry problem as eddy current. Again most vendors would be happy to look at samples.
- Try opening the crack by applying tension to the part in such a way the crack is opened. You can try cycling the tension while the penetrant dwells to see if you can work penetrant into the crack (this is sometimes called winking). This can also sometimes be done with heat.


: Dear Sir.
: I am an NDT engineer for machanical parts occupied Japanese company.
: My problem is the method of detecting very tight and small cracks occured at the non ferrous casted parts edge.
: The cracks are too tight to detect by PT, and it is hard to apply ET because of its lift-off characterization.
: Someone who has a good idea, please imform me.
: Regards.




    
 
 
Quan Zhang
Quan Zhang
08:52 Feb-14-2000
Re: Very Tight Cracks
Dear Yasu Ohgi:
What I suggest you do, contact maintainence base of big airline company, they are very experience to do PT on non ferous metal parts, you will win.
Regards.




    
 
 
M Daehling
Engineering, NDI Administrator
Bombardier Aerospace, USA, Joined Oct 1999, 5

M Daehling

Engineering, NDI Administrator
Bombardier Aerospace,
USA,
Joined Oct 1999
5
07:59 Feb-18-2000
Re: Very Tight Cracks
Dear Sir.

I found the following website that might interest you. Krypton Gas penetrant imaging might work in your application.
http://www.asnt.org/publications/materialseval/solution/decsolutions/decsolutions.htm

Good Luck

: Dear Sir.
: I am an NDT engineer for machanical parts occupied Japanese company.
: My problem is the method of detecting very tight and small cracks occured at the non ferrous casted parts edge.
: The cracks are too tight to detect by PT, and it is hard to apply ET because of its lift-off characterization.
: Someone who has a good idea, please imform me.
: Regards.




    
 
 
J. Mark Davis
Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama, USA, Joined Mar 2000, 85

J. Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
00:58 Feb-24-2000
Re: Very Tight Cracks
Yasu,


Do you have access to the crack initiation side of the component? Have you considered ID or OD Creeping Waves?

I have successfully detected cracks at about 0.005" of an inch with a Creeping Wave.

What is the grain size of the component? Please check out the Advanced UT Flaw Sizing Handbook for a description of the Creeping Technology. It is in the NDT.net library.

J. Mark Davis

: Dear Sir.
: I am an NDT engineer for machanical parts occupied Japanese company.
: My problem is the method of detecting very tight and small cracks occured at the non ferrous casted parts edge.
: The cracks are too tight to detect by PT, and it is hard to apply ET because of its lift-off characterization.
: Someone who has a good idea, please imform me.
: Regards.




    
 
 

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