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826 views
00:39 Feb-09-2001

Dave Utrata

R & D,
Center for NDE, Iowa State University,
USA,
Joined Feb 2000
37
distinguishing flaws from martensite

Hello all, have a question for the forum, slightly off course from the other martenstie detection question in thin sheet...

I am looking at friction (inertia) welded, mild steel components. The joint line exhibits significant amounts of martensitic formation, which produce apparent pronounced ultrasonic indications; their presence was verified by metallography, while revealing the absence of flaw/disbond regions. Even after normalizing heat treatment, the indications were quite pronounced.

The question is, can we possibly expect to distinguish between such formations and true flaws? By flaws, I mean regions at the interface which did not fuse during the inertia welding process. It seems as if we won't be able to see through the microstructural reflections and find flaws. But based on other samples, the process is not fully under control, and such a lack of fusion does indeed occur on occasion.

My kind thanks to any responses,
Dave Utrata


 
01:06 Feb-09-2001

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
247
Re: distinguishing flaws from martensite : Hello all, have a question for the forum, slightly off course from the other martenstie detection question in thin sheet...
.
: I am looking at friction (inertia) welded, mild steel components. The joint line exhibits significant amounts of martensitic formation, which produce apparent pronounced ultrasonic indications; their presence was verified by metallography, while revealing the absence of flaw/disbond regions. Even after normalizing heat treatment, the indications were quite pronounced.
.
: The question is, can we possibly expect to distinguish between such formations and true flaws? By flaws, I mean regions at the interface which did not fuse during the inertia welding process. It seems as if we won't be able to see through the microstructural reflections and find flaws. But based on other samples, the process is not fully under control, and such a lack of fusion does indeed occur on occasion.
.
: My kind thanks to any responses,
: Dave Utrata


Dave:
Ever try to send sound through 2 Jo blocks that have been wrung together? Try it.

What you get is sound goes right through with little loss and little relection. This is what LOF will show like on these welds.

Been there done that 20 years ago. Has anything changed since then to make it any better? I do not think so. If there is I am all ears.

Dent


 
02:28 Feb-09-2001
M. W. Moyer
Re: distinguishing flaws from martensite You don't even need gage blocks. I once set up two blocks under compressive load. The amplitude of the reflection was inversely proportional
to the load. At yield, the reflection was essentially zero. When I unloaded the system the blocks fell apart. What happens is at zero load,
only a few high points touch. As the load increases, the high point yield and more of the area is in contact until at yield the whole surface
is in contact. Since the sound wave has a very low pressure amplitude (a few psi) compared with the load, the wave is transmitted through the
interface with little or no reflection.

When ever you have an interface that is under a compressive load sound can easily travel through the interface. We have seen this condition in
partially penetrated welds. We got no reflection from the unwelded interface below the weld because it was under compression. Eddy current inspections
can suffer from the same problem.

M. W. Moyer


: Dave:
: Ever try to send sound through 2 Jo blocks that have been wrung together? Try it.
.
: What you get is sound goes right through with little loss and little relection. This is what LOF will show like on these welds.
.
: Been there done that 20 years ago. Has anything changed since then to make it any better? I do not think so. If there is I am all ears.
.
: Dent
.



 
09:30 Aug-29-1998
Ricardo Ortiz Alcantar
Asking for information about a especiality or a master degree about presstressing Hello,
I am from Guadalajara, Jalisco MEXICO, i am civil engineering, and i am looking to study about prestressing at some university or instute in USA or in Europe (Spain, France ), so i would like to know about it, and if you know some school in this speciality please let me know.

Gracias
Ricardo Ortiz



 
00:54 Dec-20-1999
Leslie Chong
Re: Asking for information about a especiality or a master degree about presstressing : Hello,
Pls tell me about the methods of prestressing
Thank you



 


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