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Technical Discussions
Gowrishankar
R & D, scientist
ISRO, India, Joined Nov 2008, 34

Gowrishankar

R & D, scientist
ISRO,
India,
Joined Nov 2008
34
05:27 Mar-03-2005
CASTING DEFECT - SHRINKAGE

Sir,
I have a doubt.I am working in X-Ray radiography area dealing with Casting radiography for aerospace quality components.most of catings having shrinkage defect. Can you please help me in answering my following questions.
1. What is shrinkage?and its physical significance? how it appearance in film?

2. How far Shrinkage can be relaxed for Aero space structural components( Highly stressed and medium stressed) ?

3.shrinkage relaxation for non structural members? and upto what extent it is allowed?

If all these above defects already exceeds in size with respect to ASTM Code, on what basis i can accept the hardware if required?
if you find some literature and figures please give me details of books and standards.
thanking you sir,
gowrishankar



 
 Reply 
 
Daniel H Rice
Daniel H Rice
05:30 Mar-04-2005
Re: CASTING DEFECT - SHRINKAGE

----------- Start Original Message -----------
: Sir,
: I have a doubt.I am working in X-Ray radiography area dealing with Casting radiography for aerospace quality components.most of catings having shrinkage defect. Can you please help me in answering my following questions.
: 1. What is shrinkage?and its physical significance? how it appearance in film?
: 2. How far Shrinkage can be relaxed for Aero space structural components( Highly stressed and medium stressed) ?
: 3.shrinkage relaxation for non structural members? and upto what extent it is allowed?
: If all these above defects already exceeds in size with respect to ASTM Code, on what basis i can accept the hardware if required?
: if you find some literature and figures please give me details of books and standards.
: thanking you sir,
: gowrishankar
------------ End Original Message ------------

shrinkage is formed during the solidification process in most cast materials. This is due in part by the change in physical sized causing stress forces to peak near square edges that have represent internal corners. And in areas where solidification is slowed by changes in mass causing residual heating during solidification.
To understand what shrinkage is it is cracks and tearing that occured during solidification. Therefore the governing bodies FAA, ASTM, and the Military came up with a unified code on how to grade the defects of cast materials. This was performed in the 40's and 50's as inspection technology increased. The standards have been constantly revised, As new inspection technology evolves. And as materials are found to tollerate more of a certian type of indication.
Therefore tampering with a code or a interperation for a code puts the inspector at a liablility that is unwarrented. Manufacturing always wants us to pass everything because "we need the production to make this months quota". The inspector is alway the one holding up production, if production does not use NDT to "trouble shoot production methods before starting production runs".
You are in a tough position, have engineering make the calls on what is ok and what is not ok to pass.
Follow the given code when it is described, production will make manufacturing methods meet criteria.
Creating short cuts will cause another "catostrophic failure" of a component. While the "thresher" and the "scorpion" were not casting related the inspection process is the same. And may not have been inspection related. Situations of catostophic failure occur from time to time as we change engineering requirements.



 
 Reply 
 
Chathuranga
Chathuranga
05:06 Jun-18-2014
Re: CASTING DEFECT - SHRINKAGE
In Reply to Gowrishankar at 05:27 Mar-03-2005 (Opening).

http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/solidification.htmL



Go this site,u can learn NDT PROPERLY

 
 Reply 
 
Alex Easton
Alex Easton
18:46 Jun-18-2014
Re: CASTING DEFECT - SHRINKAGE
In Reply to Gowrishankar at 05:27 Mar-03-2005 (Opening).

Daniel answered your questions very well.

Shrinkage is a defect that has strange failure possibilities. There is usually micro cracking associated with these defects as well. The orientation in relation to stress is another factor. The manufacturer should adjust the casting process to remove the shrinkage; not relax the acceptance criteria.

More importantly and I am sure the post readers would like to know; which aircraft type are these castings being manufactured for?

Please let us know. I will be sure not to fly in one.

 
 Reply 
 

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