HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
naperlou
User Rank
Blogger
Process cost
naperlou   8/6/2012 9:09:18 AM
NO RATINGS
This is an interesting example of a failure mode that is not going to be easy to predict.  It seems that, short of testing a sample of the parts after each process, one can only track the parts after production and remedy situations as they occur.  This requires a detailed tracking of the products after delivery and detailed reports of problems.  In general, quality control systems do this.  By linking those databases with design data in a PLM system, another big theme of Design News lately, one can avoid the problem in the future. 

TJ McDermott
User Rank
Blogger
Re: Process cost
TJ McDermott   8/6/2012 10:11:28 AM
NO RATINGS
Alternatively, it might mean derating the usable strength of the parts in order to eliminate the process cost.

Dave Palmer
User Rank
Platinum
Re: Process cost
Dave Palmer   8/6/2012 11:50:08 AM
NO RATINGS
@TJ McDermott: I would strongly recommend against derating hydrogen embrittled parts, if by derating you mean using the affected parts in a lower-stress application.  The problem is that it's extremely difficult to predict what level of stress a hydrogen-embrittled part will fail at.  Even residual stresses from the forming process may be enough to produce microcracks, which may propagate later in fatigue.  If I knew that a part was likely to be hydrogen embrittled, I wouldn't recommend using it in any application.

The same line of argument applies to baking parts as a re-work method after a problem has been found.  As I mentioned, it's important to bake parts as soon as possible after plating or welding.  Some aerospace specifications require that this be done within one hour.  The more time passes, the less effective baking will be.  This is not so much due to the hydrogen being any more difficult to remove (although you will hear this claim), so much as the fact that microcracks may have already formed as a result of residual stress.  Obviously, once cracks have formed, no amount of baking will heal them.

As naperlou pointed out, prevention of process-induced hydrogen embrittlement depends on having a good quality system in place.  If you're plating or welding high-strength parts, you need to ensure that they are always baked at the proper temperature within the specified length of time.

bdcst
User Rank
Platinum
Re: Process cost
bdcst   8/10/2012 12:17:43 PM
NO RATINGS
Well, hydrogen embrittlement is  a long known issue that has played havoc with metals at nuclear power plants and has lead to fuel rod cadding failures along with reduction of the rating of some containment vessels.

tekochip
User Rank
Platinum
Great Story
tekochip   8/6/2012 10:44:58 AM
NO RATINGS
Great story, that's an obscure and dangerous failure mode.


Tomv
User Rank
Iron
In process control mandatory
Tomv   1/29/2014 9:52:41 AM
NO RATINGS
Derating is not a good option for dealing with hydrigen embrittlement due to the unpredictability of potnetial failure.  The problem must be controlled/eliminted in process.  I know of circumstance in which a critical flight control component fialed due to hydrogen embrittlement under strictly vibratory loading - no compression or tensile load at all.  Reuslt was the death of a number of individuals.



Partner Zone
Latest Analysis
Researchers in the United Kingdom have found a sustainable way to derive hydrogen from grass to develop biofuel.
Without failure and loss, there is no success. Sadly, some failures and losses are greater than others. That’s certainly true of engineer and Space Race astronaut Gus Grissom.
Siemens and Fraunhofer Institute for Laser Technology have achieved a faster production process based on selective laser melting for speeding up the prototyping of big, complex metal parts in gas turbine engines.
Researchers in China have developed a new material that mimics coral that could help remove toxic heavy metals like mercury from the ocean.
The popularity of Pokemon Go may be break open a new rush of augmented reality products.
More:Blogs|News
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Jul 11 - 15, Embedded System Design Techniques™ - Debugging Real-time Embedded Software – Hands on
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7 | 8 | 9 | 10


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Technology Marketplace

Copyright © 2016 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service