Hi Vladimir,
A single crack signifies a non-uniform loading condition/stress concentration geometry. Even than, "accumulation of creep-fatigue damage" is still the life-time controlling process.
Werner
-----Original Message-----
From: Igoshev, Vladimir <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>; Werner engelmaier <[log in to unmask]>
Sent: Thu, 11 Dec 2008 9:42 am
Subject: RE: [TN] Xbox360 BGAs
Hi Werner,
That is a completely different story J and "Yes" it is one possible
scenario where the life time prediction can be made based on
"accumulation of creep-fatigue damage". In other words, to predict the
life time one would have to know the rate of accumulation of total
damage (voids, as I wouldn't call them cracks in that particular case)
distributed throughout the joints.
However, in many-many case a single crack starts growing in a joint,
finally causing its failure. That is the scenario I was referring to in
my original e-mail and "accumulation of creep-fatigue damage" my not be
the life-time controlling process.
Regards,
Vladimir
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner engelmaier
Sent: Wednesday, December 10, 2008 10:05 PM
To: [log in to unmask]
Subject: Re: [TN] Xbox360 BGAs
Sorry,
that's what comes from doing things waiting for an airplane- should have
been "...micro-voiding at grain boundary intersections,..."
Werner
-----Original Message-----
From: Igoshev, Vladimir <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, 10 Dec 2008 4:26 pm
Subject: Re: [TN] Xbox360 BGAs
Hi Werner,
I got used to calling it grain boundary triple junction (it's just
probably different terminologies). However, since I know what you meant
I'm confused with the whole sentence: "In any case, grain coarsening
comes first, micro-voiding and grain
boundary intersections next...", triple joints are there to begin with.
Regards,
Vladimir
________________________________
From: Werner engelmaier [mailto:[log in to unmask]]
Sent: Wednesday, December 10, 2008 4:21 PM
To: Igoshev, Vladimir; [log in to unmask]
Subject: Re: [TN] Xbox360 BGAs
Hi Vladimir,
"Grain boundary intersections" occur where 3 or more grain boundaries
come together.
Purely metallurgically speaking, things get more messy on a scale
smaller than grain size, but
in terms of SJ rel consideration on the grain-size level is sufficient.
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