h a l f b a k e r y
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
or get an account
Fatigue resistant ceramic
Utilizing a piezomagnetic phase to produce magnetic fields which increase plasticity/elasticity of ceramics
Some steels and titanium alloys exhibit fatigue limit, an
amplitude below which there appears to be no number of
cycles that will cause failure.
In steels, a magnetic field is generated that follows the
hysteresis loop, this can be used as a means of predicting
failure under fatigue.
magnetic field may be inducing magnetoplastic/elastic
effects in the material to prevent it from reaching failure,
ie reducing propagation of defects and their accumulation
leading to work hardening, then embrittlement and finally
magnetoplastic effects also occur in ceramics. potentially a
piezomagnetic phase that has good grain matching, and
appropriate orientation to produce a net magnetic field
could induce plastic/elastic effects in a ceramic.
Piezomagnetic effects are nominal in a static stress state,
they are strongest in a high frequency stress state. This
lends itself to fatigue where stress is cyclic.
||How are you going to get piezo effects to generate
enough heat to improve plasticity, again?
||its not heat, magnetic fields induce plasticity in
many materials. magnetoplastic/elastic effects.
Came across them when I found out about
electroplastic/elastic effects. unfortunately
piezoelectric fields don't extend beyond the
piezoelectric crystal so they're not much use.
||The piezomagnetic phase would need a decent fit
to the ceramic phase in order for the stress
experienced by the ceramic to be translated to
the piezomagnetic phase.
||I'm still trying to find out what size field a
piezomagnetic phase could generate, given
appropriate orientation, and i'll have to find out
what size field is required to induced
magnetoplastic effects again. it could be well
bellow what a ceramic needs.
||My bad. If you think it has merit I can run it past an
aeronautical engineer I know. He works in structural
component loading and fatigue.
||It may have merit, if the stress states and
resultant field intensities leading on to plastic
effects are in the right ball park. I want to find
that out first before concerning anyone with the
||Investigating fatigue limit in steels is also
something I need to do, see whether my theory
on this effect i'm trying to re-create exists in that
||Unfortunately I've not yet come across literature
describing piezomagnetism in any practical
(engineering) terms. All I really know about it is
the effect is minimal in static loading.
||One situation where it may have use is in ceramic
blades, instead of chipping they may just deform a
||Tea. It comes in a ceramic object and is something of a help with fatigue. Does that count?
||hey...with a pyromagnetic phase you could do the
same thing. No more thermal shock.
||Not sure you want to mix tea and pyromaniacs.