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.

The 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 failure.

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.
-- lostmind, Jun 05 2012

How are you going to get piezo effects to generate enough heat to improve plasticity, again?
-- UnaBubba, Jun 05 2012


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.
-- lostmind, Jun 05 2012


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.
-- UnaBubba, Jun 05 2012


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 idea.

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 case.

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 bit.
-- lostmind, Jun 05 2012


Tea. It comes in a ceramic object and is something of a help with fatigue. Does that count?
-- not_morrison_rm, Jun 05 2012


hey...with a pyromagnetic phase you could do the same thing. No more thermal shock.
-- lostmind, Jun 05 2012


Not sure you want to mix tea and pyromaniacs.
-- UnaBubba, Jun 05 2012



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