[Amps] General question on filament life: comments

[Harold Mandel]

Steve,

The modified sawtooth waveform from a dimmer
would seem to stress the metallic filament of a tungsten
bulb more.

Let's compare the waveform of pure D.C.,  versus a sine wave,
versus a sawtooth wave, each being loaded by a tungsten
wire that provides resistance.

I don't know this, so it's why I'm posting.

Would not the quanta of change, (highest being the sawtooth,
lowest, D.C. ), affect the molecular viability of the filament
in a bulb?

Discounting the inrush parameters, entirely, and applying the 
best means of ramping up the filament to operating voltage,
the question focuses on the stress caused a filament by 
either a non-oscillating waveform, a smooth waveform or a
waveform with spikes.

Please advise.

Thanks,

Hal  

[snip]
What might be the burn out mechanism? The thermal time constant of the 
bulb filament is much longer than the 50/60 cycle applied voltage, so I 
can't see that it's thermal. Steve
[snip]