A spoke never tears through a rim. During wheelbuilding I can break a 2mm spoke in tension without the sightlest bit of damage to even the thinnest rim. Like I said, rims fail through the mechanism of metal fatigue. When you were at school you marveled at your ability to break steal when you took a thick coat hanger wire and broke it by bending it a few dozen time. That's not the same as tearing the wire apart. LIke I said, aluminium has a fatigue limit that cannot be eradicated by spoke tension. Steel on the other hand, has a limit which if you never reach it, will give you infinite fatigue life. We make use of this limit when for instance, designing car springs. They just never break. ON a bicycle wheel, a spoke that's been stress relieved, has an infinite fatigue life. The rim as we know and I've photographed, has a limited life.
The reason it is perhaps counter intuitive is that by stressing the rim a lot through initial tension, you do not increase the amplitude of the cyclical stresses. These remain the same size, albeit overlayed on top of the tension stress. That initial stress does decrease the fatigue life a little bit.
Finally, you can't have a spoke with zero tension. Then you don't have a tensioned wheel, but that is another discussion completely.
It is fully to blame and something I've never disagreed with. The lighter the rim, the higher the amplitude of the cyclical stress will be and hence the quicker metal fatigue will set in. As important as thickness is shape. A rim with a flat spoke bed will fatigue quicker than a rim with a sharp V bed. The latter will flex less and thus fatigue less. Lightweight rims are a curse and the bane of my life.
Yes, a cheaper (thicker) rim is more durable than a more expensive, but lightweight one, all else (including alloying metals) being the same.
