All that is still true... and keep in mind that linear expansion will happen along all three axis.
The question is then what happens if you *constrain* the expansion along one axis?
You get a similar effect to if you attempted to compress a rail along its length while preventing it from bending - i.e. it will get fatter in width and height and shorted in length.
Whilst theoretically true, in the context being discussed the reality is that the constraining forces would have to be impractically large.
Chris
I have not done the sums, but if you start with the rails in tension (as they do) - so they are somewhat stretched at lower temperatures, then relax as it warms, before finally ending up in compression. I would have thought the restraining force you could achieve with solid fixings to hundreds of concrete sleepers would be fairly significant. (and no need to resist all movement since there are/can be expansion joints as well).
Sorry, it was magnesium-lithium. It was years ago.
welding of magnesium - lithium poses special challenges as both are extremely reactive metals..........
Thank you, Captain Obvious.
It had to be said !!!!
:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)
Andrew
Have to admit I did notice lithium was a bit on the volatile side when a teacher I once knew dropped a knob of it in a beaker of water, blowing it to bits.
Anyway, I have a likely candidate for a brazing torch which I picked up today in BnQ. It's this one:
It has an appreciably finer flame than the torch I use for soldering pipes, so I'm hopeful it will do the trick for brazing. I don't think I'll do any better without oxy setup which is too much for my modest requirements.
you have reminded me of an incident at my mother's workplace which was a school where she was a cleaner.
The Chemistry teacher held a lesson demonstrating the reactivity of various metals such as sodium, potassium, phosphorus, Magnesium, lithium etc.
Two school boys decided to play a prank on one of the school cleaners....
They stole the phosphorus from the lab. Phosphorus is so reactive its kept under oil within its container.
They went to the boys toilets, poured some oil onto the toilet taking into account that oil floats on water. put some toilet paper on top of the oil layer, then put the phosphorus onto the toilet paper. (the toilet paper was needed to stop the phosphorus from dropping through the oil into the water underneath and the oil was used as a barrier between the phosphorus and the water.
For good measure they dropped a couple of no 2's in, m aking sure no intimate contact was made with the phosphorus as the No 2's contain small amounts of moisture.
The last bell of the day went, and the pupils went home.
One of the cleaners went into the boys toilets to do the dialy cleaning ritual. She went into one of the cubicles, spotted that someone had not flushed the loo after their no 2's. So she pulled the flush.
There was a almighty flash in the pan, tempoarily blinding her and the reaction was so fierce that it set fire to the toilet paper and shattered the pan.
Needless to say the two school boys were identified and expelled.....
A Mapp gas torch might be a better bet...
Quest have just this week shown a Mythbusters episode featuring a few interesting reactions in water.
Chris
[...]
(It oozes out of corroded shells. Curious divers get it on their hands.)
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