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It is a billet of aluminium that he subjected to many psi of pressure to demonstrate diagonal shear as a result of compressive stress. He was very proud as it failed at an almost perfect 45° angle.
R did his degree in Aeronautical Engineering. It wasn't one of his better life choices, as he freely admitted that his decision was based on being quite good at physics and having made lots of Airfix models as a kid. After a few months he realised that the course was about 87.54% maths. Very hard maths. With huge long equations that extend over several pages.
As a result of all this maths, and possibly his discovery of beer in a big way, he ended up taking 5 years to complete a 3-year course. But he stuck at it and finished. Much to the pride (and not a little relief) of his parents.
What he should have done was to change to something like structural engineering or materials science. That was what interested him - the way materials behave when subjected to external forces. He could expound on this subject for hours if I let him. This explains how I know why the ancient Greeks removed their chariot wheels at night (to prevent them deforming due to extended loading - also known as 'creep'). Or why this arty-farty linguist could explain Hooke's Law to you if you really wanted her to.
It also explains why my thoughts this weekend were full of bending failure in copper piping.
After two weeks of tripping over the things I had moved out of the kitchen and into the corridor so that I could remove the boiler, I decided to have another go at shifting the wretched thing. It took a matter of moments to bend and break the copper pipes that I had so singularly failed to saw through. That gave me the leverage I needed to undo the last remaining nut on the pipe manifold thingummy, thus allowing a couple of gallons of the blackest water I have ever seen to pour out over the kitchen floor!
That made the whole structure light enough for me to wrestle onto the sack truck and out of the house forever. Hurrah!
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See, R. I was listening.