A few weeks ago I was discussing the loss of the OceanGate Titan tourist submarine with my brothers, one of whom is a skilled mechanical engineer. Apparently everybody expected it to collapse because a cylinder with domed ends on it is a really bad shape to put under pressure. I still find it rather had to believe, but as a species we only know how much pressure you can put on a cylinder if it's perfect. As soon as it goes slightly out of round it's much much weaker, but we can't really calculate how weak.
To demonstrate this effect to me they devised this beautiful practical demonstration. The beer can can hold my weight while it's intact. They then introduced the tiniest imperfection (by prodding it gently with a cotton bud) and it collapses catastrophically.
My least favourite thing about the loss of the Titan - apart from the loss of life - is the system of acoustic sensors and strain gauges supposed to keep it safe. Everybody was a naysayer and didn't believe they would work. They naysayers were kind-of right, in that the submarine collapsed and killed everybody inside, however, they did pick up a loud click (probably a delamination) on dive 80, and the strain gauges did show that the performance of the hull was degraded after the click. If only they'd known how to analyse the data.
Richard "I went to school with Euler Buckling" B
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