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Physics can be difficult to learn, but this blog aims to help you get into physics by connecting your GCSE physics lessons with things you see in the world around you.

Tuesday, 4 October 2011

Testing Testing 1....2....3

In the past, when things like huge steel bridges were the latest technology, sometimes they wouldn’t quite work how they were meant to. Every now and then it was a disaster. It was a puzzle for engineers, who were trying their best to make things safe. One man decided to make a difference, a Scot called Kirkaldy.

He built the world’s first testing machine that could be used to create like-real-life testing situations on large bits of the construction materials. And on Sunday I went to the museum where it’s kept. The Kirkaldy Testing Museum is a small and unassuming place, remarkable only if you happen to notice the “Facts not Opinions” motto above the door.

By all accounts, he was a rather opinionated guy, with everything he said (well, relating to testing of these large building parts anyway) meticulously based on the results of his tests, which he wrote down in a huge leger so he could check back and show people how right he was. He even kept all the pieces he’d tested to destruction until the sheer weight was in danger of bringing down the building!

The tests he carried out were of two types, one a test to stretch the item (tensile test) and another to squash the item (compressive test). These are the two main types of forces that area on major beams in construction, particularly in bridge building:

The clever part was, that although he could only make his machine go one way, as it was all about water pressure, he managed to both push and pull the samples. He did this with an ingenious method, adding an extra “space” for testing the items in compression (red), the other side of the stretching part (blue).

For a time, Kirkaldy was the go-to man for any sort of material testing, with his all-singing all-dancing machine the star of the show. It was important to test whole girders, or whole joists, because you couldn’t be sure of the material quality, because manufacturing methods for making the metals were poor. But as these improved, tests could be done on smaller and smaller samples, making this beast obsolete.

The museum has a great collection of such testing rigs that are smaller and more compact, for testing littler samples. And today we have electronic machines, capable of getting results so accurate Kirkaldy himself may have had to concede defeat. But none are quite as important as that gigantic pioneering machine!

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