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I'm really stuck and would be grateful for any help. I'm a postgraduate researcher, though not a physicist so this may be a relatively simple problem for some of you (I hope!).

I use a program called Bluehill which is coupled with an Instron machine. The instron is a mechanical testing device that stretches a material gradually and feeds the load and extension applied data to Bluehill which then draws a lovely graph for me (force vs. tensile strain). I know when to stop the machine when I see failure of the material (sudden fall in the graph). Anyway the software also gives me values for the maximum load and elastic modulus (EM) but based on pre-set values for length and area (basically for all dimensions) of the material. So, I have to re-draw the graph from the raw data (raw data containing time, extension and load applied) to recalculate the EM and I use the correct dimensions subsequently work out the correct EM. Similarly, I have to work out the correct ultimate tensile stress (UTS) but not sure how to do this. From the replotted graph, I have the maximum load but which equation do I use do work out the UTS?

If you need any more info, pleeease ask!

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# How do I work out ultimate tensile stress?

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