From some of my tensile strain-stress curves, the load keeps increasing at higher extension after yielding as in 1.png. This is really wired. Anyone knows what's wrong?
And since the load is really small generally, I cannot see any sharp load reduction at fracture, making me confused about the final elongation. Like in 2.png, fracture actually has happened at around 300mm but no load drop. Is this due to instrument accuracy or something?
Hello!
I would need more information about the setup to come up with possible explanations. For example I do not understand why you would say fracture in Figure 2 happens at around 300mm extension. Could you explain more the setup/material? and what B, M, Y points are? Have you checked if there is any sliding during the experiment? Regarding the hardening, this could be happening from polymer chain alignment under high stretch (?).
Best wishes :)
Gustavo Quino Hi. Actually, I saw it broke at around 300mm extension. At the middle, the material just became a very thin string connecting the upper and bottom part. And the string broke at around 300mm extension. However, I am curious why there is no load change then.
The points are generated automatically by the software and we can ignore them at this stage.
My materials are very soft and the original length was 1cm so I am doubtful if there should be hardening at such large elongation.
Sj Li , possibly the force was not zeroed at the beginning of the test. You could shift the history of forces according to the "zero level" you get after breakage.
You could be right about instrument accuracy. What is strain rate, max load of load cell, and data sampling rate?
Are you following a particular method for testing (e.g., an ASTM std)?
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