Are you using pneumatic grips? Be careful not to let the hose line just hang loose from your upper pneumatic grip. The hose can exert a pull on the grip, which is attached to the load cell, when the crosshead moves up during a test – and show up as erroneous load.
If you have an Instron 3300, 5500, or 5900 testing system, attach the hose to clips on the T-slot columns. Make sure there is enough play to ensure that it does not tug on the upper grip during a test. On older Instron test frames, you can attach the hose to the moving crosshead using duct tape.
If you have an Instron 3300, 5500, or 5900 testing system, attach the hose to clips on the T-slot columns. Make sure there is enough play to ensure that it does not tug on the upper grip during a test. On older Instron test frames, you can attach the hose to the moving crosshead using duct tape.
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4 comments:
If your hose hangs loose, how would that impact your final tension result? Would it be higher or lower than it should be? Can you provide details on your answer too please?
A loose hose would drag on the grip which would result in a higher load reading.
To see for oneself on a test machine, just jog the crosshead up without having a specimen in the upper grip and watch the load display on the computer or controller. You should see it creep up.
It's similar to climbing a building or tall ladder while holding onto one end of a fire hose (disclaimer: don't try this!).
One more question. If one zeros out the load cell with the weight of the hose on it, would that subtract that from total break strength of the test material and make if appear that the test material was weaker than expected?
The total break strength would most likely still be incorrect. The loose hose may steadily increase it's drag on the upper grip as the machine crosshead moves up. Thus, you do not have a single, constant "weight" value to subtract. Don't forget that all other load related results will also be off, e.g. the stress-strain curve, modulus, peak, energy, etc.
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