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Thread: How to do torsion test in a lab with only simple apparatus?

  1. #1 How to do torsion test in a lab with only simple apparatus? 
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    I was told to do a torsion test in the lab, but without using the machine, I was given a chalk(specimen), a thread, some loads, and a G-clamp. I'm not supposed to use any other scientific apparatus. but I can use things we can found in our daily life, for example, pen, pencil, eraser, etc... but i don't think those things help much.

    I thought of doing it this way. fix one end of the chalk on the table with the G-clamp so that the chalk looks horizontal, then put some load at the other end with the loads connected to the chalk by the thread. Then, I will add the load until the chalk breaks. However, i think that is more like a bending test than a torsion test for me. It didn't give the effect of twisting for this case... What should I do?


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  3. #2  
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    I think G-clamp is not a very good work locating fixture to chalk.
    Maybe wrap the chalk up with some cloth is better.
    Also the other end be wrap up with cloth.
    Put the whole chalk on one plane, like a table. Don't let any end put without holding power.
    Then apply the load to the cloth to make a eccentric force .


    You get a torsion.

    Chalk is really very brittle and its strength is too low as well.
    Good luck! :-D


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  4. #3  
    Forum Freshman Nabla's Avatar
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    You could clamp one end of the specimen to the bench and secure a pencil/pen to the other end, perpendicular to the axis of rotation. Tie the string to one end of the pencil/pen and attach the loads.

    Mark the extensions of the string with the chalk under different loads. From this you can determine the torsion.
    PHI is one 'H' of alot more interesting than PI!
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  5. #4  
    Forum Isotope Bunbury's Avatar
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    You can eliminate bending by supporting the free end on something like a wood block.

    How will you compensate for the string stretching under load?
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  6. #5  
    Forum Freshman Nabla's Avatar
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    You could do a preliminary experiment to determine the extension of the string under the applied loads, by hanging the string off the bench and loading.
    PHI is one 'H' of alot more interesting than PI!
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