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Thread: Find force of bolt

  1. #1
    Associate Engineer
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    Nov 2018
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    Find force of bolt

    Hello Everyone ,

    I study the torques and screwing and decoking forces and came into the following forces analysis which ultimately gives us the relationship for the required torque of the screw. However, a force F is involved in the formula, which as it says is the "growing tensile force that develops due to tightening." After searching, I did not find a relevant entry saying that this power can be calculated. Can you help in calculating this Force by taking into account the elasticity measures of the materials that are associated? Thanks in advance .
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  2. #2
    Administrator Kelly Bramble's Avatar
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    Interesting question and I’m long out of academia to be much help. I suspect you could substitute or modify the variable friction u to take in account he effects of material elasticity. Be aware that in design engineering practice we normally include a factor of safety (FOS) in the design of mechanisms which might be used to drive your load.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  3. #3
    Associate Engineer
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    I'm asking it because of this exercise:
    <<On a 20x5 rectangular right screw thread the screw made of Nylon 66 is exactly the same as the female thread made of Ck60 steel. The radial gaps of the two threads are all 0.1mm and the total thread height 2.7mm. As is common in all plastic threads, the screw has a slightly greater thread thickness, ie 2.51 mm instead of 2.5 mm with the hole. Considering the elasticity measures of the laminar material E1 = 3.2GPa and the steel E2 = 205GPa, calculate the torque required to screw and unscrew 7 coils from the thread. As a friction factor, consider 0.08 in all positions.>>
    Im not sure if the way i asked above is the right one but i post the exercise if it could help!

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