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  1. 1

    Hollow rectangular beam - rigidity and max torque.

    Steam King and nvk. Many thanks. It really is appreciated. Third time lucky! Here we go…. 1. I calculate torsional rigidity = GJ. 2. J = 4tA^2/S. 4 x 0.003 (wall thickness) x (0.147x0.107)^2 (enclosed area) / 0.508 (the perimeter .147+.147+.107+.107). So J = 5.84E-6 m^4 (correct...
  2. 1

    Hollow rectangular beam - rigidity and max torque.

    Steam King, thanks. 1. So I should not have used second moment of inertia or indeed parallel axis theorem because they do not apply to torques only to bending moments. 2. I should have used torsional rigidity = GJ. I have G so all I need to do is to calculate J by using your equation. In...
  3. 1

    Hollow rectangular beam - rigidity and max torque.

    Phrak and Steam King - thanks. Whilst it would be interesting to see if Eular Buckling occurred sooner than material failure I am confident that I am expected to find the material failure figures. This brings me to Steam King's equation "tau = T / (2At), where T = torque, t = wall...
  4. 1

    Hollow rectangular beam - rigidity and max torque.

    The approach to the question is supposed to be very basic in order to help us with revision (it needs to be for my level of understanding) so I doubt it will get into 3-d . I think that to get the twist angle I need torque (as above) but to get torque I need Torque = 2 x area x shear...
  5. 1

    Hollow rectangular beam - rigidity and max torque.

    Phrak, Thanks. What equation would I use to find the twist angle that uses the information that I already have? I think it may be twist angle = (torque x length) / (torsional rigidity). I have torsional rigidity (above - if it is correct?) and I have length (3m) but I am not sure about torque...
  6. 1

    Hollow rectangular beam - rigidity and max torque.

    Phrak - thanks for replying. There are no other contraints in this question.
  7. 1

    Hollow rectangular beam - rigidity and max torque.

    Revision that is turning into a learning from scratch session. Some help would be welcome! (I have laso put this on the materials section of engineering). - I have a hollow rectangular beam. 0.150m by 0.110m with uniform thickness walls at 0.003m. It is 3m long. - It has a modulus of...
  8. 1

    Hollow rectangular Beam - rigidity and max torque

    Revision that is turning into a learning from scratch session. Some help would be welcome! - I have a hollow rectangular beam. 0.150m by 0.110m with uniform thickness walls at 0.003m. It is 3m long. - It has a modulus of rigidity (G) of 27 GigaPascals. - It has a max permitted shear...
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