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Not getting stress when applying torsion on 1D beam element.

ahmad.altaf
I have modeled 1D cantilevered beam using "CBEAM" ( general section / standard formulation) and applied torque at its free end but the results show no stresses or deformation. Similarly when I used "ROD" ( general section / standard formulation) element the results showed deflections but still stresses were zero.
 
I want to know:
  • If there is something wrong with my problem setup?
  • Is there any other way to solve this problem?
 
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  • 0
    Ahmad,
     
    This question comes up every so often, here are a couple pretty good responses I found:
     
    Nastran does not calculate shear stresses in beam elements. This is because Nastran does not perform calculations using the cross section itself, but uses the properties of it, such as the area, inertia and torsional constant. This is enough information to calculate the correct displacement. However, without the cross section, it is not possible to calculate the shear flow in the cross section. The beam results that are reported only account for stress due to axial and bending loads.
     
    The torsion stress is cross section dependent and in the general case where A, I1, I2 and J are specified there no shape specified. These element only output the longitudinal stress based on beam theory. The only option available to the user is to output the element forces and knowing the cross section shape look up the torsion stress calculation from text books such as, “Formulas for Stress and Strain,” by R. J. Roark and W. C. Young. 
     
    Regards,
    Don
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  • 0
    Ahmad,
     
    This question comes up every so often, here are a couple pretty good responses I found:
     
    Nastran does not calculate shear stresses in beam elements. This is because Nastran does not perform calculations using the cross section itself, but uses the properties of it, such as the area, inertia and torsional constant. This is enough information to calculate the correct displacement. However, without the cross section, it is not possible to calculate the shear flow in the cross section. The beam results that are reported only account for stress due to axial and bending loads.
     
    The torsion stress is cross section dependent and in the general case where A, I1, I2 and J are specified there no shape specified. These element only output the longitudinal stress based on beam theory. The only option available to the user is to output the element forces and knowing the cross section shape look up the torsion stress calculation from text books such as, “Formulas for Stress and Strain,” by R. J. Roark and W. C. Young. 
     
    Regards,
    Don
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