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# Question regarding torsional stiffness in MSC NASTRAN/PATRAN

## Question regarding torsional stiffness in MSC NASTRAN/PATRAN

(OP)
Hi,
I have a question regarding torsional stiffness and angle of twist in torsional analysis

For the reference: I applied the moment to shaft in Z-axis

I want to know which value will be giving me angle of twist ?
like R3 under maximum displacement in .f06 file ???

Please explain a little and if you have some relevant document, please do share

Sincerely yours,

### RE: Question regarding torsional stiffness in MSC NASTRAN/PATRAN

Hi,
You have provided not much details to go by for answering your question. How are you modeling your shaft? Using CROD or Beam (CBAR/CBEAM) elements?

If you are using CROD, then you need to supply values of Area of Cross-Section, Polar MI/Torsional Constant (J) & Co-efficient of Torsional Stiffness/Torsion Stress Co-efficient (I provide the value of radius...this is tell the software where to calculate Torsional stresses).

For angle of twist, look for Rx value in F06 or in the displacement section of PATRAN. 'x' represents global (or local) geometric axis along which the longitudinal axis of the shaft lies along. For example, if your shaft is modeled with its length aligned with GLobal X Direction, then the angle of twist value will provided by R1 parameter. The value provided by Nastran output is in Radians.

I haven't used CBAR/CBEAM for Torsional modeling. Hope the above helps.

You can do some simple case studies and have it verified with Mechanics of Materials Torsional stresses & Angle of Twist hand calculations.

### RE: Question regarding torsional stiffness in MSC NASTRAN/PATRAN

(OP)
Thanks Burner2k,

once again thanks
cheers

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