Hot answers tagged

5 votes
Accepted

Where does weight mass conversion ratio '0.00259' come from in Nastran?

It's the inverse of the acceleration of gravity g in imperial units. $$ 1 g = 386.1 in/s^2 $$ $$ 1/g = 0.00259 s^2/in $$ You need that since: $$ weight = mass * g $$
  • 176
5 votes
Accepted

Do internal / external stresses affect modal frequency?

Consider a small piece cut out of a structure that has non-zero internal stress. To maintain equilibrium, there must be some forces applied to the boundary of the piece. (Of course when it was part ...
  • 12.5k
2 votes
Accepted

Boundary Conditions fro Static Structural Analysis of a Turbine Rotor Using FEM

If your CFD analysis for the pressure loads was correct, the resultant of all the pressure loads should contain axial load and a torque on the complete assembly. If there is no torque, the turbine is ...
  • 12.5k
2 votes
Accepted

Free pre-processor for Nastran?

As far as I know, there is no free preprocessor for Nastran. According to the docs (https://docs.salome-platform.org/5/smesh/user/importing_exporting_meshes_page.html) Salome will export to Nastran ...
  • 2,526
2 votes
Accepted

How would I do a buckling analysis with an additional fixed known lateral force?

In your example 2, Nastran is scaling both loads as part of the buckling load. In your first case, you have buckling with $90\times 1 = 90$N axially plus $90\times 1=90$N laterally. In the second, ...
  • 12.5k
2 votes

Nastran / Frequency Response / Free-Free

If your structure was literally hung on a piece of (plastic covered) wire then it was constrained vertically, at that point, by the wire. A better method is to hang it from a soft bungee cord, so its ...
  • 12.5k
2 votes

Linear Nastran model not converging

Found the solution. Looks like there is a bug in Nastran where if it doesnt see enough space in your C: drive (even if your scratch directory is in your D: drive), it just hangs. Once I cleared out ...
1 vote

Are there any instructions on how to install and run Natran-95?

Use this fork: https://github.com/AeroDME/NASTRAN-95 Use gFortan and cmake to build it on windows 10.
  • 11
1 vote
Accepted

For arc-length method in nastran, how to analyse post-buckling behaviour with load decrease

If your model is very symmetrical (e.g. a circular cylinder with an axial compressive load, modeled with a regular grid of elements not an automatically generated irregular grid) you can hit problems ...
  • 12.5k
1 vote

How to use failure criteria in isotropic material (NASTRAN)

Any NATRAN solution should output the margin-of-safety factors if you output the stresses. Whether they are meaningful for any particular analysis is up to the user to decide, of course. For example, ...
  • 12.5k
1 vote

Inertia Relief and Buckling SOL105 in Nastran

We apply a few forces for it. The forces are likely to do two different things. To begin with, they will create a rigid body acceleration in accordance with F=ma. I.e. the middle of mass of this item ...
1 vote
Accepted

Inertia Relief and Buckling SOL105 in Nastran

Here is what inertia relief does: Let's say that we have a flexible free body (e.g. satellite in space). We apply some forces to it. The forces are going to do two things. First, they are going to ...
  • 2,526

Only top scored, non community-wiki answers of a minimum length are eligible