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Hot answers tagged nastran

5

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: $$weight = mass * g$$

5

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 of the complete structure, those forces came from the stress in the adjacent parts of the structure.) When you deform the piece further, those external forces ...

2

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 useless! The axial load is not useful for the complete machine, but you can't avoid it. Whether it is rotating or not, the turbine wheel can move in space as ...

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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 format, but it's just the mesh (nodes and elements). It won't do the case controls and all the nonlinear solution control parameters and all the other things in ...

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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, you have buckling with $9.5\times 10 = 95$N axially plus $9.5\times 1 = 9.5$N laterally. From example 1 you have a buckling load of 100N axially plus zero ...

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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 natural frequency of vibration as a "mass on a spring" moving vertically is a factor of 10 (or more) lower than the frequencies you are interested in measuring....

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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 some space in my C: drive (AND restarted my computer) then it started working.

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

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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 because when you reach the instability, there are several possible unstable paths and no way for the program to choose between them. (In the circular cylinder ...

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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, they probably are not meaningful for a vibration analysis since the mode amplitudes are arbitrary, but they would be meaningful for a forced response or ...

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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 will accelerate dependent on the amount of their forces. However, since we've got a flexible figure, these forces will also be likely to trigger localized ...

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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 cause a rigid body acceleration according to F=ma. i.e. the center of mass of the object is going to accelerate based on the sum of the forces. But, because ...

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