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Questions tagged [nastran]

17 questions
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How quadrilateral elements represented in most FEA solvers for structural mechanics problems?

How quadrilateral elements represented in most FEA solvers for structural mechanics problems? I know that Nastran-95 represent quadrilaterals for membrane and bending elements as a set of triangles: At the same time there are a lot of literature…
Евгений Павлов
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In a nonlinear static two-step subcase, why does the load step decrease after the first step?

I am using MSC Nastran for nonlinear static analysis (sol 400). Step 1 contains a small perturbation load laterally on a thin-walled cylinder. Step 2 contains a very large compressive load. Usually when I do this, the Load Step increments from 0…
Jeroen
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Do internal / external stresses affect modal frequency?

Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam). If I increase the tension, does the modal frequencies of the beam change? On the one hand,…
user3533030
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Linear Nastran model not converging

I am running a SOL 101 linear statics FEA. If I fix down the whole geometry it converges. But anything less than around 90% fix down and it will sit there crunching away at the numbers forever. This is with no other boundary conditions, forces, etc.…
user1402154
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Are there any instructions on how to install and run Natran-95?

there is a source code for Natran-95 on Github. I need to install it on Window 10 but searching on the web there is no clear tutorial on installation. while I click on the nastran.exe on this package in the hyperlink to GitHub, I get windows error…
FabioSpaghetti
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In Nastran, how to ignore fatal error due to failed convergence and move on to next subcase?

At the moment the whole analysis stops when 1 subcase fails to converge. How can I keep the analysis going such that all subcases are are run, even if they all might produce an error? I'm pretty sure there is a command for this to write in the case…
Jeroen
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1 answer

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

I am currently trying to model the buckling behaviour of a cylinder using sol 400 nonlinear static analysis using Nastran. I am using the arc-length (modified Riks) method as apparently it can increment load and displacement in both positive and…
Jeroen
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2 answers

Free pre-processor for Nastran?

I want to do a non-linear analysis (possibly SOL 400) on Nastran. I used PyNastran (python module) to set-up the BDF file for a Linear buckling analysis (sol 105). However I feel like it might be too difficult to set everything up correctly with…
Jeroen
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1 answer

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

I am using Nastran for buckling analysis, and I'm new to all of this so please bear with me. For a linear buckling analysis, I understand that you must first apply any compressive load in the static subcase. Then solve the eigenvalue buckling…
Jeroen
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Nastran / Frequency Response / Free-Free

There are examples of using SOL 108 and SOL 111 to create a frequency response. In Siemens Simcenter (NX Nastran), the examples focus on a tower with a seismic mass. The model drives the mass with an acceleration, attaching the mass to the…
user3533030
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MSC Nastran - BAR3/4 elements - can't assign any properties

I'm modeling a pipe in Patran, and I'd like to try bar3 and bar4 elements. I assing the properties CBEAM to my geometry, but when I create the mesh, Patran tell me bar3 and bar4 don't support that property, and I need to use bar2. Doesn't work…
gbos
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MSC Nastran CQUAD8 on a pipe - excessive pivot ratio

I'm modelling a pipe in Patran with CQUAD8 elements, but I get this error, like the structure is not costrained. I do have costrains on both ends of the pipe. What can the problem be? If I use automatic costrains it works, but I don't know why and…
gbos
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1 answer

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

I am trying to perform static structural analysis of a turbine rotor which is rotating at a given angular speed, say 1000 rad/s. I also know the pressure distribution from CFD analysis. What are the boundary conditions for static structural…
Ali Baig
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How to create a non uniform pressure load in MSC Patran

I need to simulate an external pressure load that varies sinusoidally along a circular arc. The sinusoidal variation is with arc length. I know how to create a uniform pressure load in Patran but do not know how to create a non uniform pressure…
DJ319
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How to use failure criteria in isotropic material (NASTRAN)

I'm quite new in NASTRAN enviroment, and I am wondering how to use failure criteria which I can define when creating my isotropic MAT1 material for 1D elements (like CBEAM). From the Quick Reference Guide, (MAT1) I am able to define 3 stress limits…
marcoresk
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