Category Archives: FEM – Analysis

Finite Element Method
The finite element method (FEM) is a numerical technique for finding approximate solutions to boundary value problems for differential equations. It uses variational methods (the calculus of variations) to minimize an error function and produce a stable solution. Analogous to the idea that connecting many tiny straight lines can approximate a larger circle, FEM encompasses all the methods for connecting many simple element equations over many small subdomains, named finite elements, to approximate a more complex equation over a larger domain.

Contact simulation with MSC/Nastran

Linear Gap The linear GAP is the simpliest contact form used in Nastran simulations. Linear GAP can solve a large class of problems like hole bearing, heel-toe interaction, fitting contacts. Linear, therefore does not include frition, large displacements, and material … Continue reading

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Non linear Buckling with FEM approach

Buckling analysis assesses the stability characteristics of a structure. An accurate solution to a buckling problem requires more efforts than just following a numerical procedure, there are a number of factors to consider before a buckling solution can be accepted … Continue reading

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Buckling of an imperfection-sensitive cylindrical shell

Buckling of an imperfection-sensitive cylindrical shell (EXTRACTED FROM ABAQUS GUIDE) This example serves as a guide to performing a postbuckling analysis using Abaqus for an imperfection-sensitive structure. A structure is imperfection sensitive if small changes in an imperfection change the … Continue reading

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Nastran run in batch mode

Sometimes is necessary to perform several Nastran runs, and by running one by one could be necessary a lot of time. Hereafter are illustrated two methods to speed up these operations. There is an effective method to perform this operation … Continue reading

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Nastran launch commands

The Nastran solver is executed usually by command line like „nastran“. Generally it could be with different name,  due to the needs to specify the version of solver. The format nastran command is:   nastran2012  input_file  keyword1 = value1  keyword2 … Continue reading

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Vibration Analysis – Nastran SOL 103

    General Overview There are many reasons to compute the natural frequencies and mode shapes of a structure.  One reason is to assess the dynamic interaction between a component and its supporting structure. For example for those parts nearby … Continue reading

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Non Linear Analysis SOL 106

In the most of cases the nonlinear effects in structures occur due to nonlinear material behavior and large deformations. Geometric nonlinearity becomes relevant when the structure is subjected to large displacement and rotation. Geometric nonlinearity effects are prominent in two … Continue reading

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Fastener modelling in Nastran

This way of modelling presented in this post is one of most used, as it is simple and sufficiently accurate. For the fastener modelling generally is used a Spring type element (CBUSH), and it should be done as Mesh-indipendent, like a … Continue reading

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Linear Buckling Analysis – SOL 105

Theoretical Background Buckling analysis assesses the stability characteristics dictating the integrity limit of a structure. Let us start with a linear equation of motion for a preloaded structure: where M,C, K and  Kd are mass, viscous damping, material and differential stiffness … Continue reading

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Problems with Large XDB

If you are constantly having to work with large models and larger output in XDB format, MSC Nastran has come out with a good solution. A common fatal message encoutered while writting out large size xdb files is UFM 6062(DBC). … Continue reading

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