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Pre-stressed buckling analysis

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

Hi.

Can someone points me to a tutorial/guide on how to perform a pre-stressed buckling analysis with NX ?

Main my problem is to understand if the stress computation is performed inside the same solution involving the buckling step or has to be performed BEFORE running the buckling step (like NX does with a nonlinear analysis using thermal stresses coming from an previous NX Thermal analysis)

Thanks

Phil

5 REPLIES

Re: Pre-stressed buckling analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Phil,

 

In a nutshell, the differential stiffness comes from loads in a static subcase in the same run. This static subcase is referenced by a subsequent buckling subcase.

 

See Chapter 22 (Linear Buckling) in the NX Nastran User's Guide for more information. An excerpt that summarizes the procedure follows:

 

Solution 105
In NX Nastran you can solve a linear buckling problem by using Solution 105 and following the procedure listed below.

1.Apply the static loads to the first n subcases (n is usually equal to one) and treat them as static analysis. The distribution of element forces due to these applied loads is generated internally. The actual magnitude of these applied loads is not critical.

2.You can perform buckling analysis on any or all of the loading conditions used in Step 1. One additional subcase is needed for each buckling analysis.

3.The n+1 to the n+m subcases must each request an eigenvalue method from the Bulk Data Section to solve the eigenvalue problem shown in Eq. 22-9. In this case, m is equal to the number of buckling analyses that you want to perform. Each buckling subcase may call out a unique eigenvalue solution.

4.The differential stiffness matrix is automatically generated for each element that supports differential stiffness. See “Linear Buckling Assumptions and Limitations” for a list of elements that support differential stiffness.

5.You must then multiply the eigenvalues obtained in Step 3 by the appropriate applied loads to obtain the buckling loads (Eq. 22-8) for each buckling analysis.

6.Each subcase may have a different boundary condition.

A typical input file used to calculate the buckling loads is shown in Listing 22-1. In most applications, only one static and one buckling analysis is performed per run. Example 6 in “Buckling Examples” contains an application of multiple static and buckling analyses.

 

Regards,

Jim

 

Re: Pre-stressed buckling analysis

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor
Thanks for the info Jim

Re: Pre-stressed buckling analysis

Creator
Creator
Where can I download the full NX Nastran User's Guide?

Re: Pre-stressed buckling analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Dha,

 

There is only one download for each Nastran version at https://download.industrysoftware.automation.siemens.com/download.php. It contains installers for both the code and the documentation.

 

You can also access the documentation online at http://support.industrysoftware.automation.siemens.com/docs/nastran/

 

Regards,

Jim

 

Re: Pre-stressed buckling analysis

Creator
Creator
Thanks Jim.

Daniel Hoyos
Escuela de ingenieria, university