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05-10-2015 12:07 PM

Hi,

Can someone explain how to used scales mass function in SOL 701?

I saw the scaled mass in the GUI in ths analysis setup, but didnt quite understand what the factor means (factor of what?), do I need to define the step size from which the mass is scaled?

I didnt quite understood.

Thanks.

Solved! Go to Solution.

4 REPLIES

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05-12-2015 09:59 AM

Hey,

This is explained in the NX NASTRAN Quick Reference Guide - NXSTRAT card.

and he NX NASTRAN Advanced Nonlinear Theory and Modeling Guide Section 7.3 Time Step Management explains these a bit more thoroughly.

XMSCALE is a global mass scaling factor and is applied to the entire model at the beginning of the analysis. The NXSTRAT card allows for a non global (per element) approach with the

XDTMIN1 and XDTMIN2 parameters.

Using any of these mass scaling parameters should be done with extreme caution. Drastically increasing the mass will change the soultion. I frequently have used XMSCALE to speed up a checkout analysis solve prior to a final run without using it (XMSCALE=1.0)

Jay

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05-12-2015 01:51 PM

Thanks for the reply.

Some more questions if you will.

1. If using global mass scaling - is the density increased for all elements the same amount? If so - is this amount the original density times the factor?

2. When using XDTMIN1 and XDTMIN2 - XDTMIN1 is mass scaling and XDTMIN2 is element removal, this is defined by the min time step - i.e I input the time step from which all elements (smaller elements) below will be scaled / removed?

2. If using XDTMIN1 I am not prescribing the amout of mass scaling (factor) - so I guess the solver decides am I right? If this is the case, is it possible to see using some contour plot how much mass (or density) was added to each element?

Thanks.

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05-12-2015 04:38 PM

1) Yes, XMSCALE is a global mass scale factor. The default is 1.0.

2) Yes.

3) The solver calculates the mass scale factor on a "per element basis" to ensure the minimum XDTMIN1 step is met. It is not currently possible to generate the mass scale factors so post processing is not available. The elements which required scaling are listed in the .f06 file. This would be a good enhancement request.

Jay

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05-12-2015 04:51 PM

Thanks for the informative replies.

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