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02-12-2019 05:45 AM

Hello everyone!

I have a following question concerning NX 8.5-12 (*SOL103 Response Dynamics*): **is it possible** to introduce **different damping coefficients** **for the different properties** (shell/solid) when you evaluate **FRF in SOL103?**

For example, it's possible to do it using *SOL111* (specifying both different Damping Coefficients for the different properties and PARAM,W4),

but as I got *SOL103 Response Dynamics* **ignores** __the damping coefficients specified in the properties cards__ and considers only __a damping factor for a whole model__ (Response dynamics -> Natural Frequencies -> Modal Represantation -> Normal Modes -> Edit Damping Factor).

Thanks!

Maksim.

Solved! Go to Solution.

9 REPLIES 9

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-12-2019 07:16 AM

For Frequency and Transient events, you can include in your Response Simulation evaluations the physical viscous and/or hysteretic damping calculated by NX Nastran. Before solving the model, add the appropriate elements (such as dampers, bushings, or springs) or material damping in your FEM as listed below. You can also define global structural damping in the G parameter for the solution.

To define viscous damping:

- CDAMPi element – Define the
**Viscous Damping**values in the PDAMP physical property table. - CVISC element – Define the
**Viscous Damping**values in the PVISC physical property table. - CBUSH element – Define the
**Viscous**values in the PBUSH physical property table.

To define hysteretic (structural) damping:

- CELAS and CELAS2 elements – Define the
**Damping Coefficient**in the PELAS physical property table. - CBUSH element – Define the
**Structural**value in the PBUSH physical property table. - G parameter – Create a
**Solver Parameters**modeling object in the**Parameters**tab in the**Edit Solution**dialog box. - Material damping – Add the GE field on any of the MATi bulk data entries (must be added to the NX Nastran input file manually).

After you solve the model and create the Response Simulation solution process, use the **Physical Damping Settings** dialog box to enable the physical damping in your response evaluations and optionally enter a Scale factor.

You can view the percentage of the damping ratio for each mode in the **Response Simulation Details View** in the **%Phys Visc **and **%Phys Hyst** columns. The values displayed are the diagonal terms of the viscous damping matrix or hysteretic damping matrix multiplied by any Scale factor you defined

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-12-2019 09:36 AM - edited 02-12-2019 10:10 AM

I did as it's advised:

1. Specified a material damping GE using GUI (then checked - it's printed in the input .dat file automatically - didn't get why you advised to add it to the input file manually);

2. After I had solved it and created the Response Simulation solution process I checked in the **Physical Damping Settings** dialog box that **the physical damping** in my response evaluations **is enabled**.

3. But **still** both **%Phys Visc **and **%Phys Hyst** are **0%**.

I checked it either for **PSHELL or PCOMP** - **still** **it doesn't work in both cases** (basically, I need a damping model for **PCOMP** type).

I managed to get** %Phys Visc **or **%Phys Hyst ****greater than 0% only when** I specify the damping using "**Edit damping Factors**" dialog box, but it introduces the specified **damping for a whole model** - but **I don't need it at all**, cause **for some properties** I need a **damping** equal to **0%**.

Looking forward to your reply!

Maksim.

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-12-2019 11:01 AM

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-12-2019 12:52 PM

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-12-2019 01:11 PM

Could you attach the the input sim, fem files, please?

Thanks!

Thanks!

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-12-2019 01:17 PM

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02-13-2019 06:50 AM

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-13-2019 10:20 AM

The point is that I launched *SOL103* **Real Eigenvalues **(in conjunction with dynamic response) and if I specified __PARAM,OUGCORF,GLOBAL__ **either by GUI or manually **- anyway solver deletes this parameter - probably that's a reason why I didn't get the physical damping.

To cut the long story short, you don't even have to specify that PARAM with *SOL103* **Response Dynamics**** - **with that solver** everything works well.**

Re: Different damping coefficients (evaluating FRF in SOL103 Response Dynamics)

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02-13-2019 11:08 AM

Ok, yes, you must use the "SOL103 Response Dynamics" Solution to be be able to get the damping back to Response Dynamics. This solution outputs the necessary damping information for RD that the plain "SOL 103 Real Eigenvalues" solution does not.

Glad you got it working now. If yo uneed anything else, let me know.

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