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Safety Factor / Postprocessing

Hi All,

I have done an Advanced Simulation (SOL101) in NX9 and would like to display (do the results postprocessing) a safety factor for each element based on Von Mises Stress with respect to it's own Yield Strength.
I have more than one material so I would like to create a formula in Result Reduction that will contain specific element yield. Is it possible ?

PS: we do not have the durability module.

Any ideas ?

8 REPLIES

Re: Safety Factor / Postprocessing

Siemens Phenom Siemens Phenom
Siemens Phenom

Here's a link to a similar question posted late last year. I replied that this is possible in NX 10 and a user defined plugin function that retrieves an element's material properties (in this case the yield strength). 

 

http://community.plm.automation.siemens.com/t5/NX-CAE-Forum/Material-Data-using-in-post-processor/m-...

 

NX 10 introduces post processing results probes. These are user defined results that are associated to solutions. They are similar to the result reduction capabilities you are using in NX 9, but more managable and capable. I've demonstrated exactly the calculation you are asking for. To obtain the material property from multiple materials, I had to use a user defined plugin function (i.e. not out of the box yet). Think of a plugin function as a mathematical calculation or lookup to data based upon arguments that the user provides. NX provides many functions available in the expressions system, such as sine, cosine, absolute value, etc. The user defined plugin that I used for my safety factor calculation looked up the temperature dependent yield strength of an element/node, given the temperature of the node via a temperature result or spatial field.

 

The attached presentation provides some insight to results probes and includes the safety factor example. 

 

I realize you are looking for a solution in NX 9, but I don't think it can be done there.

 

Regards,

Mark

 

 

Mark Lamping

Simulation Product Management

Product Engineering Software

 

Siemens Industry Sector

Siemens Product Lifecycle Management Software Inc.

mark.lamping@siemens.com

Re: Safety Factor / Postprocessing

thank you a lot MarkLamping

 

This was very helpful. It seems then we have to update the soft version.

Have a nice day ! Smiley Happy

Re: Safety Factor / Postprocessing

Creator
Creator

Could somenone show a simple example on how to create a formula for a safety factor for each element based on Von Mises Stress with respect to it's own Yield Strength.

Re: Safety Factor / Postprocessing

Solution Partner Valued Contributor Solution Partner Valued Contributor
Solution Partner Valued Contributor

Freschif,

In the Result Tab:

1) Create a Result Variable (Grab Von Mises). Call it VMSTRESS

2) Create a Result Probe -> Add the MOS equation in the Formulae: Yield/VMSTRESS - 1, where Yield is your yield stress. either enter its numerical value, or define a variable for it upstream. (Using expressios from the fem).

3) Set the output Type to Parameter

4) Create the Otuput

Cheers,

JAcques

Re: Safety Factor / Postprocessing

Creator
Creator
Thank you. My question was to find an example how to create the expression to derive automatically the Yield from material properties (suppose I have 2 materials connected).



Inviato da smartphone Samsung Galaxy.

Re: Safety Factor / Postprocessing

Siemens Phenom Siemens Phenom
Siemens Phenom

If you are using NX 11 or greater, there is a built in YIELD() function in the expression system. Unfortunately, it is not documented. The following documentation will be added in NX 12.0.1:

 

YIELD()

Uses the material properties of an element to return the yield strength for an element at the temperature specified by the argument.(2)

The YIELD function is intended for use in results probes. In a result probe, the software has implicit knowledge of which element is being evaluated for yield strength and can access the material properties for the element.

Re: Safety Factor / Postprocessing

Siemens Phenom Siemens Phenom
Siemens Phenom

Attached is an example from NX 11. Some model characteristics:

 

1. 2 bars meshed identically, but having different materials - the difference is with respect to their yield strength only

2. Yield strengths are temperature dependent

3. Loads are identical on each bar

4. A thermal load applies to all subcases

5. Different mechanical loads applied in subcases

6. Stress margins defined using a result probe as: 

 

1-vmavgstress/fd("YieldStrength")

 

In the above expression, vmavgstress is a results variable - Von Mises average stress at nodes. fd("YieldStrength") is the results from another probe (YieldStrength). YieldStrength is defined as:

 

Yield(fd("AxialRampFormula"))

 

Here, Yield is the function Jim documented above. fd("AxialRampFormula") is the result from a spatial field, AxialRampFormula. That spatial field is used in the thermal load of the solution.

 

If the solution had temperature results, then one would define a results variable for the temperature output such as SolutionTemperature, then define the yield function as Yield(SolutionTemperature). For example, a multiphysics solution lets you recover temperature as output along with stresses. There you can use the temperature results in the stress margin's evaluation of yield. Linear statics solutions don't support temperature as output, therefore the example evaluates the thermal load to then evaluate the yield.

 

Regards,

Mark

Re: Safety Factor / Postprocessing

Creator
Creator
Thank you very clear