Moldflow to Ansys (mpi2ans.vbs and MSA)

[kulandaivel_palanisamy]

Dear all,

We are doing structurual analysis in ANSYS (tried both v12 and V13) for a push rod (PA66GF50) with the help of Moldflow interface.

We have done the moldflow simulation with both AMI2010 and AMI 2012. We exported the moldflow fiber orientation and material properties with method (1) mpi2ans.vbs and also method (2) MSA2012.

Buckling load results:

Practical test: 6250N
Only Ansys (MISO) material modeling:  7225 N
Ansys with Moldflow (mpi2ans) : 8025 N
Ansys with Moldflow (MSA) : 7985 N

So we like to have your feedback, how we can bring the simulation result comparable to pracatical test result.

Thanks in Advance for your reply.

Regards

JK

[John_Holtz]

Hi jk,

I cannot speak for ANSYS or the Moldflow simulation, but I can speak about buckling simulation. Whether using hand calculations or a simulation package, it is very difficult to match test data. One reason is trying to match the constraints between the simulation and test. The other factor is that it is difficult to include/predict the imperfections that may occur in the test pieces.

So getting to within 30% is pretty good!

Another factor that you can look into is the slenderness ratio for your test piece. (Something like L/radius of gyration) If it is large, then the simulation approach, along with a healthy safety factor, can give usable data. If the slenderness ratio is small, then check whether the simulation can compensate for short columns or not.

[kulandaivel_palanisamy]

Hello John,

Thanks for your reply.

We like to know, if changing the packing time and pressure will vary these results in Moldflow?

If suppose if we change the process settings (injection time, packing time, packing pressure etc), how much will be the variation?

Regards

JK

[Shawn_Gedman]

Hello JK,

John has very valid points in that we need to be aware of how we're making our comparisons and that there might be imperfections in the actual part that simulation cannot predict.

As for the influence of pack pressure and duration on your results, it could vary.  I'd say that there are probably two dominant factors that could influence the results in this scenario. 

• The fiber orientation can play a large role in this case, but I don't believe adjusting the pack time or duration would have much of an effect on the orientation.  One exception might be if you were to release the pack pressure prior to gate freeze, which would create backflow into the feed system and likely alter the fiber orientation.
• Another factor is the overall dimension of the part.  The pack profile will play a role in how much the part will shrink or even grow.  If the part is not packed adequately then the part could shrink quite a bit or it could even grow if the part were to be over-packed.  The influence that this would have on your analysis would of course depend upon the geometry of the part.  If it were a rather slender part then minor variations in the part dimensions would have a larger impact on your structural analysis than it would with a much larger, more robust part.  We should also keep in mind that region-to-region variations in shrinkage could also alter the final shape of the part.

Hopefully I've been able to answer your question, but it might be best to simply run a few scenarios with varying pack times and durations to see how they'll influence your part design.  That's the beauty of simulation.  You can run through scenarios such as this one rather quickly without having to actually produce test pieces.

[rajamurali]

Informative!!

[madeb]

Good evening, I hope you could help me with this issue:

I've been working with the Moldflow-ANSYS interface and I've found some difficulties. When I open the Moldflow exported file in ANSYS I observe some stresses in the part that match those observed in Moldflow under the name: Von Mises (warp). I've been looking through Moldflow's help for this kind of stress and I've found nothing. 

Should I take this Von Mises (warp) as a residual stress of the injected part? if that's the case, do this Von Mises (warp) occur during the injection process or after it?