"Model is inssufficiently constrained" error. Any ideas?

November 14, 2014, 10:00 am

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Hi All,

 

Well, am new to Creo Simulate, and am trying to get results of a real world part (not a sample from a book)

 

This is a 3-part assembly, all sheet metal.  I've run about 20+ Analisys, and get fairly different results each time.  The issues I'm now running into is this:

 

I've got the the parts constrained & modeled.  When I run my analysys, I get the error "Model is insufficiently constranted for the analisys", and I have 4 tets that don't seem to play nice.  Now, this is about the 5th times I get the message, and the last two are as pictured (the previous two were in the upper part of the 2nd part, so there seems to be some inconsistency..)  I have the model set to '3D' and 'contact' interface.  (If I have it set to 'bonded, it works, but two of my 'edge to surface' constrains are lost, and I get results, although predictable of a non contrained connection, is still not what I expect / hope for)

 

Any ideas on how to fix this?

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How to model a gravity load

November 17, 2014, 10:59 am

≫ Next: Joining Sheet metal edges

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Hi All,

 

OK, here's the senario.  i have a door hanging by one hinge, the top hinge.  Obviously gravity will act on teh door, and pull the door downwards & inward (so that the door's CoG falls under the load point (or close to it)).  I'd like to see how the door hangs, and more importantly, how the hinge deforms, what the stresses are on the hinge.  I'll assume I will get major deformations & stress at this constrained point!

 

I've modeled the hinge as a single block with a hole (the hinge rotational hole, the 'pin').  The door is a seperate peice, constrained to it.  I've added a 'pin' displacement contraint the pin hole, and I've added a 'gravity' load.

 

I fee there should be a way to tell Creo not to include the door in the meshing routine, but use its CoG & Material as the load (under gravity)..  And I shdou get a returned displacement plot of the hinge all deformed & stressed, not how much the bottom of the door has swung under teh hinge..  (I can't seem to find this lesson!)

 

thanks!

Joining Sheet metal edges

November 19, 2014, 1:33 pm

≫ Next: Stress in joint through prestressed bolt

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Hi All,

 

Just that, are ther any guidelines to joining sheet metal edges for Analysis?

 

If I have the edges, inner edges touch due to a chain flange, I get an error of nodes on top of nodes.  If i leave a gap, I need to add a weld or a rigid link.  Or, I can re model the part, and have the edges fully overlap so I get a bonded contact between the edges.  this should be obvious for a folded up box that has welded seams.  I'll safely assume I'd need a gap if no welding of the flanges is requried..

 

Just lookign for a rule of thumb, what works for others, what others do with sheet emtal parts & stress analysis.

Stress in joint through prestressed bolt

November 19, 2014, 7:57 am

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Hi,

 

 

I am using Creo 2.0, and I am interested in finding out more about the stress in a joint due to a prestressed bolt. I am using a dummy-model, consisting of two identical plates(aluminum) with 18mm holes in the middle. I am using the fastener feature and prestress my M16 bolt(steel) with 59.8kN. I use fixed separation=on and default bonded interface(no contact interfaces defined whatsoever). After the first run, Fastener1_axial_force=24kN, as I understand for the second run I must prestress 59.8*59.8/24=149kN, is this correct?

 

Furthermore, the stress in the joint is high, there are considerable regions where it is above 200MPa. As most aluminums have an Rp0.2 lower than this, this is a problem.

 

 

So the question is: Am I missing something? Is the Creo fastener tool a good tool to see the stresses induced in the joint?

 

 

 

Best

Andreas

Simulation License Error

November 20, 2014, 9:34 pm

≫ Next: Simple question on how to add plane to plane friction for mechanisms?

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When I Run a Analysis the analysis Results Fails with this message in Checkpoint tab.

"The License to run the Engine is not available"

 

Please help me with this Issue.

Simple question on how to add plane to plane friction for mechanisms?

November 24, 2014, 7:47 am

≫ Next: Performing a Drop test analysis in Creo-simulate for a plastic component.

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Hi,

 

I have two similar problems on trying to add friction to two flat surfaces.

 

My first problem is turntable and a small mass sitting on top of it. The turntable is to increase in speed until centripital force equals the static frictional force and the mass is meant to slide off. However I cannot get this to work, as the mass just rotates on the spot while the turntable spins, rather than being stuck to the table until the appropriate angular speed is reached.

 

I have used planar constraint, with the coincident part being between the bottom of the mass and top of the table. The first translational plane between parallel planes of the two components and I set the value to 0mm and added regeneration. The second one i set to 100mm between the two parallel planes between components, then set as zero values and added regeneration. Then the rotational constraint I added a static friction as 0.7 and kinetic as 0.6. (I didn't touch contact radius as i don't know what it does) . Is this not how you add friction?

 

My second problem is basically a mass sitting on a gradient that increases, so it is meant to slip after a certain angle. I have applied planar constraint in the same way with the same friction. This one works a bit better but slips at a very small angle, pretty much immediately?

 

I have attached the assemblies. I use CREO 2.0 but the files save as Wildfire files.

 

Any help would be much appreciated,

 

thanks

 

Cameron.

Performing a Drop test analysis in Creo-simulate for a plastic component.

November 24, 2014, 11:08 pm

≫ Next: Basic mechanism question

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Hi All,

 

Can any one help me out in,How a drop test analysis can be done in CAE using creo simulate and what are parameters to be considered while performing the analysis?

 

 

Thanks,

Anoop Krishna.

Basic mechanism question

November 25, 2014, 3:53 pm

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Ok, trying to learn something about mechanisms..

 

I have two bodies and a ground. here is a simplified image:

 

I need that body 1 and 2 slide away from ground:

 

Then I need body 2 to come in reverse direction:

 

I have to work with subassemblies because I have a lot more components than it is represented in images.

 

Now what´s the best way to deal with this?

 

1. Create a assembly for body1 and inside, another subassembly for body2?

 

2. Create independent assemblies for each? But when I create a motor, I can only choose one connection, and I need them to move simultaneously in first step...

 

Any help will be apreciated..

 

Jose

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Ptc Creo and embeded basic Moldex 3d capabilities in every seat

November 3, 2014, 1:50 am

≫ Next: Values of measures from load steps of non-linear analysis

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Dear All,

In PTC Creo 3.0 Launch Presentation from June  17, 2014 Brian Thomson announced that New basic capabilities from Moldex 3d will be embedded in every seat of Creo Parametric. I have installed Creo 3.0 M10 and there is no such analysis. Only what i can access is 3d thickness Check.  I was told that i need to buy PTC  Creo Mold Analysis  Extension, why if they said in every seat?. Please check PTC Creo 3.0 Launch Presentation at time 34:28 Where Brian Thomson said " every body gets it". I was rely looking forward of this functionality. Did i missed something? Can someone give me answer please.

 

Best Regards

Klemen

Values of measures from load steps of non-linear analysis

May 6, 2014, 7:48 am

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Hi,

 

I would like to export the values of the pre-defined measures for fasteners from the first load step in a non-linear analysis in Creo 2.0.

 

The background is that I analyze many flanged assemblies with numerous fasteners. When I have added the fasteners to a model I run an extra analysis to calibrate the preload force before I run the actual analysis with loads applied. When the design changes significantly I need to re-calibrate the preload forces for the fasteners.

 

I currently perform the extra analysis for calibrating the preload by making a separate contact analysis with only an insignificant load (I suppress the real loads). Based on the results from the first analysis I then adjust the preload forces of the fasteners, un-suppress the real loads, and run a new contact analysis to get the results I need.

 

Instead of using this procedure I would like to apply my best guess for the preload forces and run a contact analysis with all loads applied. From the second load step (Time = 1.0) I would then see the solution with my best guess for the axial preload forces. Based on these results I could decide if I wish to see results with calibrated preload forces.  If I decide to re-run the analysis with calibrated preload forces then I would like to extract the values of the measures from the first load step (Time = 0.0) to obtain the data I need for calibrating the preload forces.

 

In the summary file I find the values of the measures only for the last load step. The only way I have found to get the values of the measures from the first load step is to go to results, choose graph, and then look at the measures individually in the graphs, and export the graph data to Excel. But this is an extremely cumbersome way to get the axial forces from 40 fasteners...

 

The data I need is available in the solution, but I cannot figure out a good way to get the data out of Creo. Is it possible to export the data for the measures from the first load step in a more sensible way in Creo 2.0?

 

Best Regards and thank you in advance.

Export Promotion Request as a report

December 1, 2014, 8:42 am

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Is there a way to externally export a promotion request as a report, ie .txt etc....

 

We currently create a word document detailing the required changes and get a sign off by hand.

 

The reson for this is that I need to send proof of sign off etc to external vendors, so i would need Promotion Request name, Nominated sign off and decision, dates, description etc

 

Is this possible as it would speed up our development process??

Can an optimization analysis take LDA´s "user defined output steps" intermediate results?

December 3, 2014, 7:01 am

≫ Next: Re-using a preload step

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Hello all

 

I need to run an optimization analysis that requires LDA. The goal is to minimize or maximize a specific measure whatever is its value in any of the "user defined output steps".

 

_ Hopefully I´m clear in transmitting the main idea.

 

Is it possible to bring each step´s result into this optimization? So far only the last LDA result is available for the goal. So it does not matter if I have set the LDA output steps at “-1”, “0” and “1” because only the last master step result (1) is taken by the optimization.

 

After a quick search I could not find any topic closer to this case although this question would apply to almost any version of ProE. Thus sorry if this is an old topic. Currently I´m using Creo Simulate 2.0

 

The closest that I can do is to run one optimization and set a maximum/minimum allowed valued for each step being each "step" a stand-alone LDA analysis with a specific input.

 

However this is not a real optimization since I do not know in advance what is the maximum/minimum design limit of the system - what can take a lot of time as it is like to do a rough optimization "by hand" or to run a set of "optimal" results at each step. In both cases this would requires a lot of processing time and still would not be a truly optimization.

 

I do have BMX if it can help in anyway but so far I would like to use Simulate only.

 

Thank you in advance for any feedback.

 

R. Rabe

Re-using a preload step

December 2, 2014, 7:32 am

≫ Next: Is it possible to calculate impact between two moving bodies in Mechanica?

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Hi,

 

Take a bolted structure with fasteners preloaded and then subjected to many loadcases.

 

Contact interfaces making the problem non-linear. Using SPA. No changes to geometry and mesh re-used.

 

The first part of the calculation for each loadcase is identical.

 

Is there a way of re-using the solution to pass1?

 

This would better than halve the time. Studies I have just completed are 4 hours elapsed each.

 

Thanks

 

Charles

Is it possible to calculate impact between two moving bodies in Mechanica?

December 1, 2014, 7:21 pm

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Hi everyone.

 

I have worked on dynamic analysis for a single part/assembly but was curious if the Mechanica can analyse impact between two moving bodies.

 

Regards,

Lucky

Account for stiffness

December 4, 2014, 6:32 am

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Hi

 

I was exporing my earlier preload question and 'Stig's' question.

 

In Creo 3 we have the useful 'account for stiffness' function for fasteners which saves effort and the need for a calculator.

 

We get the baseline and final measures but ...

 

Can we get the s/w to output the preload values it has calculated or ask for fasteners to be automatically updated with these modified preload values?

 

The values are not in the .res file and in order to run a series of further studies with modified preloads I have to manually calculate and update still.

 

Thanks

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Sensitivity Analysis

December 4, 2014, 10:55 am

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I want to compare scans from CMM software in IGES with the original profile on pro e. I think it has to be done by using sensitivity analysis. Can anybody guide me how to perform it?

Access previous simulations in simulate lite,

December 3, 2014, 12:34 pm

≫ Next: Help with modeling hammer impact to simulate pyro-shock

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I have Creo 2.0 and the simulate lite package that came with it. I ran a few simulations on single components and I am trying to access the old simulations I already ran and just change the forces and constraints as existing instad of doing everything all over again. When I try to open the files, Creo tells me that I do not have the license to access the files and when I try to go through creo to open them, Creo does not see the files. Any ideas?

Help with modeling hammer impact to simulate pyro-shock

December 5, 2014, 7:00 am

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     Our senior capstone project involves building a test rig with a drop hammer to exite a fixture that will mount electronic components to simulate a pyro shock to them. We have creo avaliable at our school, yet we have no experience with simulate only with the CAD part of creo. To begin we don't really understand where we should start to be able to get some simulated results to improve our experimental model. I have a test plate fixture and we can do a static analysis using a pressure force to simulate the hammer impact, but I know this is going to be vastly different given a dynamic impact. I can also run a modal analysis, but only with a low number of modes, if I try to select a range of frequency simulate runs forever. I can also do the dynamic analysis and do the shock part, but don't really understand what its giving me.

 

     So my question is, does simulate have the capabilities I need to be able to vary input parameters? (impact force, impact location, boundary constaints on fixture plate) In order to see what effect this will have to improve the experimental model. Im also not sure exactly what outputs simulate will give us? (an acceleration response of the fixture?) It would be nice if simulate would actually give you a Shock reponse spectrum given a certain impact? Our project goal is to be able to correlate the test inputs to the acceleration output and corresponding shock response spectrum. They would like a more systematic and efficient approach in lab testing to be able to know what input variables they have to put in to get the correct shock output they are looking for.

 

Thanks for the help.

Applying Rotational Constraints?

December 5, 2014, 10:30 am

≫ Next: Stress in joint through prestressed bolt

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How do you apply rotational constraints when doing the structural simulation in Creo? I'm using rack and pinion from power steering system for the simulation.

Stress in joint through prestressed bolt

November 19, 2014, 7:57 am

≫ Next: Nonlinear Contact Analysis

≪ Previous: Applying Rotational Constraints?

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Hi,

 

 

I am using Creo 2.0, and I am interested in finding out more about the stress in a joint due to a prestressed bolt. I am using a dummy-model, consisting of two identical plates(aluminum) with 18mm holes in the middle. I am using the fastener feature and prestress my M16 bolt(steel) with 59.8kN. I use fixed separation=on and default bonded interface(no contact interfaces defined whatsoever). After the first run, Fastener1_axial_force=24kN, as I understand for the second run I must prestress 59.8*59.8/24=149kN, is this correct?

 

Furthermore, the stress in the joint is high, there are considerable regions where it is above 200MPa. As most aluminums have an Rp0.2 lower than this, this is a problem.

 

 

So the question is: Am I missing something? Is the Creo fastener tool a good tool to see the stresses induced in the joint?

 

 

 

Best

Andreas