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incorrect von mises and max principal of simple lifting lug static analysis

rcarnklev
2-Explorer

incorrect von mises and max principal of simple lifting lug static analysis

Hi folks, im new here and im also new at using CREO Simulate, havent really gotten the grabs of this p-element stuff yet.

To the point: I'm performing a static analysis of a lifting lug which is affected by a force acting on a surface inside a hole, this surface models the contact surface between the hole and the lifting tool. The lifting lug is constrained by bolts in holes and i've also constrained it to only move planar for a specified surface  (see picture i attached).

I set the solver to MPA where i seartch for convergence of strain energy, von mises and maximal principal stress for the whole model. I set a convergence criteria to 7%.

The current mesh setup allows the solver to find a solution within the specified convergence criteria.. BUT in the "Run status report", in the last pass, it also stated that there are X-number of elements not converged..

ptc1.PNG

The result give me both von mises and max principal stresses that are WAY above the value it should be. The area of interest is the bend and the hole section, stresses at the bolt holes are not of interest. The model material is S55, ive set modulus to 190 000 MPa and poisson to 0.3.

Does anyone have a any tip or tricks to get more accurate stresses? I've also attached the .prt file so that you can try the simulation yourself.

Cheers

53 REPLIES 53

ptc2.PNG

Assuming i have a case where the sling angle is 45 degree (phi). And due to the position of the lifting lug on the structure, my alpha angle is 70 degree. I have a vertical load (z-axis in picture) and a horizontal load Fcos(phi). Could i use ROTATION coordinate system and rotate around the x-axis in the model to 70 degree, so that i have the force in plane (2D). And the lifting tool, as i said before, i assume that the contact surface point/line is changing depending on how the sling angle (phi) (and alpha?) is definied. Lets say i have a horizontal force of 17000 N and vertical 18000, would that work then? I've calculated the contact point to around 20 degree from the midplane (topside)

traction is only one direction:

x-coordinate of "ROTATION".

i saw this but i did some changes to the model, though not valid computation yet. Trying to fix the constraints... I also changed to fasteners instead of the modelled bolts.

See attached file

I guess its the pin in the hole that messes up the model now but i cant find how to make the "correct" constrains.

Fastener feature is inaccurate (V9 is better).

only one direction for free constraint

and the same direction for load

V9, for me atleast, when i run the simulation i get warning about local reaction force that cant be calculated and also that there are singularities in the model. Running a simple SPA that it. I probably need to refine the region in the contact of the pin, but i can neglect the stresses around the bolts right? Im only interested in how this setup produce stresses in the bend and hole region.

example for plot

V10

example_plot.jpg

Thank you Paul, i'm going to take a look at that ! Is it me or have you changed the size of the lifting tool? Looks smaller in the picture. But not in the v10 file

R14mm in V10

I see, when i open v10 i find it to be R19. I should probably delete all files and  reset session. If something is stuck in the memory

Yes that was indeed the case the part 'EYE' had stuck in session and was not up to date.

Can i ask you, how do you get that result shown as the example picture you posted? Only the EYE part is shown and the rest components are only highlighted edges, looks really good, but cant find that option

fig1.JPG

fig2.JPG

Thank you Paul, now i'm almost there!

ptc2.PNG

The colorscheme is different, im not sure which surface to select, i want to select a volume but it asked me to select surfaces. Loadset: Summed, in your picture it's set to "Loadset1: EYE", did you remove the preload from loadset in SPA?

no, my SPA has preload+load.

colorscheme of MAX_STRESS_PRIN (SIGMA 1) is up +0

Okay so we have same SPA then, only colors and the loadset that differ. How come mine is summed and yours is Loadset1: EYE ?

your colour plot is botch

SIGMA 1 bigger +0 MPa

can you show a correct plot?

Here's a more colorful plot, SIGMA_1 +0 MPa.

Also legend max is 200 MPa.

ptc2.PNG

OK, I use Creo Simulate 2.0 M080

what ist your release?

Creo simulate 2.0 M180

Regards

Robin

that is the difference

Regards

Paul

better M080

The stress difference we get, is that from the solver in M180 and M080 ? The hotspots seem to be the same but the min and max is not.

yes, but maxima are singular

M080 is better, always

I'll see what my IT department can do. Or to you think they should install Creo 3.0 on my computer instead? Cheers

No, Creo Simulate 2.0 M080 only

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