Surface 2 Surface contact

[ahmedsal]

Dear All,

I am simulating a model with complicated surface contact .... since i know nothing on surface contact so i did on eod the examples about surface contact founded in the help section of the software its a simple problem but i need nore information regarding the following:

1- the instruction indicate that the results for the force reaction in the Y direction will be -6.4 lbf but what Iam getting is somthing off the chart 1538.17 lbf please note that I checked all my BCs 100 times and it the same as instructed so what is the reason what make the Reaction forces go that high.

2- I really need to define the value of the reaction force at the surface contact ( the reaction at the surface where the contact occurs each surface alone ) is that possible ??

3- when I modeled the problem i changed the attributes and define the surfaces of contact as surface 2 please refer to the image (surface 2) ...... when i perform analysis and tried to select serfaces i didnt find surface 2 ..... surface 2 is gone after analysis all i got is what is in the Image ( surfaces after analysis) please note that insted of the Four point mesh ( which i had the model) its 3 point mesh now??? why ????

I thought there is somthing wrong in my model which its nada... i retrived the ach file the one in the models subfolders and all lthe mentioned above happened with the ach file which its provided by autodesk

also i thought may be there is somthing wrong with the software so I uninstalled the downloaded and installed again and all the mention above is still happining

please for more information you can vew the model and the results in this archive file

http://dl.dropbox.com/u/74675313/Surface2Surface.ach

I mean if I am facing all these issues with a simple 2D surface contact problem, is it possible to me to proceed to a 3D problem involving gears and regid bodies???

Thanks all for the help

[zhuangs]

Hi,

In your model, the surface 2 is created by selecting lines and then modifying the attributes to Surface ID.  This kind of surfaces cannot be shown in Results.  Only "All Surfaces" is shown there.  I did verify this.  I am not sure whether this is as design or a bug of the product.

However, for 3D model, no matter it is from CAD file, or manually generated in Autodesk Simulation, the kind of surfaces (created by selecting lines and then modifying the attributes to Surface ID) can be shown in results.  It works.

For contact models, real 3D models will be better for most cases., especially there is friction.  For example, if a FE model without contact can use a "Plane stress" 2D model, but it is not good if there is contact.

Shoubing

[ahmedsal]

2- I really need to define the value of the reaction force at the surface contact ( the reaction at the surface where the contact occurs each surface alone ) is that possible ??!!

[zhuangs]

Even using 2D model, it is possbile to get the reaction force on the contact surface.  You can use all the reaction forces resutling from boundary conditions on Part 2, based on the balance of part 2.  The reaction force on the contact surface should be equal to all the reaction forces resutling from boundary conditions on Part 2, if the gravity of part 2 is ignored or can be deducted, and the inertia of part 2 can be ignored (for this model, static stress with nonlinear material model can be used).

Shoubing