The Reaction force in coating indentation 1

[azidah]

Hi all,

I've been using Abaqus CAE 6.5.1 to model Vickers Indentation to coating substrate. To simulate the indentation, I've used displacement in negative y-dir for the rigid body to penetrate into the coating.

My model, I believe, is running fine but when I would like to obtain certain result such as Reaction force (RF),it looks suspiciously wrong. Attached is the picture of my RF and Von misses.

Please help

Reaction force - RF2

http://i2.photobucket.com/albums/y35/toyon/RF2.jpg

Von Misses

http://i2.photobucket.com/albums/y35/toyon/Vonmisses_03mm_displacement.jpg

Thank you so much for any input

Azidah

 

[xerf]

The reaction forces are given only at the nodes where you have boundary conditions and they are zero at all other nodes. In the first plot, you have a map (contour plot) of a mostly zero-field of RF2. I think it's ok.

You might be interested in looking at nodal forces NFORC instead of RF. I think you have to modify the output request before running the analysis, since they are not ouput by default.

Also, contact stresses CSTRESS might be of interest.

 

[Yoman228]

Will CPRESS useful for you?
(Contact pressure at urface integration points)

 

[azidah]

hi xerf and Yoman228,

Thank You for responding, I will all suggestions and wait for the outcomes. Anyway,I dont really get it what's contact stress/pressure will yield? Is it going to yield result at the interface of coating and substrate or something else?

Thank You so much again,

Azidah

 

[xerf]

What do you expect to get from your model ?

 

[Yoman228]

How did you model the contact between the Vickers and coating?
The Cpress is the contact pressure between surface. You won't get this output unless you physicaly model some contact between the Vickers and coating. as the name say, it is the contact pressure the coating see and it is always in the normal direction to the deformed surface.
I perfer to use pressure instead of force as I am too lazy to mearsure the mesh size.

 

[azidah]

I am sorry for dissapearing for a while.

I followed xerf's advice to define NFORC in field output and I got some values from the result.However, I dont really understand how can I determine at which nodes/elements the values come from.

http://i2.photobucket.com/albums/y35/toyon/NFORC.jpg

Answer to xerf's latest post, I would like to obtain the reaction force of the Vickers from the given displacement (determined in STEP). How can I actually do that? I have selected the whole vickers part and defined it in set but the result shows zero value still.

I used Standard Contact control between the vickers and the surface of the coating with automatic-overclosure tolerances with 0.002 slide distance.

the other thing that left me wondered, why the force and the stress values are not symmetrical although the vickers is modelled symmetrically and displaced in -y dir accordingly

 

[skyseducer]

If you write a Python Postprocessing file calculating the sum of the RF2 values at the node node that are submitted to boundary conditions, you should have the result you want.

Cheers

 

[azidah]

hi skyseducer,

Thanks for yr tips. I didnt do like you said (writing a Python Postprocesing file) but I selected the bottom part of the substrate (where my BC is) in set and used it to generate the total force values in the field output. In order to obtain the values, I selected Report/FieldOutput/Variable- unique nodal/ total force and click apply. and the field output report was appended to file "abaqus.rpt".

http://i2.photobucket.com/albums/y35/toyon/TOTALFORCE.jpg

thank you so much all for helping

i hope this post will help others too

 

[bassmanjax]

Here's an idea...

Assuming that the indentor is significantly harder than the test piece, you can model the indentor with rigid elements. Then, tie the rigid elements together with a reference node to form a rigid body.

Apply the vertical displacement to the reference node to push the indentor into the test piece.

Then, in Viewer, you have the option to plot RF2 for the reference node/point - hence the load required to indent the material is readily available.

Regards

Martin

Martin Stokes CEng MIMechE

 

[azidah]

thanks martin