## General Mechanical

#### Bonded Contact between a member face to a member face

• sameerfares
Subscriber

Hi All,

I chose a bonded contact as shown below between the rod member in red  which is only in contact with the chord angle blue face. Does Ansys assume the rest of the rod that is not  contact with blue face, and assume this rod member is unbraced and can buckle  between the top and bottom chords of the truss? or does it assume the entire red member is in contact with blue face?

Thanks,

Sam

• peteroznewman
Subscriber

Hi Sam,

Bonded contact uses a Pinball radius which defines a spherical volume. Whatever part of the red and blue faces are inside this ball get contact elements holding them together.  In the Contact Details window, select MPC as the contact formulation. Specify a Pinball radius. Solve the model. After it has solved, you can display the contact elements (CE) as a red spider of elements that holds the two faces together. Click the Solution Information Folder, it will switch the window to the Worksheet, but use the Graphics tab to see those elements.

The rest of the red and blue surfaces that are not within the pinball radius do not have any contact and are free to deform, or buckle as they may.

Regards,
Peter

• sameerfares
Subscriber

Thank you so much Peter!

Two Additional questions regarding bonded contacts:

1. if two surfaces are not contact with each other, but i select bonded contact between these two surfaces, does the  software assume as if they are in contact even though they are not physically in contact with each other?

2.  Do i need to select MPC formulation for all these webs or the software is  intelligent enough to run it so the surfaces that don't have contact are free to deform or buckle as they may be?

Regards,

Sam

• peteroznewman
Subscriber

If two surfaces are identified as a contact pair for bonded contact, whenever those two surfaces are closer to each other than the pinball radius, contact elements will be created, and whenever those two surfaces are farther away from each other than the pinball radius, no contact elements will be created.

It doesn't matter if the surfaces ever touch each other, it only matters if one surface is inside the pinball radius of the other surface.

The above behavior occurs for any contact formulation. I just like MPC for Bonded Contact because I get to see the elements after the solution is complete.

Buckling can occur within a contact pair or outside a contact pair's pinball radius. It's just less likely to be found inside the pinball radius because the stiffness is higher inside the pinball radius because the two parts are bonded.

Regards,
Peter