Contact forces in Hyper View

Altair Forum User

Hi
 

I have a question regarding the contact forces results.

I am not sure these contact forces in Hyper view demonstrate what.
 

I have done a simple nonlinear analysis

<?xml version="1.0" encoding="UTF-8"?>

 

 

 

Pressure is applied on the core cap

<?xml version="1.0" encoding="UTF-8"?>

 

and 6 bolt forces each one equal to 120 KN as shown below

 

and this bottom surface is constrained fully

 

 

 

The follwing is the results I got for the contact forces
 

Contact forec on the core cap piece, 4.58 E3 N

 

 

Contact force on the core piece 8.9E3 N

 

I don't understand why these two numbers are not equal. They are action and reaction forces. contact force here in this problem is internal force right? so the amount of force that core applies to the core cap should be equal to what core cap applies to core just in opposit direction to have equilibrium

 

Even if I consider core cap only and write the equilibrium equation for that
 

bolt force + Normal contact force applied the core cap is not equal to pressure* cross area which is weird
 

i appreciate if you can explain me what these contact forces really are in Hyperview.

 

 

 

Altair Forum User

Hi @bita

 

I think contact stiffness depends on contact force and contact penetration.

 

Penetration needs to be removed by applying contact force. More contact force means more penetration. 

Altair Forum User

Would you please explain more. i don't understand why contact force on two pieces are different. they are action and reaction forces and they should be equal just in opposit direction of each other

Altair Forum User

Hi Bita,

 

Contact force depends on contact stiffness and penetration. Contact stiffness is is dependent on material stiffness of two contacting bodies.

 

According to Newton's third law what you are saying is correct but the assumption there is the bodies are rigid. 

 

Altair Forum User

What is Contact traction/ Normal (pressure)? someone told me you need to compare the value of contact traction / Normal (presure) in Hyperview. But I don't know what exactly this traction is?

Altair Forum User

Hi Bita,

 

Pressure is the force per unit area on a node with area taken as surrounding elements.  If the pressure value is positive it is compression otherwise it is tension. 

covadonga

Hello, 

 

I am trying to compare the Average Normal Pressure/ total contact area and the resulting Normal Force from the .CNTF file. The figures I obtained are in different order of magnitude.

 

I have three questions in this regard:

 

the total contact area seems to be very low in the .CNTF file, how is it calculated? should I use the total available contact area instead?

Can I obtain the Average Normal Pressure directly in the software?

More importantly, previously  in this discussion, it is mentioned that the contact force depends on the stiffness and the penetration, does it mean  the normal pressure would also depend on the stiffness and the penetration? Would I get different answers depending of the K?