NX Hertz contact problem in SOL 101

[nastranuser123]

Hi,

I'm carryng out the solution to the Hertz contact problem in 101 with 8 noded hex mesh.

I have uploaded my dat file as in the link below.

I have applied a load of 10.90 N to 22 nodes to make a total of 240 N.It is the normal load.

I used surface to surface contact by craeting regions of eleemnt faces as you might notice.

I applied the constraints as seen.

Howveer, my contact is not established as you can make out from contact force distribution.

Can someone please have a look? I've been struggling really.

Chris

 

[nastranuser123]

In the attached dat file, you will notice that I have created a group of nodes at the contact interface.

You can see that the dum of contact foces is '0' indicating that contact is not established.

If someone can have a look, it will be useful.

I understand from earlier posts that Blas Molero Hidalgo sir is an expert in contact simulations and his input/help with regards to this model will be very useful

 

[BlasMolero]

Dear Chris,
Well, a few errors here:
1.- Your model is singular, then you will receive the error "Run Terminated Due to Excessive Pivot Ratios” because the cylinder can move freely in the space in the Z and X axis. You need to stabilize the "wheel": take advanced of double symmetry, doing TX=TY=0 in the planes of symmetry.

http://iberisa.wordpress.com/2011/0...run-terminated-due-to-excessive-pivot-ratios/

2.- Your mesh is a disaster, between others violations you have ASPECT RATIO = 255.7, not all is valid in Finite Element Analysis, a minimum mesh quality is required, if not NX NASTRAN will give you error. This problem can be studied perfectly as 2-D PLANE STRAIN using 2-D QUAD elements, not need at all to use 3-D solid elements.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[nastranuser123]

Thank you Sir..

I have solved the above problem and I get good results.

I have another question:

1) See attached figure.

2)I have a shear load along with normal load

3)I have used plane strain elements

4) I tried restraining the end nodes (where you see the reaction of y0Q/2xo in the figure) but resulted in unreasonable values.

5)IS the shear load resisted by friction alone?

Christy

 

[BlasMolero]

Dear Christy,
You are simulating a motion, and this is a very complex task for Finite Element Method where we only want to deal with structures or restrained parts.
You can try, but you need to stabilize the model using "soft springs" to avoid to have a mechanism, and of course to solve as dynamic nonlinear (SOL129) using an iterative process.
Enforced motion helps to achieve convergence.
Good luck!.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[nastranuser123]

Sir, actually I'm not sure if I got that correctly.

I'm just applying a tangential load at the location.

I was thinking how to equilibrate that in rotation.

The frictional force will provide the horizontal equilibrium. I was wondering about the rotational equilibrium ...

Christ