Learning Forum

[Ahmed Baig]

Hi I am new to using ANSYS mechanical and Transient. I am performing a validation study on a low tension dead end clamp as pictured below. The wedge within the Clamp is fixed at the top end and the Clamp itself is being pulled away using the anchoring points on either side using a force of 15KN total. The wedge is nearly rigid and serves to break the clamp apart as its being pulled away with enough force. The simulation is currently being performed within a 1 second end time. The force is ramped up over that period from 5KN to 15KN. The clamp is made of material ADC 12

A real stress test was conducted similarly using a Universal Testing Machine. And the Clamp achieved failure at a specified force of 14 to 16 KN. However within ANSYS I am unable to achieve the desired result. Location of failure is correct however the value at which failure should occur is not being achieved.

Do you have any idea what I could be doing wrong? Could it be a contact issue? Perhaps a time step issue? Any help would be greatly appreciated.

I can provide WB files if needed.

[dlooman]

This type "stick/slip" analysis is usually done with a gradually applied displacement, not an applied force.  The reaction force at the applied displacement provides the force deflection information.  The failure load is going to be somewhat dependent on the coefficient of friction between the wedge and the clamp.  What value did you use for that?

[Ahmed Baig]

My static friction coefficient is 0.36. I calculated that myself using the pieces I have available at hand.

Regarding the displacement, how do I apply displacement gradually? I know that the UTM functioned under the setting of guarenteeing 5mm/min of displacement by varying the load magnitude as the piece deformed.

The UTM was able to achieve failure after 8 minutes.

[dlooman]

It seems like the force to extract the wedge would initially be small and then increase as the wide end of the wedge reached the narrower portion of the clamp.  How far is the wedge moving under your current loading?  It would be interesting to test a smaller coefficient of friction.  The dynamic coefficient of friction can be specified for the contact.  I don't think this is really a dynamic analysis and could be solved as a static.  It's easy to specify a non-zero Displacement that varies from 0 to the length of the wedge.