## General Mechanical

#### Possible Contact Related Issue to Simple Tensile Simulation

• solidus
Subscriber

I encountered an error with a tensile simulation I tried to run in ANSYS Mechanical. I'm looking at a rectangular dog bone geometry with different interlocking joints, and defining a frictionless contact for just the sides of the joint (see attached image). One end is fixed and the other is displaced .1mm in the positive tensile direction; both parts of the structure are modeled with the same simple isotropic linear elastic model. I was able to successfully run this simulation for two different geometries (one of which is pictured in the Simulation Set Up image), but for one geometry (picture attached), I keep receiving a solver pivot warning and the solver is unable to provide a solution for the von Mises and principal stresses. I'm not sure why this geometry is throwing an error when my set-up is identical to other successfully run simulations so any help is appreciated.

• Rameez_ul_Haq
Subscriber
,why do you want to use a frictionless contact? A solver pivot error means rigid body motion is possible on any of the bodies within the structure, and the static solver is not sophisticated enough to solve these kinda Rigid Body problems.
You can try Rough contact (which is again a non-linear contact), but a more straight forward approach would be to use bonded (linear contact).
• solidus
Subscriber
I went with a frictionless contact because I wanted to visualize stress concentrations along the sides of the interface. I thought with a bonded interface the stresses would be perfectly distributed so this wouldn't be possible to visualize. It is a moderate displacement, so meaningful separation along the interface is unlikely; maybe it is more realistic to use a bonded condition? I started out with a bonded condition with some of the other geometries and got stress distributions that didn't make sense to me, but it could be worth looking into again. Thanks for your response!
• Rameez_ul_Haq
Subscriber
the physical joints in reality can be modelled using contacts in FEA, yes. But if the choice of contact is not appropriate, then the static solver might give a rigid body motion error, since it doesn't have the ability to solve these type of analysis. If you are definitely sure that the structure that you are considering under the respective loads should not perform a rigid body motion in reality and should only behave static, then you should be using those contacts which will make the overall structure become static.
If you don't wanna go for bonded, then first try rough contact and check if it works. If it does, then try changing the contact to frictional with a certain frictional coefficient (like 0.3 or something) and then again check if it works. If it doesn't then try increasing the frictional coefficient.