About Contact Interference

When you define surface-to-surface contact, you can specify interference fit options to help resolve excessive overclosure between surfaces in the initial configuration of a model.

Small overclosures in the initial geometry of the model can be dealt with by using the strain-free adjustments option of surface-based contact. For larger overclosures, you must define contact interference features that result in stresses and strains in the model as the overclosures are resolved during the simulation. The contact interference options allow the overclosures to be resolved gradually over multiple increments within the step.

The default contact constraint imposed at each contact location defines the current penetration, $h\left(t\right)$, to be less than or equal to zero. Penetration (overclosure) exists when $h\left(t\right)$ is positive. To alter this constraint, you can specify a uniform allowable value for the interference, $v\left(t\right)$, that will be ramped down over the course of a step. Therefore, specifying a positive value for $v\left(t\right)$ causes the simulation to ignore penetrations up to that magnitude. Amplitude curves can be used to modify the magnitude of the uniform allowable penetration.

If the penetration in the model is $h$, you can declare $v=h$ or request an automatic shrink fit. In either case, the two bodies are considered to be exactly in contact at the start of the simulation. As the allowable interference, $v$, is decreased during the step, the simulation pushes the surfaces apart until there is no more allowable penetration.

By default, the value of the specified allowable interference is applied instantaneously at the start of the step and then ramped down to zero linearly over the step.