Which method has more accurate friction modeling between penalty force method and skin method?
The correct answer and explanation is:
It is important to clarify that “skin method” is not a standard, widely recognized term in computational contact mechanics literature comparing directly against the “penalty force method.” Common methods compared to penalty include augmented Lagrangian, Lagrange multipliers, or surface-based methods like Mortar methods.
Assuming “skin method” might refer to an approach that models the surface properties or the contact interface more directly or precisely than a basic penalty method, we can compare the general accuracy implications.
The Penalty Force Method models contact and friction by applying a repulsive force proportional to the amount of artificial penetration between bodies. The normal contact force is derived from this penetration (Stiffness * Penetration). Friction is then typically calculated using Coulomb’s law, based on this derived normal force.
- Accuracy Limitation of Penalty for Friction: The primary limitation is that it requires penetration to generate a normal force. Friction is thus dependent on an artificial numerical artifact (penetration). The accuracy is heavily dependent on the penalty stiffness parameter – too low allows excessive penetration; too high can cause numerical instability. It does not intrinsically model complex surface physics beyond simple Coulomb friction unless added as an overlay.
If a “skin method” refers to an approach that:
- Models the contact interface or surface properties more explicitly.
- Enforces contact constraints more accurately (e.g., minimizing or eliminating artificial penetration, as in Lagrange Multipliers or Augmented Lagrangian methods).
- Potentially incorporates more complex surface physics (adhesion, roughness, detailed constitutive models for the surface layer).
Then such a “skin method” would generally have more accurate friction modeling than the basic penalty force method. By reducing or eliminating reliance on artificial penetration and potentially modeling the true surface interaction or properties, it can provide a more physically realistic basis for calculating friction forces.
In summary, while “skin method” isn’t standard, any method that moves beyond the basic penalty’s reliance on artificial penetration and parameter tuning, or models surface physics more directly, will typically offer improved accuracy in friction simulation. Therefore, if “skin method” represents such an approach, it would be more accurate.