  Current engineering wear models are often based on empirical parameters
rather than built upon physical considerations. Here, we look for a physical
description of adhesive wear at the microscale, at which the interaction
between two surfaces comes down to the contact of asperities. Recent
theoretical work has shown that there is a critical micro-contact size above
which it becomes energetically favorable to form a wear particle. We extend
this model by taking into consideration the elastic interaction of multiple
closely-spaced micro-contacts in 2D, with different sizes and separation
distances. Fundamental contact mechanics solutions are used to evaluate the
elastic energy stored by shearing the micro-contacts, and the stored energy is
compared to the energy needed to detach a single joined debris particle or
multiple debris particles under the micro-contacts. Molecular dynamics
simulations are used to test the predictions of the outcome for various sets of
parameters. Our model provides simple criteria to evaluate the energetic
feasibility of the different wear formation scenarios. Those criteria can be
used to rationalize the transition between mild and severe wear regimes and
help define the notion of asperity.
