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[FAQ]

The contact energy is an accumulated value on a per part basis. At timestep n+1 it is defined as E_n+1 = E_n + Sum_over_part_nodes(dE), with dE = K*dx. In contact, Autodyn uses a penalty method to put the nodes back on the surface. This penalty force is proportional to the penetration depth, so in effect we have dE=K*dx where K is a sort of penalty spring which can store and release energy. That energy is accounted for in contact energy. Large contact energy therefore means we still have a lot of contact with substantial penetration depths (if it is positive) or we lost energy in contact (negative).