Molecular dynamics simulations of energetic bombardment of amorphous hydrocarbon (a-C:H) materials by Ar ions up to 200 eV in energy have been performed. In addition to erosion of carbon and hydrogen atoms, the Ar bombardment causes damage and subsequent structural changes in the sample. We present a model based on potential energy analysis to characterize the damage and structural changes. The model identifies both the newly created damage due to bombardment and the local restructuring and subsequent annihilation of already existing damage. The analysis shows that although a large number of carbon atoms are displaced during the collision cascade, most of them do not contribute to the local structural change. Most of the damage creation and restructuring of the local neighborhood happens within the ion range, and, at high energy (200 eV), the restructuring continues beyond the ion range.