Molecular Dynamics Research For The Effect Of Lattice Defects On The Damping Capacities Of Metallic Coatings

As thermal barrier coatings and corrosion-resistant structures, inorganic coatings have been widely used in the aerospace field with their good strength and excellent insulation properties. In recent years, experimental studies suggested that hard coatings also exhibit good damping capacities due to their microstructure which consists of microscopic defects and can absorb vibration energy to protect engine components from vibration damage. Currently, the energy dissipation mechanism of inorganic coating material is not yet conclusive.In this paper, molecular dynamics simulation method is employed to investigate the effect of several common lattice defects on the capacities of energy suppression of copper under external tensile load. The internal mechanism of energy dissipation is interpreted through the evolution snapshot of defective atoms and then damping mechanisms responsible for the energy dissipation in metallic coatings is explained. Five crystal structure models are developed successfully by molecular dynamics method which includes a perfect copper crystal model and four defective models with embedded micro-cracks, vacancies, embedded dislocations and grain boundary respectively. The equilibrium configurations of these five models with minimized energy are obtained by conjugate gradient algorithm as a basis for the next tensile loading and unloading simulation calculations. And the simulation results show that following microstructural behaviors are responsible for the energy dissipation:such as the proliferation of dislocation lines nearby initial dislocations which are regarded as dislocation emission source; dislocation emission resulted from concentrated stress near micro-cracks; dislocation climb and expansion achieved through vacancies and dislocations accumulation near the grain boundary and grain boundaries collapse caused by dislocations.The damping capacities of copper coating samples were analyzed under in-suit loading and unloading and the result agrees to the simulated result. It is concluded that the main energy dissipation is achieved through dislocations emission, transmission and the interaction between dislocations and other defects.