Failure characterization of nodular defects in multi-layer dielectric coatings

摘要

Nodular defects in multi-layer dielectric coatings have been computer modeled to characterize the electro-mechanical responses to laser pulses with wavelengths of 1.06 (mu)m and pulse lengths between 1 and 20 ns. The simulation begins with an axisymmetric electric field model using AMOS, a full-wave Maxwell solver with lossy (dispersive) electric and magnetic material models. Electric fields calculated by this code determine the spatial distribution of absorbed laser energy in the vicinity of the nodule. This data is linked to a thermal/stress model and mechanical calculations are executed using the general purpose finite element code COSMOS/M. The simulation estimates the transient temperature response of the nodule and the surrounding medium and predicts the dynamic stresses caused by the thermal impulse. This integrated computer process has been exercised to characterize failure of nodules as a function of defect characteristics, including seed size and depth.