Abstract:Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight. A finite element method was adopted to simulate the thermal and stress response of microscale functional film for infrared window under different aerodynamic heats/forces conditions. Temperature and stress distribution were obtained with different heat fluxes. There is almost constant stress distribution along the film thickness except a sudden decrease near the substrate. The maximum stresses are located at the points which are 0.5 mm away from the edges. Different film materials result in different stress values. The temperature and stress in ZrN are larger than those in Y₂O₃. Besides the numerical simulation, an oxygen propane flame jet impingement test was performed to investigate thermal shock failure of the infrared window. Some place of the window surface has spots damage and some place has line crack damage after thermal shock.

Key words: infrared window; thin films; finite element method; thermal stress; aerodynamic heating