Infrared Window Plate Subjected To Aerodynamic Pressure And Aerodynamic Heating

Under the joint action of the aerodynamic heating and aerodynamic load, infrared window material will be in complex temperature field and stress-strain field, which can cause infrared window breaking, light distortion, thermal radiation interference and membrane layer fall off. Consequently, the window structure will lose specific function. Such a phenomenon is referred to infrared window material structural/functional failure.This thesis studies the deformation and stability of infrared window material plates subjected to joint action of aerodynamic pressure and aerodynamic heating. It considers two important boundary conditions of infrared window plates: simply-supported and clamped. Two types of materials are studied: sapphire and ZnS. The functional film is BP.When studying the aerodynamic pressure on the infrared window plate, the boundary condition is supposed to be simply-supported. The deflection of the plate is expressed as a trigonometric function, which is solved by using specific boundary conditions of the plate. After obtaining the full-field expressions of the deflection and stress of the plate, the highest deflection and stress for the two different infrared window materials become known. Similarly, for the clamped boundary of the infrared window, a displacement function is expressed in terms of some unknown parameters. Based on the thermomechanical constitutive equations of the material, an energy function is established. Using of the variational principle yields these unknown parameters. As a result, the expressions of the deflection and stresses of the infrared window material plate are obtained. Since the aerodynamic pressure and aerodynamic heating are independent of each other, the responses of the infrared window plate subjected to joint action of aerodynamic pressure and aerodynamic heating are the combination of the responses of infrared window plate under independent aerodynamic pressure and aerodynamic heating.For the buckling between the functional film and infrared window material, the problem is solved by the energy method though the variational principle. Due to the fact that the functional film is very thin, it is treated as an elastic membrane on a substrate. The buckling deflection function is expressed as some functions which contain unknown parameters. From the thermal/mechanical constitutive equations, the energy expression of the delaminate parts is established. From the variational principle the unknown parameters are obtained and the critical load of the plate is given.