Production And Application Of Amplitude And Phase Gratings For High Temperature

Based on combination photoetching method with vacuum coating technique, this paper first develops a new technique for producing amplitude and phase gratings for high temperature on specimen. With the aid of two deposited metal films on specimen surface, the gratings can provide high contrast or good diffraction effects during the high temperature tests. Either metal or non-metal can be selected as the object of producing grating. Furthermore, when sheets of oxidation-resistant metal are selected, the gratings can be applied in situ measurement.Some typical experiments at high temperature are constructed for the application of the high temperature gratings. The amplitude gratings are used to measure the creep deformation of tensile specimen and the holographic gratings are used to measure the residual creep deformation of tensile specimen with stress concentration .The experimental results are analysed in detail.Finally, in order to examine the feasibility of amplitude grating in hostile environments, the test program is directed toward studing the long-term creep measurement of the main steam pipe at power plant. The principle of measurement and explanation on Moire fringes of cylindrical surface are discussed in this study. The results of error analysis of measurement show that the creep measurment accuracy of Moire method is higher than that of joints method which is usually used in the majority ofpower plants. At the same time, the good experimental results pfove that the amplitude gratings made with two—deposited-film method are suitable for the deformation measurement of long—term installations of high temperature in the industrial environment.