A special X-radiography,used in obtaining the deformed specimen grating inin-plane moire method is introduced.The density of gridline is up to 50 lines / mm.Thismethod is suitable not only for the copy of grating in fiat surface but also for that incurved surface.From unfolding the copy and superposing it with a reference grating,themoire effect arises.By processing this moire fringes with the digital image processing unit,the strain distribution would be obtained.Furthermore,the u-and v-displacementfields could be separated by the optical processing of this copy.Themeasurment sensitivity and accuracy become better simultaneously because ofthe fringe multiplication.Thus,this method makes it possible to measure theelastic-plastic strain precisely in any developable curved surfaces,for example,the surface of shaft,rotary-wing,cylindrical shell and cone shell etc.
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