HIGH-RESOLUTION STRAIN-MEASUREMENTS BY DIRECT OBSERVATION IN THE SCANNING ELECTRON-MICROSCOPE

A technique for measuring strain with an accuracy of ±100 μΕ by direct observation in the scanning electron microscope has been developed and tested. The technique involves placing a fine metallic mesh loosely on the surface of a tensile coupon and observing the motion of the surface with respect to this mesh. It was evaluated by tensile loading of aluminum and carbon fiber-reinforced epoxy specimens for strains up to 600 μΕ using an instrumented miniature loading stage. Applications and limitations of the technique have been discussed.