A Developed Method of Measuring Plastic Strain in a Micro-surface and its Application to Practical Use

Films containing scribed circles of the same size were prepared and used for measurements of large plastic strain in various sizes of the surface dimension in an aluminum specimen. The circle diameter in each film was varied from the largest one of two millimeters to the smallest one of ninety microns. Sensitivity in measuring strain depends on the ratio of the scribed circle diameter to the average grain diameter of a tension specimen to be tested. The large ratio of nearly one hundred shows the macroscopic behaviour of homogeneous, isotropic and continuous deformation in a specimen. The small value of nearly a one-hundredth shows the microscopic behaviour of non-homogeneous, non-isotropic and discontinuous deformation in a grain. The intermediate value of it in the above two shows the mixture of them. Application to strain distribution measurements in the non-homogeneous, non-isotropic and discontinuous deformation of a coarse grain in an aluminum specimen has been performed and results of the non-homogeneous strain distribution are given.