Discussion on plastic strain measurements and an application of the developed scribed circle method to shear strain measurements of a micro-surface

The best method, avairable at present, of measuring the largest plastic strain in the smallest area of a specimen surface is discussed on the developed scribed circle method presented in the previous report, the strain gage method and three different X-ray methods of diffraction profiles, Debye films and the residual stress measurement. The developed scribed circle method is found to be the best one among the above. The application test of this method to measure large shear strain in a micro-surface was performed on a thin walled tube specimen of aluminum. Shear strain of nearly forty percent was measured with sufficient accuracy and that of nearly ninety percent was possibly obtained within a five percent off the condition of pure shear.