Abstract
The moiré fringe with enhanced sensitivity, as much as ten times of conventional method, can be obtained by a newly developed strain measuring system based on multiplied fringe shift moiré technique. The system is useful for in situ strain measurement and features the stability against vibration and air-turbulence. Two-dimensional strain distribution can be determined at a time. Metal itself can be used as a test specimen and the measurement is carried out without contacting the test specimen. The system has been applied to the assessment of elastic and elastic-plastic strain and deformation around crack tip. The experimental results and the comparison with the theoretical prediction have verified the usefulness of the newly developed method.