High strain gradient measurements using modified automated grid technique

The automated grid technique, which was constantly used to measure strain field mapping, is a full field optical technique with the character of high efficiency, good adaptability and simple applicability. Due to the limitation of the spot pattern preparation, it was restricted for the measurement of strain distribution in regions of high strain gradient. In this paper, an modified automated grid technique, in which the grid spots were made by using the lithography technique, was applied for the measurement of the high strain gradient. To validate the modified automated grid technique, aluminum specimens with circular holes were employed as the test specimens and the deformation behaviors in the regions of stress concentration were investigated. The testing results agreed well with the analytical and numerical analysis. In comparison with the traditional automated grid technique, the modified method is more accurate. All the results indicate that the high strain gradient test method based on the modified automated grid technique is reliable and appropriate.