Figure 2. Comparison of areas measured by a) strain gauge, b) optical methods [7]

From

Modern Trends in the Field of Measurement of Residual Stresses Using Hole-Drilling Method

Patrik Šarga, František Trebuňa

American Journal of Mechanical Engineering. 2016, 4(7), 353-356 doi:10.12691/ajme-4-7-21