A Novel Low-Cost DIC-Based Residual Stress Measurement Device

Residual stress analysis via existing non-destructive or semi-destructive methods can be costly and time-consuming, and therefore a cheaper and faster methodology is sought. This paper proposes a novel measurement device that combines hole drilling and digital image correlation methodology comparable to ASTM E-837-13a. Cross-validation of the methodology was performed on a test specimen using conventional methods and the results were found to be within +/−30 MPa. This device reduces measurement time from 2 h per point to 45 min and the cost of the experiment is reduced from £50 to £1 per measurement. Highlights: Residual stress often has a significant impact on part performance and lifetime. Existing measurement techniques using strain gauges or non-destructive methods are often expensive and time-consuming. This paper presents a low-cost, novel measurement device that uses digital image correlation with the hole-drilling method to quantify the magnitude and preferred orientation of these locked-in forces. A two-axis measurement device that rapidly drills and images the surface around the hole was developed to measure residual stresses as a function of depth with sub-millimetre resolution. Validation of the device and DIC methodology was performed using a four-point bending specimen and comparison with conventional strain gauge methods. The results showed strong correlations between the two measurement techniques, as well as the theoretical estimates. The total cost of production was estimated to be approximately £380, which is significantly cheaper than competitors. The device also substantially reduced the cost per measurement point (less than £1 vs. £50+) and shortened the experiment duration from 2 h per point to 45 min per measurement. A functional, rapid, economical device has been designed and produced, which is currently being used for residual stress analysis of industrial samples. The presented design is completely open-source, and the relevant links are provided.