Measurement of Non-uniform Residual Stresses Using the Incremental Hole Drilling Method and Digital Image Correlation: A Feasibility Study on Deep Rolled Specimens

This study explores the applicability of digital image correlation (DIC) techniques for measuring non-uniform residual stresses using the incremental hole drilling method. Specifically, it examines the residual stresses induced by a deep rolling treatment on 7075-T6 aluminum specimens, characterized by strong depth gradients. The aim is to assess the potential of replacing traditional strain gauge rosettes with DIC systems. After the deep rolling treatment, residual stresses were measured using the classic hole drilling method with a strain gauge rosette according to ASTM E837, providing a reference for the DIC measurements. The specimens and camera were mounted on a CNC machine, which allowed precise repositioning of both elements at each drilling step. Experimental results show that DIC measurements allow for the calculation of residual stresses with good accuracy. While their precision is lower than traditional strain gauge measurements, full-field DIC techniques partially compensate for this disadvantage by measuring the entire deformation field around the hole. This approach offers statistically advantageous data redundancy and captures displacements in areas immediately surrounding the hole, which are more sensitive to residual stresses. Considering the time and cost savings by avoiding the use of strain gauge rosettes, DIC techniques offer a valid alternative for determining residual stresses with the hole drilling method. The key factor for their application lies in the ease of repositioning both the camera and the drill at each depth increment.