Residual Stress Measurements of Unblasted and Sandblasted Mild Steel Specimens Using X-Ray Diffraction, Strain-Gage Hole Drilling, and Electronic Speckle Pattern Interferometry (ESPI) Hole Drilling Methods

The objectives of this research are to measure residual stress in both unblasted and sandblasted mild steel specimens by using three different techniques: X-ray diffraction (XRD), strain-gage hole drilling (SGHD), and electronic speckle pattern interferometry (ESPI) hole drilling, and to validate the new ESPI hole drilling method by comparing its measurement results to those produced by the SGHD method. Both the XRD and SGHD methods were selected because they are accurate and well-verified approaches for residual stress measurements. The ESPI hole drilling technique is a new technology developed based on the SGHD technique, without the use of strain gage. This technique is incorporated into a new product referred to as the PRISM system, manufactured by Hytec, Incorporated, in Los Alamos, New Mexico. Each method samples a different volume of material at different depths into the surface. XRD method is especially different compared to the other two methods, since XRD only measures stresses at a depth very close to the surface (virtually zero depth). For this reason, no direct comparisons can be made between XRD and SGHD, as well as between XRD and ESPI hole drilling. Therefore, direct comparisons can only be made between SGHD and ESPI hole drilling methods