Full field strain measurement in welds

Abstract

The intent of this study is to examine the stress-strain response of small material subsets in a weld subjected to some nominal loading using a full- field surface strain mapping technique. This process makes use of the digital image correlation program (VIC_2D) developed by the University of South Carolina. Full-Field surface strain mapping will be used to help determine the basic material properties of the various regions within a weld, which are the heat-affected zone and the mechanically affected zone (weld nugget). During development of this process, various specimens were tested to verify the accuracy of the strain mapping procedure. A tapered stainless steel tensile specimen was studied and the results verified by a finite element model of the test specimen. The results from the full-field strain mapping matched very closely with the strain distribution predicted by the finite element model. To further prove the validity of the strain mapping process, a .0135 inch diameter hole was drilled in a 5454-0 aluminum tensile specimen. The strain measurement process detected the perturbations in the strain field caused by the defect at displacements as low as three-hundredths of an inch within the three-inch gage length. Furthermore, the strain measured near the edge of the specimen using the mapping technique matched to within .01 % the strain measured by an extensometer attached to the test specimen