Inverse Iterative Methodology for Welded Joints Characterization in Construction Designing and Comparison to Classical Approach

Abstract

Traditional approach in structural designing and strength assessment that observes structure without welded joints is sufficiently accurate in terms of elastic response, in comparison to yield strength. The main idea of this paper is to show that it is necessary to consider welded joints and all their regions in the elastic-plastic domain. This methodology proposes obtaining of mechanical properties of welded joint regions using inverse iterative procedure developed by the authors of this paper. Taking into account tensile testing of specimens containing welded joints, strain field was obtained using Digital Image Correlation. Finite Element Method model of test specimens is formed using the same parameters as in the experimental one (such as welded joint geometry, boundary conditions, loads, etc.). Strain fields of all regions of welded joint (parent material, weld metal, and heat affected zone) are imported into finite element model, setting ground for development a new, improved, finite element model. Consequently, material properties of all three welded joint regions were obtained. Demonstration of the proposed procedure is shown in the analysis of two significant structures: (i) a pipeline (membrane stress), and (ii) a girder of a bucket wheel excavator (bending of plates). Based on this analysis it was shown within the plastic deformation domain the differences in stresses (and structural behavior in overall) between structure with and without welded joints are considerable, while there is no difference in the elastic domain. Stress concentration factors are formulated for each analyzed type of structure, in order to quantify those differences.