Abstract: The internal welding longitudinal residual stress is measured using contour method for a bead-on-plate welding specimen and a T type welding structure. The welded specimen is cut along a plane perpendicular to the weld line, and the deformed profiles (contours) of the cut surfaces are precisely measured. Then, the measured contours are fitted and taken as displacement boundary conditions to an elastic finite element model to calculate the corresponding stresses normal to the cutting plane. The fitted contours of the cut surfaces with different fitting methods are compared, and the measuring results are also compared with those of three-dimensional thermal-elastic-plastic finite element simulation. Investigated results show that the internal residual stress of thick welded structures can be measured with good precision by the contour method; due to the errors introduced by the electric discharge machining (EDM) and the profile measurement, the subsurface residual stress within 2 mm depth measured by the contour method would be inaccurate in magnitude, but the good distribution trend can be got by the method; broken wire during EDM process can lead to local profile error that produce a abrupt change in measured stress.

Key words: Contour measurement, Finite element method, Residual stresses, Welding