阴APP导航

A 3D transient fusion zone microstructure model is described that begins with a solidification model that predicts the evolution of 3D solidification n microstructure with solute difiusion. The fusion zone microstructure model is coupled to a weld pool model that predicts the composition and cooling rate of the weld pool liquid-solid interface with a typical spatial resolution of 0.5 microns. The solidified microstructure then transforms as it cools through the usual sequence of phase transformations of austenite, primary ferrite, pearlite, bainite and/or martensite depending on the composition, austenite grain size and cooling rates. As it cools, the micro-stress is computed for a visco-thermo-elastic-plastic constitutive model. After cooling to room temperature, analyses of 3D tensile tests predict stress-strain curves for the microstructure. The initial state for a tensile test includes the microstructure and residual stress on cooling to room temperature. Tensile tests parallel and transverse to the cooling direction are computed. In addition to the coupling to the weld pool micro-model, the fusion zone microstructure model is coupled to a macro-analyses of the transient temperature, microstructure evolution and stress evolution in a larger structure. In this paper, a multi-pass girth weld in an HSLA natural gas pipeline is used to demonstrate use of the model in a larger structure.