The welding numerical simulation involves thermal and mechanical analyses and metallurgical consideration. The thermal analysis determines the transient temperature distribution on the welded part, and its accuracy is relevant for the following analyses on structural integrity, in particular buckling and fatigue failure modes of steel-plated structures. The temperature distribution is strongly influenced by the size and shape of the heat source, which can be represented as a double ellipsoid and defined by Goldak's parameters. The main difficulty is that the adjustment of these parameters to obtain a suitable temperature distribution is usually determined by trial and error. In this paper, a parametric study is performed to analyze the influence of Goldak's parameters on the weld bead size for 2D and 3D numerical welding simulations. A method to estimate the parameters of a double ellipsoidal heat source in motion is proposed. An algorithm has been implemented based on the combination of analytical formulation, experimental data, and numerical simulation. As an analytical formulation, the Fachinotti's solution is used to determine the isotherms. The weld bead dimensions are defined from the melting temperature isotherm of the material. Experimental data, such as the welding process parameters and the weld bead dimensions are input to the algorithm. Numerical simulations of the welding process have been developed to calibrate and validate the method. The numerical simulation results from the obtained Goldak's parameters by the proposed method are correlated with the experimental results of fillet-welded specimens.

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Sandwich pipes (SP) combining high structural resistance with thermal insulation have been considered as an effective solution for using in ultra deepwater pipelines. Research has been conducted at COPPE/UFRJ with different core materials aiming to develop qualified pipes to transport deepwater oil and gas, especially for the pre-salt reservoirs in offshore Brazil. SPs using SHCC material are easy to manufacture and cost-effective. Moreover, the composition of the SHCC material can be controlled to achieve structural requirements along with good thermal insulation. Investigation on the buckling under external pressure and feasibility of installation by reel-lay method is required. This study presents numerical analysis of the collapse, collapse propagation and bending of sandwich pipes with different geometries. The Drucker-Prager formulation is employed for SHCC constitutive model and it is calibrated through small-scale tests. Model geometries match full scale specimens manufactured and tested in bending apparatus and hyperbaric chamber. Numerical/experimental correlation is also presented.

Numerical–experimental correlation study for small scale damaged stiffened panels was performed. Six small scale models were fabricated. Two of them were employed for the correlation of intact panels and the remaining four for the correlation of dented panels. Ultimate strength analyses were carried out in order to adjust the numerical model for further use in parametric studies. The damage was imposed by a local indentation of the panels. Measurements of geometric imperfection distributions and damage shapes have been performed before and after the damage using a laser tracker equipment. The numerical models were represented by shell elements assuming finite membrane strains and large rotations, considering both geometric and material nonlinearities. Results obtained showed very good agreement between experimental and numerical analyses for both intact and dented panels. Additionally, numerical simulations of damaged stiffened panels were performed. The aim of the parametric study was to evaluate the behavior up to and beyond buckling, to observe the strength loss due to the presence of the damage on the panel. The explicit nonlinear finite element code from abaqus program was employed to simulate the dent damage. Therefore, distortions and the residual stresses due to the damage were both considered in subsequent numerical compression analyses.