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Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Computational Materials Science | Year: 2012

To increase productivity, welding process with large heat input such as electro slag welding (ESW) process has been used to connect the joints between the diaphragm and the column plate in high-rise steel building. However, the heat input of ESW is much higher than those of the other welding processes, and the high heat input not only largely alters the properties of steel but also results in large residual stresses. Consequently, the changes of steel properties and residual stresses induced by ESW have significantly effects on the safety of a structure. In this study, a three dimension (3-D) finite element model with considering moving heat source was developed to simulate the welding temperature field, Δt 8/5 time, welding residual stress and distortion in a typical thick plate joint performed by ESW. The thermal cycles computed by finite element model were compared with experimental measurements. Meanwhile, the features of welding residual stress and distortion distributions in the ESW joint were investigated numerically. In addition, the influences of heat input on the size of heat affected-zone (HAZ), Δt 8/5 time welding residual stress and distortion were examined. The thermal cycle curve and simulated by FEM model can be used to deduce the micro-structure as well as toughness of weld zone and HAZ, while the welding residual stress distribution estimated by numerical model can be helpful to assess the structural integrity. © 2012 Elsevier B.V. All rights reserved.


Takase S.,Computational Mechanics Inc | Kashiyama K.,Chuo University | Tanaka S.,University of Notre Dame | Tezduyar T.E.,Rice University
International Journal for Numerical Methods in Fluids | Year: 2010

We present a new space-time SUPG formulation of the shallow-water equations. In this formulation, we use a stabilization parameter that was introduced for compressible flows and a new shock-capturing parameter. In the context of two test problems, we evaluate the performance of the new shock-capturing parameter. We also evaluate the performance of the space-time SUPG formulation compared to the semi-discrete SUPG formulation, where the system of semi-discrete equations is solved with the central-difference (Crank-Nicolson) time-integration algorithm. © 2010 John Wiley & Sons, Ltd.


Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Computational Materials Science | Year: 2010

A finite element approach based on Quick Welder software is developed to simulate welding temperature field and welding residual stress distribution in a 3D multi-pass girth-welded pipe model. The characteristics of welding residual stress distributions in a SUS304 stainless steel pipe induced by heating with a tungsten inert gas arc welding torch are investigated numerically. Meanwhile, an emphasis is focused on examining the welding residual stress distributions in and near the weld start/end location. Moreover, the residual stresses predicted by the present computational approach are compared with the measured data; and the comparison suggests that the numerical simulation method has basically captured the feature of welding residual stress distribution near the weld start/end region. The numerical simulation results show that both the hoop and the axial residual stresses near the weld start/end region have sharp gradients and are significantly different from those in the steady range. © 2010 Elsevier B.V. All rights reserved.


Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Nuclear Engineering and Design | Year: 2010

With the development of computer hardware and software, numerical simulation technology has been widely used to predict welding temperature field, residual stresses and distortion. However, till now the influences of initial stresses induced by the manufacturing process before welding on the welding-induced residual stresses are rarely investigated experimentally and numerically. In the present work, we have developed a computational approach based on thermal elastic plastic FEM to clarify how the initial stresses due to heat treatment affect the welding-induced residual stresses in an austenitic stainless steel pipe. A heat treatment process, which is similar to solution heat treatment, is employed to produce initial stresses in the pipe before welding. After the heat treatment, the laser beam welding is used to perform a girth weld in the middle of the pipe. Through comparing the residual stress distributions after heat treatment and laser beam welding, we have investigated the influence of the initial residual stresses on the welding-induced residual stresses. The numerical results suggest that the initial residual stresses prior to welding have significant effects on the residual stresses after welding in the pipe model. © 2009 Elsevier B.V. All rights reserved.


Takase S.,Computational Mechanics Inc | Kashiyama K.,Chuo University | Tanaka S.,University of Tokyo | Tezduyar T.E.,Rice University
Computational Mechanics | Year: 2011

We show that combination of the Deforming-Spatial-Domain/Stabilized Space-Time and the Streamline-Upwind/Petrov-Galerkin formulations can be used quite effectively for computation of shallow-water flows with moving shorelines. The combined formulation is supplemented with a stabilization parameter that was originally introduced for compressible flows, a compressible-flow shock-capturing parameter adapted for shallow-water flows, and remeshing based on using a background mesh. We present a number of test computations and provide comparisons to theoretical results, experimental data and results computed with nonmoving meshes. © 2011 Springer-Verlag.

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