Engineering topics

Murakawa, Hidekazu

Publications and source records attributed to Murakawa, Hidekazu.

3 records

DOE OSTI2020

Progressive collapse analysis of stiffened panel structure with consideration of actual welding distortion and residual stresses

To date, inclusion of welding distortion and residual stresses in determining the strength of marine structures is based on empirical formulations due to welding complexity. In this study, a more feasible numerical model was developed from the perspective of inherent strain theory. The accuracy of this simplified numerical model was confirmed by transient thermo-elastic–plastic finite element analysis using a novel dynamic mesh refining and iterative substructure method which is 50 times faster than conventional finite element method. Welding distortion by the two numerical approaches was validated with experimental measurement. The collapse analyses indicated that the inherent strain model predicted a compressive strength and load-displacement curve with high accuracy, as validated by the transient thermo-mechanical model. The global stiffness and the ultimate strength of the welded structure would be overestimated by about 22% if no welding effects were considered. The proposed computation procedure for determining the ultimate strength of welded structures is accurate, simple, and practical and enables improvement of ultimate strength through optimization of welding joint design to reduce the welding residual stress and distortion.

Huang, Hui↗

DOE OSTI2020

Toward large-scale simulation of residual stress and distortion in wire and arc additive manufacturing

In this study, we aim to advance the structural analysis of wire and arc additive manufacturing (WAAM) by considering the thermomechanical features inherent in direct energy deposition. Simulation approaches including the iterative substructure method (ISM), dynamic mesh refining method (DMRM), and graphics processing unit (GPU) based explicit finite element method (FEM) were developed for accelerating additive manufacturing stress analysis that is very time consuming by conventional numerical methods. ISM and DMRM take advantage of the strong nonlinearity phenomenon near the moving heat source by reducing the global iterations and refining the local mesh, respectively. In addition to the use of GPUs, the explicit FEM is accelerated by a time scaling technique based on the inherent strain concept. The residual stress and distortion of two large builds were analyzed, showing very consistent numerical results and good agreement with experiments. Compared with the commercial software Abaqus, the novel approaches reduced the computational cost substantially without compromising accuracy. The GPU code showed the highest computational efficiency (30~70×), while DMRM and ISM had acceleration factors of 9× and 3×, respectively. Finally, such high-fidelity modeling approaches will be very useful for building up a digital twin of WAAM to reduce development time and cost.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Efficient thermo-mechanical simulation approaches for arc-and-wire based additive manufacturing

This study aims at the thermo-mechanical features inherent with the arc and wire metal deposition process to advance the structural simulation of additive manufacturing. Simulation approaches including iterative substructure method (ISM), dynamic mesh refining method (DMRM), and graphics processing unit (GPU) based explicit FEM code (GPU code) were developed for accelerating stress analysis and compared in terms of efficiency and accuracy. ISM and DMRM both take advantage of the strong nonlinearity phenomenon near the moving heat source, by reducing the global iterations and refining the local mesh respectively. The explicit FEM code was accelerated by a mass scaling technique based on the inherent strain concept. Two large parts by wire and arc additive manufacturing were analyzed, and the numerical results agreed very well with each other. The predicted distortion and residual stresses in the deposited layers were validated by experimental measurement. Compared with commercial software ABAQUS, the novel approaches reduced the computation cost substantially without compromising on accuracy. GPU code shows the highest computation efficiency (x30~70), while DMRM and ISM has an acceleration factor of x9 and x3 respectively. Owing to the minimum model simplification, such advanced simulation approaches will be very useful for structural analysis of additive manufacturing with complex deposition paths and product geometry.

Huang, Hui↗