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Development and Verification of a Weld Simulation Capability for VAST

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Technical rept.

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This report presents work aimed at developing a weld simulation capability for the VAST suite of finite element codes and the SubSAS submarine structural modeling software. In this study, a number of features required for weld simulations were implemented and verified. For heat transfer analyses, these included an element birth algorithm for tracking the states of weld elements with moving heat sources, a capability for generating thermal load vectors based on Goldaks model, and a capability for treating temperature-dependent thermal properties. For structural analysis, thermal induced strains were first implemented in the elastic-plastic material model to facilitate coupled thermal-mechanical analyses, and the resulting thermal-elastic-plastic constitutive model was adjusted to treat melting and solidification of materials during the welding process. Temperature-dependent structural material properties were implemented and multi-pass welding was supported. For heat transfer analysis, weld simulations with different weld sequences were performed successfully. For structural analyses, the VAST capabilities were tested by using various test cases designed to reflect certain features of weld simulations. The VAST element and material model behaved favourably and no convergence difficulties were observed. However, when VAST was applied to a full weld simulation, divergence occurred after the first few solution steps. Further investigations are required to identify the cause of the numerical problem. The new weld simulation tools were not implemented in SubSAS, but a methodology was developed for implementing SubSAS support to define welding simulation models. Modifications to SubSASs underlying RMGScript schema to support capturing the welding model parameters are detailed. Advanced algorithms for enhancing SubSASs meshing capability to create brick elements from surface geometry, including a representation of the weld deposit material, also are described.

Subject Categories:

  • Fabrication Metallurgy
  • Computer Programming and Software
  • Submarine Engineering
  • Mechanics
  • Thermodynamics

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