Modelo Termo-mecânico-metalúrgico de chapa de aço naval DH36 soldada com MAG/John

Abstract

Welding process in naval steel plates is widely used in the naval and offshore industry due to its great potential for automation among other advantages. Residual stresses and deformations from the welding process have a significant influence in the performance and reliability of the welded structures. From a thermo-mechanicalmetallurgical numerical model sequentially coupled, developed in a finite element program, the thesis contributes proposing methods that will aid in the study of the influence of metallurgical analysis on residual stresses and deformations in a naval steel plate. The thesis was divided into three models: the thermal, metallurgical and mechanical. In the thermal model, a methodology was proposed to determine the heat source parameters to ensure a suitable temperature distribution, through a mathematical model, experimental data, and numerical models to calibrate and verify the methodology. Different cases were studied, such as weld bead deposition and fillet joint. In the metallurgical model, the deformations were determined due to the phase transformations of the microstructures considering the prior austenite grain size, through a method proposed from welding CCT diagrams. In the mechanical model, the constitutive equations were modified, using the finite element program subroutines to introduce the increments of the deformations due to the phase transformation in the ZTA. Finally, the influence of the phase transformations on the residual stresses and deformations for the naval steel DH-36 was analyzed.