Abstract
High-strength steel suffers from an increasing susceptibility to solidification cracking in welding due to increasing carbon equivalents. However, the cracking mechanism is not fully clear for a confidently completely crack-free welding process. To present a full, direct knowledge of fracture behavior in high-strength steel welding, a three-dimensional (3-D) modeling method is developed using the extended finite element method (XFEM). The XFEM model and fracture loads are linked with the full model and the output of the thermo-mechanical finite element method (TM-FEM), respectively. Solidification cracks in welds are predicted to initiate at the upper tip at the current cross-section, propagate upward to and then through the upper weld surface, thereby propagating the lower crack tip down to the bottom until the final failure. This behavior indicates that solidification cracking is preferred on the upper weld surface, which has higher weld stress introduced by thermal contraction and solidification shrinkage. The modeling results show good agreement with the solidification crack fractography and in situ observations. Further XFEM results show that the initial defects that exhibit higher susceptibility to solidification cracking are those that are vertical to the weld plate plane, open to the current cross-section and concentratedly distributed compared to tilted, closed and dispersedly distributed ones, respectively.
Highlights
High-strength steel (HSS) is widely used as a cost-effective, high load-carrying capacity, and light self-weight solution in modern shipbuilding and marine structure engineering
Since solidification cracking is an important consideration in HSS welding, understanding the fracture behavior of the solidification cracking in HSSs has, driven modeling efforts for decades
The thermo-mechanical finite element method (TM-finite element modeling (FEM)) has been proven to be accurate enough to detail the mechanical performance of solidification cracking in the welding process
Summary
High-strength steel (HSS) is widely used as a cost-effective, high load-carrying capacity, and light self-weight solution in modern shipbuilding and marine structure engineering. Alloying is a general process for HSS to achieve better tensile properties. Various modeling methods were employed to reveal the mechanical aspects and corresponding parameters were proposed to correlate with the mechanical behavior of solidification cracking. The thermo-mechanical finite element method (TM-FEM) has been proven to be accurate enough to detail the mechanical performance of solidification cracking in the welding process. With the output of TM-FEM, mechanical parameters such as stress and strain [3,4,5], equivalent plastic strain [6], and critical strain rate [7] were characterized as driving forces of solidification cracking. The phase field method (PFM) has gained much popularity for modeling mechanical aspects of solidification cracking by focusing on the formation of weld microstructure during solidification. Based on the output of PFM, the tensile strain introduced by weld solidification shrinkage and thermal deformation [8,9], Materials 2020, 13, 483; doi:10.3390/ma13020483 www.mdpi.com/journal/materials
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