The primary purpose of this investigation was to study the characteristics of the armor steel weldment of combat vehicles by using GMAW narrow gap welding (NGW). The results showed that the mechanical properties and residual stress distribution of NGW weldment were improved, compared with conventional X-groove weldment. Additionally, ballistic tests according to MIL-HDBK-1941 were carried out to verify the ballistic ability of NGW weldment and the result showed that the NGW process was qualified for welding the armor steel of combat vehicle.

The primary purpose of this investigation was to study welding residual stress relaxation by repeated loading. A coupling finite element analysis model for prediction of the welding residual stress and the mechanical stress relaxation after external repeated loads was presented. The accuracy of this model was verified through experiments. Also, it is found that the residual stress of weldment is relaxed by external loads, and the greatest amount of relaxation was obtained by early repeated loads. As the repetition count increased, the amount of relaxation became smaller than the amount of relaxation in the early stage.