어코스틱에미션 신호를 활용한 고장력강 용접성 평가에 관한 연구

A Study on the Evaluation of Weldability for High Tensile Stregnth Steel Using Acoustic Emission Signals

The purpose of this thesis is to investigate the welding characteristics and residual stress behavior of 60 high tensile strength steels, commonly used in steel structures for power transmission automobiles, and ship. The experimental material were welded by gas metal arc welding process in order to evaluate the characteristics according to the notch position, and compare these with other materials. The residual stress distribution was also measured under nonrestraint welding conditions. According to these test, we reached the following conclusions : The residual stress in welded specimens was much higher in the restraint nonrestraint condition. In case of restraint welding, the the residual stress in the σx-direction was measured as the tensile residual stress. In case of nonrestraint welding, this was rapidly changed to compressive residual stress at 15～18mm from the welding bead center. In the case of nonrestraint welding, the residual stress in the σy-direction was measured as the tensile residual stress. In the case of restraint welding, this changed to compressive residual stress at 55～70mm from the welding bead center.