Ti 용접재의 잔류응력에 의한 피로크랙 진전거동에 관한 연구

Abstract

The purpose of this thesis was to investigate the welding characteristics and the fatigue crack propagation behavior according to the residual stress of titanium, commonly using power station, aircraft and ship. The experimented material was TIG welded in order to look over the characteristics according to the notch position and compare with other materials. We compared and reviewed the fatigue crack propagation behavior of nonwelded base metal and welded specimens having different notch position to evaluate the fatigue crack propagation behavior by welding condition. The summerized results are as fallows; 1. As the result of specimens data, specimen2 Crack Behavior rate was lower 30 times than base metal, and so total fracture life was very influenced by it. 2. The fatigue life was shown higher as following the order, boundary zone> HAZ >Welding Zone > Base metal. Especially the fatigue life of boundary zone notched specimen was shown 700% higher than that of base metal. 3. The initial fatigue crack propagation rate is slower in this order, Boundary zone < Welding zone < HAZ < Base metal. 4. Notch tip of specimen2 was offsetted 6.7mm from boundary HAZ and it formed 25percent in total fracture length.