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유한요소법과 초음파 메카트로닉스 시스템에 의한 강도적 불균질 이음부의 노치위치에 따른 균열발생 한계 조건
안규백,방한서,풍전정남,An Gyu-Baek,Bang Han-Sur,Toyoda Masao 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.6
It has been well hewn that ductile fracture of steels is accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using a two-parameters criterion based on equivalent plastic strain and stress triaxiality. The present study focuses on the effects of strength mismatch, which can elevate plastic constraint due to heterogeneous plastic straining, on the critical condition for ductile fracture initiation usinga two-parameter criterion. Fracture initiation testing has been conducted under static loading using notched round bar specimens which had different notch locations. This study provides the fundamental clarification of the effect of strength mismatching and effect of notch location on the critical condition to ductile crack initiation from notch root using fuite element method and ultrasonic-mechatronics system. The critical condition of ductile crack initiation from notch root of strength mismatched tensile specimens under static loading appeared to be almost the same as those of homogeneous tensile specimens with circumferential sharp notch specimen. Also, the effect of notch location in mismatched specimens was estimated using finite element(FE) analyses.
동적하중 하에서의 강도적 불균질부를 갖는 용접이음재의 강도 및 파괴 특성
안규백,방한서,望月正人,大細充,豊田政男 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.6
Welded joint generally has heterogeneity of strength, material, and fracture toughness and it is important to understand the characteristics of material strength and fracture of welded joint considering heterogeneous effect. Characteristics of strength and fracture of an undermatched joint under dynamic loading was studied by round-bar tension tests and thermal elastic-plastic analyses in this paper. The strength and fracture of the undermatched joints should be evaluated based on the effects of the strain rate and the temperature including temperature rise during the dynamic loading. The differences of fracture characteristics like such as ductile-to-brittle transition behavior are well precisely explained from the stress-strain distribution obtained by numerical analysis.