조선 해양 구조물용 강재의 소성 및 파단 특성 I: 변형률 경화 및 변형률 속도 경화의 이론적 배경

Abstract

*Dep't of Naval Architecture and Ocean Engineering, Inha Univer sity, Incheon, Korea**Dep't of Naval Architecture and Marine Engineering, Mokpo Nat ional University, Mokpo, KoreaKEY WORDS: Plasticity 소성, Strain hardening 변형률 경화, Strain rate hardening 변형률 속도 경화, Fracture 파단, True stress 진응력ABSTRACT: In this paper, the global study trends for material behaviors a re investigated regarding the static and dynamic hardenings and final fractures of marine structural steels. In particular, after rev iewing all of the papers published at the 4th and 5th ICCGS (In ternational Conference on Collision and Grounding of Ship), the used hardening and fra cture properties are summarized, explicitly presenting the mate rial properties. Although some studies have attempted to employ new plasticity a nd fracture models, it is obvious that most still employed an i deal hardening rule such as perfect plastic or linear hardening and a simple shear fracture criterion with an assumed value of failure strain. HSE (2001) presented pioneering study results regarding the temperature dependency o f material strain hardening at various levels of temperature, b ut did not show strain rate hardening at intermediate or high strain rate range s. Nemat-Nasser and Guo (2003) carried out fully coupled tests for DH-36 steel: strain hardening, strain rate hardening, and temperature harden ing and softening at multiple steps of strain rates and tempera tures. The main goal of this paper is to provide the theoretical background for stra in and strain rate hardening. In addition, it presents the procedure and methodology needed to derive the material constants for the static hardenin g constitutive equations of Ludwik, Hollomon, Swift, and Ramber g-Osgood and for the dynamic hardening constitutive equations of power from Cowper-S ymonds and Johnson-Cook.교신저자 정준모: 인천광역시 남구 용현동 253, 032-860-7346, jmchoung@inha.ac.kr