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Joo, Geunsu,Huh, Hoon Elsevier 2018 International journal of mechanical sciences Vol.146 No.-
<P><B>Abstract</B></P> <P>This paper presents a rate-dependent isotropic‒kinematic hardening model in tension‒compression of TRIP and TWIP steel sheets. The isotropic‒kinematic hardening model is widely utilized to describe the Bauschinger effect, transient behavior and permanent softening under reverse loading which are indispensable for numerical simulation of springback in sheet metal forming. The isotropic‒kinematic hardening model, however, has not yet been suggested for the strain rate effect higher than several tens per second although the high strain rate prevails in practical automotive sheet metal forming. This paper proposes a rate-dependent model based on tension‒compression tests of TRIP980 and TWIP980 steel sheets at various strain rates ranging from 0.001 s<SUP>−1</SUP> to 100 s<SUP>−1</SUP>. A proposed rate-dependent model is extended from the rate-independent Chaboche type model based on single-surface plasticity. Among three Chaboche type models, the Zang's model is selected as the basic rate-independent model considering both a small change of the work-hardening rate in monotonic loading and a constant stress offset of permanent softening in reverse loading. With the basic rate-independent model, the material parameters are acquired at each strain rate to check their dependency on the strain rate and then formulated as linear or exponential functions of the logarithmic scale of the strain rate. Consequently, the present rate-dependent model is proposed with incorporation of the basic rate-independent model and the rate-dependent functions for the material parameters.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A rate-dependent isotropic‒kinematic hardening model is proposed. </LI> <LI> Rate-dependent tension‒compression tests are performed for TRIP980 and TWIP980. </LI> <LI> The present model is extended from the rate-independent Chaboche type model. </LI> <LI> Material parameters are interpolated by rate-dependent functions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>This paper presents a rate-dependent isotropic‒kinematic hardening model in tension‒compression of TRIP and TWIP steel sheets. </P> <P>[DISPLAY OMISSION]</P>
주근수(Geunsu Joo),허훈(Hoon Huh),정영혁(Yeong Hyuk Jung),김주영(Ju Yeong Kim),서송원(Songwon Seo) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.9
본 논문에서는 포신의 강선을 고려한 포 발사 해석기법을 다룬다. 포 발사 환경에서 탄두는 고충격 및 고회전의 동적 거동이 발생한다. 이러한 동적 거동에서 탄두 및 탄두 내 전자 장비가 손상되는 사례가 발생하고 있다. 따라서 포 발사 환경에서 탄두의 동적 거동 분석 및 생존성 평가를 위한 포 발사 해석기법의 개발이 필요한 실정이다. 본 논문에서는 앞서 선행연구자들의 단순화된 포 발사 해석기법을 개선하여, 포신의 강선과 탄대의 접촉에 따른 탄두의 회전을 구현할 수 있는 포 발사 해석기법을 개발하였다. 개발된 포 발사 해석기법은 실험결과와 비교를 통하여 검증하였으며, 제안된 해석기법을 이용하여 포 발사 시 탄두의 동적 거동 및 생존성을 평가하였다. This paper is concerned with numerical simulation of a gun-launched projectile considering a rifled gun-tube. Gun-launched conditions induce dynamic behaviors, such as high pressure and high speed rotation. A projectile and its internal electronic components may be damaged in such harsh environments. Hence, it is necessary to perform numerical simulation of a gun-launched projectile to predict its dynamic behaviors and stability. In this work, preceding research studies on gun-launched projectiles are investigated, and the simulation method is developed to rotate the projectile through between its rotating band and a rifled-gun tube. The proposed method is verified by comparison with experimental results, and the dynamic behaviors and stability of the projectile are evaluated under gun-launched conditions.
유한요소해석을 이용한 압축 하중을 받는 오픈 홀 복합재 시편의 점진적 손상 및 파손 분석
김영철,주근수,장홍규,김진봉,강민규,이우경,김지훈,Young Cheol Kim,Geunsu Joo,Hong-Kyu Jang,Jinbong Kim,Min-Gyu Kang,Woo-Kyoung Lee,Ji Hoon Kim 한국복합재료학회 2023 Composites research Vol.36 No.5
In this paper, a Progressive Damage and Failure Analysis (PDFA) modeling method was developed using ABAQUS/EXPLICIT to predict in-plane damage and delamination for Open-Hole Compression (OHC) testing. The proposed PDFA model was constructed based on Hashin criteria and cohesive behavior. The strength and stiffness of OHC specimens with three types of stacking sequences [(45/-45/0<sub>2</sub>)<sub>3</sub>]<sub>s</sub> , [(45/0/-45/90)<sub>3</sub>]<sub>s</sub> and [45/-45/0/45/-45/90/(45/-45)<sub>2</sub>]<sub>s</sub> were compared to comprehensively evaluate the validity of the Finite Element(FE) model of PDFA. The strength and stiffness of the OHC specimens were predicted relatively well, with less than a percentage error 10.0 %. For the numerical simulation case for each layup, the damage initiation/evolution of OHC specimens were evaluated for delamination and tension/compression matrix damage before and after failure.