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Impact Bending Test Simulations of FH32 High-strength Steel for Arctic Marine Structures
Choung, Joonmo,Han, Donghwa,Noh, Myung-Hyun,Lee, Jae-Yik,Shim, Sanghoon Korean Society of Ocean Engineers 2016 Journal of advanced research in ocean engineering Vol.2 No.1
This paper provides theoretical and experimental results to verify the crashworthiness of FH32 high-strength steel for arctic marine structures against ice impact. Assuming that side-shell structures of the Korean arctic research vessel, ARAON, with ice-notation PL10, collide with sheet ice, one-third-scale test specimens with a single transverse frame are manufactured. Impact-bending tests were conducted using a rigid steel striker that mimics sheet ice. Drop height was calculated by considering the speed at which sheet ice is rammed. Prior to impact-bending tests, tensile coupon tests were conducted at various temperatures. The impact-bending tests were carried out using test specimens fully fixed to the inside bottom frame of a cold chamber. The drop-weight velocity and test specimen deformation speed were measured using a high-speed camera and digital image correlation analysis (DICA). Numerical simulations were carried out under the same conditions as the impact-bending tests. The simulation results were in agreement with the test results, and strain rate was a key factor for the accuracy of numerical simulations.
Residual ultimate strength of a very large crude carrier considering probabilistic damage extents
Joonmo Choung,Ji-Myung Nam,Gokhan Tansel Tayyar 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.1
This paper provides the prediction of ultimate longitudinal strengths of the hull girders of a very large crude carrier considering probabilistic damage extent due to collision and grounding accidents based on IMO Guidelines (2003). The probabilistic density functions of damage extent are expressed as a function of non-dimensional damage variables. The accumulated probabilistic levels of 10%, 30%, 50%, and 70% are taken into account for the estimation of damage extent. The ultimate strengths have been calculated using the in-house software called Ultimate Moment Analysis of Damaged Ships which is based on the progressive collapse method, with a new convergence criterion of force vector equilibrium. Damage indices are provided for several probable heeling angles from 0° (sagging) to 180° (hogging) due to collision- and grounding-induced structural failures and consequent flooding of compartments. This paper proves from the residual strength analyses that the second moment of area of a damage section can be a reliable index for the estimation of the residual ultimate strength. A simple polynomial formula is also proposed based on minimum residual ultimate strengths.
Residual ultimate strength of a very large crude carrier considering probabilistic damage extents
Choung, Joonmo,Nam, Ji-Myung,Tayyar, Gokhan Tansel The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.1
This paper provides the prediction of ultimate longitudinal strengths of the hull girders of a very large crude carrier considering probabilistic damage extent due to collision and grounding accidents based on IMO Guidelines (2003). The probabilistic density functions of damage extent are expressed as a function of non-dimensional damage variables. The accumulated probabilistic levels of 10%, 30%, 50%, and 70% are taken into account for the estimation of damage extent. The ultimate strengths have been calculated using the in-house software called Ultimate Moment Analysis of Damaged Ships which is based on the progressive collapse method, with a new convergence criterion of force vector equilibrium. Damage indices are provided for several probable heeling angles from $0^{\circ}$ (sagging) to $180^{\circ}$ (hogging) due to collision- and grounding-induced structural failures and consequent flooding of compartments. This paper proves from the residual strength analyses that the second moment of area of a damage section can be a reliable index for the estimation of the residual ultimate strength. A simple polynomial formula is also proposed based on minimum residual ultimate strengths.
조선 해양 구조물용 강재 변형률 경화 및 변형률 속도 경화의 이론적 배경
정준모(Joonmo Choung),심천식(Chun-Sik Shim),김경수(Kyung Su Kim) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
In this paper, global study trends of material behaviors are investigated regarding static and dynamic hardenings and final fractures of marine structural steels. Especially, after reviewing all papers published in the 4th and 5th ICCGS (International Conference on Collision and Grounding of Ship), the used hardening and fracture properties are summarized explicitly presenting material properties. Although some papers have tried to employ new plasticity and fracture models, it is obvious that most papers still employed ideal hardening rule such as perfect plastic or linear hardening and simple shear fracture criterion with assumed value of failure strain. HSE (2001) presented pioneering study results regarding temperature dependency of material strain hardening at the various level of temperatures, but did not show strain rate hardening at intermediate or hight strain rate ranges. Nemat-Nasser and Guo (2003) carried out fully coupled tests for DH-36 steel: strain hardening, strain rate hardening, and temperature hardening and softening at multiple steps of strain rates and temperatures. Main pillars of this paper are to provide theoretical backgrounds of strain and strain rate hardening. In addition, the procedure and methodology to derive material constants for static hardening constitutive equations of Ludwik, Hollomon, Swift, and Ramberg-Osgood and for dynamic hardening constitutive equations of power, Cowper-Symonds and Johnson-Cook.
부유식 재생에너지 플랜트의 개념설계를 통한 계류라인의 피로설계
정준모(Joonmo Choung),이민성(Min-Sung Lee),전상익(Sang-Ik Jeon) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
This paper presents the concept design precedure of floating-type combined renewable energy platform based on hydrodynamic analyses and the fatigue design procedure of taut-type mooring lines. Two types of combined renewable energy platforms are taken into account: first combination of wind, wave, and photovoltanic energies and second combination of wind , current, photovoltanic energies. The concept design is from the literature survey, but main dimensions have been decided based on the basic hydrostatic calculation. Fully coupled hydrodynamic analyses have been carried out to identify motion characteristics of the floating body and tension histories of each mooring lines. Further fatigue lives using rainflow cycle counting method, API stress-life diagram, and Palmgren-Miner rule are predicted for chain link-type taut mooring system. Finally mooring lines satisfying design life of twenty years are proposed.
국내 연안 카페리 차량 고박 장치 안전성에 관한 연구 제2부
정준모(Joonmo Choung),조희상(Huisang Jo),이경훈(Kyunghoon Lee),이영우(Young Woo Lee) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.6
For a carferry with a displacement of 1,633 tonf, a seakeeping analysis-based direct load approach (DLA) was used in Part I of these series, where the final deliverable was the long-term probabilistic acceleration components. In Part II of these series, the tangential acceleration components are explained based on two approaches: a standard called the IMO CSS code and simple formulas with the probable maximum roll and pitch rotations. The subsequent tangential acceleration-induced external force components are also introduced for these two approaches. The lashing strength components were selected from the IMO CSS code. It was assumed that two different vehicles (a car and a truck) were stowed at the most distant locations on the main deck to assume the largest tangential acceleration components and were secured with four steel wires with longitudinal and transverse lashing angles of 45∘. Four cases were considered, with different methods for predicting the acceleration components and different tools for the external loads and lashing strengths involved: cases Rule-LS (rule-based maximum probable roll and pitch angles for predicting the acceleration components in conjunction with LashingSafety), DLA-LS (seakeeping-based long-term acceleration components with LashingSafety), CSS-LC (IMO CSS code-based acceleration components using LashCon), and CSS-LS (IMO CSS code-based acceleration components using LashingSafety). In terms of the acceleration and external force components, the CSS-LC and CSS-LS results are more than two times the results of Rule-LS. Thus, when the external forces and lashing strengths are evaluated using CSS-LC and CSS-LS, the truck needs more lashing wires, while Rule-LS and DLA-LS predict that the present lashing configuration is on the safe side.