• 대한조선학회논문집
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• 제49권4호
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• pp.281-286
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• 2012

Single frame structures with notches were fractured by applying drop impact loadings at room temperature and low temperature. Johnson-Cook shear failure model has been employed to simulate the fractured single frame structures. Through several numerical analyses, material constants for Johnson-Cook shear failure model have been found producing the cracks resulted from experiments. Fracture strain-stress triaxiality curves at both room temperature and low temperature are presented based on the extracted material constants. It is expected that the fracture strain-stress triaxiality curves can offer objective fracture criteria for the assessment of structural fractures of polar class vessel structures fabricated from DH36 steels. The fracture experiments of single frame structures revealed that the structure on low temperature condition fractures at much lower strain than that on room temperature condition despite the same stress states at both temperatures. In conclusion, the material properties on low temperature condition are essential to estimate the fracture characteristics of steel structures operated in the Northern Sea Route.

• 한국전산구조공학회논문집
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• 제29권2호
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• pp.105-114
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• 2016

구조물에 충격하중이 작용하면, 그 구조물은 통상적으로 대변형을 동반하는 소성변형과 최종적으로 그에 따른 파단을 경험하게 된다. 본 연구에서는 사고적 극한 상태에 대한 합리적인 설계를 위해 열성형된 판과 냉간성형된 판의 재료상수를 고속인장시험에 대한 수치시현을 통해 정의하였다. 변형율이 중간 속도 이하인 경우에는 변형율 속도의 영향을 무시할 수 있다는 가정과 함께 Cower-Symond 모델과 John-Cook 모델에 포함되는 재료상수들의 유용성을 참고문헌들의 결과와 비교하여 입증하였다. 본 논문은 향후 연구 내용에 대한 언급을 포함하면서 마무리하였다.

• 대한조선학회논문집
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• 제46권6호
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• pp.611-621
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• 2009

This paper first reviews the physical meanings and the expressions of two representative strain rate models: CSM (Cowper-Symonds Model) and JCM (Johnson-Cook Model). Since it is known that the CSM and the JCM are suitable for low-intermediate and intermediate-high rate ranges, many studies regarding marine accidents such as ship collision/grounding and explosion in FPSO have employed the CSM. A formula to predict the material constant of the CSM is introduced from literature survey. Numerical simulations with two different material constitutive equations, classical metal plasticity model based on von Mises yield function and micromechanical porous plasticity model based on Gurson yield function, have been carried out for the stiffened plates under impact loading. Simulation results coincide with experimental results better when using the porous plasticity model.