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변형률 속도를 고려한 원형 튜브의 동적 좌굴 현상의 상계 해석에 관한 연구
박충희(Chunghee Park),고윤기(Younki Ko),허훈(Hoon Huh) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
A circular tube undergoes bucking behavior when it is subjected to axial loading. An upper bound analysis can be an attractive approach to predict the buckling load and energy absorption efficiently. The upper bound analysis obtains the load or energy absorption by means of assumption of the kinematically admissible velocity fields. In order to obtain an accurate solution, kinematically admissible velocity fields should be defined by considering many factors such as geometrical parameters, dynamic effect, etc. In this study, experiments and finite element analyses are carried out for circular tubes with various dimensions and loading conditions. As a result, the kinematically admissible velocity field is newly proposed in order to consider various dimensions and the strain rate effect of material. The upper bound analysis with the suggested velocity field accurately estimates the mean load and energy absorption obtained from results of experiment and finite element analysis.
박충희(Chunghee Park),정세환(Sehwan Jeong),허훈(Hoon Huh),박정수(Jungsu Park) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
This paper deals with mechanical properties of PBX(polymer bonded explosives) simulant at various strain rates ranging from 10?⁴/sec to 10?²/sec. Mechanical properties of PBX at high strain rates are important in prediction of deformation behaviors of PBX in a warhead system which undergoes severe dynamic loading. Inert PBX stimulant which has analogous mechanical properties with PBX was utilized for material tests due to safety issues. Uniaxial tensile tests at quasi-static strain rates were conducted at strain rates ranging from 10?⁴/sec to 10?²/sec using a tensile testing machine, INTRON 5583. Results of these tests were compared with those of uniaxial compressive tests conducted at quasi-static strain rates. Deformation behaviors of PBX simulant were investigated using captured images obtained from a high-speed camera.
하중평형 격자법을 이용한 자동차용 플라스틱의 진응력-진변형률 선도의 개선
박충희(Chunghee Park),김진성(Jinsung Kim),허훈(Hoon Huh),안창남(Changnam Ahn),최석진(Seokjin Choi) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
This paper is concerned with the tensile characteristics of auto-body plastics at strain rates ranging from 0.001/sec to 100/sec. The tensile characteristics at high strain rates are important in prediction of deformation modes of the plastic components which undergo the high-speed deformation during car crash. Uniaxial tensile tests at the quasi-static strain rate were conducted at strain rates ranging from 0.001/sec to 0.01/sec by using a tensile testing machine (INTRON 5583). Uniaxial tensile tests at the intermediate strain rate were conducted at strain rates ranging from 0.1/sec to 100/sec by using a high-speed material testing machine developed. Since the deformation of the plastics is accompanied with localized deformation and a conventional extensometry method(CEM) is no longer valid for strain measurement, a force equilibrium grid method(FEGM) is newly proposed in order to acquire accurate true stress-true strain curves of the plastics. FEGM is utilized with image capture of non-uniform distribution of deformation at each elongation stage from a high speed camera in aids of grid methods. The true stress-true strain relations at the designated true strain rate and increment were obtained by collecting the load data by the equilibrium and the deformation images.
격자법을 이용한 자동차용 플라스틱의 진응력-변형률 선도 도출
박충희(Chunghee Park),김진성(Jinsung Kim),허훈(Hoon Huh),안창남(Changnam Ahn),최석진(Seokjin Choi) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
The plastics are widely utilized in the inside of vehicles. The dynamic tensile characteristics of auto-body plastics are important in a prediction of deformation mode of the plastic component which undergoes the high speed deformation during car crash. This paper is concerned with the dynamic tensile characteristics of the auto-body plastics at intermediate strain rates. Quasi-static tensile tests were carried out at the strain rate ranged from 0.001/sec to 0.1/sec using the static tensile machine (Instron 5583). Dynamic tensile tests were carried out at the strain rate ranged from 1/sec to 100/sec using the high speed material testing machine developed. Conventional extensometry method is no longer available for plastics, since the deformation of plastic is accompanied with localized deformation. In this paper, quasi-static and dynamic tensile tests were performed using ASTM Ⅳ standard specimens with grids and images from a high speed camera were analyzed for strain measurement. True stress-strain relations and the strain rates at each deformation step were obtained by processing load data and deformation images, assuming the plastics to deform uniformly in each grid.
동적하중을 받는 기능성 고폭화약조성 시뮬런트 재료물성 연구
박정수,염기선,박충희,정세환,이근득,허훈,Park, Jungsu,Yeom, Kee Sun,Park, Chunghee,Jeong, Sehwan,Lee, Keundeuck,Huh, Hoon 한국군사과학기술학회 2013 한국군사과학기술학회지 Vol.16 No.6
This paper is concerned with the material properties of functional high explosive(FHX) simulant at various strain rates ranging from $10^{-4}/sec$ to $10^1/sec$. Material properties of FHX at high strain rates are important in prediction of deformation modes of FHX in a warhead which undergoes dynamic loading. Inert FHX stimulant which has analogous mechanical properties with FHX was utilized for material tests due to safety issues. Uniaxial tensile tests at quasi-static strain rates ranging from $10^{-4}/sec$ to $10^{-2}/sec$ and intermediate strain rates ranging from $10^{-1}/sec$ to $10^1/sec$ were conducted with JANNAF specimen using a tensile testing machine, INTRON 5583, and developed high speed material testing machine, respectively. Uniaxial compressive tests at quasi-static strain rates and intermediate strain rates were conducted with cylindrical specimen using a dynamic materials testing machine, INSTRON 8801. And cyclic compressive loading tests were performed with various strain rates and strains. Deformation behaviors were investigated using captured images obtained from a high-speed camera.