• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1996년도 춘계학술대회
• /
• pp.167-171
• /
• 1996

Impact force and strains induced by impact between the occluder and the struts have been measured with force senfor and strain gages. The maximum reaction force was about 25N, and the calculated impact force on the root of the struts amount about $9{\sim}17N$. Impact force on the inlet strut is greater than that of the outlet strut, but the strain on the outlet strut is much higher than that of the inlet strut. These values might cause severe damage on the valve in the critical cases. The results of this study may be extended for the analysis of the endurance limit and optimal design of the struts and occluder.

• 대한기계학회논문집
• /
• 제19권4호
• /
• pp.1041-1050
• /
• 1995

The deformed shape of rod specimen of copper alloys was measured after the high-velocity impact against a rigid anvil and analyzed with one-dimensional theory to determine dynamic yield stress and strain-rate sensitivity which is defined as the ratio of dynamic yield stress to static flow stress. The evvect of two-dimensional deformation on the determination of dynamic yield stress by the one-dimensional theory, was investigated through comparison with the analysis by hydrocode. It showed that the one-dimensional theory is relatively consistent with two-dimensional hydrocode in spite of its simplicity in analysis.

• Computers and Concrete
• /
• 제6권5호
• /
• pp.377-390
• /
• 2009

In this paper an improved one-dimensional frame element for modelling of reinforced concrete beams and columns subjected to impact is presented. The model is developed in the framework of a flexibility fibre element formulation that ignores the shear effect at material level. However, a simple shear cap is introduced at section level to take account of possible shear failure. The effect of strain rate at the fibre level is taken into account by using the dynamic increase factor (DIF) concept for steel and concrete. The capability of the formulation for estimating the element response history is demonstrated by some numerical examples and it is shown that the developed 1D element has the potential to be used for dynamic analysis of large framed structures subjected to impact of air blast and rigid objects.

• Smart Structures and Systems
• /
• 제31권6호
• /
• pp.585-599
• /
• 2023

Field monitoring techniques offer an attractive approach for understanding bridge behavior under in-service loads. However, the investigations on bridge behavior under high-speed train load using field monitoring data are limited. The focus of this study is to explore the structural behavior of an in-service long-span steel truss arch bridge based on field monitoring data. First, the natural frequencies of the structure, as well as the train driving frequencies, are extracted. Then, the train-induced bearing displacement and structural strain are explored to identify the effects of train loads and bearings. Subsequently, a sensitivity analysis is performed for the impact factor of strain responses with respect to the train speed, train weight, and temperature to identify the fundamental issues affecting these responses. Additionally, a similar sensitivity analysis is conducted for the peak acceleration. The results indicate that the friction force in bearings provides residual deformations when two consecutive trains are in opposite directions. In addition, the impact factor and peak acceleration are primarily affected by train speed, particularly near train speeds that result in the resonance of the bridge response. The results can provide additional insight into the behavior of the long-span steel truss bridges under in-service high-speed train loads.

• 항공우주시스템공학회지
• /
• 제6권4호
• /
• pp.29-33
• /
• 2012

This paper is focusing on the difference from experiment result and method through dynamic loaded from impact analysis about inertia measure unit of high speed projectile. At Inertia measure unit dynamic load is applied when the high speed projectile is operated by impact to inside. it is necessary to design inertia measure unit enduring from external effect with operating environment. Investigation of material deformation with high strain speed is performed for military purpose, and still concerned to many scientist. From this study, this paper will prove of impact analysis result through comparing with experiment result and method when applied dynamic load.

• Structural Engineering and Mechanics
• /
• 제58권5호
• /
• pp.799-823
• /
• 2016

A finite element model for the non-linear dynamic analysis of a reinforced concrete (RC) containment shell of a nuclear power plant subjected to extreme loads such as impact and earthquake is presented in this work. The impact is modeled by using an uncoupled approach in which a load function is applied at the impact zone. The earthquake load is modeled by prescribing ground accelerations at the base of the structure. The nuclear containment is discretized spatially by using 20-node brick finite elements. The concrete in compression is modeled by using a modified $Dr{\ddot{u}}cker$-Prager elasto-plastic constitutive law where strain rate effects are considered. Cracking of concrete is modeled by using a smeared cracking approach where the tension-stiffening effect is included via a strain-softening rule. A model based on fracture mechanics, using the concept of constant fracture energy release, is used to relate the strain softening effect to the element size in order to guaranty mesh independency in the numerical prediction. The reinforcing bars are represented by incorporated membrane elements with a von Mises elasto-plastic law. Two benchmarks are used to verify the numerical implementation of the present model. Results are presented graphically in terms of displacement histories and cracking patterns. Finally, the influence of the shear transfer model used for cracked concrete as well as the effect due to a base slab incorporation in the numerical modeling are analyzed.

• 한국항공우주학회지
• /
• 제34권8호
• /
• pp.41-46
• /
• 2006

충격응답함수와 조정법(regularization methods)을 이용하여 항공기 날개의 충격하중 복원 가능성을 검토하였다. 충격하중에 대한 구조의 응답을 내타낼 수 있는 충격응답함수를 날개 유한요소모델의 강성과 질량 자료로 유도하였다. 일반적으로 부적합(ill-posed) 특성을 지닌 충격응답함수의 역행렬은 반복 Tikhonov 조종법(Iterative Tikhonov Regularization Method)과 일반화 특이치 분해법(Generalized Singular Value Decomposition Method)을 사용하여 구하였다. 수치적 입증을 위하여 전투기급 주익을 사용하였다. 해당 주익의 유한요소해석을 통하여 임의의 충격하중에 대한 변위와 변형률을 계산하였으며, 이를 충격응답함수로 계산한 결과와 비교하였다. 또한, 유한요소해석에서 계산된 변형률을 사용하여 충격하중을 복원하였다. 수치적 입증 결과 항공기 구조의 충격하중 모니터링이 본 방법으로 가능할 수 있음을 보여주었다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제5권1호
• /
• pp.176-187
• /
• 2001

Most bridges have expansion joints to accommodate thermal expansion and contraction without inducing large forces in the bridges. To evaluate the effects of earthquake-induced at expansion joints of concrete bridges, the first part of this paper deals with a collinear impact between concrete segments, which have the same cross section but different lengths. Especially, impact force, momentum, strain energy and kinetic energy are formulated in mathematically. These results are then used in the second part of this paper to simulate a realistic yet simple analysis of seismic pounding in concrete bridges. Analysis of seismic pounding in idealized concrete bridges is carried out by using a simple lumped-mass model and rationally determined values of the coefficient of restitution and the duration of impact.

• Journal of Advanced Research in Ocean Engineering
• /
• 제2권1호
• /
• pp.28-39
• /
• 2016

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.

• 항공우주시스템공학회지
• /
• 제17권5호
• /
• pp.19-27
• /
• 2023

본 연구에서는 유한요소해석을 이용하여 터빈 케이스의 컨테인먼트 성능 평가를 수행하였다. 충격 하중을 받는 구조물의 경우 변형률 속도가 증가함에 따라 유동 응력이 증가하기 때문에 충격 거동을 해석하기 위해서는 변형률 속도가 필수적으로 고려되어야 한다. 본 연구에서는 3가지 재료 모델(Cowper-Symonds, Johnson-Cook, Modified Johnson-Cook)을 충격 해석에 적용하고자 하였다. 해석에 적용된 재료 모델을 검증하기 위해서 알루미늄 6061 평판에 대한 충격 시험을 진행하였다. 실험과 해석 결과를 비교, 분석한 결과 Modified Johnson-Cook 모델이 가장 적은 오차를 보였다. 끝으로 해당 재료 모델을 터빈 케이스의 컨테인먼트 성능 평가에 적용하여 블레이드의 초기 속도에 따른 관통 여부와 충돌 부위에서 발생한 응력과 변형률을 제시하였다.