• 대한토목학회논문집
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• 제30권3A호
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• pp.257-264
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• 2010

일반적으로 대형구조물의 건전성평가에 있어 중요한 인자인 변위를 추정함으로써 구조물의 성능 저하 및 노후도를 판단하는 근거가 된다. 그러나 변위응답의 계측이 중요함에도 불구하고 계측 방법의 부재로 말미암아 현수교와 같은 대형구조물의 변위응답을 측정하는 방법이 용이치 않은 것이 현실이다. 본 논문에서는 변형률신호로부터 변위응답을 추정하는 방법인 모드분해기법을 제시하였다. 모드분해기법은 등가정적 변위응답과 구조물의 주요거동을 나타내는 저차모드의 변위응답을 합하여 최종변위응답을 추정하는 방법이다. 변형률신호의 계측시 전기저항식 변형률센서를 사용할 경우 전기적 노이즈 문제가 발생할 소지가 크며, 측점이 많아질수록 경제적 부담감이 커진다. 이런 문제점을 극복하기 위하여 전기적 노이즈의 영향이 없고 다중측정이 가능한 광섬유 브래그 격자 센서를 사용하였다. 현수교와 플레이트거더교의 동재하실험을 통하여 모드분해기법의 사용성을 검토하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.76-85
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• 2017

본 연구에서는 유압식 급속재하 시험 장치를 제작하여 변형 속도에 따른 후크형 강섬유 및 폴리아미드 섬유보강 시멘트 복합체의 압축강도 및 인장강도 특성을 평가하였다. 그 결과, 변형 속도가 증가함에 따라 압축강도, 최대 응력 점에서의 변형 및 탄성계수는 증가하였으며, 섬유 종류 및 혼입률은 변형 속도에 의한 압축강도의 영향은 크지 않았다. 본 연구에서 평가된 압축강도의 DIF는 CEB-FIP model code 2010에 비해 상회하였으며, ACI-349의 예측값과 유사한 경향이 나타났다. 인장특성의 경우에도 변형 속도가 증가함에 따라 인장강도와 변형능력이 크게 향상되었다. 후크형 강섬유보강 시멘트 복합체는 변형 속도가 증가함에 따라 섬유와 매트릭스의 부착력이 증가하는 것에 의해 인장강도와 변형능력이 크게 향상되었으며, 섬유가 매트릭스로부터 인발되는 파괴 특성이 나타났다. 한편, 폴리아미드 섬유보강 시멘트 복합체의 경우 섬유와 매트릭스의 부착력이 크기 때문에 섬유가 매트릭스로부터 인발되지 않고 끊어지는 파괴 특성이 나타났으며, 폴리아미드 섬유보강시멘트 복합체의 인장특성에 대한 변형 속도 효과는 섬유의 인장강도에 큰 영향을 받는 것으로 판단되었다. 이러한 결과로부터 폴리아미드 섬유보강 시멘트 복합체의 인장강도에 대한 변형 속도의 효과는 후크형 강섬유의 부착력에 대한 민감도 보다 큰 것으로 사료된다.

• 산업기술연구
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• 제20권A호
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• pp.93-100
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• 2000

This research is to investigate the self-weight consolidation settlement and desiccation shrinkage settlement of soft marine dredging clay by performing numerical and experimental works. Large column test were carried out investigate the consolidation settlement considering effect of the self-weight and desiccation shrinkage, and centrifuge model test was also carried out investigate self-weight consolidation settlement. Results of centrifuge model and large column experiments about changes of settlement with time were analyzed by using the numerical technique of explicit finite difference method considering effect of the self-weight and desiccation based on the finite strain consolidation theory. Centrifuge model test results were in relatively good agreements with analyzed results in terms of self-weight consolidation settlement with time. Large column test results showed quite different values from the numerically estimated one, carried by experimental conditions.

• 대한기계학회논문집
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• 제17권12호
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• pp.2982-2994
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• 1993

Low-velocity impact responses of composite laminates are investigated using the finite element method based on various theories. In two-dimensional nonlinear analysis, a displacement field considering higher order shear deformation and large deflection of the laminate is assumed and a finite element formulation is developed using a C$^{o}$-continuous 9-node plate element. Also, three-dimensional linear analysis based on the infinitesimal strain-displacement assumptions is performed using 8-node brick elements with incompatible modes. A modified Hertzian contact law is incorporated into the finite element program to evaluate the impact force. In the time integration, the Newmark constant acceleration algorithm is used in conjuction with successive iterations within each time step. Numerical results from static analysis as well as the impact response analysis are presented including impact force histories, deflections, strains in the laminate. Impact responses according to two typical low-velocity impact conditions are compared each other.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.736-739
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• 1995

The meshless adaptive method based on multiple scale analysis is developed to simulate large deformation problems. In the procedure, new particles are simply added to the orginal particle distribution because meshless methods do not require mesh structures in the formulations. The high scale component of the approximated solution detects the localized region where a refinement is needed. The high scale component of the second invariant od Green-Lagrangian strain tensor is suggested as the new high gradient detector for adaptive procedures. The feasibility of the proposed theory is demonstrated by a numerical experiment for the large deformation of hyperelastic materials.

• 한국농공학회논문집
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• 제46권4호
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• pp.75-84
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• 2004

The evaluation technique of seismic performance on agricultural infrastructure based on dynamic numerical simulations, which Included a cyclic elasto-plastic and a viscoelastic-viscoplastic constitutive model to actual multi-layered ground conditions during large earthquake were performed by a liquefaction analysis in the present study. From the liquefaction analysis, it was verified that the models can give a good description of the damping characteristics and liquefaction phenomena of ground accurately during large event which induces plastic deformation in large strain range.

• 한국지반공학회논문집
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• 제16권4호
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• pp.183-190
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• 2000

본 연구에서는 피에조콘 시험의 유한요소해석을 점탄소성 bounding surface 구성모델과 large displacement large deformation 개념을 이용하여 수행하였다. 이에 따라 구성모델, 가상일의 방정식 및 관련 유한요소 식 등을 Updated Lagrangian reference frame에서 formulation 하였으며 지반의 거동은 theory of mixtures를 통하여 설명하였다. Theory of mixtures 역시 Updated Lagrangian reference frame에서 formulation하였다. 구성모델 중 점성 부분이 전체 formulation 과정에 중요한 영향을 미친다는 사실이 고찰되었다. 유한요소 해석의 결과는 실내에서 실시한 대형 모델시험의 결과와 비교, 분석하였다. Formulation 과정은 'I' 결과는 'II'에서 설명된다.

• 교육녹색환경연구
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• 제10권2호
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• pp.1-7
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• 2011

An experimental study to evaluate structural capacity of an embedded plate connected with prestressed concrete beam was performed. Embedded steel plates and prestressed concrete beam were connected with stud-bolts at the ends of concrete beam specimens. About 1,000 kN concentrated load was applied at 450mm away from the end of beam specimen. A 3,000 kN capacity static Oil-jack was used to direct concentrated load. The maximum strain of stud-bolt recorded $90{\times}10^{-6}$(mm/mm) and wide width cracks were not founded. Any falling failures of concrete and large deformations were not founded either between steel plate and prestressed concrete specimen. As a result, construction performance can be improved using this embedded steel plate connection system apply to large space educational facilities.

• 대한기계학회논문집A
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• 제25권4호
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• pp.619-628
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• 2001

A viscoelastic constitutive equation of rubber is proposed under small oscillatory load superimposed on large static deformation. The proposed model is derived through linearization of Simos nonlinear viscoelastic constitutive model and reference configuration transformation. Statically pre-deformed state is used as reference configuration. The model is extended to a generalized viscoelastic constitutive equation including widely-used Mormans model. Static deformation correction factor is introduced to consider the influence of pre-strain on the relaxation function. The model is tested for dynamic behavior of rubbers with different carbon black fractions. It is shown that the constitutive equation with static deformation correction factor agrees well with test results.

• Journal of Welding and Joining
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• 제32권3호
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• pp.53-59
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• 2014

The mechanical stability of solder joints in electronic devices with Sn-Ag-Cu is a continuous issue since the material was applied to the industry. Various shock test methods were developed and standardized tests are used in the industry worldwide. Although it is applied for several years, the detailed mechanism of the shock induced failure mechanism is still under investigation. In this study, the effect of external temperature was observed on large Flip-chip BGA components. The weight and size of the large package produced a high strain region near the corner of the component and thus show full fracture at around 200G level shock input. The shock performance at elevated temperature, at $100^{\circ}C$ showed degradation based on board pad designs. The failure mode and potential failure mechanisms are discussed.