The Interactive Mechanism of Static and Dynamic Analysis in the Reverse Analysis of Embedded Software

LiuTie-ming,Jinag Lie-hui,Zhu Jing-si,Meng Gang 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.10

Because the software reverse analysis method which combined the dynamic and static analyses lacks normative interactive mode, the work of the software reverse analysis is inefficient, and its reusability is poor. Based on dynamic and static analysis process of the embedded software,three kinds of interactive mechanismare proposed, including Static To Dynamic (STD), Dynamic To Static (DTS), Static and Dynamic simultaneous (SDM), and has also presented the method of realizing these three interaction mechanisms in detail. The test results show that interactive mechanisms of STD, DTS and SDM are suitable for correction of abnormal nodes in the results of static analysis, optimization of dynamic information extraction, identification of hidden codes and so on. It can greatly improve work efficiencyof the embedded software reverse analysis.

터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측 한국지반공학회논문집 제26권 제6호터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측

박두희,신종호,윤세웅 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.6

Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

An application of wave equation analysis program to pile dynamic formulae

Tokhi, H.,Ren, G.,Li, J. Techno-Press 2015 Geomechanics & engineering Vol.9 No.3

Wave equation analysis programs (WEAP) such as GRLWEAP and TNOWave were primarily developed for pre-driving analysis. They can also be used for post-driving measurement applications with some refinements. In the case of pre-driving analysis, the programs are used for the purpose of selecting the right equipment for a given ground condition and controlling stresses during pile driving processes. Recently, the program is increasingly used for the post-driving measurement application, where an assessment based on a variety of input parameters such as hammer, driving system and dynamic behaviour of soil is carried out. The process of this type of analysis is quite simple and it is performed by matching accurately known parameters, such as from CAPWAP analysis, to the parameters used in GRLWEAP analysis. The parameters that are refined in the typical analysis are pile stresses, hammer energy, capacity, damping and quakes. Matching of these known quantities by adjusting hammer, cushion and soil parameters in the wave equation program results in blow counts or sets and stresses for other hammer energies and capacities and cushion configuration. The result of this analysis is output on a Bearing Graph that establishes a relationship between ultimate capacity and net set per blow. A further application of this refinement method can be applied to the assessment of dynamic formulae, which are extensively used in pile capacity calculation during pile driving process. In this paper, WEAP analysis is carried out to establish the relationship between the ultimate capacities and sets using the various parameters and using this relationship to recalibrate the dynamic formula. The results of this analysis presented show that some of the shortcoming of the dynamic formula can be overcome and the results can be improved by the introduction of a correction factor.

Finite element analysis of knee and ankle joint during gait based on motion analysis

Park, Sangbaek,Lee, Seungju,Yoon, Jeongro,Chae, Soo-Won Elsevier 2019 Medical engineering & physics Vol.63 No.-

<P><B>Abstract</B></P> <P>Contact pressures in the articular cartilage during gait affect injuries and the degenerative arthritis of knee and ankle joints. However, only contact forces at the knee and ankle joints during gait can be estimated by using a rigid body dynamic model. The contact pressure distribution can be obtained quantitatively for a static posture by using finite element (FE) analysis in most cases. The purpose of this study is to develop a new method to obtain the contact pressure distribution at the knee and ankle joints during gait by integrating FE analysis with rigid body dynamic analysis. In this method, a reference FE model of the lower extremity is constructed first and is then transformed to each stance phase of the gait obtained from dynamic analysis by using homogeneous transformation. The muscle forces and ground reaction force (GRF) during gait obtained from the dynamic analysis were used as loading conditions for FE analysis. Finally, the contact pressure distribution at the tibia plateau cartilage and talus cartilage were estimated at the 1st peak, mid-stance, and the 2nd peak at the same time. The present method can provide the contact pressure distribution at the knee and ankle joints over the entire gait.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new method that integrates FE analysis with rigid body dynamic analysis is proposed. </LI> <LI> Interface program with self-written codes is developed to apply the results of motion analysis to the FE analysis. </LI> <LI> Coordinate system matching OpenSim model and FE model is performed to transform the FE model. </LI> <LI> Contact pressure distribution at the knee and ankle joints can be obtained according to the desired stance phase. </LI> </UL> </P>

터널구조물의 내진해석

이인모,안대진 사단법인 한국터널지하공간학회 2001 한국터널지하공간학회논문집 Vol.3 No.4

Generally, it has been noted that underground structures have a consistent record of suffering much less damage thansurface facilities during earthquakes; but it is still necessar subject to earthquake loadings and to provide the appropriate m ethod for the seismic analysis of underground tunnelstructures since many types of underground structures have been and will be constructed in countries situated withinground tunnel structures are performed by using quasi-static analysis method and dynamic analysis method. Second, se ismic analyses in tunnel portals are performed by usingabove methods. The results of seismic analyses for the tunnel s tructure show that the tunnel structure conforms toground deformation and that seismic design by using the quasi-s tatic analysis method is more conservative than that byusing the dynamic analysis. The results of the dynamic FEM anal ysis for the tunnel structure show that the simplified 2-is can be adopted for seismic analysis. Finally, theresults of the dynamic FEM analysis in tunnel portals show that the force acting on the lining is largest near to thetunnel portal when an earthquake wave propagates parallel to tu nnel axis.

폭발하중을 받는 콘크리트 벽체구조의 HFPB 해석

남진원(Nam Jin Won),김호진(Kim Ho Jin),김성배(Kim Sung Bae),변근주(Byun Keun Joo) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.3A

폭발하중은 매우 빠른 시간 내에 구조물에 큰 압력으로 작용하는 하중이므로 변형률 속도와 구조물의 국부적인 손상을 고려하여 동적응답을 평가해야한다. 그러나 폭발하중을 받는 구조물의 설계 및 해석에 일반적으로 사용되고 있는 기존의 근사적 해석기법은 폭발하중에 대한 경계조건과 동적재료특성을 정확하게 반영하지 못할 뿐 아니라 폭발하중을 받는 구조물이 나타내는 국부적인 거동을 나타내지 못한다. 또한 근사적 해석기법 결과의 정확도와 신뢰성에 대한 문제는 꾸준히 지적되어오고 있다. 게다가 동적하중에 대한 콘크리트와 철근의 응답은 정적하중에 대한 응답과 상이하므로 폭발하중에 대한 응답을 계산하는데 있어 정적하중이나 준정적하중상태로 정의되는 재료 모델을 사용하는 것은 적합하지 않다. 따라서, 본 연구에서는 폭발하중에 대한 콘크리트 구조물의 동적거동을 예측하기 위해 물리적 현상에 충실하는 정밀해석 방법인 HFPB(high fidelity physics based) 해석방법을 사용하였다. HFPB 해석을 위해서는 양함수적(explicit) 유한요소 코드인 LS-DYNA가 사용되었고, 해석결과의 비교를 위해서 단자유도 시스템 해석이 수행되었다. 해석결과를 통해 HFPB 해석방법은 단자유도 해석방법에 비해 합리적인 결과를 나타내며, 단자유도 해석방법은 경우에 따라 구조물의 성능을 과대 또는 과소평가할 수도 있는 것으로 분석되었다. 따라서, 정확하고 상세한 방호성능의 평가 및 설계가 요구되는 경우에는 적합한 재료모델을 사용하는 정밀해석 방법이 필요할 것이다. As blast load is impulsive load of extremely short duration with very high pressure, the strain rate and local damage effect of concrete structures subjected to blast loads should be considered in the dynamic analysis. However, the approximate and simplified analysis techniques, which have been generally used in the design and analysis of structures subjected to blast load, cannot accurately consider effect of boundary conditions and dynamic material properties. Problems on the accuracy and reliability of approximate analysis results have also been pointed out. In addition, as the response of concrete and reinforcement on dynamic load is different from that on static load, it is not appropriate to the use material model defined in the static or quasi-static conditions in calculating the response on the blast load. Therefore, this study suggest the dynamic analysis method using high fidelity physics based (HFPB) analysis to predict damage and failure of a concrete structure under the blast loading condition. The explicit finite element code LS-DYNA is adopted for HFPB analysis and single-degree-of-freedom (SDOF) system is used for comparison of results. From the analysis results, it is found that HFPB analysis could represent reasonable results compared to those of SDOF analysis and SDOF analysis might overestimate or underestimate the resistance of structure under blast load. In case of detailed analysis, HFPB analysis with proper material model is needed to evaluate the resistance of structure correctly.

동하중을 고려한 설계의 필요성에 관한 고찰

강병수(B. S. Kang),김주성(J. S. Kim),박경진(G. J. Park) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

All the loads in the real world are dynamic loads and it is well known that structural optimization under dynamic loads is very difficult. Thus the dynamic loads are often transformed to the static loads using dynamic factors. However, due to the difference of load characters, there can be considerable differences between the results from static and dynamic analyses. When the natural frequency of a structure is high, the dynamic analysis result is similar to that of static analysis due to the small inertia effect on the behavior of the structure. However, if the natural frequency is low, the inertia effect should not be ignored. Then, the behavior of the dynamic system is different from that of the static system. The difference of the two cases can be explained from the relationship between the homogeneous and the particular solutions of the differential equation that governs the behavior of the structure. Through various examples, the difference between the dynamic analysis and the static analysis are shown. Also the optimization results considering dynamic loads are compared with static loads.

Development of a coupled analysis regarding the rotor/dynamic components of a rotorcraft

조해성,류한열,신상준,조인정,장진석 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12

This paper presents a combined analysis for the rotor and dynamic components of a rotorcraft. The dynamic components consist of thefollowing elements: a rotor shaft, a drive train, the engine shafts, and an engine and its governor. In this paper, the dynamic componentswere developed in a modularized fashion and combined with the rotor analysis. The present rotor structural analysis was derived basedon the mixed variational formulation of moving beams and combined with finite-state dynamic inflow aerodynamics. A linear massspring-damper connection was used for a drive train representation and a simple linear control algorithm was used for an engine governor. To analyze the response of the components, a state-space equation was established based on the torque equilibrium. The present multicomponentstructural and aerodynamic analysis was solved for by measuring the steady-state trim and time-transient response. Numericalvalidation was performed using a sample hingeless rotor in a tiltrotor aircraft. The present prediction showed good agreement withCAMRAD II for both the trim analysis and the transient analysis with the trimmed state. And distinctions between the rotor with andwithout dynamic components were verified. Thus, an accurate framework for the rotor system including the dynamic components wasdeveloped, which would be useful during the preliminary design stage of creating a rotorcraft.

동적 하중을 받는 암반 구조물의 수치해석 변수에 대한 고찰

류창하 ( Chang-ha Ryu ),최병희 ( Byung-hee Choi ),장형수 ( Hyung-su Jang ) 대한화약발파공학회 2018 화약발파 Vol.36 No.3

동적 하중을 받는 암반의 역학적 거동은, 같은 크기의 최대 하중이라도 정적으로 가해지는 경우와는 다른 특성을 보인다. 동적 하중 하에서의 거동 특성을 규명하기 위한 실험적 접근 방법은 동적 하중의 제어와 계측 및 해석에 있어서 정적 조건에서의 실험 방법보다 더 많은 어려움이 있다. 수치해석적 방법은 물리적 실험이 아니라 수치해석적으로 실험을 실시함으로써 물리적 제약을 덜 받으므로 설계 단계에서 매우 유력한 해석 도구가 될 수 있다. 그러나 수치해석방법은 해석방법의 알고리즘이 적정하더라도, 입력 자료와 경계조건의 설정에 따라 계산 결과가 많이 달라질 수 있으므로 해석 시 세심한 주의가 필요하다. 본 논문에서는 동적 하중을 받는 암반 구조물의 거동을 수치해석적으로 검토할 때, 경계 조건, 동적 하중과 계산 시간 간격, 동적 하중 특성이 계산 결과에 미치는 영향을 검토하여, 동적 해석 시 경계조건과 계산 시간 간격의 설정 지침을 제공하고자 하였다. The dynamic behaviour of the rock mass under the dynamic load is different from the static application of the maximum load of the same size. An experimental approach to investigating rock behavior under dynamic loads is more difficult than that under static conditions in control of dynamic loads, measurement and analysis of the results. Numerical methods are less constrained by performing the experiments numerically, rather than experimental ones, so they can be very powerful analytical tool at the design stage. However, even if the algorithms of the analysis method are appropriate, careful analysis is required because the calculation results may vary largely depending on input data and boundary conditions. In this paper, when investigating the behavior of rock structures under dynamic load numerically, the effects of boundary conditions, dynamic load and calculation time step, and dynamic load characteristics on the calculation results were reviewed to provide guidance on setting up boundary conditions and calculation time step related to dynamic analysis.

핵연료집합체 3 차원 축소모델 개발 및 모드해석

무하마드 수반(Muhammad Subhan),남궁인(Ihn Namgung) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

APR1400 원전의 지진해석은 집중질량 빔요소로 구성된 2 차원 모델로서 수직 방향과 수평 방향 모델로 분리되어 있다. 원자로 코어의 모든 핵연료는 모두 합쳐져서 몇 개의 빔요소와 집중질량으로 모델이 이루어져 있다. AP1000의 경우에는 3 차원 집중질량과 빔요소를 사용하여 모델을 개발하였으며, 3 차원 지진해석을 수행하였다. 본연구의 목적은 노심의 핵연료집합체를 통합하지 않고 개별 핵연료집합체에 대한 축소 동해석 모델을 개발하여 노심 동해석을 가능하게 하는 것이다. 이를 위해 본 논문에서는 최신 컴퓨터 기술 및 모델링 기술을 접목해서 핵연료집합체의 3 차원 동해석 방법론을 개발하는 것이다. 3 차원 핵연료 집합체의 축소모델을 개발하기 위해 핵연료봉은 질량으로 나타냈고, CEA 가이드 튜브와 스페이서 그리드는 빔요소를 사용하였고, 하단지지체와 상단지지체는 쉘요소로 취급하여 전체적으로 축소된 모델을 개발하였다. 이렇게 개발된 축소모델은 2,740 개의 요소와 5,148 개의 요소를 가진다. 이 모델에 대해 모드해석을 하여 시험결과와 비교를 통해 1 차모드를 수렴하도록 하였다. 모드해석을 통해 2 차, 3 차 및 4 차 모드도 시험 결과와 유사한 경향을 보임을 확인하였다. 따라서 본 축소모델을 사용하여 지진해석 및 시간이력해석이 가능할 것으로 판단된다. 본 연구에서 모드해석 결과 기존의 통합 모델에서 관찰할 수 없던 트위스트 모드를 보였다. 이 결과는 핵연료사이의 접촉가능성을 보여주는 것으로서 핵연료 사이의 동적 거동에 대한 추가적인 연구가 필요하다. Currently, the seismic analysis model of APR 1400 consists of beam and lumped mass in 2D separated model in horizontal direction and vertical direction. Also in the core, fuel assemblies are aggregated and simplified into few beam and lumped masses. WEC also used beam and lumped mass elements for the AP1000 seismic analysis model, but used 3D beam and mass to represent whole core where fuel assemblies are aggregated as well. The main purpose of the lumped mass and beam modeling of fuel assembly is to simplify model and make core dynamic analysis possible without aggregating all fuels in core into few beam elements and lumped masses. This research investigates 3D dynamic analysis modeling methodology of nuclear fuel assembly reflecting performance improvement of computer technology and analysis software functionality. A 3D modeling approach of FA was proposed in which fuel rods mass was lumped, CEA guide tubes and spacer grid are represented by beam elements and lower end-fitting and upper end-fitting are represented by shell elements. The FA dynamic analysis model so developed consists of 2,740 elements and 5,148 nodes. The model was optimized for the 1st mode from the test results of FA applying modal analysis. The model was successfully represents 1st mode modal values. Also the modal analysis results exhibits similarities for 2nd, 3rd and 4th modes, hence the model can be used for further dynamic analysis of fuel assembly such as seismic analysis or time-history analysis. The corresponding mode shapes revealed additional mode of twist motion that was not shown by current FA dynamic model of APR1400 or AP1000. This research revealed there are extra modes of twist motion that could induce contact between FAs and would require further investigation of dynamic interaction between FAs.