강도감소법에 의한 3차원 사면안정해석에 대한 매개변수 연구

김영민(Young-Min Kim) 한국지반신소재학회 2016 한국지반신소재학회 논문집 Vol.15 No.4

지반공학에서 평면변형율을 가정하는 2차원 사면안정해석은 일반적으로 널리 사용되고 있다. 이 가정은 사면활동이 넓은 영역에 걸쳐서 발생되는 가정이므로 3차원 효과가 무시된다. 대다수 연구에서 2차원해석의 최소안전율값은 3차원해석에 비하여 작게 평가되는 보수적인 결과를 나타낸다. 최근에는 컴퓨터의 소프트웨어와 하드웨어를 포함한 해석방법의 발달로 3차원해석에 대한 요구가 커지고 있다. 본 논문에서는 원호모드, 병진모드사면을 이용하여 유한요소에 의한 2, 3차원해석 및 2차원 한계평형해석을 통하여 수치해석을 실시하였다. 해석결과 매개변수(요소망크기, 체적팽창각(dilatency angle), 경계조건, 응력이력, 모델차원)에 따른 사면안정해석에 미치는 영향을 분석하였다. 해석결과 2차원 해석보다 3차원 해석에 의한 사면의 안전율 값은 항상 크게 평가되며, W 뱡향 경계조건이 롤러지지인 경우, 사면폭에 의한 결과 차이는 없는 것으로 조사되었다. The two-dimensional (2D) analysis is widely used in geotechnical engineering for slope stability analysis assuming a plane-strain condition. It is implicitly assumed that the slip surface is infinitely wide, and thus three-dimensional (3D) end effects are negligible because of the infinite width of the slide mass. The majority of work on this subject suggests that the 2D factor of safety is conservative (i.e. lower than the ‘true’ 3D factor of safety). Recently, the 3D finite element method (FEM) became more attractive due to the progress of computational tools including the computer hardware and software. This paper presents the numerical analyses on rotational mode and translational mode slopes using the 2D and 3D FEM as well as 2D limit equilibrium methods (LEM). The results of the parametric study on the slope stability due to mesh size, dilatency angle, boundary conditions, stress history and model dimensions change are analysed. The analysis showed that the factor of safety in 3D analysis is always higher than that in the 2D analysis and the discrepancy of the slope width in W direction on the factor of safety is ignored if the roller type of W direction conditions is applied.

Development of NUFORM3D module with FRAPCON3.4 for simulation of pellet-cladding mechanical interaction

Kim, Hyo Chan,Seo, Sang Kyu,Lee, Sung Uk,Yang, Yong Sik Elsevier 2017 Nuclear engineering and design Vol.318 No.-

<P><B>Abstract</B></P> <P>In order to evaluate the PCMI (pellet-to-cladding mechanical interaction) behavior in fuel rods, a three-dimensional finite element (FE) module, termed NUFORM3D, was developed by KAERI. In the NUFORM3D module, a thermo-mechanical model considering elasto-plastic deformation and a contact model were formulated to simulate the PCMI behavior. The NUFORM3D module was implemented to compensate for the weaknesses of the analytical methods used in traditional fuel performance codes for PCMI simulations. In this work, NUFORM3D was coupled with FRAPCON-3.4, which is the NRC’s fuel performance code for a steady state, to evaluate the NUFORM3D module with an irradiated database. The REGATE experiment, involving the use of a power ramp database in a test reactor, was employed to evaluate the coupled code system. The coupled NUFORM3D was able to simulate bamboo-shaped deformation of cladding as well as stress concentrations in cladding due to pellet hourglass deformation in the power ramp. Secondary ridges of the cladding on the mid-pellet plane were found in the experimental results. To simulate the secondary ridge, a transversally fragmented pellet model was adopted. As a result, the coupled NUFORM3D module can improve the simulation capability of fuel performance codes for PCMI.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NUFORM3D, which can simulate the pellet cladding mechanical interaction (PCMI) in 3D based on finite element method (FEM), has been developed. </LI> <LI> NUFORM3D was coupled with FRAPCON-3.4. </LI> <LI> A power ramp database (REGATE experiment) was simulated by the coupled NUFORM3D. </LI> </UL> </P>

Application of Patient-Specific 3D-Printed Orthopedic Splint for Bone Fracture in Small Breed Dogs

강성수 한국임상수의학회 2023 한국임상수의학회지 Vol.40 No.4

In this paper, we designed 3D-printed orthopedic splint models for patient-specific external coaptation on fracture healing and analyzed the sta- bility of the models through finite element method (FEM) analysis under com- pressive load conditions. Polylactic acid (PLA) and acrylonitrile-butadiene-sty- rene (ABS) based 3D splint models of the thicknesses 1, 3, 5 and 7 mm were designed, and Peak von Mises stress (PVMS) and maximum displacement (MD) of the models were analyzed by FEM under compressive loads of 50, 100, 150, and 200 N. The FEM results indicated that PVMS and MD values, regardless of material, had a negative correlation with the thickness of the models and a posi- tive correlation with the compressive load. There was a risk of splint deformation under conditions more extreme than 100 N with 5 mm thickness. For successful clinical application of 3D-printed orthopedic splints in veterinary medicine, it is recommended that the splint should be produced not less than 5 mm thickness. Also, it is expected to be stable when the splint is applied to situations with a compressive load of 100 N or less. There is an advantage of overcoming the limitations of the existing bandage method through 3D-printing technology as well as verifying the stability through 3D modeling before application. Such 3D printing technology will be widely used in veterinary medicine and various fields as well as orthopedics.

냉간 압연에서 압하력 분포 예측 - Part II : 적용 및 검증

남승연,황상무 한국소성∙가공학회 2019 소성가공 : 한국소성가공학회지 Vol.28 No.4

This paper proposes a precise mathematical model for the prediction of the variation of the roll force across a strip in cold rolling. It further describes the deformation characteristics of the strip using a 3-D finite element method. The different features of hot rolling and cold rolling through a 3-D finite element method are shown. The predicted roll force profile and tension profile are verified through comparison with the prediction from a 3-D finite element method.

3차원 확장유한요소를 사용한 철근콘크리트 휨 부재의 다중균열 해석

김한수(Kim, Han-Soo),김건형(Kim, Geon-Hyeong) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.1

In this paper, the extended finite element method (XFEM) is used to simulate a crack initiation and propagation and to predict post-failure behavior of reinforced concrete flexural members. The reinforced concrete beams modeled by 2-dimension plane element and 3-dimension solid element are compared with the result of RC beam experiments. The analysis results of 2D and 3D XFEM elements are similar to experimental results. It confirmed the validity of the use of the 3D XFEM model for the analysis of RC flexural members. In this process, the locking phenomenon in enriched degree of freedoms was detected. The ways to prevent the locking phenomenon are presented; reducing the time increments or the tolerance of fracture criterion. Subsequently, a reinforced concrete slab modeled by 3-dimensional XFEM was analyzed and compared with the result of a RC slab test as well as the analysis with concrete damaged plasticity (CDP) model which can represent realistic post-failure behavior of concrete. The analysis with XFEM showed a similar load capacity and crack propagation patterns. The validity of 3D XFEM to predict crack patterns and post-failure behavior of RC members was demonstrated.

Large displacement geometrically nonlinear finite element analysis of 3D Timoshenko fiber beam element

Hu, Zhengzhou,Wu, Minger Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.4

Based on continuum mechanics and the principle of virtual displacements, incremental total Lagrangian formulation (T.L.) and incremental updated Lagrangian formulation (U.L.) were presented. Both T.L. and U.L. considered the large displacement stiffness matrix, which was modified to be symmetrical matrix. According to the incremental updated Lagrangian formulation, small strain, large displacement, finite rotation of three dimensional Timoshenko fiber beam element tangent stiffness matrix was developed. Considering large displacement and finite rotation, a new type of tangent stiffness matrix of the beam element was developed. According to the basic assumption of plane section, the displacement field of an arbitrary fiber was presented in terms of nodal displacement of centroid of cross-area. In addition, shear deformation effect was taken account. Furthermore, a nonlinear finite element method program has been developed and several examples were tested to demonstrate the accuracy and generality of the three dimensional beam element.

A Simplified Approach for Estimating Settlement of Soft Clay under Vacuum Consolidation

Sandeep Bhosle,Devendra Kumar Verma,Vivek Balwantrao Deshmukh 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.5

In general, the ground improvement by Prefabricated Vertical Drains (PVD) consolidation involves a high magnitude of settlement, which results in a change in the consolidation characteristic of the soil during the process of consolidation. Under such circumstances, the consolidation problem must be treated as a large strain problem. The large strain 3-Dimensional consolidation analysis requires a large number of parameters, making it difficult for practicing engineers to carry out such analysis for a practical application. This paper aims to provide a simplified method for estimation of settlement during 3D vacuum consolidation using a single parameter, the coefficient of horizontal Consolidation (Ch). For this, the variation in Ch during the 3D consolidation was backcalculated using Hansbo’s method from a series of large-scale 3D vacuum consolidation tests carried on reconstituted marine clay. As the varying Ch cannot be employed in available analytical models, a simplified finite element analysis is presented to employ varying Ch. The estimated settlement was further compared with settlement obtained utilizing constant Ch, by trial and error method. The paper also demonstrates a potential advantage of the proposed method that the variation in Ch can also be determined from 3D consolidation carried out previously for similar strata, as it requires only basic data, which are usually available.

내부 위상 형상에 따른 3D 프린트 복합재 방향타의 구조 성능 평가

조영재,서형석,박희승 한국복합재료학회 2023 Composites research Vol.36 No.6

최근 온실가스 배출량에 대한 규제가 높아지면서 IMO는 온실가스 배출량을 2050년까지 순 배출량 ‘0’을 목표로 하며 온실가스 규제를 강화하고 있다. 또한 조선/해양 분야에서는 추진 효율 향상, 구조 경량화와 같이 운항비 절감이 중요하다. 현재 이와 관련하여 구조 경량화와 고강성을 만족하기 위하여 3D 프린트 복합재료를 이용한 위상 최적화에 대한 연구가 수행되고 있다. 본 연구에서는 3D 프린트 복합재료를 활용하여 선박 구조물인 방향타의 내부에 3가지 위상 형상(육각형, 사각형, 삼각형)을 적용하였다. 방향타에 위상 형상을 적용하였을 때 적합한 형상을 알아보기 위해 구조해석을 수행했다. 선속 8Knots의 조건에서 타 각 0°에서 30°까지 10°간격으로 CFD 해석을 수행하였으며, CFD 해석 결과를 바탕으로 하중조건을 설정하였다. 방향타 내부 위상 형상을 고려한 구조해석 결과 삼각형, 사각형, 육각형 위상 형상 순으로 우수한 성능을 갖는 것을 확인하였다. 사각형 위상 형상을 가지는 방향타가 삼각형 형상을 가지는 방향타의 78.5%의 무게를 가지며 경량화 측면을 고려하였을 때 사각형 위상 형상이 우수하다고 판단된다. Recently, regulations on greenhouse gas emissions have been strengthened, and the International Maritime Organization (IMO) has been strengthening greenhouse gas regulations with a goal of net 'zero' emissions by 2050. In addition, in the shipbuilding/offshore sector, it is important to reduce operating costs, such as improving propulsion efficiency and lightening structures. In this regard, research is currently being conducted on topology optimization using 3D printed composite materials to satisfy structural lightness and high rigidity. In this study, three topology shapes (hexagonal, square, and triangular) were applied to the interior of a rudder, a ship structure, using 3D printed composite materials. Structural analysis was performed to determine the appropriate shape for the rudder. CFD analysis was performed at 10° intervals from 0° to 30° for each rudder angle under the condition of 8 knots, and the load conditions were set based on the CFD analysis results. As a result of the structural analysis considering the internal topology shape of the rudder, it was confirmed that the triangular, square, and hexagonal topology shapes have excellent performance. The rudder with a square topology shape weighs 78.5% of the rudder with a triangular shape, and the square topology shape is considered to superior in terms of weight reduction,

Large displacement geometrically nonlinear finite element analysis of 3D Timoshenko fiber beam element

Zhengzhou Hu,Minger Wu 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.4

Based on continuum mechanics and the principle of virtual displacements, incremental total Lagrangian formulation (T.L.) and incremental updated Lagrangian formulation (U.L.) were presented. Both T.L. and U.L. considered the large displacement stiffness matrix, which was modified to be symmetrical matrix. According to the incremental updated Lagrangian formulation, small strain, large displacement, finite rotation of three dimensional Timoshenko fiber beam element tangent stiffness matrix was developed. Considering large displacement and finite rotation, a new type of tangent stiffness matrix of the beam element was developed. According to the basic assumption of plane section, the displacement field of an arbitrary fiber was presented in terms of nodal displacement of centroid of cross-area. In addition, shear deformation effect was taken account. Furthermore, a nonlinear finite element method program has been developed and several examples were tested to demonstrate the accuracy and generality of the three dimensional beam element.

3D 프린팅을 이용한 해수분사용 노즐 시제품 개발의 가능성 연구

윤석태(Seok-Tea Yoon),박종천(Jong-Chun Park),조용진(Yong-Jin Cho) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.3

함정의 해수냉각 시스템은 화생방전에 의한 유해물질의 세척과 선체 외부의 적외선 신호를 저감하기 위해 설치된다. 시스템은 압력펌프, 각종 배관 그리고 해수분사용 노즐로 구성된다. 그리고 해수의 분사 압력과 노즐 종류에 따라 산포 범위가 결정된다. 따라서 해수의 산포 범위를 넓히고 해수냉각 시스템의 효율을 극대화하기 위해서는 적절한 분사압력의 설정과 노즐의 최적 설계가 필요하다. 금속재료로 만들어지는 해수분사용 노즐은 초기 개발단계에서 금속 틀을 만들고 최적 성능을 만족할 때까지 수정된다. 이는 많은 시간과 비용을 유발하여 노즐개발에 어려움을 일으킨다. 따라서 본 연구에서는 해수분사용 노즐의 초기 개발단계에서 시제품을 생성하기 위한 3D 프린팅 기술의 적용 가능성을 확인하였다. 이를 위해 3D 프린팅 기술을 이용하여 압출 플라스틱 시험편을 제작하고 인장시험을 통해 시험편의 물리적 특성값을 측정하였다. 그리고 측정 결과를 유한요소해석 조건에 적용해 해수의 분사 압력에 따른 노즐의 변형과 응력을 계산하였다. 유한요소해석 결과 노즐은 최적 압력에서 탄성 범위 내로 변화하였으며, 구조적으로 안정하다고 판단되어 본 연구의 가능성을 확인하였다. The seawater cooling system of naval ships is installed to remove the toxic substances generated by CBR (Chemical, Biological, and Radiological) warfare and reduce the infrared signature of naval ships from outside the hull. The dispersion range of the nozzle is determined according to the injection pressure of seawater and the nozzle type. Therefore, it is necessary to select the appropriate injection pressure and design the optimal nozzles to increase the seawater dispersion area and maximize the efficiency of the cooling system. In this study, the applying feasibility of 3D printing technology to produce an injection nozzle for the seawater cooling system was examined. To this end, the extruded plastic specimens were fabricated by 3D printing, and the physical properties of the specimens were estimated through tensile testing. After this, the strain and stress of the nozzle as a function of the pressure were simulated by applying the estimated results to the finite element analysis. The finite element analysis results showed that the nozzle remained within the elastic range at the optimal pressure. The nozzle was estimated to be structurally stable, and the possibility of this study was confirmed.