• 한국전산구조공학회논문집
• /
• 제23권6호
• /
• pp.659-665
• /
• 2010

The finite element method(FEM) is proven to be an effective approximate method of structural analysis if proper element types and meshes are chosen, and recently, the method is often applied to solve complex dynamic and nonlinear problems. A properly chosen element type and mesh yields reliable results for dynamic finite element structural analysis. However, dynamic behavior of a structure may include unpredictably large strains in some parts of the structure, and using the initial mesh throughout the duration of a dynamic analysis may include some elements to go through strains beyond the elements' reliable limits. Thus, the finite element mesh for a dynamic analysis must be dynamically adaptive, and considering the rapid process of analysis in real time, the dynamically adaptive finite element mesh generating schemes must be computationally efficient. In this paper, a computationally efficient dynamically adaptive finite element mesh generation scheme for dynamic analyses of structures is described. The concept of representative strain value is used for error estimates and the refinements of meshes use combinations of the h-method(node movement) and the r-method(element division). The shape coefficient for element mesh is used to correct overly distorted elements. The validity of the scheme is shown through a cantilever beam example under a concentrated load with varying values. The example shows reasonable accuracy and efficient computing time. Furthermore, the study shows the potential for the scheme's effective use in complex structural dynamic problems such as those under seismic or erratic wind loads.

• 한국정밀공학회지
• /
• 제16권12호
• /
• pp.99-108
• /
• 1999

A four-degree-of-freedom non-linear model with time varying mesh stiffness has been developed for the dynamic analysis of spur gear trains. The model includes a spur gear pair, two shafts, two inertias representing load and prime mover. In the model, developed several factors such as time varying mesh stiffness and damping, separation of teeth, teeth collision, various gear errors and profile modifications have been considered. Two computer programs are developed to calculate stiffness of a gear pair and transmission error and the dynamic analysis of modeled system using time integration method. Dynamic tooth and mesh forces, dynamic factors are calculated. Numerical examples have been given, which shows the time varying mesh stiffness ha a significant effect upon the dynamic tooth force and torsional vibrations.

• 대한기계학회논문집A
• /
• 제28권9호
• /
• pp.1359-1367
• /
• 2004

The purpose of this study is to predict the dynamic transmission error of the helical gear system. To do so, the equations of motion in the helical gear system which consists of motor, coupling, gear, torque sensor, and brake are derived. As the input parameters, the mass moment of inertia by a 3D CAD software and the equivalent stiffness of the bearings and shaft are calculated and the coupling stiffness is measured. The static transmission error as an excitation is calculated by in-house program. Dynamic transmission error is predicted by solving the equations of motion. Mode shape, the dynamic mesh force and the bearing force are also calculated. In this analysis, the relationship between the dynamic mesh force and the bearing force and mode shape behavior in gear mesh are checked. As a result, the magnitude of mesh force is highly related with the gear mesh behavior in mode shape. The finite element analysis is conducted to find out the natural frequency of gear system. The natural frequencies by finite element analysis have a good agreement with the results by equation of motion. Finally, dynamic transmission error is measured by the specially designed experiment and the results by equation of motion are validated.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.224-231
• /
• 2006

A six-degree-of-freedom dynamic model with time-varying mesh stiffness/damping and friction has been developed for the dynamic analysis of a gear driving system. This model includes a spur gear pair, bearing, friction and prime mover. Using Newton???s method, equations of motion for the gear driving system were derived. Two computer programs are developed to calculate mesh stiffness, transmission error and friction force and analyze the dynamics of the modeled system using a time integration method. The influences of mesh stiffness/damping, bearing, and friction affecting the system were investigated by performing eigenvalue analysis and time response analysis. It is found that the reduction of the maximum peak magnitude by friction is decided according to designing the positions of pitch point and maximum peak in the responses.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제50권2호
• /
• pp.53-58
• /
• 2001

This paper describes a moving mesh technique for dynamic characteristics analysis of permanent magnet linear synchronous motor with the secondary aluminium sheet. The moving mesh technique applied to the linear induction motor can be used to analyze the linear synchronous motor with the rectangular permanent magnet. But in case of the permanent magnet with taper, the shape of the permanent magnet is presented. The time-stepped finite element method is used for the dynamic characteristics simulation of the permanent magnet linear synchronous motor, The results of application example(hysteresis current controlled inverter fed control) such as thrust, current and flux plots are shown.

• Journal of Computational Design and Engineering
• /
• 제1권2호
• /
• pp.96-102
• /
• 2014

In the field of design and manufacturing, there are many problems with managing dynamic states of three-dimensional (3D) objects. In order to solve these problems, the four-dimensional (4D) mesh model and its modeling system have been proposed. The 4D mesh model is defined as a 4D object model that is bounded by tetrahedral cells, and can represent spatio-temporal changes of a 3D object continuously. The 4D mesh model helps to solve dynamic problems of 3D models as geometric problems. However, the construction of the 4D mesh model is limited on the time-series 3D voxel data based method. This method is memory-hogging and requires much computing time. In this research, we propose a new method of constructing the 4D mesh model that derives from the 3D mesh model with continuous rigid body movement. This method is realized by making a swept shape of a 3D mesh model in the fourth dimension and its tetrahedralization. Here, the rigid body movement is a screwed movement, which is a combination of translational and rotational movement.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.1441-1446
• /
• 2009

Numerical analysis is a powerful method in evaluating the soil-pile-structure interaction under the dynamic loading, and this approach has been applied to the practical area due to the development of computer technology. Finite Difference Method, one of the most popular numerical methods, is sensitive to the shape and the number of mesh. However, the trial and error approach is conducted to obtain the accurate results and the reasonable simulation time because of the lack of researches about mesh size and the number. In this study, FLAC 3D v3.1 program(FDM) is used to simulate the dynamic pile model tests, and the numerical results are compared with the 1G shaking table tests results. With the different size and shape of mesh, the responses of pile behavior and the simulation time are estimated, and the optimum mesh sizes in dynamic analysis of single pile is studied.

• Journal of Korean Neurosurgical Society
• /
• 제41권2호
• /
• pp.111-117
• /
• 2007

Objective : The objective of this study was to validate the effects of a titanium mesh cage and dynamic plating in anterior cervical stabilization after corpectomy. Methods : A retrospective study was performed on 31 consecutive patients, who underwent anterior cervical reconstruction with a titanium mesh cage and dynamic plating, from March 2004 to February 2006. Twenty-four patients had 1-level and 7 had 2-level corpectomies. Ten patients underwent surgery with a cage of 10-mm diameter and 21 with 13-mm diameter. Neurological status and outcomes were assessed according to Odom's criteria. Sagittal angle, coronal angle, settling ratio, sagittal displacement, and cervical lordosis were used to evaluate the radiological outcomes. Results : In overall, 26 [83.9%] of 31 showed excellent or good outcomes. Thirteen percent [4 cases] of the patients developed surgical complications, such as hoarseness, transient dysphagia, or nerve root palsy. Seven [22.6%] patients had reconstruction failure:5 [20.8%] in the 1-level corpectomy group and 2 [28.5%] in the 2-level corpectomy group. Revisions were required in 2 patients with plate pullout due to significant instability. However, none of 5 patients who demonstrated cage displacement or screw pullout, underwent a revision. Radiographs revealed bony consolidation in 96.3% of the patients, including 6 patients with implantation failure during the follow-up period. Conclusion : Based on our preliminary results, the titanium mesh cage and dynamic plating was effective for cervical reconstruction after corpectomy. The anterior cervical reconstruction performed with dynamic plates is considered to reduce stress shielding and greater graft compression that is afforded by the unique plate design.

• 방송공학회논문지
• /
• 제28권3호
• /
• pp.314-328
• /
• 2023

본 논문에서는 동적 메쉬 부/복호화 시 스케일러빌리티 기능을 지원하기 위해 SHVC의 계층적 부호화 방식을 기반으로 텍스처 맵을 압축하는 방법을 제안한다. 제안하는 방법은 고해상도 텍스처 맵을 다운샘플링하여 다해상도의 텍스처 맵을 생성하고 이를 SHVC로 부호화함으로써 효과적으로 다해상도 텍스처 맵들의 중복성을 제거한다. 동적 메쉬 복호화기에서는 수신기 성능, 네트워크 환경 등에 따라 적합한 해상도의 텍스처 맵을 복호화하여 메쉬 데이터의 스케일러빌리티를 지원할 수 있도록 한다. 제안하는 방법의 성능을 검증하기 위해 V-DMC (Video-based Dynamic Mesh Coding) 참조 소프트웨어인 TMMv1.0에 제안하는 방법을 적용하고 본 논문에서 제안하는 스케일러블 부/복호화기와 TMMv1.0 기반의 시뮬캐스트 방식의 성능을 비교하였다. 제안하는 방법은 시뮬캐스트 방법 대비 AI, LD 환경에서 Luma BD-rate (Luma PSNR)가 각각 평균 -7.7%, -5.7%의 향상된 결과를 얻어 제안하는 방법을 통해 효과적으로 동적 메쉬 데이터의 텍스처 맵 스케일러빌리티 지원이 가능함을 확인하였다.

• 한국항공우주학회지
• /
• 제35권2호
• /
• pp.87-93
• /
• 2007

항공기 설계를 할 때에는 CFD를 이용한 해석 과정을 수반하는 것이 일반적이다. 그러나 CFD 해석은 많은 계산 시간과 비용이 소요되는데 동적 격자를 이용하면 다양한 모델의 해석 시 격자의 재구성 과정에 소요되는 시간을 줄일 수 있다. 뿐만 아니라 공탄성 해석처럼 격자를 갱신하면서 해석을 수행하는 경우, 설계 모델의 최적화 과정과 같이 다양한 격자를 구성해야 하는 경우에 동적 격자를 사용하면 전체 해석 시간을 줄일 수 있으므로 효율적인 해석이 가능하다.