• Structural Engineering and Mechanics
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• 제4권5호
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• pp.569-586
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• 1996

A new three-dimensional 8-node solid element with rotational degrees of freedom is presented. The proposed element is established by adding rotational degrees of freedom to the basic 8-node solid element. Thus the element has three translations and three rotational degrees of freedom per node. The corner rotations are introduced by transforming the hierarchical mid-edge displacements which are parabolic shape along an edge. The derivation of the element is based on the mixed variational principles in which the rotations are introduced as independent variables. Several types of non-conforming modes are selectively added to the displacement fields to obtain a series of improved elements. The resulting elements do not have the spurious zero energy modes and Poisson's ratio locking and pass patch test. Numerical examples show that presented non-conforming solid elements with rotational degrees of freedom show good performance even in the highly distorted meshes.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.161-168
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• 1995

The variable-node solid element with rotational degrees of freedom has been developed far efficient connection of transition zones and far connection of different types of elements with rotational degrees of freedom. In applying this new element to engineering problems, it is necessary to fine the relations between tractions and equivalent nodal farces. In this case, the equivalent forces in solid element with rotational degrees of freedom and ratational forces are a bit different from that af conventional solid elements. Some typical examples are presented.

• 구강회복응용과학지
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• 제24권1호
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• pp.57-65
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• 2008

연구목적 : 본 연구에서는 rotational freedom을 측정할 수 있는 기구를 개발하여 시중에서 유통되고 있는 국산 임플란트 및 다양한 국적의 임플란트들의 기계적인 가공오차들을 측정하여 다양한 임플란트 시스템의 component간의 기계적인 안정성을 평가하고자 한다. 또한 본 연구에서는 더 나아가 최근에 임플란트 abutment로 각광을 받고 있는 각종 ceramic abutment의 절삭 가공오차에 관한 항목을 측정하여 임플란트 제조사 및 임상의들에게 올바른 정보를 제공하고자 한다. 연구재료 및 방법 : 국내에서 유통되는 외부연결구조의 외국산 임플란트 시스템(Nobel Biocare, Anthorgyr)과 국산 시스템(Neobiotec)과 내부연결구조의 임플란트 시스템(외국산:Nobel Biocare, Anthorgyr, Straumann, Frident Dentsply, 국산:Dentium) 별로 임플란트 fixture, abutment, analog를 서로 교차 연결하여 회전각도측정기(rotational angle measuring device)로 freedom of rotational angle을 측정하였다. 국산 외부연결구조의 지르코니아 abutment(ZirAce)를 외부연결구조의 임플란트 시스템(Neobiotec, Nobel Biocare, Anthorgyr)의 fixture와 analog와 교차연결하여 freedom of rotational angle을 측정하였다. 연구결과 : 국산 외부연결구조의 임플란트 시스템은 약 2.67도(fixture와 abutment 연결시), 내부연결구조의 임플란트는 약 4.3도(fixture와 abutment 연결시)의 rotational freedom을 보였다. 국산 지르코니아 abutment는 외국산 및 국산 외부연결구조 임플란트 시스템과 상관없이 3도 이하(fixture와 연결시)의 결과를 보였다. 결 론 : 시제품으로 제작된 디지털 회전각도측정기는 높은 분해능을 갖고 있었으며, 국산 임플란트의 기계적 가공오차는 외국산 임플란트와 거의 유사했다. 국산 세라믹 abutment의 기계적 가공오차는 fixture 제조회사별로 다르게 나타났지만 같은 회사의 절삭가공된 금속 abutment와 비교시 가공오차가 더 적었다.

• 한국정밀공학회지
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• 제17권2호
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• pp.201-210
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• 2000

The large deflection of plate is analyzed by co-rotational formulations using small local displacements and rotating unit vectors on the nodal points. The rotational degrees of the freedom are represent ed by the unit vectors1 In the nodal points, and the equilibrium equations are formulated by using small deflection theories of the plates by assuming that the directions of the unit vectors of the nodal points are known apriori. The translational degrees of freedom are independently solved from the rotational degrees of freedom in the equilibrium equations, and the correct directions of the unit vectors are computed by the iterative scheme by imposing the moment equilibrium constraint. The equilibrium equations and the associated solution procedure are explained, and the verification problems are solved.

• The Journal of Advanced Prosthodontics
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• 제13권6호
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• pp.343-350
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• 2021

PURPOSE. The success of an implant-prosthetic rehabilitation is influenced by good implant health and an excellent implant-prosthetic coupling. The stability of implant-prosthetic connection is influenced by the rotational tolerance between anti-rotational features on the implant and those on the prosthetic component. The aim of this study is to investigate the rotational tolerance of a conical connection implant system and its titanium abutment counterpart, in various conditions. MATERIAL AND METHODS. 10 preparable titanium abutments, having zero-degree angulation (MegaGen, Daegu, Korea) with an internal 5-degree conical connection, and 10 implants (MegaGen, Daegu, Korea) were used. Rotational tolerance between the connection of implant and titanium abutments was measured through the use of a tridimensional optics measuring system (Quick Scope QS250Z, Mitutoyo, Kawasaki, Japan) in the as-received condition (Time 0), after securing with a titanium screw tightening at 35 Ncm (Time 1), after tightening 4 times at 35 Ncm (Time 2), after tightening one more time at 45 Ncm (Time 3), and after tightening another 4 times at 45 Ncm (Time 4). RESULTS. The group "Time 0" had the lowest values of rotational freedom (0.22 ± 0.76 degrees), followed by the group Time 1 (0.46 ± 0.83 degrees), the group Time 2 (1.01 ± 0.20 degrees), the group Time 3 (1.30 ± 0.85 degrees), and the group Time 4 (1.49 ± 0.17 degrees). CONCLUSION. The rotational tolerance of a conical connection is low in the "as received" condition but increases with repetitive tightening and with application of a torque greater than 35 Ncm.

• 한국자동차공학회논문집
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• 제9권2호
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• pp.185-191
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• 2001

In many papers, the powertrain system generally has been madeled as one-dimensional torque model. One-dimensional powertrain model may calculate the torque correctly but it does not consider the non-rotational degrees-of-freedom of the powertrain components and the interaction of these degrees-of-freedom with the vehicle body frame and suspension. To consider the non-rotational degrees of freedom, the differential is modeled as a three-dimensional rigid body in this paper. A constant velocity joint is newly formulated and a relative constraint is also formulated to model the motion transfer due to gear ratio of the differential. Implementing the proposed powertrain system in the multibody model, more detail dynamic responses can be obtained. Obtained outputs such as reaction torques on the constant velocity joint and reaction forces on the rack can be useful data in the design of a powertrain.

• Structural Engineering and Mechanics
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• 제10권6호
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• pp.603-619
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• 2000

Analysis of a framed structure for vertical vibration requires a lot of computational efforts because large number of degrees of freedom are generally involved in the dynamic responses. This paper presents an efficient modeling technique for vertical vibration utilizing substructuring technique and super elements. To simplify the modeling procedure each floor in a structure is modeled as a substructure. Only the vertical translational degrees of freedom are selected as master degrees of freedom in the inside of each substructure. At the substructure-column interface, horizontal and rotational degrees of freedom are also included considering the compatibility condition of slabs and columns. For further simplification, the repeated parts in a substructure are modeled as super elements, which reduces computation time required for the construction of system matrices in a substructure. Finally, the Guyan reduction technique is applied to enhance the efficiency of dynamic analysis. In numerical examples, the efficiency and accuracy of the proposed method are demonstrated by comparing the response time histories and the analysis time.

• 한국전산구조공학회논문집
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• 제13권4호
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• pp.475-484
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• 2000

본 연구에서는 찌그러진 요소에서의 휨거동 개선을 위한 추가적인 비적합변위형과 효율적인 비적합변위형의 수정방법의 개발을 통하여 기존 비적합 입체요소의 개선을 시도하였으며, 회전자유도가 독립변수로 존재하는 범함수를 이용하여 매개변수의 값에 따라 회전자유도의 도입유무가 결정되도록하는 입체요소를 개발하였다. 제시된 요소에서는 변위장과 회전장에 동일한 형상함수를 적용하였으며, 비적합변위형은 변위장에만 적용하였다. 다양한 예제를 통한 수치실험결과 개발된 요소는 양호한 거동을 보여주었으며, 특히 휨거동에 있어서 개선된 거동을 보였다.

• Structural Engineering and Mechanics
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• 제21권5호
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• pp.571-590
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• 2005

An 8 node assumed stress hexahedral element with rotational degrees of freedom is proposed for static and free vibration analyses. The element formulation is based directly on an 8-node element. This direct formulation requires fewer computations than a similar element that is derived from an internal 20-node element in which the midside degrees of freedom are eliminated by expressing them in terms of displacements and rotations at corner nodes. The formulation is based on Hellinger-Reissner variational principle. Numerical examples are presented to show the validity and efficiency of the present element for static and free vibration analysis.

• Structural Engineering and Mechanics
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• 제11권1호
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• pp.105-122
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• 2001

A new three-dimensional 13-node hexahedral element with rotational degrees of freedom, which is designated as MR-H13 element, is presented. The proposed element is established by adding five nodes to one of the six faces of basic 8-node hexahedral element. The new element can be effectively used in the connection between the refined mesh and the coarser mesh. The derivation of the current element in this paper is based on the variational principles in which the rotation and skew-symmetric stress are introduced as independent variables. Numerical examples show that the performance of the new element is satisfactory.