• Title, Summary, Keyword: rotational freedom

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Three dimensional non-conforming 8-node solid elements with rotational degrees of freedom

  • Choi, Chang-Koon;Chung, Keun-Young;Lee, Nam-Ho
    • Structural Engineering and Mechanics
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    • v.4 no.5
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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.

Machining Tolerance of Various Implant Systems and their Components (치과용 임플란트 시스템의 기계적 가공오차에 관한 연구)

  • Kim, Hyeong-Seob;Kwon, Kung-Rock;Han, Jung-Suk
    • Journal of Dental Rehabilitation and Applied Science
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    • v.24 no.1
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    • pp.57-65
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    • 2008
  • Purpose: Misfit of implant components was very important in terms of prosthodontics. they has been linked to prosthetic complications such as screw loosening and fracture. Although there are many results about rotational freedom or machining tolerance between fixture and abutments, the data about domestic implant systems are lacking. The aim of this in vitro study was to evaluate the rotational freedom of domestic external and internal connection implant systems between their fixtures/anlaogs and abutments comparing imported systems. Materials and Methods: Rotational freedom between abutments and fixtures/analogs was investigated by using digitalized rotational angle measuring device. (1) 1 domestic external connection system(Neobiotec) and 2 imported external connection systems(Nobel Biocare, Anthorgyr), (2) 1 domestic internal connection system(Dentium) and 4 imported external connection systems(Nobel Biocare, Anthorgyr, Straumann, Frident Dentsply), and (3) 1 domestic zirconia external connection abutment(ZirAce) were evaluated. Each group has 3 samples. Mean values for each group were analyzed. Results: The differences relative to rotational freedom between domestic and imported implant systems were observed but domestic external connection implant system showed about 2.67 degrees(in case of fixture) and internal connection system showed about 4.3 degrees(in case of fixture). Domestic zirconia abutment showed less than 3 degrees of rotational freedom in a situation where the abutment was connected to an implant fixture egardless of domestic or imported systems. Conclusion: Newly developed digitalized rotational angle measuring device has high measuring resolution. The rotational freedom of domestic implant systems were similar to imported implant systems.

Equivalent Nodal Forces of The Solid Element with Rotational Degrees of Freedom (회전자유도가 있는 입체요소의 등가절점하중)

  • 최창근;정근영
    • Proceedings of the Computational Structural Engineering Institute Conference
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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.

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The change of rotational freedom following different insertion torques in three implant systems with implant driver

  • Kwon, Joo-Hyun;Han, Chong-Hyun;Kim, Sun-Jai;Chang, Jae-Seung
    • The Journal of Advanced Prosthodontics
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    • v.1 no.1
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    • pp.37-40
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    • 2009
  • STATEMENT OF PROBLEM. Implant drivers are getting popular in clinical dentistry. Unlike to implant systems with external hex connection, implant drivers directly engage the implant/abutment interface. The deformation of the implant/abutment interface can be introduced while placing an implant with its implant driver in clinical situations. PURPOSE. This study evaluated the change of rotational freedom between an implant and its abutment after application of different insertion torques. MATERIAL AND METHODS. Three kinds of internal connection implants were utilized for the current study($4.5{\times}12\;mm$ Xive, $4.3{\times}11.5\;mm$ Inplant Magicgrip, $4.3{\times}12\;mm$ Implantium MF). An EstheticBase, a 2-piece top, a Dual abutment was used for its corresponding implant system. The rotational freedom between an implant and its abutment were measured before and after applying 45, 100 Ncm insertion torque. Repeated measures ANOVA was used for statistical analysis. RESULTS. Under 45 Ncm insertion torque, the rotational freedom between an implant and its abutment was significantly increased in Xive(P = .003). However, no significant change was noted in Inplant Magicgrip and Implantium MF. Under 100 Ncm torque, both in Xive(P = .0005) and Implatium MF(P = .03) resulted in significantly increased rotational freedom between the implant and its abutment. DISCUSSION. The design of the implant/implant driver interface effectively prevented the deformation of implant/abutment interface. Little change was noted in the rotational freedom between an implant and its abutment, even though the insertion torque was far beyond clinical application. CONCLUSIONS. The implant/abutment joint of internally connecting implants were quite stable under insertion torque in clinical situation.

The Shell Elements with vertex Degree of Freedoms (Shell요소의 Normal Rotation)

  • Cho, Soon-Bo
    • Proceeding of KASS Symposium
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    • pp.256-264
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    • 2006
  • This paper describes the formulation of rectangular flat shell element that is modeled with the six degree of freedoms including a rotational degree of freedom. The rectangular finite element matrix with a rotational degree of freedom is developed using a beam stiffness matrix and compared with other methods. The outputs of the quantity of vertical deflection of cantilever beam show us the improving evidence of the Frame-Shell finite element matrix in a calculation of vertical deflections of cantilever beam.

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Large Deflection Analysis of Plates By Using Small Local Deflections And Rotational Unit Vectors (미소 변형 및 회전 단위 벡터를 이용한 판의 대변형 해석)

  • 이기수
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.2
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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.

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Comparison of fit accuracy and torque maintenance of zirconia and titanium abutments for internal tri-channel and external-hex implant connections

  • Siadat, Hakimeh;Beyabanaki, Elaheh;Mousavi, Niloufar;Alikhasi, Marzieh
    • The Journal of Advanced Prosthodontics
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    • v.9 no.4
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    • pp.271-277
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    • 2017
  • PURPOSE. This in vitro study aimed to evaluate the effect of implant connection design (external vs. internal) on the fit discrepancy and torque loss of zirconia and titanium abutments. MATERIALS AND METHODS. Two regular platform dental implants, one with external connection ($Br{\aa}nemark$, Nobel Biocare AB) and the other with internal connection (Noble Replace, Nobel Biocare AB), were selected. Seven titanium and seven customized zirconia abutments were used for each connection design. Measurements of geometry, marginal discrepancy, and rotational freedom were done using video measuring machine. To measure the torque loss, each abutment was torqued to 35 Ncm and then opened by means of a digital torque wrench. Data were analyzed with two-way ANOVA and t-test at ${\alpha}=0.05$ of significance. RESULTS. There were significant differences in the geometrical measurements and rotational freedom between abutments of two connection groups (P<.001). Also, the results showed significant differences between titanium abutments of internal and external connection implants in terms of rotational freedom (P<.001). Not only customized internal abutments but also customized external abutments did not have the exact geometry of prefabricated abutments (P<.001). However, neither connection type (P=.15) nor abutment material (P=.38) affected torque loss. CONCLUSION. Abutments with internal connection showed less rotational freedom. However, better marginal fit was observed in externally connected abutments. Also, customized abutments with either connection could not duplicate the exact geometry of their corresponding prefabricated abutment. However, neither abutment connection nor material affected torque loss values.

SURFACE CHANCE OF EXTERNAL HEXAGON OF IMPLANT FIXTURE AND INTERNAL HEXAGON OF ABUTMENT AFTER REPEATED DELIVERY AND REMOVAL OF ABUTMENT (지대주의 반복적인 착탈에 따른 임플랜트 고정체의 external hexagon과 지대주 internal hexagon의 변화에 관한 연구)

  • Jung Seok-Won;Kim Hee-Jung;Chung Chae-Heon
    • The Journal of Korean Academy of Prosthodontics
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    • v.43 no.4
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    • pp.528-543
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    • 2005
  • Statement of problem: Repeated delivery and removal of abutment cause some changes such as wear, scratch or defect of hexagonal structure. It may increase the value of rotational freedom(RF) between hexagonal structures. Purpose: The purpose of this study was to evaluate surface changes and rotational freedom between the external hexagon of the implant fixture and internal hexagon of abutment after repeated delivery and removal under SEM and toolmaker's microscope. Materials and methods: Implant systems used for this study were 3i and Avana. Seven pail's of implant fixture, abutment and abutment screws for each system were selected and all fixtures were perpendicularly mounted in liquid unsaturated polyesther with dental surveyor. Each one was embedded beneath the platform of fixture. Surfaces of hexagonal structure before repeated closing and opening of abutment were observed using SEM and rotational freedom was measured by using toolmaker's microscope. Each abutment was secured to the implant future by each abutment screw with recommended torque value using a digital torque controller and was repeatedly delivered and removed by 20 times respectively. After experiment, evaluation for the change of hexagonal structures and measurement of rotational freedom were performed. Result : The results were as follows; 1. Wear of contact area between implant fixture and abutment was considerable in both 3i and Avana system. Scratches and defects were frequently observed at the line-angle of hexagonal structures of implant fixture and abutment. 2. In the SEM view of the external hexagon of implant fixture, the point-angle areas at the corner edge of hexagon were severely worn out in both systems. It was more notable in the case of 3i systems than in that of Avana systems. 3. In the SEM view of the internal hexagon of abutment, Gingi-Hue abutment of 3i systems showed severe wear in micro-stop contacts that were machined into the corners to prevent rotation and cemented abutment of Avana systems showed wear in both surface area adjacent to the corner mating with external hexagon of implant fixture. 4 The mean values of rotational freedom between the external hexagon of the implant fixture and internal hexagon of abutment were 0.48$\pm$0.04$^{\circ}$ in pre-tested 3i systems and 1.18$\pm$0.25$^{\circ}$ after test, and 1.80$\pm$0.04$^{\circ}$ in pre-tested Avana systems and 2.61$\pm$0.16$^{\circ}$ after test. 5. Changes of rotational freedom after test shouted statistical)y a significant increase in both 3i and Avana systems(P<0.05, paired t-test). 6. Statistically, there was no significant difference between amount of increase in the rotational freedom of 3i systems and amount of increase in that of Avana ones(P>0.05, unpaired t-test). Conclusion: Conclusively, it was considered that repeated delivery and remove of abutment by 20 times would not have influence on screw joint stability. However, it caused statistically the significant change of rotational freedom in tested systems. Therefore, it is suggested that repeated delivery and remove of abutment should be minimal as possible as it could be and be done carefully Additionally, it is suggested that the means or treatment to prevent the wear of mating components should be devised.

A Study on the Substructural Synthesis Method using the Spatial Properties (특성행렬을 이용한 부분구조합성법에 관한 연구)

  • 정우진;이헌곤
    • Journal of KSNVE
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    • v.3 no.2
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    • pp.145-153
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    • 1993
  • The Substructural Synthesis Method is effectively used for the calculation of complex structures. An alternative substructural synthesis, using spatial properities which can be directly inedtified from the frequency reponse function, was proposed. It has been shown that the rotational degree of freedom in the coupled region should be required to synthesize the substructures and the residual effect in the rotational degree of freedom should be considered. Through the simulations and experiments, this alternative was proven to be useful for the dynamic analysis of complex structures.

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Improved Nonconforming 8-node Solid Element with Rotational Degrees of Freedom (회전자유도를 갖는 비적합 8-절점 입체요소의 개선)

  • 최창근;정근영;이태열
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.13 no.4
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    • pp.475-484
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    • 2000
  • In this paper, new additional nonconforming modes for the improvement of bending behavior in the distorted 8 node hexahedral element and their effective modification method are studied. The rotational degrees of freedom are introduced by using a functional in which the rotations are independent variables. In an element formulation, the same interpolations are used in displacement and rotation fields, but nonconforming modes we applied only in displacement fields. To verify the developed element various numerical tests are carried out and test results show good behavior.

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