• The Journal of Korean Academy of Prosthodontics
• /
• v.46 no.5
• /
• pp.479-489
• /
• 2008

Statement of the problem: Under anatomical limitations on maxillary posterior region, a poor crown-to root ratio acting on dental implants can result in undesirable stress in surrounding bone, which in turn can cause bone defects and eventual failure of implants. Purpose: The purpose is to compare stress distribution due to different crown-root ratio and effect of splinting between natural teeth and implants in maxillary molar area under different loads. Material and methods: Analysis of stress arising supporting bone of the natural teeth and the implant was made with 3-dimensional finite element method. The model simulated naturel teeth was made with 2nd premolar and 1st molar in the maxillary molar region (Model T). The model simulated implants placed on same positions with two parallel implants of Straumann Dental Implant cemented abutment (Model I). Each model was designed in different crown-root ratio (0.7:1, 1:1, 1.25:1) and set cement type gold crown to make it non-splinted or splinted. After that, 300 N force was loaded to each model in five ways (Load 1: middle of occlusal table, Load 2: middle of buccal cusp, Load 3: middle of lingual cusp, Load 4: horizontal load to buccal cusp of anterior abutment only, Load 5: horizontal load to middle of buccal cusp of each abutment), and stress distribution was analyzed. Results and conclusion: On all occasions, stress was concentrated at the cervical region of the implant. Under load 1, 2 and 3, stress was not increased even when crown-root ratio increases, but under load 4 and 5, when crown-root ratio increases, stress also increased. There was difference in stress values between natural teeth and implants when crown-root ratio gradually increases; In case of natural teeth, splinting decreased stress under vertical and horizontal loads. In case of implants, splinting decreased stress under vertical loads 1,2 and 3, but increased maximal stress under loads 2 and 3. Under horizontal loads, splinting decreased stress, however the effect of splinting decreased under load 5 than load 4. Furthermore, the stress was increased, when crown-root ratio is 1.25:1. Clinical implications: This limited finite element study suggests that the stress on supporting bone may be increased under non-axial loads and poor crown-root ratio. Under poor crown-root ratio, excessive stress was generated at the cervical region of the implant, and decreased splinting effect for stress distribution, which can be related to clinical failure.

• Journal of Ocean Engineering and Technology
• /
• v.6 no.2
• /
• pp.71-75
• /
• 1992

기구나 구조물의 피로수명은 노치에서의 피로균열 방생수명에 의하여 지배되기때문에 노치로 인한 피로강도감소계수 $K_f$는 피로설계상 대단히 중요한 인자이다. 노치 선단(Notch root)에서의 피로균열발생명수 N$_c$를 기준으로하면 탄성응력집중계수 $K_t$가 10 정도까지 $K_f$와 $K_t$간에는 거의 직선적인 관계가 있음이 이다- 고에 의하여 명석해졌으나 이는 인장,압축의 축력이 작용하였을 때이며 따라서 기구나 구조부재는 축력외에도 굽힘 피로 하중이 작용하였을때도 많으므로 본 연구에서는 굽힘 피로 하중을 받았을때도 있다. -고의 결론이 적용되는지는 검시코져 본 연구를 실시하였다.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2017.04a
• /
• pp.16-16
• /
• 2017

국내 농업인구 감소 대비 식품소비량이 증가함에 따라 농가의 인력을 대체하고 다양한 작업이 가능하며 가격이 저렴한 국내 기계화 기술이 필요하다. 무동력 디스크해로우 작업기는 경운과 배토가 가능한 복합작업기로서 작업기를 구성하는 주요 구성품들은 필드작업에 의해 발생되는 하중에 구조적 강도와 신뢰성이 충분히 확보되어야 한다. 또한, 실제로 필드 작업 시 작업기에 걸리는 하중은 복합하중 형태로 전달되기 때문에 단순한 형태 하중에 비해 하중계측에 어려운 점이 있으므로 하중계측점의 선정이 매우 중요하다. 본 논문에서는 하중계측점을 선정하기 위하여 복합기의 주요 구성품인 치즐(chisel) 및 디스크해로우암(disk harrow arm)에 대하여 구조해석을 수행하였으며, 3축 방향의 단위하중 응력 계산결과로부터 load reconstruction을 위한 스트레인 게이지 위치를 선정하였다. 또한, 스트레인 게이지의 신호가 하중해석에 적절한 값이 되도록 기존의 형상을 수정하였다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.10
• /
• pp.4642-4647
• /
• 2011

Solution for elastic foundation of plane strain state was derived by the application of variational method. Functions of the transverse distribution of the displacements for the analysis were chosen as linear functions. Loading conditions considered for the analysis were concentrated load and distributed load. Under the loading condition of the concentrated load, surface displacement was decreased drastically as the distance from the point of the loading increased. Under the loading condition of the distributed load, surface displacements were more uniformly distributed beneath the loading area when the ratio of the half of the loading width to the depth(B/H) of the compressible layer was greater. The surface displacement was more quickly converged from the edge of the loading area as the ratio(B/H) increased.

• Proceedings of the KIEE Conference
• /
• 2008.04b
• /
• pp.16-18
• /
• 2008

연약지반에 시공된 콘크리트전주가 풍하중에 의해 받는 웅력-변형 특성을 파악하기 위해 전주 매설깊이, 버팀대의 위치 및 수량 등을 변수로 하중 파괴 시험을 실시한 결과, 전주가 깊이 묻혀질수록 재하하중에 따른 수평변위는 감소하였고 전주의 버팀대는 2개일 경우 가장 안정되는 것으로 조사되었다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.05a
• /
• pp.791-792
• /
• 2010

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.1047-1052
• /
• 2010

Influence of lateral spring constant on energy dissipation and load reduction factor with erespect to lateral vibration of steel sheet pile installed by vibratory pile driver. Energy dissipation and load reduction factor varying with free length of steel sheet pile are more affected by eccentricity than flexural rigidity of steel sheet pile regardless of the magnitudes of lateral spring constants. Load reduction factors were converged when lateral spring constant was equal or larger than 10000N/m.

• Journal of the Korean GEO-environmental Society
• /
• v.22 no.10
• /
• pp.31-36
• /
• 2021

Estimation of accumulated rotational angles and settlements are critical in design of wind turbine foundation. However, there have been few exploring the response of bucket foundation to long-term cyclic loading. We performed a series of three-dimensional finite element analyses of bucket foundations installed in sands. An empirical formulation which captures the stiffness degradation observed in cyclic triaxial tests implemented into the finite element analysis in the form of a user subroutine. Using the stiffness degradation model the accumulated rotation and displacement of bucket foundation were calculated. Additionally, important factors affecting the response under cyclic loading were assessed.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.38.1-38.1
• /
• 2021

본 발표에서는 Transformable Reflective Telescope(TRT kit)의 새로운 버전을 소개한다. TRT kit는 기본형인 뉴턴식 반사망원경에서 부경 교체를 통해 카세그레인식, 그레고리식으로 간단하게 변형 할 수 있는 광학 실험장치이다. 본 장치는 주로 망원경 교육이나 광학계 개발에 필요한 실험에 활용된다. 모듈화 설계를 통해서 여러 종류의 광학계를 쉽게 탈착하여 다양한 실험을 할 수 있다. 광기계부는 정밀하게 제작된 알루미늄 프로파일과 Isogrid구조를 채택하여 경량화 구조로 설계되었다. 이러한 경량부품들을 통해 이전 버전보다 50~70%의 중량 감소율을 달성하였다. 유한요소해석 결과 경량화된 뉴턴식 TRT kit는 이전 버전과 비교해서 자체 하중에 의한 최대 구조 변형이 0.11mm에서 0.023mm로 감소하였다. 부경 지지대 설계에는 자체 하중으로 인한 변형을 최소화하기 위해 트러스 (Truss) 구조가 도입되었다. 부경부의 자체 하중으로 인한 변형은 기존의 80㎛에서 21㎛로 감소하였다. 또한, 십자 레이저 정렬 장치가 추가되어 뉴턴식과 카세그레인식에서 공차 1.5' 이내로 광학계 정렬이 가능하다.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.11
• /
• pp.97-110
• /
• 2019

Piles that support offshore wind turbine structures are dominantly subjected to cyclic lateral loads of wind, waves, and tidal forces. For a successful design, it is imperative to investigate the behavior of the cyclic laterally loaded piles; the p-y curve method, in which the pile and soil are characterized as an elastic beam and nonlinear springs, respectively, has been typically utilized. In this study, model pile tests were performed in a 1 g gravitational field so as to investigate the p-y behaviors of cyclic laterally loaded piles installed in saturated dense silty sand. Test results showed that cyclic lateral loads gradually reduced the overall stiffness of the p-y curves (initial stiffness and ultimate soil reaction). This is because the cyclic lateral loads disturbed the surrounding soil, which led to the decrement of the soil resistance. The decrement effects of the overall stiffness of the p-y curves became more apparent as the magnitude of cyclic lateral load increased and approached the soil surface. From the test results, the cyclic p-y curve was developed using a p-y backbone curve method. Pseudo-static analysis was also performed with the developed cyclic p-y curve, confirming that it was able to properly predict the behaviors of cyclic laterally loaded pile installed in saturated dense silty sand.