• 제목/요약/키워드: Bending

검색결과 8,596건 처리시간 0.036초

APPLICATION OF FINITE ELEMENT ANALYSIS TO EVALUATE IMPLANT FRACTURES

  • Kim Yang-Soo;Kim Chang-Whe;Lim Young-Jun;Kim Myung-Joo
    • 대한치과보철학회지
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    • 제44권3호
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    • pp.295-313
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    • 2006
  • Statement of problem. Higher fracture rates were reported for Branemark implants placed in the maxilla and for 3.75 mm diameter implants installed in the posterior region. Purpose. The purpose of this study was to investigate the fracture of a fixture by finite element analysis and to compare different diameter of fixtures according to the level of alveolar bone resorption. Material and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for the 3i implant systems. Models were processed by the software programs HyperMesh and ANSA. Three-dimensional finite element models were developed for; (1) a regular titanium implant 3.75 mm in diameter and 13 mm in length (2) a regular titanium implant 4.0 mm in diameter and 13 mm in length (3) a wide titanium implant 5.0 mm in diameter and 13 mm in length each with a cementation type abutment and titanium alloy screw. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized as 650 N, and round and flat type prostheses were 12 mm in diameter, 9 mm in height were loaded to 600 N. Four loading offset points (0, 2, 4, and 6 mm from the center of the implants) were evaluated. To evaluate fixture fracture by alveolar bone resorption, we investigated the stress distribution of the fixtures according to different alveola. bone loss levels (0, 1.5, 3.5, and 5.0 mm of alveolar bone loss). Using these 12 models (four degrees of bone loss and three implant diameters), the effects of load-ing offset, the effect of alveolar bone resorption and the size of fixtures were evaluated. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView programs were used for post processing. Results. The results from our experiment are as follows: 1. Preload maintains implant-abutment joint stability within a limited offset point against occlusal force. 2. Von Mises stress of the implant, abutment screw, abutment, and bone was decreased with in-creasing of the implant diameter. 3. With severe advancing of alveolar bone resorption, fracture of the 3.75 and the 4.0 mm diameter implant was possible. 4. With increasing of bending stress by loading offset, fracture of the abutment screw was possible.

티타늄의 표면처리 방법에 따른 저온소성도재와의 결합강도 (EFFECT OF SURFACE MODIFICATION ON BOND STRENGTH IN TITANIUM-PORCELAIN SYSTEM)

  • 로성욱;방몽숙;양홍서;박상원;박하옥;임현필
    • 대한치과보철학회지
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    • 제45권5호
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    • pp.589-600
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    • 2007
  • Statement of Problem: Titanium has many advantages of high biocompatibility, physical porperties, low-weight, low price and radiolucency, but it is incompatible with conventional dental porcelain due to titanium's oxidative nature. Many previous studies have shown that they used the method of sandblast surface treatment prior to porcelain application, the researchs are processing about the method of acid etching or surface coating. Purpose: The purpose of this research is to study the effect on bond strength between titanium and porcelain when using macro-surface treatment and micro-surface treatment and macro and micro surface treatment. Material and method: In this study, we evaluated the bond strength by using 3-point bending test based on ISO 9693 after classified 7 groups-group P : polished with #1200 grit SiC paper, group SS : sandblasted with $50{\mu}m$ aluminum oxides, group LS : sandblasted with $250{\mu}m$ alumium oxides, group HC : treated with 10% hydrochloric acid, group NF : treated with 17% solution of fluoric acid and nitric acid, group SHC : treated with 10% hydrochloric aicd after sandblsting with $50{\mu}m$ alumium oxides, group SNF treated with 17% solution of fluoric acid and nitric acid. Results : Within the confines of our research, the following results can be deduced. 1. Group SS which was sandblasted with $50{\mu}m$ aluminum oxides showed the highest bond strength of 61.74 MPa and significant differences(P<0.05). The bond strengths with porcelain in groups treated acid etching after sandblasting decreased more preferable than the group treated with sandblasting only. It gives significant differences(P<0.05). 2. After surface treatments, the group treated with sandblasting showed irregular aspect formed many undercuts, in the SEM photographs. The group treated with hydrochloric acid had the sharp serrated surfaces, the group treated with the solution of fluoric acid and nitric acid had the smooth surfaces, the group with sandblasting and hydrochloric acid had irrigular and porous structure, the group with sandblasting and the solution of fluoric acid and nitric acid had crater-like surfaces. But all of the groups treated with acid etching was not found and undercut. Conclusion: In above results, average surface roughness increase, bond strength also increase, but surface topographs influences more greatly on bond strengths.

ES모델을 이용한 해상교량 하부 적정 직선항로 길이에 대한 기초 연구 (A Basic Study on Proper Straight Route Distance under Marine Bridge using ES Model)

  • 박영수;최광영;박상원
    • 해양환경안전학회지
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    • 제24권2호
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    • pp.133-139
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    • 2018
  • 해상교량 하부의 직선항로 길이 확보는 선박 통항 안전을 위한 중요한 요소 중 하나이다. 그러나 항만 및 어항 설계기준에 따르면 해상교량 하부 직선항로 길이는 선박길이의 8배로 획일적인 가이드라인을 적용하고 있다. 본 연구는 적정 해상교량 하부직선길이를 도출하기 위해 ES 모델을 이용하여 항로폭, 통항량, 항로의 곡률, 직선항로길이에 따른 위험도 비율을 확인했다. 확인 결과 항로의 곡률이 $45^{\circ}$의 경우 항로길이가 3L에서 10L로 길어짐에 따라 위험도 비율이 2.27 % 감소했다. 곡률에 따른 위험도는 직선항로의 길이가 3L의 경우 곡률이 $45^{\circ}$에서 $0^{\circ}$로 변하면서 위험도 비율이 4.83 % 감소하는 것을 확인했다. 또한 항로폭 400 m, 시간당 발생선박이 20척의 조건에서 항로의 곡률별, 직선항로에 따른 위험도 비율은 최대 1.45 % 감소하는 것을 확인했다. 이를 통해 해상 교량 건설 시 항로의 혼잡도 및 곡률에 따라 일정 길이 이상의 직선항로가 필요함을 검증했다.

저심도 모듈식 구조체의 벽체간 연결 조인트 성능검증 실험 (Performance Test of Wall to Wall Modular Structure Joint for Near-surface Transit)

  • 이종순;김희성;이성형;이준경
    • 한국철도학회논문집
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    • 제18권3호
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    • pp.261-269
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    • 2015
  • 자갈궤도에서 레일과 침목을 연결하는 체결장치의 레일패드 강성이 증가함에 따라 윤중이 증가하고 궤도틀림진전이 증가되어 궤도유지보수비가 증가하게 된다. 반면에 레일패드강성이 감소하면 차량운행에 따른 전력소모비가 증가하게 된다. 따라서 자갈궤도 설계 시에 차량과 궤도 및 운영조건을 고려하여 궤도유지보수비와 전력소모비를 가급적 작게 할 수 있는 적정 레일패드강성을 결정하는 것은 철도 경제성 확보차원에서 중요한 과제라 할 수 있다. 본 연구에서는 $L{\acute{o}}pez$ Pita 등이 제시한 자갈궤도에서의 최적레일패드 강성을 평가하는 프로세서를 기초로 적정 레일패드강성 범위를 구하였다. 연구결과에 중요한 영향을 주는 레일패드강성에 따른 윤중변화를 보다 정확하게 평가하기 위하여 궤도구성품의 거동특성을 보다 상세하게 고려할 수 있는 고도화된 수치해석적 기법을 사용하여 평가하였다. 또한 국내에서의 차량, 궤도 운영조건을 고려함으로써 국내에서 궤도설계에 적용할 수 있는 적정 레일패드강성 범위를 도출하였다.

Surface-modified Nanoparticle Additives for Wear Resistant Water-based Coatings for Galvanized Steel Plates

  • Becker-Willinger, Carsten;Heppe, Gisela;Opsoelder, Michael;Veith, H.C. Michael;Cho, Jae-Dong;Lee, Jae-Ryung
    • Corrosion Science and Technology
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    • 제9권4호
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    • pp.147-152
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    • 2010
  • Conventional paints for conversion coating applications in steel production derived mainly from water-based polymer dispersions containing several additives actually show good general performance, but suffer from poor scratch and abrasion resistance during use. The reason for this is because the relatively soft organic binder matrix dominates the mechanical surface properties. In order to maintain the high quality and decorative function of coated steel sheets, the mechanical performance of the surface needs to be improved significantly. In fact the wear resistance should be enhanced without affecting the optical appearance of the coatings by using appropriate nanoparticulate additives. In this direction, nanocomposite coating compositions (Nanomer$^{(R)}$) have been derived from water-based polymer dispersions with an increasing amount of surface-modified nanoparticles in aqueous dispersion in order to monitor the effect of degree of filling with rigid nanoparticles. The surface of nanoparticles has been modified for optimum compatibility with the polymer matrix in order to achieve homogeneous nanoparticle dispersion over the matrix. This approach has been extended in such a way that a more expanded hybrid network has been condensed on the nanoparticle surface by a hydrolytic condensation reaction in addition to the quasi-monolayer type small molecular surface modification. It was expected that this additional modification will lead to more intensive cross-linking in coating systems resulting in further improved scratch-resistance compared to simple addition of nanoparticles with quasi-monolayer surface modification. The resulting compositions have been coated on zinc-galvanized steel and cured. The wear resistance and the corrosion protection of the modified coating systems have been tested in dependence on the compositional change, the type of surface modification as well as the mixing conditions with different shear forces. It has been found out that for loading levels up to 50 wt.-% nanoparticles, the mechanical wear resistance remains almost unaffected compared to the unmodified resin. In addition, the corrosion resistance remained unaffected even after $180^{\circ}$ bending test showing that the flexibility of coating was not decreased by nanoparticle addition. Electron microscopy showed that the inorganic nanoparticles do not penetrate into the organic resin droplets during the mixing process but rather formed agglomerates outside the polymer droplet phase resulting in quite moderate cross linking while curing, because of viscosity. The proposed mechanisms of composite formation and cross linking could explain the poor effect regarding improvement of mechanical wear resistance and help to set up new synthesis strategies for improved nanocomposite morphologies, which should provide increased wear resistance.

볏짚재를 혼입(混入)한 콘크리트의 공학적(工學的) 성질(性質) (Engineering Properties of Concrete with Rice-Straw Ash)

  • 성찬용;이희만;김영익;김경태;서대석;남기성
    • 농업과학연구
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    • 제25권2호
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    • pp.285-292
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    • 1998
  • 이 연구는 보통 포틀랜드 시멘트와 천연골재 및 볏짚재를 혼입한 볏짚재 콘크리트의 공학적 성질을 실험적으로 구명한 것으로써, 이 연구를 통해 얻어진 결과를 요약하면 다음과 같다. 1. 볏짚재를 혼입한 콘크리트의 단위중량은 $2,250{\sim}2,335kgf/m^3$으로써 보통 시멘트 콘크리트에 비해 1~5% 정도 감소되었다. 2. 각 강도는 볏짚재를 결합재량의 5% 혼입한 콘크리트에서 가장 크게 나타났으며, 보통 시멘트 콘크리트에 비해 압축강도는 17%, 인장강도는 30%, 휨강도는 21% 증가되었다. 3. 볏짚재를 혼입한 콘크리트의 초음파진동속도는 4,059~4,360m/s로써 보통 시멘트 콘크리트와 유사하게 나타났으며, 볏짚재를 5% 혼입한 콘크리트에서 가장 큰 값을 보였다. 4. 내산성은 볏짚재의 혼입량이 많을수록 증가되었으며, 볏짚재를 5% 혼입한 콘크리트와 10% 및 15% 혼입한 콘크리트의 내산성은 보통 시멘트 콘크리트보다 각각 1.15배와 1.45배 및 1.60배 정도 크게 나타났다. 5. 적정량의 볏짚재를 혼입하여 콘크리트를 제조할 경우, 볏짚재 콘크리트의 공학적 성질이 보통 시멘트 콘크리트보다 우수할 뿐만 아니라, 농업부산물의 활용으로 인한 경제적 측면에서도 많은 기여를 할 수 있을 것이다.

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플라이 애쉬와 탄산칼슘을 혼입(混入)한 투수성(透水性) 폴리머 콘크리트의 공학적(工學的) 성질(性質) (Engineering properties of Permeable Polymer Concrete with Fly Ash and CaCO3)

  • 성찬용;한영규;윤준노;김경태;서대석;남기성
    • 농업과학연구
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    • 제25권2호
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    • pp.278-284
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    • 1998
  • 이 연구는 폴리머와 충전재를 혼입한 투수성 폴리머 콘크리트의 공학적 성질을 구명한 것으로써, 이 연구를 통해 얻어진 결과를 요약하면 다음과 같다. 1. 단위중량은 $1,830{\sim}1,932kgf/m^3$로써 보통 시멘트 콘크리트에 비해 16~20%정도 감소되었고, 플라이 애쉬만을 충전재로 사용한 투수성 폴리머 콘크리트에서 가장 작게 나타났다. 2. 강도는 플라이 애쉬와 탄산칼슘의 양이 같은 투수성 폴리머 콘크리트에서 가장 크게 나타났고, 보통 시멘트 콘크리트보다 압축강도에서는 26%, 인장강도에서는 121%, 휨강도에서는 275%가 증가되었으며, 압축강도에 대한 인장강도와 휨강도비가 보통 시멘트 콘크리트보다 2.5배와 3.5배이상 크게 나타나 취성이 크다는 것을 알 수 있다. 3. 초음파진동속도는 2,805~2,904m/s로써 보통 시멘트 콘크리트와 거의 비슷하게 나타났으며, 충전재별로는 플라이 애쉬와 탄산칼슘을 같은 양으로 혼입한 투수성 폴리머 콘크리트에서 비교적 큰 값을 보였다.

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Current Status of the Synchrotron Small-Angle X-ray Scattering Station BL4C1 at the Pohang Accelerator Laboratory

  • Jorg Bolze;Kim, Jehan;Huang, Jung-Yun;Seungyu Rah;Youn, Hwa-Shik;Lee, Byeongdu;Shin, Tae-Joo;Moonhor Ree
    • Macromolecular Research
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    • 제10권1호
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    • pp.2-12
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    • 2002
  • The small-angle X-ray scattering (SAXS) beamline BL4C1 at the 2.5 GeV storage ring of the Pohang Accelerator Laboratory (PAL) has been in its first you of operation since August 2000. During this first stage it could meet the basic requirements of the rapidly growing domestic SAXS user community, which has been carrying out measurements mainly on various polymer systems. The X-ray source is a bending magnet which produces white radiation with a critical energy of 5.5 keV. A synthetic double multilayer monochromator selects quasi-monochromatic radiation with a bandwidth of ca. 1.5%. This relatively low degree of monochromatization is sufficient for most SAXS measurements and allows a considerably higher flux at the sample as compared to monochromators using single crystals. Higher harmonics from the monochromator are rejected by reflection from a flat mirror, and a slit system is installed for collimation. A charge-coupled device (CCD) system, two one-dimensional photodiode arrays (PDA) and imaging plates (IP) are available its detectors. The overall performance of the beamline optics and of the detector systems has been checked using various standard samples. While the CCD and PDA detectors are well-suited for diffraction measurements, they give unsatisfactory data from weakly scattering samples, due to their high intrinsic noise. By using the IP system smooth scattering curves could be obtained in a wide dynamic range. In the second stage, stating from August 2001, the beamline will be upgraded with additional slits, focusing optics and gas-filled proportional detectors.

내화약제(耐火藥劑)의 처리방법(處理方法) 및 처리단판(處理單板)의 조판형태(調板形態)가 합판(슴板)의 성능(性能)에 미치는 영향(影響) (Effects of Treatment Methods of Fire-retardant and Layup of Treated Veneers on the Performances of Plywoods)

  • 손정일;조재성;서진석
    • Journal of the Korean Wood Science and Technology
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    • 제27권3호
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    • pp.39-50
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    • 1999
  • 라디에타소나무, 케루잉, 딜레니아, 터미날리아 및 칼로필롬 단판에 내화약제로서 20% 제2인산암모늄 수용액을 상압 침지 및 진공가압침지 처리한 시험을 실시 하였으며, 라디에타소나무와 케루잉 단판의 구성형태와 내화약제의 침지처리 조건들을 여러형태로 조합한 합판을 요소 멜라민 수지와 페놀수지 접착제를 사용하여 제조하였다. 결과, 라디에타소나무가 케루잉보다 약제보유도 및 처리효과가 뛰어났으며, 진공가압침지가 상압침지보다 약제보유면에서는 유효하였다. 그리고, 기계적 성질에 있어 단판첨지법으로 내화처리를 하여 제조한 합판이 반드시 접착력 및 휨강도적 성질의 저하를 가져오지는 않았으며, 내화성에 있어서는 요소 멜라민수지 접착이 우수한 성능을 보였다. 결과적으로, 접착 강도성능과 내화성능을 고려한 단판 수종의 적정한 선택, 층간구성(조합) 및 교호약제처리가 실제 사용시 가능할 것이다.

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핸드스프링 몸접어 앞공중돌기동작의 운동학적 분석 (The Kinematic Analysis of Handspring Salto Forward Piked)

  • 권오석
    • 한국운동역학회지
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    • 제17권1호
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    • pp.145-153
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    • 2007
  • The purpose of this study is to compare and analyze the phase-by-phase elapsed time, the COG, the body joint angle changes and the angular velocities of each phase of Handspring Salto Forward Piked performed by 4 college gymnasts through 3D movement analysis program. 1. The average elapsed time for each phase was .13sec for Phase 1, .18sec for Phase 2, .4sec for Phase 3, and .3sec for Phase 5. The elapsed time for Phase 1 to Phase 3 handspring was .35sec on average and the elapsed time for Phase 4 to Phase 5 handspring salto forward piked was .7sec on average. And so it showed that the whole elapsed time was 1.44sec. 2. The average horizontal changes of COG were 93.2 cm at E1, 138. 5 cm at E2, 215.7 cm at E3, 369.2 cm at E4, 450.7 cm at E5, and 553.1 cm at E6. The average vertical changes of COG were 83.1 cm at E1, 71.3 cm at E2, 78.9 cm at E3, 93.7 cm at E4, 150.8 cm at E5, and 97.2 cm at E6. 3. The average shoulder joint angles at each phase were 131.6 deg at E1, 153.5 deg at E2, 135.4 deg at E3, 113.4 deg at E4, 39.6 deg at E5, and 67.5 deg at E6. And the average hip joint angles at each phase were 82.2 deg at E1, 60 deg at E2, 101.9 deg at E3, 161.2 deg at E4, 97.7 deg at E5, and 167 deg at E6. 4. The average shoulder joint angular velocities at each phase were 130.9deg/s E1, 73.1 deg/s at E2, -133.9 deg/s at E3, -194.4 deg/s at E4, 29.4 deg/s at E5, and -50.1 deg/s at E6. And the average hip joint angular velocities at each phase were -154.7 deg/s E1, -96.5 deg/s at E2, 495.9 deg/s at E3, 281.5 deg/s at E4, 90.3 deg/s at E5, and 181.7 deg/s at E6. The results shows that, as for the performance of handspring salto forward piked, it is important to move in short time and horizontally from the hop step to the point to place the hands on the floor and jump, and to stretch the hip joints as much as possible after the displacement of the hands and to keep the hip joints stretched and high in the vertical position at the takeoff. And it is also important to bend the shoulder joints and the hip joints fast and spin as much as possible after the takeoff, and to decrease the speed of spinning by bending he shoulder joints and the hip joints quickly after the highest point of COG and make a stable landing.