• 제목/요약/키워드: Single fracture

검색결과 654건 처리시간 0.041초

In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants

  • Garcia-Roncero, Herminio;Caballe-Serrano, Jordi;Cano-Batalla, Jordi;Cabratosa-Termes, Josep;Figueras-Alvarez, Oscar
    • The Journal of Advanced Prosthodontics
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    • 제7권2호
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    • pp.160-165
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    • 2015
  • PURPOSE. In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS. Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous$^{(R)}$; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at $30^{\circ}$ in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS. Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION. Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants.

단일 시험편법에 의한 극저온용 구조재료의 파괴인성 저하에 관한 연구 (A study on the fracture toughness degradation in cryogenic structural material using single-specimen method)

  • 권일현
    • 대한기계학회논문집A
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    • 제22권2호
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    • pp.343-351
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    • 1998
  • This paper was investigated degradation of the fracture toughness caused by sensitizing heat-treatment of the cryogenic structural material JN1 base metal using unloading compliance method reported as useful a method in evaluating the elastic-plastic fracture toughness at cryogenic temperature. The specimens used in this paper were 20% side-grooved 0.5T-CT specimens which were machined in the JN1 base metal. Also, to investigate cryogenic fracture toughness of the fusion line region in the JN1 GTA weldments, it was also used 20% side-grooved 0.5T-CT specimens that was machined fusion line to located in the middle of the specimen. The cryogenic fracture toughness values of the JN1 base metal were significantly decreased with increasing the time and temperature of the heat treatment. The fracture toughness value obtained from the fusion line specimen was invalid, but it was lower value than that of the JN1 base metal. Especially, this value was approximately equal with that obtained from the JN1 650.deg. C-5h heat-treated material.

A NUMERICAL STUDY ON CHARACTERISTICS OF FLUID FLOW AND SOLUTE TRANSPORT IN A SELF-AFFINE VARIABLE-APERTURE FRACTURE UNDER NORMAL COMPLIANCE EFFECT

  • JEONG WOOCHANG;HWANG MANHA;KO ICKHWAN;SONG JAIWOO
    • Water Engineering Research
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    • 제6권2호
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    • pp.49-61
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    • 2005
  • This paper presents the numerical study to examine characteristics of fluid flow and solute transport in a rough fracture subject to effective normal stresses. The aperture distribution is generated by using the self-affine fractal model. In order to represent a nonlinear relationship between the supported normal stress and the fracture aperture, we combine a simple mechanical model with the local flow model. The solute transport is simulated using the random walk particle following algorithm. Results of numerical simulations show that the flow is significantly affected by the geometry of aperture distribution varying with the effective normal stress level while it is slightly affected by the fractal dimension that determines the degree of the fracture surface roughness. However, solute transport is influenced by the effective normal stress as well as the fracture surface roughness.

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압력용기용강의 고온파괴인성에 관한 연구 (A Study on HIGH TEMPERATURE FRACTURE TOUGHNESS of Pressure Vessel Steel SA516 at High Temperature.)

  • 박경동;김정호
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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    • pp.228-231
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    • 2001
  • Elastic-plastic fracture toughness $J_{1c}$ can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are operated at high temperature and $J_{1c}$ values are affected by temperature. therefore, the $J_{1c}$ valuse at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness $J_{1c}$ tests were performed on SA516 carbon steel plate and test results were analyzed according to ASTM E 813-8, ASTM 1813-89. Safety and integrity are required for reactor pressure vessels vecause pthey are operated in high temperature. there are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness$(J_{1c})$ and $J-\Delta{a}$ of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room Temperature, $150^{\circ}C$, $250^{\circ}C$ and $370^{\circ}C$ according to unloading compliance method.

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압력용기용 SA516/70강의 고온파괴인성평가 (Evaluation on High Temperature Fracture toughness of Pressure Vessel SA516/70 Steel)

  • 박경동;김정호;윤한기;박원조
    • 한국해양공학회지
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    • 제15권2호
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    • pp.99-104
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    • 2001
  • Elastic-plastic fracture toughness $J_{lc}$ can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are$J_{lc}$ $J_{lc}$ value at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness $J_{lc}$ tests were performed on SA516/70 carbon steel plate and test results were analyzed according to ASTM E 813-87, ASTM E 813-89 and ASTM E 1152-87.safety and integrity are required for reactor pressure vessels because, they are operated in high temperature. There are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness($J_{lc}$) and J-$\Delta$a of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room temperature, 150$^{\circ}C $, 250$^{\circ}C $ and 370$^{\circ}C $ according to unloading compliance method.

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하악 과두 골절의 관혈적 정복시 고정 방법에 따른 임상적 평가 (CLINICAL EVALUATION OF TREATMENT OUTCOME OF PLATING TECHNIQUE OF FIXATION FOR MANDIBULAR CONDYLAR FRACTURE)

  • 손정희;박지화;김진수;변기정
    • Maxillofacial Plastic and Reconstructive Surgery
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    • 제27권2호
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    • pp.164-170
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    • 2005
  • The purpose of this study was to compare a sample of patients who had condylar fractures treated with open reduction using different plating techniques, to evaluate which plating technique is useful for stable fixation for fractures of the mandibular condyle and to evaluate effectiveness of resorbable miniplate. There were 60 patients (41 males, 19 females) whose condylar fractures were treated with open reduction. Rigid fixation was performed with a single miniplate, double miniplate ot one miniplate & one microplate and single resorbable plate. All patients remained intermaxillary fixation for 1 week postoperatively. Active physiotherapy was started after 2 weeks postoperatively. Radiographic evaluation (plate fracture, plate bending, screw loosening, displacement of condyle etc.) was performed at pre-operative, immediate, 2 weeks, 1 month, 3 months, 6 months after surgery. Clinical evaluation included degree of mouth opening, occlusion, mandibular lateral excursion, infection and facial nerve paralysis. In radiographic evaluation, displacement of fractured condylar segment associated with plate bending or screw loosening were showed 6 cases and 3 cases for single miniplate system and resorbable miniplate system. There was no patients who have this problem on double miniplate system. The results revealed that the application of two miniplates were more recommendable than single miniplates. When we select resorbable miniplate system, we should consider the type of fractures, post-operative treatment protocol and surgical technique.

싱글모드 파이버 레이저를 이용한 SUS304와 Cu의 고속 겹치기 용접에서 접합부 및 인장시험 파단부의 특성에 관한 연구 (A Study on the Characteristic of Weld Joint and Tensile Fracture of SUS304 and Cu High-Speed Dissimilar Lap Welds by Single Mode Fiber Laser)

  • 이수진;김종도;카타야마 세이지
    • Journal of Welding and Joining
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    • 제32권6호
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    • pp.56-63
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    • 2014
  • To develop and understand dissimilar metals joining of Stainless steel and Copper, ultra-high speed laser lap welding was studied using single mode fiber laser in this study. SUS304 and Cu have large differences in materials properties, and Cu and Fe have no intermetallic compounds by typical binary phase of Cu and Fe system. In this study, ultra-high speed lap welds of SUS304 and Cu dissimilar metals using single-mode fiber laser was generated, and weldability of the weld fusion zone was evaluated using a tensile shear test. To understand the phenomenon of tensile shear load, weld fusion zone of interface weld area and fracture parts after tensile shear test were observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis system. And it was confirmed that Cu was easily melting and penetrating in the grain boundaries of SUS304 because of low melting temperature. And high thermal conductivity of copper occurred dissipate heat energy rapidly. These properties cause the solidification cracking in weld zone.

점용접시편의 극한하중과 피로특성에 관한 실험적 고찰 (An Experimental Investigation of Limit Loads and Fatigue Properties of Spot Welded Specimens)

  • 이형일;김남호;이태수
    • 대한기계학회논문집A
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    • 제24권1호
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    • pp.38-51
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    • 2000
  • The study on the mechanical behavior of a spot-welded specimen is largely divided into the quasi-static overload failure analysis and the fatigue failure prediction. The main issue in an overload analysis is to examine the critical loads, thereby providing a generalized overload failure criterion. As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. In this study, we first present the limit loads of 4 representative types of single spot-welded specimens in terms of the base metal yield strength and specimen geometries. Recasting the load vs. fatigue life relationships experimentally, obtained here, we then predict the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key, role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot.

에지계면균열을 갖는 단순겹치기 접착이음의 강도평가 (Analysis on the Bonded Single Lap-Joint Containing the Interface Edge Crack)

  • 유영철;박정환;이원
    • 한국정밀공학회지
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    • 제15권6호
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    • pp.159-166
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    • 1998
  • The problem of interface crack in the bonded structures has received a great deal of attention in recent years. In this paper the aluminum bonded single lap-joint containing the interface edge crack is investigated. The tensile load and the average shear stress of the adhesive joints which have different crack length are obtained from the static tensile tests. The critical value of crack length to provoke the interface fracture is determined to a/L=0.4, where a is the interface crack length and L is the adhesive lap-length. The fracture mechanical parameters are introduced to confirm the existence of the critical crack length. The compliance and the stress intensity factors are calculated using the displacement and the stress near the interface crack tip by the boundary element method. These numerical results support the experimental results that the critical value of a/L is 0.4. It is known that the compliance and the stress intensity factors are the efficient parameters to estimate the bonded single lap-joint containing the interface edge crack.

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