• Title/Summary/Keyword: Stress Concentration

Search Result 2,825, Processing Time 0.032 seconds

Effects of crown retrieval on implants and the surrounding bone: a finite element analysis

  • Ozkir, Serhat Emre;Unal, Server Mutluay;Yurekli, Emel;Guven, Sedat
    • The Journal of Advanced Prosthodontics
    • /
    • v.8 no.2
    • /
    • pp.131-136
    • /
    • 2016
  • PURPOSE. The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS. Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant ($3.7mm{\times}10mm$) with a straight abutment, and the other model was designed as a 30-degree inclined implant ($3.7mm{\times}10mm$) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS. The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION. The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. CLINICAL IMPLICATIONS. These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.

FINITE ELEMENT ANALYSIS OF STRESS DISTRIBUTION ACCORDING TO THE METHOD OF RESTORATION AFTER ROOT CANAL THERAPY (상악 소구치 근관치료후 수복방법에 따른 응력 분포의 유한 요소 분석)

  • Lee, Chung-Sik;Lee, Jae-Young;Cho, Hyo-Sun
    • Restorative Dentistry and Endodontics
    • /
    • v.21 no.1
    • /
    • pp.339-352
    • /
    • 1996
  • Many dentists have been taken an interest in restoration of severly damaged teeth after endodontic treatment and it is a true that there are lots of studies about it. In these days, although we have used Para-Post, pins, threaded steel post, cast gold post and core, and so on, as a method of restoration frequently, it has been in controversy with the effects of them on the teeth and surrounding periodontal tissue. In this study, we assume that the crown of the upper 1st premolar was severly damaged, and after the root canal therapy, two most common types of restoration were carried out ; 1) coronal-radicular amalgam restoration, 2) after setting up the Para-Post, restore with amalgam core and gold crown. After restoration, in order to present the concentration of stress at internal portion of the tooth and the surrounding periodontal tissue, we doveloped a 2-dimensional finite element model of labiopalatal section, then loaded forces from 2 long perpendicular to the lingual incline of buccal ridge an the middle point, parallel to the long direction axis of tooth at the fossa-were applied. The analyzed results were as follows : 1. Stress of the normal first premolar was concentrated on the most weakest anatomical structure, that is, cervical area, and no stress on the bifurcated area of the canal. 2. Crown restoration after root canal therapy causes large stress concentration on the bifurcated area of the canal. This stress concentration has larger value in case of lateral movement of mandible, and there are decrease in the stress concentration compared with natural tooth. 3. Coronal-radicular amalgam restoration method transports more stress to the tooth structure than restoration using Para-Post. 4. There are more stress concentration around Para-Post in the case of lateral movement, and we have more favo rable result when restored with Para-Post. 5. Generally, stress in the lateral movement is larger than stress in the perpendicular load.

  • PDF

Measurement of Structural Stress Concentration by PVDF Film Sensors (압전필름센서에 의한 구조물의 응력집중의 측정)

  • Kwon, Il-Bum;Kim, Chi-Yeop;Choi, Man-Yong;Lim, Jong-Mook;Kim, In-Gul
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.4 no.4
    • /
    • pp.109-119
    • /
    • 2000
  • PVDF film sensor was applied to measure the stress concentration for monitoring the structural integrity. The strain calibration of this film sensor was performed by the bending test of aluminum beam. The PVDF sensor and the electrical strain gage were bonded on the beam. When the beam was loaded, the output of electrical strain gage was compared with the output of the PVDF sensor. The waveform of PVDF sensor output was shown as the same form of the output of electrical strain gage. The gain was determined as 1.7 by comparing these two signals to determine the exact value of the strain. In order to experiment the stress concentration, the stress field was analyzed by finite element analysis. The tensile test of notched steel specimens was conducted to develop the measurement technique of stress concentration. The output voltage ratio between the PVDF sensor near the notch and the PVDF sensor far from the notch could give the information about the load bearing capacity of steel specimen.

  • PDF

Effect of Stress Concentration Factors on the Fatigue Evaluation of the Direct Vessel Injection Nozzle (원자로 직접주입노즐의 피로평가에 미치는 응력집중계수의 영향)

  • Kim, Tae-Soon;Lee, Jae-Gon
    • Journal of the Korean Society of Safety
    • /
    • v.25 no.6
    • /
    • pp.53-59
    • /
    • 2010
  • A fatigue damage caused by cyclic load is considered as one of the important failure mechanisms that threaten the integrity of structures and components in a nuclear power plant. In ASME code section III NB, the fatigue analysis procedure and standard S-N curves for the class 1 components are described and these criteria should be met at the design step of components. As the current ASME S-N curves are based on the very conservative assumptions such as a local stress concentration effect, immoderate transient frequencies and a constant Young's modulus, however, they can not precisely address the fatigue behavior of components. In order to find out the technical solution for these problems, a number of researches and discussion have been carried out continuously at home and abroad over the decades. In this study, detailed fatigue analyses for DVI nozzle with various mesh density of finite elements were performed to evaluate effect of stress concentration factors on the fatigue analysis procedure and the excessive conservatism of stress concentration factors are confirmed through the analysis results.

X-joint stress concentration of offshore wind turbine jacket support structures (해상 풍력 발전 Jacket 지지구조물의 X-joint 응력 집중 현상)

  • Lee, Jusang;Park, Hyunchul;Shi, Wei;Lee, Jongsun;Beak, Jaeha
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2011.11a
    • /
    • pp.39.1-39.1
    • /
    • 2011
  • Due to less turbulence and no land limitation, offshore wind energy gets more attention than onshore. Jacket structure is regarded as a suitable solution for the water depth ranging from 30 to 80 meters. In general, joint stress concentration of jacket support structures affects their fatigue life. Nowadays, most jacket structures for offshore wind turbines have tubular X-joint between legs. In this paper, a study on X-joint stress concentration of offshore wind turbine jacket structure is performed by using 50m water depth model. Stress of X-joint on offshore environmental conditions are discussed.

  • PDF

Variation of Stress Concentration Ratio with Area Replacement Ratio for SCP-Reinforced Soils under Quay Wall (치환율에 따른 안벽구조물 하부 SCP 복합지반의 응력분담비)

  • 김윤태
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.16 no.1
    • /
    • pp.18-26
    • /
    • 2004
  • In order to accelerate the rate of consolidation settlement, to reduce settlement, and to increase bearing capacity for soft ground under quay, sand compaction pile method (SCP) has usually been applied. SCP-reinforced ground is composite soil which consists of the sand pile and the surrounding soft soil. One of main important considerations in design and analysis for SCP-reinforced soils is stress concentration ratio according to area replacement ratio. In this paper, the numerical analysis was conducted to investigate characteristics of stress concentration ratio in composite ground. It was found that stress concentration ratio of composite ground is not constant as well as depends on several factors such as area replacement ratio, depth of soft soil, and consolidation process. The values of stress concentration ratio increase during loading stage due to stress transfer of composite soil, and reach up to 2.5∼12 according to area replacement ratio at the end of construction. After the end of consolidation, however, these values are converged to 2.5 to 6.0 irrespective of area replacement ratio due to increase in effective stress of soft soil during consolidation process.

A Study on the Stress Distribution and Stress Concentration of Pipe with Respect to Attached Shape and Method of the Bracket in a Welding Structure (브래킷 결합형식에 따른 용접 구조물의 파이프에서 발생하는 응력분포와 응력집중에 관한 연구)

  • Jeon, Hyung-Yong;Sung, Rak-Won;Han , Geun-Jo
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.16 no.8
    • /
    • pp.28-37
    • /
    • 1999
  • This investigation is the result of the structural analysis by finite element method and test for considering stress distribution and stress concentration to be generated according to the change of attached shape and method of the bracket to pipe in welding structure. Generally, members that consist structures are subjected to various forces and are jointed each other with a number of bracket. In this case, circular pipe was adapted in order to weld these members easily and to study the optimal design which is used a beam with shape section as main components of the structure, According to attached shape and method, distributed stress on circular pipe is appeared so differently. This may result deeply effects with respect to thickness, material properties. So a study on attaching shape and method of bracket to circular pipe is needed. In this paper, to obtain the maximum equivalent stress or stress concentration was used experimental and F.E.M. analysis. First five parameter was defined with respect to attached a shape and method to circular pipe i.e. the variation of the attached area, the variation of the attached shape, the variation of the attached length, the variation of both directin angles, the variation of the upper angle. Afterward the experimental analysis was practiced as the variation of the both direction angel and the finite element analysis was practiced as each parameters. We can discover stress distribution and stress concentration according to the change of form of bracket. And the result can be referenced for a design of similar structure.

  • PDF

Prediction of the fatigue life of a box weldment with residual stress (잔류응력을 고려한 box 용접부의 피로수명 예측)

  • 김현수;윤중근;김하근;박동환
    • Proceedings of the KWS Conference
    • /
    • 2004.05a
    • /
    • pp.252-254
    • /
    • 2004
  • Fatigue life a box weldment was predicted with the stress concentration and residual stress using the equation reported. In order to change the stress concentration and residual stress of the box weldment, Post treatments such as smooth grinding of weld bead, weld toe grinding and hammer peening were applied. The fatigue life of the weldment after post treatment clearly increased, which is attributed to the reduction of stress concentration and/or introduction of compressive residual stress at the weld toe. The predicted fatigue life was a relatively good agreement with the experiment for a long fatigue life, while it was underestimated for a short fatigue life.

  • PDF

Analysis on contact stress concentration at the end of strip mill rolls (압연기용 Roll의 동견부(Chamfer=Barrel Edge)에서의 음력집중의 완화 대책)

  • Ono, Shinichi
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2009.04a
    • /
    • pp.13-16
    • /
    • 2009
  • In order to investigate the effects of geometry factors such as a roil diameter ratio and backup roll crown of the stress concentration factor on the edge of backup roil end, 3-dimensional FEM analyses of stress at the contact of backup roll and work roll assembled in a 4-high strip mill were carried out, It was made clear that the peak stress at the edge is about 2 to 3 times of that at the longitudinal center of the roll barrel and the peak stress proportionally increase with decreasing the ratio of backup roll diameter to work roll diameter Furthermore a crowning on the backup roll is effective to decrease the maximum edge stress.

  • PDF

An efficient computational method for stress concentration problems

  • Shrestha, Santosh;Ohga, Mitao
    • Structural Engineering and Mechanics
    • /
    • v.22 no.5
    • /
    • pp.613-629
    • /
    • 2006
  • In this paper a recently developed scaled boundary finite element method (SBFEM) is applied to simulate stress concentration for two-dimensional structures. In addition, a simple and independent formulation for evaluating the coefficients, not only of the singular term but also higher order non-singular terms, of the stress fields near crack-tip is presented. The formulation is formed by comparing the displacement along the radial points ahead of the crack-tip with that of standard Williams' eigenfunction solution for the crack-tip. The validity of the formulation is examined by numerical examples with different geometries for a range of crack sizes. The results show good agreement with available solutions in literatures. Based on the results of the study, it is conformed that the proposed numerical method can be applied to simulate stress concentrations in both cracked and uncracked structure components more easily with relatively coarse and simple model than other computational methods.