• Title/Summary/Keyword: Stress distribution

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A Study on the Fatigue Crack Propagation Analysis Using Equivalent Stress Distribution (등가분포응력을 이용한 피로균열전파해석에 관한 연구)

  • C.W. Kim;I.S. Nho;K.S. Do
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.2
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    • pp.61-68
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    • 2002
  • From the viewpoint of linear fracture mechanics, the crack propagation behavior of two different structures having the same K-a relationship could be considered identical. In this study the stress distribution in an infinitely wide cracked plate with the same K-a relationship as in a real structure is defined as the equivalent stress distribution. Fatigue life of a real structural element can be predicted by applying the equivalent stress distribution to a simple structural element, and performing a fatigue crack propagation analysis. The K-a relationship for a structural member can be estimated by a finite element method or a simplified prediction method. The validity to obtain effective crack driving stresses by using the equivalent stress-distribution is examined.

A two-short-implant-supported molar restoration in atrophic posterior maxilla: A finite element analysis

  • Song, Ho-Yong;Huh, Yoon-Hyuk;Park, Chan-Jin;Cho, Lee-Ra
    • The Journal of Advanced Prosthodontics
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    • v.8 no.4
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    • pp.304-312
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    • 2016
  • PURPOSE. The aim of this study was to investigate the stress distribution of 2-short implants (2SIs) installed in a severely atrophic maxillary molar site. MATERIALS AND METHODS. Three different diameters of internal connection implants were modeled: narrow platform (NP), regular platform (RP), and wide platform (WP). The maxillary first molars were restored with one implant or two short implants. Three 2SI models (NP-oblique, NP-vertical, and NP-horizontal) and four single implant models (RP and WP in a centered or cantilevered position) were used. Axial and oblique loadings were applied on the occlusal surface of the crown. The von Mises stress values were measured at the bone-implant, peri-implant bone, and implant/abutment complex. RESULTS. The highest stress distribution at the bone-implant interface and the peri-implant bone was noticed in the RP group, and the lowest stress distribution was observed in the 2SI groups. Cantilevered position showed unfavorable stress distribution with axial loading. 2SI types did not affect the stress distribution in oblique loading. The number and installation positions of the implant, rather than the bone level, influenced the stress distribution of 2SIs. The implant/abutment complex of WP presented the highest stress concentration while that of 2SIs showed the lowest stress concentration. CONCLUSION. 2SIs may be useful for achieving stable stress distribution on the surrounding bone and implant-abutment complex in the atrophic posterior maxilla.

FEA model analysis of the effects of the stress distribution of saddle-type implants on the alveolar bone and the structural/physical stability of implants

  • Kong, Yoon Soo;Park, Jun Woo;Choi, Dong Ju
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.38
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    • pp.9.1-9.9
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    • 2016
  • Background: As dental implants receive masticatory stress, the distribution of stress is very important to peri-implant bone homeostasis and implant survival. In this report, we created a saddle-type implant and analyzed its stability and ability to distribute stress to the surrounding bone. Methods: The implants were designed as a saddle-type implant (SI) that wrapped around the alveolar bone, and the sizes of the saddles were 2.5, 3.5, 4.5, and 5.5 mm. The X and Y displacement were compared to clarify the effects of the saddle structures. The control group consisted of dental implants without the saddle design (CI). Using finite element modeling (FEM), the stress distribution around the dental implants was analyzed. Results: With saddle-type implants, saddles longer than 4.5 mm were more effective for stress distribution than CI. Regarding lateral displacement, a SI of 2.5 mm was effective for stress distribution compared to lateral displacement. ASI that was 5.6 mm in length was more effective for stress distribution than a CI that was 10 mm in length. Conclusions: The saddle-type implant could have a bone-gaining effect. Because it has stress-distributing effects, it might protect the newly formed bone under the implant.

Finite element stress analysis on supporting bone by tripodal placement of implant fixture (유한요소법을 이용한 임플란트 고정체의 삼각배열에 따른 지지골의 응력 분석)

  • Son, Sung-Sik;Lee, Myung-Kon
    • Journal of Technologic Dentistry
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    • v.31 no.1
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    • pp.7-15
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    • 2009
  • Purpose: This study was to propose the clear understanding for stress distribution of supporting bone by use of staggered buccal offset tripodal placement of fixtures of posterior 3 crown implant partial dentures. We realized posterior 3 crown implant fixed partial dentures through finite element modeling and analysed stress effect of implant arrangement location to supporting bone under external load using finite element method. Method: To understand stress distribution of 3 crown implant fixed partial dentures which have 2 different arrangement by finite element analysis. In each model, for loading condition, we applied $45^{\circ}$ oblique load to occlusal surface of crown and applied 100 N for 3 crown individually(total 300 N) for imitating possible oral loading condition. at this time, we calculated Von Mises stress distribution in supporting bone through finite element method. Result: When apply $45^{\circ}$ oblique load to in-line arrangement model, maximum stress result for 100 N for each 3 crown 47.566MPa. In tripodal placement, result for 1mm buccal offset tripodal placement implant model was maximum distributed load 51.418MPa, so result was higher than in-line arrangement model. Conclusion: In stress distribution result by placement of implant fixture, the most effective structure was in-line arrangement. The tripodal placement does not effective for stress distribution, gap cause more damage to supporting bone.

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Stress Distribution of Buried Concrete Pipe Under Various Environmental Conditions

  • Lee, Janggeun;Kang, Jae Mo;Ban, Hoki;Moon, Changyeul
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.12
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    • pp.65-72
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    • 2016
  • There are numerous factors that affect stress distribution in a buried pipe, such as the shape, size, and stiffness of the pipe, its burial depth, and the stiffness of the surrounding soil. In addition, the pipe can benefit from the soil arching effect to some extent, through which the overburden and surcharge pressure at the crown can be carried by the adjacent soil. As a result, the buried pipe needs to support only a portion of the load that is not transferred to the adjacent soil. This paper presents numerical efforts to investigate the stress distribution in the buried concrete pipe under various environmental conditions. To that end, a nonlinear elasto-plastic model for backfill materials was implemented into finite element software by a user-defined subroutine (user material, or UMAT) to more precisely analyze the soil behavior surrounding a buried concrete pipe subjected to surface loading. In addition, three different backfill materials with a native soil were selected to examine the material-specific stress distribution in pipe. The environmental conditions considering in this study the loading effect and void effects were investigated using finite element method. The simulation results provide information on how the pressures are redistributed, and how the buried concrete pipe behaves under various environmental conditions.

A Study of Stress Analysis and Interaction of Stress between Micro Flaws and Inclusions (미소결함간의 응력의 간섭과 응력장 해석)

  • 송삼홍;김진봉
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.5
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    • pp.1259-1268
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    • 1995
  • The stress distribution around micro holes and the behavior of stress interaction between micro holes are considerd in the study. Several conclusions are extracted as follows : (1) The stress interaction varies with the distance e between micro holes. When the two micro holes are spaced in such a manner that theri two closest points are separated by a distance of micro hole radius (e=1), stress distribution is affected by a opposite micro hole in all the closest region. In addition, if two closest points are seperated by twice the distance of a micro hole radius (e=2), stress distribution is affected by a opposite micro hole in the region of -0.8.leq.x/r.leq.0.8 and the interaction effect can be neglected for e=4. (2)If the depth becomes larger than the radius, or the radius varies, the shape and magnitude of stress distribution around micro holes varies. (3) Hoop stress around a micro hole for the two dimensional configuration is larger than that of the three dimensional micro hole located on the surface of material for .theta. < 60.deg., but it is reversed for .theta > 60.deg.

An Analysis of the Fatigue Crack Opening Behaviour in the Welding Residual Stress Field by the Finite Element Method (압축잔류응력장을 전파하는 피로균열의 개구거동의 유한요소법을 이용한 해석적 검토)

  • 박응준;김응준;유승현
    • Journal of Welding and Joining
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    • v.21 no.6
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    • pp.77-83
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    • 2003
  • The finite element analysis was performed for the cracks existing in residual stress fields in order to investigate the effects of configuration of residual stress distribution to the fatigue crack opening behaviour. And the variation of stress distributions adjacent to the crack caused by uploading was examined. The finite element model with contact elements for the crack plane and plane stress elements for the base material and the analytical method based on the superposition principle to estimate crack opening behaviour and the stress distribution adjacent to the crack subjected to uploading were used. The results of the analysis showed that crack opening behaviors and variations of stress distribution caused by uploading were changed depending on the configuration of residual stress distribution. When the crack existed in the region of compressive residual stress and the configuration of compressive residual stress distribution were inclined, a partial crack opening just behind of a crack tip occurred during uploading. Based on the above results, it was clarified that the crack opening behaviour in the residual stress field could be predicted accurately by the finite element analysis using these analytical method and model.

Gradient of the Residual Stress distribution in the Mechanical Defect on the Optical Fiber Surface (광섬유 표면의 기계적 손상에 대한 잔류응력 분포의 변화)

  • Sin, In-Hui;Kim, Deok-Yeong
    • Proceedings of the Optical Society of Korea Conference
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    • pp.206-207
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    • 2005
  • The gradient of the residual stress distribution in the mechanical defect on the optical fiber surface was investigated. This gradient of the residual stress distribution appeared in both of the core and the clad of the mechanical defect region on the optical fiber. The residual stress measurement was suggested as a investigation method of the mechanical defect on the optical fiber.

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Stress Analysis of the S-CVT using Finite Element Method (FEM을 이용한 구체무단변속기의 응력해석)

  • Kim, J.Y.
    • Journal of Power System Engineering
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    • v.12 no.2
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    • pp.41-47
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    • 2008
  • This article deals with the stress analysis of the friction drive, which transmits the power via the rolling resistance on the contract area between the two rotating bodies. On the contact area, friction drives are normally involved with shear stress due to the transmitted force, as well as normal stress. Thus the stress analysis including the shear stress is necessary for the design of the friction drive. Hertzian results can be used to estimate the normal stress distribution and elastic deflection of the contact area, although the shear stress distribution is not well defined. In order to investigate the shear stress distribution and its effects in a friction drive, we have performed the stress analysis of the spherical continuously variable transmission(CVT) using finite element method. The spherical CVT is one of friction drives, which is used in small power applications. The numerical results show that the normal stress distribution is not affected by the transmitted shear force, and the maximal shear stress is increased in small amount along with the shear force.

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Stress Properties in Multilayer Piezoelectric Ceramic Actuators using Finite Element Analysis (유한요소 해석을 이용한 적층 압전 세라믹 액츄에이터의 응력 특성)

  • 홍재일
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.11
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    • pp.963-968
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    • 1998
  • The stress distribution in multilayer piezoelectric ceramic actuators was investigated by Finite element analysis. The y direction stress was concentrated at electrode tip. The y direction maximum stress was decreased to 4.9$\times10^ 7 N/m^2$ with internal electrode gap(a) until 0.4 mm and was not much difference with external electrode thickness(c). The stress distribution with internal layers was almost same and the stress distribution of load condition was higher than that of no load condition The y direction maximum stress increased with the number of layer and saturated at 260 layers. In the case of defective actuator, the stress distribution was disconnected around the defect and larger than that of normal actuator.

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