• Title/Summary/Keyword: compressive stress distribution

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Stress and Strain Distribution of Thick Composites with Various Types of Fiber Waviness under Tensile and Compressive Loadings (다양한 형태의 보강섬유 굴곡을 가지는 두꺼운 복합재료의 인장/압축 하중 하에서의 응력/변형률 분포)

  • 신재윤;이승우;전흥재
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2000.04a
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    • pp.97-100
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    • 2000
  • A FEA(finite element analysis) model was proposed to study stress and strain distributions in thick composites with various types of fiber waviness under tensile and compressive loadings. Three types of model were considered in this study: uniform fiber waviness, graded fiber waviness and localized fiber waviness models. In the analysis, both material and geometrical nonlinearities due to fiber waviness were incorporated into the model utilizing energy density and incremental method. The strain distributions of uniform fiber waviness model were strongly influenced whereas the stress distributions were little influenced by fiber waviness. The stress and strain distributions of graded and localized fiber waviness models showed more complex distributions than those of uniform fiber waviness model due to the variation of fiber waviness along the thickness and length directions. It was concluded that the stress and strain distributions of composites with fiber waviness were significantly affected by types of fiber waviness.

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The Finite Element Analysis of the Mandrel Shape's Influence on the Residual Stress Distribution by Cold Expansion Method (형상봉의 모양이 홀확장 잔류응력 분포에 미치는 영향에 대한 유한요소해석)

  • Jang, Jae-Soon;Cho, Myoung-Rae;Yang, Won-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.9 s.186
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    • pp.127-133
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    • 2006
  • Cold expansion method is used to protect a fatigue fracture from fastener hole in the structure and aerospace industry. Cold expansion is that an oversized tapered mandrel goes through the hole and produces a compressive residual stress as well as plastic deformation around the hole. Here, mandrel shapes are one of the factors which are influenced on the residual stress distribution by cold expansion method. This paper, according to mandrel shapes (diameter of mandrel, length of mandrel and length of taper), we are performed a finite element analysis of residual stress distribution by cold expansion method. From this study, it has been found that diameter of mandrel and length of taper are an important factor which was generated a low compressive residual stress surround of fastener hole by cold expansion method.

An Experimental Study on the Residual Stress Distribution at Circumferential Welds in Pipes (파이프 원주방향 용접부의 잔류응력분포 특성에 관한 실험적 연구)

  • Namkoong, Jae-Gwan;Hong, Jae-Hak
    • Journal of the Korean Society for Precision Engineering
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    • v.8 no.1
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    • pp.41-49
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    • 1991
  • A knowledge of the resdual stress distribution at circumferential weldments can normally increase the accuracy of a fracture assessment in pipe line. In this paper, we present the measurements about the residual stress distributions at three kinds of circumferential butt welded pipes using the holl drilling strain gage method. By this experiment, we have obtined the following characteristics. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed from compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self-restraint bending force in the pipe welding.

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Applicability of exponential stress-strain models for carbonate rocks

  • Palchik, Vyacheslav
    • Geomechanics and Engineering
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    • v.15 no.3
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    • pp.919-925
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    • 2018
  • Stress-strain responses of weak-to-strong carbonate rocks used for tunnel construction were studied. The analysis of applicability of exponential stress-strain models based on Haldane's distribution function is presented. It is revealed that these exponential equations presented in transformed forms allow us to predict stress-strain relationships over the whole pre-failure strain range without mechanical testing of rock samples under compression using a press machine and to avoid measurements of axial failure strains for which relatively large values of compressive stress are required. In this study, only one point measurement (small strain at small stress) using indentation test and uniaxial compressive strength determined by a standard Schmidt hammer are considered as input parameters to predict stress-strain response from zero strain/zero stress up to failure. Observations show good predictive capabilities of transformed stress-stress models for weak-to-strong (${\sigma}_c$ <100 MPa) heterogeneous carbonate rocks exhibiting small (< 0.5 %), intermediate (< 1 %) and large (> 1 %) axial strains.

A Proposal of the Compressive Stress Distribution Model of Ultra High-Strength Concrete (초고강도 콘크리트에 적합한 응력분포 모델의 제안)

  • 박훈규;윤영수;한상묵;장일영
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.10a
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    • pp.436-441
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    • 1997
  • This paper presents the compressive stress distribution model appropriate to predict the ultimate strength of structural elements using ultra high-strength concrete. From the results of this investigation, the following conclusions are drawn: 1. The constant value of strain at extreme concrete compression fiber of 0.0027 is seen to represent satisfactorily the experimental result for ultra high-strength concrete. 2. The current ACI-318 rectangular stress block parameters were found to overestimate the moment capacity of ultra high-strength concrete columns with eccentrically loaded. 3. The equivalent trapezoidal stress distribution model with new parameter $\lambda_1$ and $\lambda_2$ was developed.

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A Photoelastic Stress Analysis of Bilateral Distal Extension Removable Partial Denture with Attachment Retainers (정밀 부착형 유지장치에 따른 양측성 유리단 국소의치의 광탄성 응력분석)

  • Cho, Hye-Won;Chang, Ik-Tae
    • The Journal of Korean Academy of Prosthodontics
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    • v.23 no.1
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    • pp.97-112
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    • 1985
  • The purpose of this study was to evaluate the stress patterns developed in supporting structures by removable partial denture with attachment retainers. The attachments tested were Dalbo(miniature) attachment, resilient Ceka attachment, rigid Ceka attachment, precision and sleeve attachment, and R.P.I. clasp as a contrast. 3-dimensional photoelastic stress analysis was used to record the isochromatic and isoclinic fringe patterns and to calculate principal stress components at measuring points. The results showed that: 1. The maximum compressive stress on residual ridge was produced under the loading point with Dalbo and resilient Ceka attachment, distal to the loading point with rigid Ceka and precision and sleeve attachment, and mesial to the loading point with R.P.I. clasp. 2. The Dalbo attachment produced the most stress on residual ridge, and the least stress on abutment teeth. and resilient Ceka attachment showed favorable stress distribution. 3. Rigid Ceka attachment produced higher compressive stress on buccal. alveolar crest, and precision and sleeve attachment produced higher compressive stress on distal alvelolar crest and mesial surface of the root apex in abutment teeth. 4. R.P.I. clasp produced higher compressive stress on mesial alveolar crest.

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Residual Stress Distribution according to Working Conditions in Grinding Operation (연삭가공시 연삭조건에 따른 잔류응력 분포에 관한 연구)

  • Cheong, Chae-Cheon;Cha, Il-Nam;Kim, Gyung-Nyun
    • Journal of the Korean Society for Precision Engineering
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    • v.7 no.4
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    • pp.23-28
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    • 1990
  • This study is to investigate the magnitude, direction and distribution of residual stresses in surface ground plate according to working conditions. The specimens were made of structural carbon steel and were machined in various grinding conditions. These were divided in two groups; heat-treated materials and non-heat-treated materials. In each working condition, let the ground specimen generate displacements using deflection-etching techniques. At the same time, these displacements were precisely measured with electronic micrometer. Through the relation formula between the plane stress and strain, which was derived using these measured data, the values of residual stress are calculated, and the results are analyzed. These results are as follows : 1. According to the working conditions in this experiment, it can be seen that the distribution of residual stress generally had same trend and the maximum residual stress remained in 20~30 ((${\mu}m$) beneath the surface. 2. It is observed that compressive residual stress changes into tensile stress in 5~20 (${\mu}m$) beneath the surface. It is suggested that such phenomenon is originated from the friction effect in grinding process. 3. As the hardness increases by the heat treatment, residual stress increases. 4. As the fatigue strength increases by the compressive residual stress, it is desirable that the dowm feed and table feed reduce. 5. It can be seen that the more great the down feed and table feed increase, the more close the changing point, where the stress changed from compressive to tensile, is colse to the surface. This is due to the resultant effects of the grinding temperature and resistence are larger than the effect of the friction.

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A Study on the Residual Stresses by the Hole Drilling Measuring in the WeldZone (용접부의 천공 측정법에 의한 잔류 응력에 관한 연구)

  • NamKoong, Chai-Kwan
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.3
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    • pp.115-121
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    • 2008
  • A knowloedge of the residual stress distribution at circumferential welds can increase the prediction accuracy of a fracture assessment in pipe lines. In this study, in order to predict the residual stress distribution in the circumferential butt-welded pipes were measured, using the hole-drilling strain gauge method. Their practical applications were performed in to two kinds of pipes. As the results, the following characteristics were found. On the inner surface of pipes, the circumferential and axial residual stresses were both tensile near the center line of welding and both of them changed from tensile to compressive as the distance from the center line increased. On the outer surface, however, the circumferential residual stress was shown to be tensile wile the axial residual stress was compressive near the center line of welding, and later they were revered at the region far away from the centerline.

THREE DIMENSIONAL FINITE ELEMENT STRESS ANALYSIS OF THE MANDIBULAR CONDYLE DURING UNILATERAL CLENCHING (편측저작시 하악골 과두의 응력분포에 관한 삼차원 유한요소분석적 연군)

  • Nam, Do-Hyun;Hoe, Seong-Joo;Kim, Kwang-Nam
    • The Journal of Korean Academy of Prosthodontics
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    • v.35 no.3
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    • pp.517-534
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    • 1997
  • It has been held that excessive mechanical forces to the osseous and soft tissues of the TMJ result in joint dysfunction. Understanding the stress pattern on TMJ is very important in TMJ research. But, it is very difficult to measure directly the biomechanical stress distribution in the TMJ when the mandible is loaded. Therefore, stress distribution in the TMJ during functional movement was studied through animal experiment or mathematical model. It was observed and compared the stress distribution occuring in the working and balancing condyle when lower right canine, lower right first molar and lower right second molar were clenched by the three dimensional finite element analysis. Also, stress distribution in the working and balancing condyles were observed and compared when $20^{\circ}$ forward and buccal bite forces were applied to the first molar. The results were as follows : 1. Stress distribution in the condyles during unilateral clenching of the first molar, second molar, canine showed no difference. In the working condyle, tensile force was concentrated on the lateral aspect of the condylar articular surface and condylar neck. And compressive force was concentrated on the anteromedial and lateral aspect of condyle. In the balancing condyle, tensile and compressive forces were concentrated on the lateral aspect of the condylar articular surface and stress transmission to the temporal bone was not observed. 2. When lateral forces were applied to the first molar, tensile forces were concentrated on the medial aspect of the condylar neck and condylar posterior surface in working and balancing condyle. Compressive force was concentrated on the anteromedial and lateral surface of the condyle and stress transmission to the temporal bone was not observed. 3. During unilateral clenching, stress in the working condyle decreased as the occlusal load moved posteriorly while the stress in the balancing condyle increased. when lateral force was applied to first molar, the incremental amount of stress was greater than vertical load. 4. During unilateral clenching, the average balancing/working condyle stress ratio was 2.52. There was a greater concentration of stress in the balancing condyle. The ratio increased as the occlusal load moved posteriorly and decreased considerably when lateral forces were applied to the first molar.

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Finite Element Analysis of Re-Cold Expansion in Order to Improve the Fatigue Life of Fastener Hole that has been Cold Expanded Before (홀확장법을 적용한 체결홀의 피로수명 개선을 위한 재 홀확장 효과에 대한 유한요소 해석)

  • Jang, Jae-Soon;Yang, Won-Ho;Cho, Myoung-Rea
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.9 s.252
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    • pp.1110-1115
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    • 2006
  • Cold expansion of fastener holes has been successfully used for many years to impart beneficial compressive residual stresses. Beneficial compressive residual stress of fastener hole that has been cold expanded before is reduced by using of materials for a long time. As a result, fatigue life of material is reduced. So, compressive residual stresses of material have to regenerate by re-cold expansion method. In this paper, it was carried out a finite element analysis about variation of residual stress due to tensile stress and residual stress distribution that was regenerated by re-cold expansion method in the fastener hole. Here, a diversity tensile stress was used. Also, it was performed a finite element analysis according to cold expansion rate of re cold expansion in order to obtain a beneficial compressive residual stress.