• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.45-48
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• 2005

In manufacturing process of composite cylinders with metal liner, the autofrettage process which induces compressive residual stress on liner to improve cycling life can be applied. In this study, finite element analysis technique is presented, which can predict accurately the compressive residual stress on liner induced by autofrettage and stress behavior after. Material and geometry non-linearity is considered in finite element analysis, and the Von-Mises stress of a liner is introduced as a key parameter that determines pressure cycling life of composite cylinders. Presented methodology is verified through fatigue test of liner material and pressure cycling test of composite cylinders.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.171-180
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• 2003

One of the most significant problems in the processing of composite materials is residual stress. The high residual stress may cause cracking in the matrix without external loads and degrade the integrity of composite structures. In this study, thermo-viscoelastic residual stresses occurred in an aluminum liner-inserted polymer composite cylinder are investigated. This type of the structure is used for rocket fuselage due to the convenience to attach payloads and equipment to the metal liner by machining. The time and degree of cure dependent thermo-viscoelastic constitutive equations are developed and coupled with a thermo-chemical process model. These equations are solved with the finite element method to predict the residual stresses in the composite cylinder and also in the interface between the liner and the composite during cure.

• Geomechanics and Engineering
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• 제20권5호
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• pp.399-410
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• 2020

Cavities often develop behind the vault during the construction of double-arch tunnels, generally in the form of various defects. The study evaluates the impact of cavities behind the vault on the mechanical and failure behaviors of double-arch tunnels. Cavities of the same sizes are introduced at the vault and the shoulder close to the central wall of double-arch tunnels. Physical model tests are performed to investigate the liner stress variation, the earth pressure distribution and the process of progressive failure. Results reveal that the presence of cavities behind the liner causes the re-distribution of the earth pressure and induces stress concentration near the boundaries of cavities, which results in the bending moments in the liner inside the cavity to reverse sign from compression to tension. The liner near the invert becomes the weak region and stress concentration points are created in the outer fiber of the liner at the bottom of the sidewall and central wall. It is suggested that grouting into the foundation soils and backfilling injection should be carried out to ensure the tunnel safety. Changes in the location of cavities significantly impact the failure pattern of the liner close to the vault, e.g., cracks appear in the outer fiber of the liner inside the cavity when a cavity is located at the shoulder close to the central wall, which is different from the case that the cavity locates at the vault, whereas changes in the location of cavities have a little influence on the liner at the bottom of the double-arch tunnels.

• 한국터널지하공간학회 논문집
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• 제14권2호
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• pp.131-139
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• 2012

본 연구에서는 도심지 소구경 터널굴착공법에서 파형강판으로 제작된 liner plate의 거동특성에 대해 알아보기 위해 유한요소 해석 프로그램인 MIDAS/GTS를 이용하여 수치해석을 실시하였다. 토피고 변화에 따라 liner plate의 거동특성을 알아보기 위해 토피고는 5 m, 10 m, 15 m, 20 m, 25 m 5가지 각 조건으로 해석을 실시하였다. 수치해석결과 liner plate의 최대변위와 최대축응력은 부재의 하단부에서 발생되며, 최대전단응력의 경우 부재의 천단부에서 발생되는 것으로 확인되었다. 또한 토피고에 따른 liner plate의 변위, 응력, 전단응력의 변화는 있었으나 그 차이가 미미하고 토피고가 증가함에 따라 점점 구조적 안정성이 확보되는 것으로 판단된다.

• Composites Research
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• 제19권1호
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• pp.22-28
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• 2006

금속재 라이너를 갖는 복합재 압력용기는 라이너의 반복 수명 향상을 위해 제조 공정 중 라이너가 압축잔류응력을 갖도록 하는 자긴처리 공정을 적용할 수 있다. 본 연구에서는 자긴처리에 의한 라이너의 압축잔류응력과 이후의 응력 거동을 정확히 예측할 수 있는 유한요소해석 기법을 제시하고, 이러한 해석 결과를 바탕으로 복합재 압력용기의 반복 수명을 예측할 수 있는 방법을 제안한다. 재료 및 기하학적 비선형성을 고려한 3차원 비선형 유한요소해석을 통해 라이너의 응력 거동을 정확히 예측하고, 압력용기의 반복수명을 결정짓는 파라미터로 금속재 라이너의 폰미세스 응력을 도입한다. 라이너 재료에 대한 피로시험과 복합재 압력용기 시제품에 대한 반복시험을 통해 제안된 방법의 타당성과 유효성을 입증한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제6권1호
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• pp.51-61
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• 2006

Failure analyses were conducted on a crank shaft and a chock liner by using X-ray diffraction, optical microscopy and SEM/EDS techniques. In the crank shaft, a crack developed where a maximum tensile stress coincided with band structure formed by hot forging. The maximum tensile stress was observed to originate from volume expansion during high frequency induction heat treatment and the band structure to develop between upper and lower dies during hot forging. In the chock liner, the wear mechanism varied with the chemical affinity and hardness of liner material relative to friction pair of housing liner. Brass of low chemical affinity and hardness compared to housing liner showed uniform adhesive wear. STS 304 and STS 420J2 of high chemical affinity showed galling and scoring respectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1996년도 토목섬유(Geosymthetics) 학술발표회 논문집
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• pp.67-78
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• 1996

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.607-614
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• 2000

Settlement with crack on the hardened liners may occur in the weak clay due to waste load since the stiffness of the hardened liner is greater than that of the clay layers. Way of reducing deformation crack in the hardened liner is investigated using two computer programs, CONSOL and FLAC. The computer program CONSOL estimates the magnitude of settlement with time in clay layers and FLAC analyses the stress and deformation relationship between the foundation of landfill and waste load. The results show that a representative block of the analyzed area reaches the consolidation settlement of 1.32m, 8.8 years after the disposal of waste started with the degree of consolidation U=90%. The stress within the hardened liner exceeds the allowable vertical stress of 5kg/$\textrm{cm}^2$ and horizontal stress of 1.67kg/$\textrm{cm}^2$ at the concave part of the liner where the main and branch drainage pipes of leachate are located. It was recognized that the thickness of the interested area should be enlarged or the strength of the same area should be improved to tolerate the planned waste load.

• Structural Engineering and Mechanics
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• 제27권3호
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• pp.277-292
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• 2007

Based on the composite finite element simulation and a series of hydrostatic pressure and burst tests, autofrettage effects on strength and deformation of fiber reinforced pressure vessel with metallic liners have been studied in the paper (autofrettage: during the course of one pressure taking effect, the increasing internal stress in metallic liner can surpass the yielding point and the plastic deformation will happen, which result in that when there is no internal pressure, there are press stress in liner while tensile stress in fiber lamination). By making use of a composite finite element Ansys code and a series of experiments, the autofrettage pressure is determined in order to make the aluminium liner be totally in elastic state, under given hydrostatic test pressure. The stress intensity factors of the longitudinal crack in aluminum liner end under internal pressure and thermal loads have been computed and analyzed before and after the autofrettage processing. Through numerical calculation and experiment investigations, it is found that a correct choice for autofrettage pressure can improve the gas-tightness and fatigue strength of FRP vessel.

• Journal of Ship and Ocean Technology
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• 제8권4호
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• pp.34-44
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• 2004

Engine visualization is the most important process to develop the new engine. But this step has a major difficulty that is almost impossible to access the engine on running. Therefore, little indication from the experimental and analytical results has been so far. This work has conducted the important issue of developing a quartz liner. And it has given us good qualitative and quantitative results of temperature and stress fields in the quartz cylinder by considering forced convection of outside quartz liner, thickness of the quartz liner and preheating effect to operate quartz engine safely.