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  • Title/Summary/Keyword: 인장 전단 시험

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Feasibility Study on Packaged FBG Sensors for Debonding Monitoring of Composite Wind Turbine Blade (풍력발전기 복합재 블레이드의 접착 분리 모니터링을 위한 패키징 광섬유 브래그 격자 센서 탐촉자의 사용성 검토)

  • Kwon, Il-Bum;Choi, Ki-Sun;Kim, Geun-Jin;Kim, Dong-Jin;Huh, Yong-Hak;Yoon, Dong-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.4
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    • pp.382-390
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    • 2011
  • Smart sensors embedable in composite wind turbine blades have been required to be researched for monitoring the health status of large wind turbine blades during real-time operation. In this research, the feasibility of packaged FBG sensor probes was studied through the experiments of composite blade trailing edge specimens in order to detect cracking and debonding damages. The instants of cracking and debonding generated in the shear web were confirmed by rapid changes of the wavelength shifts from the bare FBG sensor probes. Packaged FBG sensor probes were proposed to remove the fragile property of bare FBG sensor probes attached on composite wind blade specimens. Strain and temperature sensitivity of fabricated probes installed on the skin of blade specimen were almost equal to those of a bare FBG sensor. Strain sensitivity was measured to be με/pm in a strain range from to 0 to 600 με, and the calculated temperature sensitivity was to be 48 pm/C in the heating test up to 80 degree.

Characteristic of Mechanical Clinching for Al5052 to High-Strength Steels (Al5052 합금소재와 고장력강판의 이종재료 클린칭 접합특성)

  • Lee, Chan-Joo;Lee, Sang-Kon;Lee, Seon-Bong;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.997-1006
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    • 2010
  • For manufacturing modern cars, so-called multi-materials, such as aluminum alloy with high-strength steels, are used. For obtaining such materials, a new joining method is required to achieve the multi-material design. Mechanical clinching is one of joining methods used to join the dissimilar materials. The objective of this study is to investigate the characteristics of mechanical clinching of Al5052 alloy to high-strength steels (SPFC440, 590, 780). Using FE-analysis and clinching experiment, the joinability of Al5052 alloy to high-strength steel is evaluated by geometrical shape of mechanical clinched joint, such as neck-thickness and undercut. Further, the joint strength is evaluated by performing a single-lap shear test. The upper high-strength steel SPFC780 was not clinched because of the necking of the upper sheet. The joint strength increased with increasing strength of the upper sheet. For the lower high-strength steel sheet, the joinability and joint strength decreased with increasing strength of the lower sheet.

Fracture Mechanics Approach to X-Ray Diffraction Method for Spot Welded Lap Joint Structure of Rolled Steel Considered Residual Stress (잔류응력을 고려한 압연강 용접구조물의 X-ray 회절법에 의한 파괴 역학적 고찰)

  • Baek, Seung-Yeb;Bae, Dong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1179-1185
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    • 2011
  • Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ΔPNf relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.

A Study on Manufacturing Method of Standard Void Specimens for Non-destructive Testing in RFI Process and Effect of Void on Mechanical Properties (RFI 공정 부품 비파괴검사용 표준 기공률 시편 제조 방법 및 기공률에 따른 기계적 물성 영향에 대한 연구)

  • Han, Seong-Hyeon;Lee, Jung-Wan;Kim, Jung-Soo;Kim, Young-Min;Kim, Wee-Dae;Um, Moon-Kwang
    • Composites Research
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    • v.32 no.6
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    • pp.395-402
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    • 2019
  • The RFI process is an OoA process that fiber mats and resin films are laminated and cured in a vacuum bag. In case that resin film is insufficient to fill empty space in fibers, it makes void defect in composites and this void decrease mechanical properties of the composites. For this reason, non-destructive testing is usually used to evaluate void of manufactured composites. So, in this study, a manufacturing method of standard void specimens, which are able to be used as references in non-destructive testing, was proposed by controlling resin film thickness in the RFI process. Also, a fiber compaction test was proposed as a method to set the resin film thicknesses depending on target voids of manufacturing panels. The target void panels of 0%, 2%, and 4% were made by the proposed methods, and signal attenuation depending on void was measured by non-destructive testing and image analysis. In addition, voids of specimens for tensile, in-plane, short beam and compressive tests were estimated by signal attenuation, and mechanical properties were evaluated depending on the voids.

Characteristics of Settlement for Non-woven Geotextile through Cyclic Loading Model Test (원형토조 시험을 통한 반복하중에 따른 부직포의 침하특성)

  • Choi, Chan-Yong;Lee, Jin-Wook;Kim, Hyun-Ki
    • Journal of the Korean Geosynthetics Society
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    • v.8 no.2
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    • pp.47-54
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    • 2009
  • The ballast track, the most common type of conventional railroad track in Korea, is deteriorated by abrasion of ballast, it's penetration into roadbed, and rugged surface of roadbed caused by cyclic loading of train. Persistent occurrence of those phenomena lead to insufficient drain capacity, one of major factors in track design, and it increases pore water pressure and decreases of shear strength under rainfall condition leading to unstable roadbed. In this study, cylindrical model tests are executed for 3 types of geotextile applying cyclic loading in order to observe the characteristics of displacement and bearing capacity of geotextile, and undrained condition has been applied for 0 day, 3 days and 7 days to each geotextiles. The results showed that there was about 1% difference at the final displacement rates between reinforced soils and nature soils and the displacement of the ground surface increases along with the degrees of the saturation. And in case that water contents exceeds the threshold, it is also apparent that weight and tensile strength of geotextile influences displacement of the ground surface. And the larger weight of geotextile is, the smaller plastic displacement. It is evaluated that non-woven fabric comes into effect on reducing the bearing capacity but, the weight of geotextile has little influence on it.

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Study on the Durability of Composite Tilting Pad Journal Bearing for Turbo Compressor System under Oil-cut Situation (터보 컴프레셔용 복합재료 틸팅 패드 저널 베어링의 오일 공급 중단 상황에서의 내구성 연구)

  • Choe, Kang-Yeong;Jung, Min-Hye;You, Jun-Il;Song, Seung-A;Kim, Seong-Su
    • Composites Research
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    • v.29 no.3
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    • pp.111-116
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    • 2016
  • The tilting pad journal bearing for the turbo compressor application has a role to support high speed and heavy loading rotor. White metal has been widely used for the bearing material but the conventional bearing is immediately suspended and induces serious serious damage to the rotor under the unexpected oil cut situation or the insufficient oil film formation. The carbon fiber reinforced composite having high specific stiffness, specific strength and excellent tribological characteristics can solve these seizure problems. In this work, the study on the durability of high thermal resistance carbon fiber/epoxy composite tilting pad journal bearing under oil cut situation was conducted. The material properties of the composite materials including tensile, compressive and interlaminar properties were measured at room and high temperature of oil cut situation. To investigate the possibility of failure of composite tilting pad journal bearing under oil cut situation, the stress distribution of the composite bearing was analyzed via finite element analysis and the Tsai-Wu Failure index was calculated. To verify the failure analysis results, the oil cut tests for the composite tilting pad journal bearing were conducted using industrial test bench.

Finite Element Analysis of Reinforced Concrete Masonry Infilled Frames with Different Masonry Wall Thickness Subjected to In-plane Loading (채움벽 두께에 따른 철근콘크리트 조적채움벽 골조의 면내하중에 대한 유한요소해석)

  • Kim, Chungman;Yu, Eunjong;Kim, Minjae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.1
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    • pp.85-93
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    • 2016
  • In this study, finite element analyses of masonry infilled frames using a general purpose FE program, ABAQUS, were conducted. Analysis models consisted of the bare frame, infilled frames with masonry wall thickness of 0.5B and 1.0B, respectively. The masonry walls were constructed using the concrete bricks which were generally used in Korea as infilled wall. The material properties of frames and masonry for the analysis were obtained from material tests. However, four times increased the tensile strength was used for 1.0B wall, which is seemingly due to the differences in locating the bricks. The force-displacement relation and development of crack from the FE analysis were very similar to those from the experiments. From the FEA results, contact force between the frame and masonry, distribution of shear force and bending moments in frame members were analyzed. Obtained contact stress shows a trianglur distribution, and the contact length for 0.5B speciment and 1.0B specimen were close to the value estimated using ASCE 41-06 equation and ASCE 41-13 equation, respectively. Obtained shear force and bending moment distribution seems to replicate actual behavior which originates from the contact stress and gap between the frame and masonry.

A Study on the Evaluation of Shear Strength of Geotextile & Geomembrane by Traffic Load in Landfill Final Cover System (폐기물 매립지 최종복토층에서 교통하중에 의한 부직포 및 Geomembrane의 전단강도의 변화에 대한 사례연구)

  • Park, Sang-Hyun;Lee, Jai-Young;Choi, Mun-Young
    • Journal of the Korean Geosynthetics Society
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    • v.1 no.1
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    • pp.3-11
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    • 2002
  • The Geotextiles have been used for the protection of Geomembrane and the prevention of clogging phenomenon; however, the material can be easily damaged by construction equipments. It generally recommended to use at least 500g/m2 of Geotextile in Korea landfill, but few researcher were performed about the damage of Geotextile. Therefore, we intended to evaluate the potential damage of Geotextile by the traffic load simulating the final cover system in a field scale. Tensile strength and strain were appraised to understand the degree of damaged Geotextile. The tests were conducted under the condition of cross direction of Geotextile. Four different weight of Geotextile was used for the evaluation 500g/m2, 700g/m2, 1,000g/m2 and 1,500g/m2. The initial strain of 500g/m2 of Geotextile showed 50% that did not meet the standard 60%. The strain of 700g/m2 of Geotextile was below the standard after the traffic load test; however, the others met the requirement in the test. In conclusion, the weight of Geotextile used in landfill to protect the Geomembrane should be at least 700g/m2 in a view of strain requirement. We expect this study provides fundamental information for the construction of Geotextile in landfill.

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Polygonal Grain-Based Distinct Element Modelling of Mechanical Characteristics and Transverse Isotropy of Rock (다각형 입자 기반 개별요소모델을 통한 암석의 역학적 특성과 횡등방성 모사)

  • Park, Jung-Wook;Park, Chan;Ryu, Dongwoo;Choi, Byung-Hee;Park, Eui-Seob
    • Tunnel and Underground Space
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    • v.26 no.3
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    • pp.235-252
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    • 2016
  • This study presents a methodology to reproduce the mechanical behavior of isotropic or transversely isotropic rock using the polygonal grain-based distinct element model. A numerical technique to monitor the evolution of micro-cracks during the simulation was developed in the present study, which enabled us to examine the contribution of tensile cracking and shear cracking to the progressive process of the failure. The numerical results demonstrated good agreement with general observations from rock specimens in terms of the behavior and the evolution of micro-cracks, suggesting the capability of the model to represent the mechanical behavior of rock. We also carried out a parametric study as a fundamental work to examine the relationships between the microscopic properties of the constituents and the macroscopic behavior of the model. Depending on the micro-properties, the model exhibited a variety of responses to the external load in terms of the strength and deformation characteristics. In addition, a numerical technique to reproduce the transversely isotropic rock was suggested and applied to Asan gneiss from Korea. The behavior of the numerical model was in good agreement with the results obtained in the laboratory-scale experiments of the rock.

Slope Stability for Bridge Access Road on Sedimentary Rocks using Geological Cross Sections (지질단면을 이용한 교량 접속도로 퇴적암 비탈면의 안정성 검토 연구)

  • Ihm, Myeong Hyeok
    • The Journal of the Convergence on Culture Technology
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    • v.8 no.1
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    • pp.507-512
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    • 2022
  • The subjects of the study are the sedimentary rock slope of the Mesozoic Gyeongsang Supergroup, which has a high risk of failure. The rocks of the slope shall be sandstone, siltstone and dacite, and discontinuities shall develop beddings, shear joints, extension joints, and dacite dyke boundary planes. The type and scale of failure varies depending on the type of rock and the strike/dip of the discontinuities, but the planar failure prevails. Based on the face-mapping data, SMR, physical and mechanical testing of rocks, the critical equilibrium analysis, all representative sections required a countermeasure method because the acceptable safety factor during dry and rainy seasons were far below Fs=1.5 and Fs=1.2. After applying the countermeasure method, both the dry and wet conditions of the slope exceeded the allowable safety factor. In particular, the face-mapping data of the slope-face, the geological cross-sections of several representative sections perpendicular to the slope-face, and the critical equilibrium analysis and the presentation of countermeasure methods that have been reviewed based on them are expected to be reasonable tools for the slope stability.