• Title, Summary, Keyword: Fracture behaviour

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Analysis Study on Influence that the Center Hole Notch of CFRP with Laminated Structure Affects (적층구조를 가진 CFRP의 중앙 노치구멍이 미치는 영향에 관한 해석적 연구)

  • Park, Jae-Woong;Kim, Eundo;Cho, Jae-Ung
    • Journal of the Korea Convergence Society
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    • v.9 no.2
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    • pp.177-182
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    • 2018
  • In this paper, the fracture behaviour at CFRP laminated structure due to the vertical falling impact of the fight drone frame composed of CFRP was investigated through the analytical study. As CFRP consists of fiber differently from the existing plastic material, the fracture behaviour becoms complex. So, the preceding study is important through the analytical study before this experiment. By comparing with the existing study model at the same condition as the result of this study, the applied stress value is shown to decrease greatly at the analysis model with the center notch hole of the laminated CFRP drone frame. On the basis of this study result, the esthetic sense can be shown as the foundation data about the notch hole of drone frame are grafted onto the convergence technique.

Behaviour Analysis of Crown Collapse under Tunnel Construction After Completing Reinforcement (보강완료 후 시공 중 터널 천단부 붕락 거동 분석)

  • Kim, Nagyoung;Baek, Seungchol;Min, Kyungjun;Kim, Bongsu;Heo, Yol
    • Journal of the Korean Geoenvironmental Society
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    • v.17 no.4
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    • pp.39-46
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    • 2016
  • The final stability analysis of the tunnel structure is generally evaluated by performing site monitoring to determine whether or not the measured value through the convergence after the completion of excavation in the face. When the ground conditions are so poor, the reinforcement around the tunnel was applied for enhancing the stability of tunnels. For the additional tunnel crown collapse or excessive displacement have occurred under construction, correlation analysis were performed for the comparison construction and numeric analyses. In this paper, we investigated the collapse types, tunnel collapse were mostly occurs at the crown and they were analyzed because of the geological conditions in the collapse zone. And also, it was analyzed as being correlated in the crown of tunnel exists a fault fracture zone which extends to the surface part. Thus, in case of ground conditions such as fault fracture zone with a tunnel extending from the crown to the surface, the behavior is larger than the behavior predicted by numerical method.

A STUDY ON THE FRACTURE TOUGHNESS OF DENTAL COMPOSITE RESINS (치과용 복합레진의 파괴인성에 관한 실험적 연구)

  • Park, Jin-Hoon;Min, Byung-Soon;Choi, Ho-Young;Park, Sang-Jin
    • Restorative Dentistry and Endodontics
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    • v.15 no.2
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    • pp.17-33
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    • 1990
  • The purpose of this study was to evaluate the fracture toughness of dental composite resins and to investigate the filler factor affecting the fracture behaviour on which the degree of fracture toughness depends. Six kinds of commercially available composite resin;, including two of each macrofilled, microfilled, and hybrid type were used for this study, The plane strain fracture toughness ($K_{10}$) was determined by three-point bending test using the single edge notch specimen according to the ASTM-E399. The specimens were fabricated with visible light curing or self curing of each composite resin previously inserted into a metal mold, and three-point bending test was conducted with cross-head speed of 0.1mm/min following a day's storage of the specimens in $37^{\circ}C$ distilled water. The filler volume fractions were determined by the standard ashing test according to the ISO-4049. Acoustic Emission(AE), a nondestructive testing method detecting the elastic wave released from the localized sources In material under a certain stress, was detected during three-point bending test and its analyzed data was compared with, canning electron fractographs of each specimen. The results were as follows : 1. The filler content of composite resin material was found to be highest in the hybrid type followed by the macrofilled type, and the microfilled type. 2. It was found that the value of plane strain fracture toughness of composite resin material was in the range from 0.69 MPa$\sqrt{m}$ to 1 46 MPa$\sqrt{m}$ and highest In the macrofilled type followed by the hybrid type, and the microfilled type. 3. The consequence of Acoustic Emission analysis revealed that the plane strain fracture toughness increased according as the count of Acoustic Emission events increased. 4. The higher the plane strain fracture toughness became, the higher degree of surface roughness and irregularity the fractographs demonstrated.

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Ductile Fracture Behaviour of SA 533B Pressure Vessel Steel Under Mixed Mode (I/II) Loading (혼합 모드(I/II) 하중에 의한 SA533B 압력용기강의 연성파괴 특성에 관한 연구)

  • O, Dong-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.11
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    • pp.1829-1834
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    • 2001
  • The aim of this study is to investigate the ductile fracture behavior under mixed mode (I/II) loading using SA533B pressure vessel steel. Anti-symmetric 4-point (AS4P) bonding tests were performed to obtain the J-R curves under two different mixed mode (I/II) loadings. In addition, the fractographic examination of fracture surfaces was carried out to compare with those of pure Mode I and Mode II. In conclusions, the J-R curves under Mixed Mode (I/II) loading were located between those of Mode I and Mode II loadings. When the mixture ratio of mixed mode (I/II) loading was high, the J-R currie of mixed mode (I/II) loading approached that of pure mode I loading after some amount of crack propagation. In contrast with the above fact, if the mixture ratio was low, the J-R curve looked after that of pure mode II loading. The fractographic evidences such as the shape of dimples under different loading conditions supported these conclusions.

Mechanical Properties of Carbon/Phenolic Ablative Composites (Carbon/Phenolic 내열 복합재료의 기계적 특성)

  • Kim, P.W.;Hong, S.H.;Kim, Y.C.;Yeh, B.H.;Jung, B.
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.160-163
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    • 1999
  • The mechanical properties and failure behaviour of carbon/phenolic composites were inverstigated by tension and compression. Carbon/phenolic composites were fabricated by infiltration of matrix into 8 harness satin woven fabric of PAN-based carbon fibers. The tensile and compressive tests were performed at 25℃ under air atmosphere and, at 400℃ and 700℃ under N₂ atmosphere. The tensile strengths of carbon/phenolic composites in with-laminar/0° warp direction were about 10 times higher than those in with-laminar/45° warp direction, which was analyzed due to a change of fracture mode from fiber pull-out by shear to tensile fracture of fibers. The fracture of carbon/phenolic composites in with-laminar/45° direction was analyzed due to delamination by buckling. Tensile and compressive strength of carbon/phenolic composites decreased to about 50% at 400℃, and to about 10% at 700℃ compared to that at room temperature. The main reason for the decrease of tensile or compressive strength with increasing temperature was analyzed due to a reduction of bond strength between fibers and matrix resulting from thermal degradation of phenolic resin.

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Influence of particle packing on fracture properties of concrete

  • He, Huan;Stroeven, Piet;Stroeven, Martijn;Sluys, Lambertus Johannes
    • Computers and Concrete
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    • v.8 no.6
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    • pp.677-692
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    • 2011
  • Particle packing on meso-level has a significant influence on workability of fresh concrete and also on the mechanical and durability properties of the matured material. It was demonstrated earlier that shape exerts but a marginal influence on the elastic properties of concrete provided being packed to the same density, which is not necessarily the case with different types of aggregate. Hence, elastic properties of concrete can be treated as approximately structure-insensitive parameters. However, fracture behaviour can be expected structure-sensitive. This is supported by the present study based on discrete element method (DEM) simulated three-phase concrete, namely aggregate, matrix and interfacial transition zones (ITZs). Fracture properties are assessed with the aid of a finite element method (FEM) based on the damage materials model. Effects on tensile strength due to grain shape and packing density are investigated. Shape differences are shown to have only modest influence. Significant effects are exerted by packing density and physical-mechanical properties of the phases, whereby the ITZ takes up a major position.

Simulation of fracture in plain concrete modeled as a composite material

  • Bui, Thanh T.;Attard, Mario M.
    • Computers and Concrete
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    • v.2 no.6
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    • pp.499-516
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    • 2005
  • A composite model is used to represent the heterogeneity of plain concrete consisting of coarse aggregates, mortar matrix and the mortar-aggregate interface. The composite elements of plain concrete are modeled using triangular finite element units which have six interface nodes along the sides. Fracture is captured through a constitutive single branch softening-fracture law at the interface nodes, which bounds the elastic domain inside each triangular unit. The inelastic displacement at an interface node represents the crack opening or sliding displacement and is conjugate to the internodal force. The path-dependent softening behaviour is developed within a quasi-prescribed displacement control formulation. The crack profile is restricted to the interface boundaries of the defined mesh. No re-meshing is carried out. Solutions to the rate formulation are obtained using a mathematical programming procedure in the form of a linear complementary problem. An event by event solution strategy is adopted to eliminate solutions with simultaneous formation of softening zones in symmetric problems. The composite plain concrete model is compared to experimental results for the tensile crack growth in a Brazilian test and three-point bending tests on different sized specimens. The model is also used to simulate wedge-type shear-compression failure directly under the loading platen of a Brazilian test.

Analysis of the Reinforced I section UHPCC (Ulrea High Performance Cementitous Composites) beam without stirrup (전단철근이 없는 I형 휨보강 UHPCC 보의 거동해석)

  • Kim Sung Wook;Han Sang Muk;Kang Su Tae;Kong Jeong Shick;Kang Jun Hyung;Jun Sang Eun
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.409-412
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    • 2004
  • Over last decade extensive researches have been undertaken on the strength behaviour of Fiber Reinforced Concrete(FRC) structures. But the use of Ultra-High Strength Steel Fiber Cementitious Concrete Composites is in its infancy and there is a few experiments, analysis method and design criteria on the structural elements constructed with this new generation material which compressive strength is over 150 MPa and characteristic behaviour on the failure status is ductile. The objective of this paper is to investigate and analyze the behaviour of reinforced rectangular structural members constructed with ultra high performance cementitious composites (UHPCC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The variables of test specimens were shear span ratio, reinforcement ratio and fiber quantity. Even if there were no shear stirrups in test specimens, most influential variable to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone could be defined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

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Effect of Mo Addition on the Sinterability and Mechanical Properties of TiB$_2$-Fe Cermets (TiB$_2$-Fe 서메트의 소결성 및 기계적성질에 미치는 Mo첨가의 영향)

  • 최덕순
    • Journal of the Korean Ceramic Society
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    • v.36 no.5
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    • pp.471-477
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    • 1999
  • Fe and Fe-Mo binder were used to produce TiB2 based cermet by a pressureless sintering. The densification behaviour of TiB2-Fe-Mo cermet during liquid-phase sintering in argon was studied in relation to binder phase charactertics. The effects of Mo addition and sintering condition on the sintering behaviour and mechanical properties were also investigated. TiB2-based cermets with Fe-Mo binder composition showed a better sinterability than the cermets with only Fe binder. In TiB2-Fe-Mo cermet higher densities in the wide temperature range were obtained and also fully densified sintered cermet were obtained at 1873K The enhancement in the densification phenomenon of TiB2-Fe-Mo system can be explained by improved liquid phase wettability associated with the roles of Mo components as solute atoms. When Fe-Mo binders were used cermets with a finer grain size and enhanced mechanical properties wereproduced and new phases such as Fe2B and Mo2FeB2 were observed in the sintered cermet. The highest bending strength was obtained from the 20vol% Fe-Mo cermet and these hardness-fracture toughness combination in the wide binder compositions is better than that of TiB2-Fe cermet. In order to improve mechanical properties microstructure control with high purity powders is desirable because high purity powders prevent the formation of Fe2B and Mo2FeB2 phase which comsume the ductile binder phase.

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Analysis of the UHP-SFRCC(Ultra High Performance Steel Fiber Reinforced Cementitious Composites) I section Prestressed beam. (초고강도 섬유보강 시멘트 복합체 I형 프리스트레스트 보의 거동 해석)

  • Han Sang Mook;Kim Sung Wook;Kang Su Tae;Kang Jun Hyung
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.57-60
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    • 2005
  • The objective of this paper is to investigate and analyze the behaviour of prestressed I section structural members constructed with ultra high perfomance steel fiber reinforced cementitious concrete (SFR-UHPC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The parameters of test specimens were span to depth ratio, prestressing force, prestressing wire placement and web width. Most influential parameter to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone should be redefined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

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