• Title/Summary/Keyword: Dynamic fracture

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Detemination of Dynamic Stress Intensity Factor of Brittle Materials under Impact Loading (충격하중을 받는 취성재료의 동적응력확대계수 결정)

  • 이억섭;이찬석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.10a
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    • pp.381-386
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    • 1993
  • This paper describes the dynamic fracture behavior of brittle materials under impact loading by using INSAMCR program with instrumented charpy test machine. To calculate the Dynamic Stress Intensity Factor The finite element analysis methods program, INSAMCR, was used. Dynamic fracture characteristic was researched to verify a relationship between Dynamic Stress Intensity Factor and crack tip propagation velocity in WC-6%Co. The relationship between Dynamic Stress Intensity Factor and crack tip velocity revealed typical .GAMMA. shape. INSAMCR was run to verify experimental results in WC-6%Co and shows a good coincidence.

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Cohesive modeling of dynamic fracture in reinforced concrete

  • Yu, Rena C.;Zhang, Xiaoxin;Ruiz, Gonzalo
    • Computers and Concrete
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    • v.5 no.4
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    • pp.389-400
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    • 2008
  • In this work we simulate explicitly the dynamic fracture propagation in reinforced concrete beams. In particular, adopting cohesive theories of fracture with the direct simulation of fracture and fragmentation, we represent the concrete matrix, the steel re-bars and the interface between the two materials explicitly. Therefore the crack nucleation within the concrete matrix, through and along the re-bars, the deterioration of the concrete-steel interface are modeled explicitly. The numerical simulations are validated against experiments of three-point-bend beams loaded dynamically under various strain rates. By extracting the crack-tip positions and the crack mouth opening displacement history, a two-stage crack propagation, marked by the attainment of the peak load, is observed. The first stage corresponds to the stable crack advance, the second one, the unstable collapse of the beam.

Interlaminar Fracture Toughness of CFRP Laminate Plates by Resin Content (CFRP 적층판의 수지함량이 층간파괴인성치에 미치는 영향)

  • 강태식;김지훈;심재기
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.675-678
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    • 2001
  • In this paper, an investigation was performed on the dynamic interlaminar fracture toughness of CFRP(carbon fiber reinforcement plastics). Specimens used in this experiment are CF/EPOXY laminated plates. In this experiments, Split Hopkinson s Bar test was applied to dynamic and notched flexure test. The mode II fracture toughness of each unidirectional CFRP was estimated by the analyzed deflection of the specimen and J-integral with the measured impulsive load and reactions at the supported points. As an experimental result, the vibration amplitude of 〔$0_{10}F_4/0_{10}$〕laminates appear more than that of 〔0_{10}/F_2/0_{10}$〕laminates for the J-integral and displacement velocity at a measuring point. Also, it is thought that the dynamic fracture toughness of two kind specimen with the increase of displacement velocity becomes great at a measuring point with in range of measurement.

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Influence of Ion-Nitriding on Dynamic Fracture Toughness in Cr Alloy Steels (크롬합금강의 동적파괴인성에 미치는 이온실화처리의 영향)

  • 오세욱;윤한기;장래웅;김기술
    • Journal of Ocean Engineering and Technology
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    • v.2 no.1
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    • pp.150-162
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    • 1988
  • The dynamic fracture toughness, $K_{Id}$,is measured in the heat-treated and ion-nitrided Cr-Mo, Ni-Cr-Mo steel using standard and Precracked Charpy specimens an imstrumented impact machine. The value of $K_{Id}$and both the energy of initiate fracture, and the total energy of fracture. Since the $K_{Id}$values of the precraked impact specimens are in accord with their theoretical ones, this testing method is sufficently practical. The effect of ion-nitriding are found to be larger than the heat-treaded specimen.

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Fatigue Behavior of Alumina Ceramics under the Repeated Dynamic Loading (반복 동적하중에 의한 알루미나 세라믹스의 피로거동)

  • 이규형;박성은;이홍림
    • Journal of the Korean Ceramic Society
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    • v.35 no.8
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    • pp.850-856
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    • 1998
  • The dynaamic fatigue behavior of alumina ceramics was observed at room temperature using four-point bending method. Dynamic fatigue fracture strength was observed as function of down speed and notch length. The crack growth exponent of the specimens was calculated from the fracture strength and lifetime in dynamic fatigue test. After loading the stresses in the range of 0% to 105% compared with the average in-ert strength the value of residual fracture strength was measured for unnotched and 0.5mm notched speci-mens at the 0.001 and 0.0005 mm/min down speed respectively. After the 95% stress of the average inert strength was applied repeatedly the value of rsidual fracture strength was measured for 0.5mm notched specimens at the 0.001 and 0.0005 mm/min down speed respectively. The material constant A was found to be almost the same and not to depend on the loading mode or the down speed for unnotched and notched specimen. The value of fracture strength with time calculated from the constants n and A was in good agreement with the measured value.

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Toward Improving the Dynamic Deformation Properties of Metallic Materials via Role of Microstructure Factor (미세조직 인자의 영향을 고려한 금속 소재의 동적변형 특성 향상에 관한 연구)

  • Kim, Y.G.;Hwang, B.;Lee, D.G.;Ko, Y.G.;Lee, S.
    • Transactions of Materials Processing
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    • v.30 no.5
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    • pp.247-254
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    • 2021
  • This study reviews dynamic deformation behavior of ultra-fine-grained Al alloys, ultra-fine-grained conventional low carbon steel and dual phase steel and Zr-based amorphous alloys. Dynamic tests were conducted using a Kolsky bar then the test data was analyzed in relation to resultant microstructures, mechanical properties and propensity of adiabatic shear band. In addition, deformed microstructures and fracture surfaces were used to investigate the behavior of both the dynamic deformation and fracture, and adiabatic shear banding. As a result, increasing microstructural homogeneity, strain hardenability and forming multiple shear bands could be a better way to increase the fracture resistance under dynamic loading as the formation of adiabatic shear bands was reduced or prevented.

A Study on the Fracture Phenomena in Optical Disks Due to Increase of the Rotating Speed (회전속도 증가에 의한 광디스크의 파괴현상에 관한 연구)

  • 조은형;좌성훈;정진태
    • Journal of KSNVE
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    • v.11 no.3
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    • pp.437-442
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    • 2001
  • In this study, the fracture phenomena of optical disks are discussed by theoretical and experimental approaches and then some recommendations are presented to prevent the fracture. Linear equations of motion are discretized by using the Galerkin approximation. From the discretized equations, the dynamic responses are computed by the generalized- time integration method. As a fracture criterion for optical disks, the critical crack length is presented. From experimental methods, the fracture procedure is analyzed. The fracture occurs when disks have crack on the inner radius of the disks. Since the crack growth and the fracture result from the stress concentration on the tip of the crack, a measure should be taken to overcome the stress concentration. This problem can be resolved by the structural modification of a disk. This study proposes 3 types of improved optical disks.

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Fracture Toughness of Wheelset for High Speed Train on the Critical Locations (임계위치에서의 고속철도용 윤축의 파괴인성)

  • Kwon Seok-Jin,
    • Proceedings of the KSR Conference
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    • 2004.06a
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    • pp.865-871
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    • 2004
  • The safety evaluations of railway wheel sets make use of the static fracture toughness obtained in ingot materials. The static fracture toughness of wheelset materials has been extensively studied by experiments, but the dynamic fracture toughness with respect to wheel set materials has not been studied enough yet. It is necessary to evaluate the characteristics of the fracture mechanics depending on each location for a full-scale wheel set for high-speed trains, because the load state for each location of the wheel set while running is different the contact load between the wheel and rail, cyclic stress in the wheel plate, etc. This paper deals with the fracture toughness depend on load rates. The fracture toughness depending on load rate data shows that once the downward curve from quasi-static values was reached, subsequent values showed a slow increase with respect to the impact velocity. This means that dynamic fracture toughness should be considered in the design code of the wheelset material.

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Dynamic Ductile Fracture Analysis of Natural Gas Pipelines on the Basis of Material Grade and Charpy V-Notch Impact Energy (가스배관의 재질등급 및 충격에너지에 따른 연속연성파괴 거동분석)

  • Jeong, Hyo-Tae;Choe, Byung-Hak;Lee, Young-Jin;Lee, Jeong-Hwa;Hong, Key-Yong;Baek, Jong-Hyeon;Kim, Woo-Sik
    • Journal of the Korean Institute of Gas
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    • v.16 no.5
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    • pp.35-40
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    • 2012
  • To analyze the macroscopic fracture behavior as functions of the gas pipeline grade and the working environment, following analyses have been accomplished. Computer analysis of changes in fracture behaviors according to the working conditions of pipelines and Analysis of dynamic ductile fracture behaviors using the Battelle Two Curve Method. Recently, an economic and reliable pipe materials with improved performance has been needed for the severe pipeline working condition and new transporting materials. As the grade of pipe materials became higher, the possibility of dynamic ductile fracture could be increased. Therefore, the understanding of the technology to control and arrest the dynamic ductile fracture is important.

Study on the Precise Controlling of Fracture Plane in Smooth Blasting Method (SB발파에서 파단면 제어의 고도화에 관한 연구)

  • Cho, Sang-Ho;Jeong, Yun-Young;Kim, Kwang-Yum;Kaneko, Katsuhiko
    • Tunnel and Underground Space
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    • v.19 no.4
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    • pp.366-372
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    • 2009
  • Recently, in order to achieve smooth fracture plane and minimize the excavation damage zone in rock blasting, controlled blasting methods which utilize new technologies such as electronic delay detonator (EDD) and a notched charge hole have been suggested. In this study, smooth blastings utilizing three wing type notched charge holes are simulated to investigate the influence of explosive initial density on the resultant fracture plane and damage zone using dynamic fracture process analysis (DFPA) code. Finally, based on the dynamic fracture process analyses, novel smooth blasting method, ED-Notch SB (Electronic Detonator Notched Charge Hole Smooth Blasting) is suggested.