• Title/Summary/Keyword: dynamic crack propagation analysis

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Fracture Analysis on Crack Propagation of RC Frame Structures due to Extreme Loadings (극한 진동에 의한 철근콘크리트 뼈대구조물에 균열전파의 파괴 역학적 특성 연구)

  • Jeong, Jae-Pyong;Lee, Myung-Gon;Kim, Woo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.7 no.4
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    • pp.191-199
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    • 2003
  • The inelastic response of many structural steel and reinforced concrete structures subject to extreme loadings can be characterized by elastoplastic behaviors. Although excursion beyond the elastic range is usually not permitted under normal conditions of service, the extent of permanent damage a structure may sustain when subjected to extreme conditions, such as severe blast or earthquake loading, is frequently of interest to the engineer. A blast is usually the result of an explosion defined as a "sudden expansion". This paper discusses the basic concept that defines blast loadings on structures and corresponding elastoplastic structural response (displacement, velocity, and acceleration) and try to explain a crack propagation of concrete in sudden expansion. According to nonlinear finite element analysis, the crack forms of static and dynamic states displayed different in RC structural members. This paper also provides useful data for the dynamic fracture analysis of RC frame structures.

AN EVALUATION OF THE CRACK PROPAGATION CHARACTERISTICS OF PORCELAIN AND THE BOND STRESS OF CERAMO-METAL SYSTEM (치과용 도재의 균열전파 특성과 도재 -금속간의 응력분석)

  • Park, Ju-Mi;Bae, Tae-Sung;Song, Kwang-Yeob;Park, Charn-Woon
    • The Journal of Korean Academy of Prosthodontics
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    • v.32 no.1
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    • pp.47-76
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    • 1994
  • This study was carried out to evaluate the effect of the crack propagation characteristics and bond stress of ceramo-metal system. In order to characterize the crack propagation, the static crack propagation stored in $37^{\circ}C$ distilled water of two commerical porcelains and the dynamic crack propagation under cyclic flexure load of ceramo-metal system were examined. In order to characterize the bond stress, the shear bond test, the 3-point flexure bond test, and the finite element stress analysis of ceramo-metal system were conducted. The results obtained were as follows : 1. Bulk densities and Young's moduli of opaque porcelains increased with repeated firing. 2. Maximum fracture toughness during 4 firing cycles showed at the group of 4 firing cycles in Ceramco porcelain and 2 firing cycles in Vita porcelain. 3. Shear bond strength and flexure bond strength of Ceramco-Verabond specimen were larger than those of Ceramco-Degudent G specimen (p<0.05). 4. Interfacial stresses under three point flexure bond test were concentrated at the edges of ceramometal system. 5. When a cyclic flexure load was applied, the crack growth rate of porcelain surface of ceramometal specimens was decreased as load cycles increased.

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Crack Identification Using Neuro-Fuzzy-Evolutionary Technique

  • Shim, Mun-Bo;Suh, Myung-Won
    • Journal of Mechanical Science and Technology
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    • v.16 no.4
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    • pp.454-467
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    • 2002
  • It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. Toidentifythelocation and depth of a crack in a structure, a method is presented in this paper which uses neuro-fuzzy-evolutionary technique, that is, Adaptive-Network-based Fuzzy Inference System (ANFIS) solved via hybrid learning algorithm (the back-propagation gradient descent and the least-squares method) and Continuous Evolutionary Algorithms (CEAs) solving sir ale objective optimization problems with a continuous function and continuous search space efficiently are unified. With this ANFIS and CEAs, it is possible to formulate the inverse problem. ANFIS is used to obtain the input(the location and depth of a crack) - output(the structural Eigenfrequencies) relation of the structural system. CEAs are used to identify the crack location and depth by minimizing the difference from the measured frequencies. We have tried this new idea on beam structures and the results are promising.

Analysis of Unsteady Propagation of Mode III Crack in Arbitrary Direction in Functionally Graded Materials (함수구배재료에서 임의의 방향을 따라 비정상적으로 전파하는 모드 III 균열해석)

  • Lee, Kwang Ho;Cho, Sang Bong;Hawong, Jai Sug
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.2
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    • pp.143-156
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    • 2015
  • The stress and displacement fields at the crack tip were studied during the unsteady propagation of a mode III crack in a direction that was different from the property graduation direction in functionally graded materials (FGMs). The property graduation in FGMs was assumed based on the linearly varying shear modulus under a constant density and the exponentially varying shear modulus and density. To obtain the solution of the harmonic function, the general partial differential equation of the dynamic equilibrium equation was transformed into a Laplace equation. Based on the Laplace equation, the stress and displacement fields, which depended on the time rates of change in the crack tip speed and stress intensity factor, were obtained through an asymptotic analysis. Using the stress and displacement fields, the effects of the angled property variation on the stresses, displacements, and stress intensity factors are discussed.

Simulation of Dynamic Crack Propagation in Uni-Directional and Cross-Ply Fiber-Reinforced Composites (단일방향 및 크로스-플라이 섬유강화 복합체에서의 동적균열 전파모사)

  • Hwang, Chan-Gyu
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.4
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    • pp.383-390
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    • 2008
  • This paper presents the formulation and numerical implementation of a spectral scheme specially developed to simulate dynamic fracture events in unidirectional and cross-ply fiber-reinforced composites. The formulation is based on the spectral representation of the transversely isotropic elastodynamic relations between the traction stresses along the fracture plane and the resulting displacements. Example problem of dynamically propagating cracks in fiber-reinforced composites is investigated and compared with reference solutions available in the literature and/or experimental observations. This scheme can be directly applicable to the interfacial fracture analysis in the FRP reinforced concrete structures.

Dynamic Fracture Analysis with State-based Peridynamic Model: Crack Patterns on Stress Waves for Plane Stress Elastic Solid (상태 기반 페리다이나믹 모델에 의한 동적취성파괴 해석: 평면응력 탄성체의 응력 전파와 균열패턴 분석)

  • Ha, Youn Doh
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.3
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    • pp.309-316
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    • 2015
  • A state-based peridynamic model is able to describe a general constitutive model from the standard continuum theory. The response of a material at a point is dependent on the deformation of all bonds connected to the point within the nonlocal horizon region. Therefore, the state-based peridynamic model permits both the volume and shear changes of the material which is promising to reproduce the complicated dynamic brittle fracture phenomena, such as crack branching, secondary cracks, cascade cracks, crack coalescence, etc. In this paper, the two-dimensional state-based peridynamic model for a linear elastic plane stress solid is employed. The damage model incorporates the energy release rate and the peridynamic energy potential. For brittle glass materials, the impact of the crack-parallel compressive stress waves on the crack branching pattern is investigated. The peridynamic solution for this problem captures the main features, observed experimentally, of dynamic crack propagation and branching. Cascade cracks under strong tensile loading and secondary cracks are also well reproduced with the state-based peridynamic simulations.

Fatigue Characteristics of High Strength Fire Resistance Steel for Frame Structure and Time-Frequency Analysis its Acoustic Emission Signal (고강도 구조용 내화강의 피로특성 및 음향방출신호의 시간-주파수 해석)

  • Kim, Hyun-Soo;Nam, Ki-Woo;Kang, Chang-Young
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.67-72
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    • 2000
  • Demand for now nondestructive evaluation are growing to detect fatigue crack growth behavior to predict long term performance of materials and structure in aggressive environments especially when they are In non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we analysed acoustic emission signals obtained in fatigue and tensile test of high strength fire resistance steel for frame structure with time-frequency analysis methods. The main frequency range is different in the noise and the fatigue crack propagation. It could be classified that it were also generated by composite fracture mechanics of cleavage, dimple, inclusion separation etc.

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Crack Identification Based on Synthetic Artificial Intelligent Technique (통합적 인공지능 기법을 이용한 결함인식)

  • Sim, Mun-Bo;Seo, Myeong-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.12
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    • pp.2062-2069
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    • 2001
  • It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure, a method is presented in this paper which uses synthetic artificial intelligent technique, that is, Adaptive-Network-based Fuzzy Inference System(ANFIS) solved via hybrid learning algorithm(the back-propagation gradient descent and the least-squares method) are used to learn the input(the location and depth of a crack)-output(the structural eigenfrequencies) relation of the structural system. With this ANFIS and a continuous evolutionary algorithm(CEA), it is possible to formulate the inverse problem. CEAs based on genetic algorithms work efficiently for continuous search space optimization problems like a parameter identification problem. With this ANFIS, CEAs are used to identify the crack location and depth minimizing the difference from the measured frequencies. We have tried this new idea on a simple beam structure and the results are promising.

Crack identification based on synthetic artificial intelligent technique (통합적 인공지능 기법을 이용한 결함인식)

  • Shim, Mun-Bo;Suh, Myung-Won
    • Proceedings of the KSME Conference
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    • 2001.06c
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    • pp.182-188
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    • 2001
  • It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure, a method is presented in this paper which uses synthetic artificial intelligent technique, that is, Adaptive-Network-based Fuzzy Inference System(ANFIS) solved via hybrid learning algorithm(the back-propagation gradient descent and the least-squares method) are used to learn the input(the location and depth of a crack)-output(the structural eigenfrequencies) relation of the structural system. With this ANFIS and a continuous evolutionary algorithm(CEA), it is possible to formulate the inverse problem. CEAs based on genetic algorithms work efficiently for continuous search space optimization problems like a parameter identification problem. With this ANFIS, CEAs are used to identify the crack location and depth minimizing the difference from the measured frequencies. We have tried this new idea on a simple beam structure and the results are promising.

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Numerical Study on the Crack-propagation Controlling in Blasting Using Notched Charge Hole (노치 장약공을 이용한 발파균열제어에 관한 수치해석적 연구)

  • Cho, Sang-Ho;Park, Seung-Hwan;Kim, Kwang-Yeom;Nakamura, Yuichi;Kaneko, Katsuhiko
    • Explosives and Blasting
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    • v.26 no.1
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    • pp.49-55
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    • 2008
  • Mechanical excavation techniques employing tunnel boring machines (TBM) and rock splitters have been proposed to minimize rock damage for tunnel and underground waste repository facilities. Such a mechanical excavation, however, is extremely expensive and not applicable in all cases. For these reasons, controlled blasting using notched charge holes have been suggested to achieve crack growth along specific directions and inhibit growth along other directions. This study introduces a dynamic fracture process analysis code to simulate fracture processes of rock which has a notched charge hole.