• Title/Summary/Keyword: 횡크랙

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Free Vibration Characteristics of a Composite Beam with Multiple Transverse Open Cracks (다중 크랙이 있는 복합재료 보의 자유진동 특성)

  • 하태완;송오섭
    • Composites Research
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    • v.13 no.3
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    • pp.9-20
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    • 2000
  • Free vibration characteristics of a cantilevered laminated composite beam with multiple non-propagating transverse open cracks are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The multiple open cracks are modelled as equivalent rotational springs whose spring constants are calculated based on the fracture mechanics of composite material structures. Governing equations of a composite beam with open cracks are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect is adopted. The effects of various parameters such as the ply angle, fiber volume fraction, crack numbers, crack positions and crack depthes on the free vibration characteristics of the beam with multiple cracks are highlighted. The numerical results show that the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack.

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A Study on Transverse Cracking and Fatigue Properties of 50mm Thick FACW Weld Metal ; Effects of Preheating and Interpass Temperature (FCAW 50t 후판용접에 있어 예열 및 층간온도 변화에 따른 횡크랙 발생과 피로특성에 관한 연구)

  • 이해우;강성원
    • Journal of Welding and Joining
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    • v.15 no.3
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    • pp.56-64
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    • 1997
  • Macrostructural characteristic of the transverse cracks and fatigue behavior were studied for EH 32 TMCP 50mm thick plate welded with FACW under the variation in preheat and interpass temperatures. Transverse cracks were detected in specimen welded with preheat and interpass temperature below $30^{\circ}C$, but cracks were not detected in the specimens welded with preheat and interpass temperatures at the range of $100~120^{\circ}C$.C. The location of crack formation was found to strongly depend upon the thickness of weld layers as regard to the plate thickness.

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An Experimental Study on Damage Mechanism of Glass Resulting Frojm Particle Impact (입자충격에 의한 유리의 손상기구에 관한 실험적 연구)

  • Seo, Chang-Min;Sin, Hyeong-Seop;Hwang, Byeong-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.6
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    • pp.1903-1912
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    • 1996
  • A quantitative study of impact damage of a soda-lime glass was carried out. An initiation and a propagation of cracks by the impact of two inds of steel ball was investigated. The fron, side and rear view of cracks were observed by a stereo-microscope. And the lowering of the benidng strength due to the impact of steel balls was examined through the 4-point bending test. A transparent glass is very helpful to understand and analyze the impact damage behavior of another brittle matereial. A deagdram about crack patterns according to the threshold impact velocity was sketched. A ring crack and a cone crack were formed at the low impact velocity. And as the impact velocity was higher, initial lateral crack was generated on the slanting surface of cone crack, and radial cracks were generated from the outermost ring crack. When the impact velocity of steel balls exceed a critical velocity, the contact site of specimens were crushed. According to the propagation of a cone crack, a rapid strength degradation occurred. In the specimen having crushed region, a bending strength was converged to a constant value instead of strength degradation.

An Experimental Study on the Damage Mechanism of Particle Impact in a Scratched Glass (표면거칠기를 가진 유리의 입자충격 손상기구에 관한 실험적 연구)

  • Suh, Chang-Min;Chung, Seong-Muk;Lee, Mun-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.7
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    • pp.2196-2204
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    • 1996
  • The damage mechanism by the impact of steel ball on the soda-lime glass having a different surface roughness was investigated. An initiation and a propagation behavior of cracks formed by each impact velocity were quantitatively studied. A 4-point bending test was carried out to evaluate the remaining bending strength of a scratched soda-lime glass which impacted by the steel ball. As the surface roughness was increased, the shape of cracks became more irregular rather than those of the smooth specimens. The phenomenon of turning up in the wing of cone cracks occurred even at the lower velocity than the critical velocity caused the crushing. The threshold velocity of cracks initiation generally became lower than those of smooth specimen. An initiation and a propagation behavior of radial cracks had no relation with the direction of scratch on the surface. The remaning benidng strength of the scratched specimen according to impact velocity had no big difference compared with those of the smooth specimen.

Experimental Study on Detection of Crack for Coupled Bending-torsional Vibrations of L-beams (횡-비틀림 연성진동하는 L형 단면 보의 크랙 검출에 대한 실험적 연구)

  • Son, In-Soo;Lee, Doo-Ho;No, Tae-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.2
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    • pp.169-177
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    • 2011
  • In this paper, the natural frequency of a cracked cantilever L-beams with a coupled bending and torsional vibrations is investigate by theory and experiment. In addition, a method for detection of crack in a cantilever L-beams is presented based on natural frequency measurements. The governing differential equations of a cracked L-beam are derived via Hamilton's principle. The two coupled governing differential equations are reduced to one sixth order ordinary differential equation in terms of the flexural displacement. Futher, the dynamic transfer matrix method is used for calculation of a exact natural frequencies of L-beams. The crack is assumed to be in the first mode of fracture and to be always opened during vibrations. In this study, the differences between the actual and predicted positions and sizes of crack are less than about 10 % and 39.5 % respectively.

Coupled Bending and Torsional Vibrations Analysis of Cracked L-shaped Beam (크랙을 가진 L형 단면 보의 횡-비틀림 연성진동 해석)

  • Son, In-Soo;Kim, Chang-Ho;Cho, Jeong-Rae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.4
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    • pp.8-15
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    • 2011
  • In this paper, the influence of a crack on the natural frequency of cracked cantilever L-shaped beam with coupled bending and torsional vibrations by analytically and experimentally is analyzed. The L-shaped beam with a crack is modeled by Hamilton's principle with consideration of bending and torsional energy. The two coupled governing differential equations are reduced to one sixth-order ordinary differential equation in terms of the flexural displacement. The crack is assumed to be in the first, second and third mode of fracture and to be always opened during the vibrations. The theoretical results are validated by a comparison with experimental measurements. The maximal difference between the theoretical results and experimental measurements of the natural frequency is less than 7.5% in the second vibration mode.

Free Vibration Characteristics of a Composite Beam with Multiple Transverse Open Cracks (다중 크랙이 있는 복합재료 보의 자유진동 특성)

  • 하태완;송오섭
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 1999.11a
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    • pp.5-14
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    • 1999
  • Free vibration characteristics of a cantilevered laminated composite beam with multiple non-propagating transverse open cracks are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The multiple open cracks are modelled as equivalent rotational springs whose spring constants are calculated based on the fracture mechanics of composite material structures. Governing equations of a composite beam with open cracks are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect is adopted. The effects of various parameters such as the ply angle, fiber volume fraction, crack numbers, crack positions and crack depthes on the free vibration characteristics of the beam with multiple cracks are highlighted. The numerical results show that the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack.

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Prediction of Transverse Surface Crack using Classification Algorithm of Neural Network in Continuous Casting Process (연주공정에서 신경망의 분류 알고리즘을 이용한 횡방향 표면크랙 예측)

  • Roh, Y.H.;Cho, D.H.;Kim, D.H.;Seo, S.;Lee, J.D.;Lee, Y.S.
    • Transactions of Materials Processing
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    • v.27 no.2
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    • pp.100-106
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    • 2018
  • In the continuous casting process, the incidence of transverse surface cracks on the piece may occur by multiple and diverse variables. It is noted that mathematical models may predict only the occurance of the transverse surface cracks, but can require a lot of time (more than three days) to produce a result with this process. This study applied neural networks to predict whether the cracks on the piece surface occurs or does not occur. The computation time was shortened to three minutes, making it applicable to an on-line program, which predicts the non-cracks or cracks of the piece surface in the actual continuous casting process. In addition, the operating conditions to prevent the occurrence of the transverse surface cracks, using decision boundaries were also suggested.