• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1033-1040
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• 1995

To simulate strength reliability and durability of ceramic parts under gas turbine application environments, particle impact damage behaviors in silicon carbide oxidized at 1673 K and 1523 K for 200 hours in atmosphere were investigated. The long-term oxidation produced a slight increase in the static fracture strength. Particle impact caused a spalling of oxide layer. The patterns of spalling and damage induced were dependent upon the property and impact velocity of the particle. Especially, the difference in spalling behaviors induced could be explained by introducing the formation mechanism of lateral crack and elastic-plastic deformation behavior at impact sit. At the low impact velocity regions, the oxidized SiC showed a little increase in the residual strength due to the cushion effect of oxide layer, as compared with the as-received SiC without oxide layer.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.15-16
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• 2012

The estimation of crack damages is studied using the radio frequency system and tilt switch sensors in RC beams. If load is received on the center of the flexible specimen, sensor housing using cement mortar of the flexible specimen will be destroyed, and these are become to send signals of damages at the radio frequency system connected with tilt switch sensors. This study is fundamental research for the estimation of the damage using tilt switch sensors in RC beams.

• Journal of the Korean Society of Safety
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• v.17 no.1
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• pp.1-5
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• 2002

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

• Structural Engineering and Mechanics
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• v.25 no.2
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• pp.131-146
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• 2007

This paper presents the results of a study to show how the development of a crack alters the structural behavior of I-shaped steel beams and how this can be used to evaluate nondestructive evaluation techniques. The approach is based on changes in the dynamic behavior. An approximate finite element model for a cracked beam with I-shaped cross-section is developed based on a simplified fracture model. The model is then used to review different damage cases. Damage detection techniques are studied to determine their ability to identify the existence of the crack and to identify its location. The techniques studied are the coordinate modal assurance criterion, the modal flexibility, and the state and the slope arrays.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.57-64
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• 1999

In order to decide critical vibration level on structural damages induced by near blasting, deformation of existing cracks in structure was investigated and ground vibrations were measured. New criteria to evaluate blasting damage to structure are proposed considering daily deformation of cracks in structures. Results from 2 brick houses in fishing village show that new design criteria far more than current are required to cause structural damage for brick houses.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.157-158
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• 2011

The monitoring to crack damages is studied using the radio frequency system and static displacement sensors. If load is received on the center of the flexible specimen, bonded sensors will be destroyed, and these are become to send signals of damages at the radio frequency system connected with sensors. This study is fundamental research of the monitoring damage system for diagnostic concrete elements using the radio frequency system and static displacement sensors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.969-974
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• 2004

Although guided-waves are very efficient for long-range nondestructive damage inspection, it is not easy to extract meaningful pulses of small magnitude out of noisy signals. The ultimate goal of this research is to develop an efficient signal processing technique for the current guided-wave technology. The specific contribution of this investigation towards achieving this goal, a two-stage Gabor pulse-based matching pursuit algorithm is proposed : rough approximations with a set for predetermined parameters characterizing the Gabor pulse and fine adjustments of the parameters by optimization. The parameters estimated from the measured signal are then used to assess not only the location but also the size of a crack existing in a rod. To validate the effectiveness of the proposed method, the longitudinal wave-based damage detection in rods is considered. To estimate the crack size, Love's theory for the dispersion of longitudinal waves is employed.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.34-39
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• 2003

In this paper, when CF/PEEK laminates for high efficiency space structure are subjected to FOD(Foreign Object Damage), the effects of temperature change on the impact damages(interlaminar separation and transverse crack) of CF/PEEK laminates and the relationship between residual lift and impact damages are experimentally investigated. Composite laminates used in this experiment are CF/PEEK orthotropic laminated plates, which have two-interlaces [$0^{\circ}_4/90^{\circ}_8/0^{\circ}_4$]. A steel ball launched by the air gun collides against CF/PEEK laminates to generate impact damages. And then CF/PEEK specimens with impact damages are observed by a scanning acoustic microscope under room and high temperatures. In this experimental results, various relations are experimentally observed including the delamination area vs. temperature change, the bending strength vs. impact energy and the residual bending strength vs. impact damage of CF/PEEK laminates.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.66-75
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• 1994

In this paper, the effects of temperature change on the impact damages of CF/PEEK laminates are experimentally investigated. Composite laminates used in this experiment are CF/PEEK orthotropic laminated plates, which have two-interfaces$[0^{\circ}_4/90^{\circ}_4]_{9+} A steel ball launched by the air gun collides against CFRP laminates to generate impact damage. The delamination damages are oberved by a scanning acoustic microscope. And various relations are experimentally observed including the impact energy vs. delamination area, the specimen temperature vs. transverse crack, and the impact energy vs. residual bending strength of carbon fiber peek composite laminates subjected to FOD(Foreign Object Damage) under high temperatures.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.174-179
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• 2005

In this paper, a computational model for nonlinear crack damage analysis of concrete gravity dam-foundation boundary region subjected to earthquake loading is suggested. An enhanced model based on the Lee-Fenves plastic-damage model is used as the inelastic material model for a concrete dam structure and rock foundation. The suggested model is implemented numerically and used for computational earthquake simulation of Koyna dam, which was severly damaged from the strong earthquake in 1967. From the numerical result it is demonstrated that the suggested computational model can realistically represent crack initiation and propagation in the dam-foundation boundary region.