• Journal of the Korean Society for Precision Engineering
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• v.31 no.1
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• pp.15-20
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• 2014

Thermal barrier coating (TBC) is used to protect the substrate and extend the operating life of the gas turbine for a power plant and an aircraft. The major cause of failure of such a coating is the spallation of coating, and it results from the thermal stress between top coating and bond coating. To improve the durability of TBC system, the dense vertical cracked (DVC) coating method to insert vertical cracks is applied to a gas turbine blade. In this study, a criterion for the design of vertical crack in the DVC coating was presented using the finite element analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.820-825
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• 1994

It is improtant to examine life or crack propagation behavior of structures because of its safety evaluation. The purpose of this study is to investigate the effect of crack-crack interaction to evaluate fatigue life and crack behavior. In this study, the behavior of the interaction of two cracks is studied by experiment. The vertical distance of two cracks is varied to make different interaction stress field. In addition, the effect of plastic zone is considered to examine crack propagation path and propagation rate.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.579-584
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• 1997

This experimentation is to apperciation an efficiency of repair for processing crack by corrosion of steel reinforcing, Crack on concrete by corrosion of steel reinforcing is the fact that the first crack appear on the surface of water because of supplying is of oxygen and water. The crack processing is on surface to be contacted by air and to bottom as mainly the vertical direction from a surface of water. The experimentation gives rise to crack in model by electricity. Crack by corrosion of steel reinforcing is more internal crack than external crack. since it is so. crack by corrosion of steel reinforcing have to attention to repair or intermal crack.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.71-78
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• 1998

Real crack and fracture surfaces have irregularities producing zigzag contours. These irregularities are analysed by a fractal geometry which has been by a Mandelbrot. We obtained a fractal dimension which is one of the fractal characteristics. It is also estimated by an vertical section method that fractal characteristics in the fractured surfaces can be obtained as the crack grows. Moreover fractal fracture energy that corresponds to an energy release rate is shown to find relationships between fractal dimensions and crack behaviors. From these results, we concluded that a fractal characteristics analysis for a crack can be applied to a fracture mechanics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1863-1870
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• 2000

When an impact stress is applied on the external boundary of double cantilever beam of orthotropic material which crack length is greater than specimen hight and anistropic ratio is very high, dyna mic energy release rate is derived, and the relationship between dynamic energy release rate and crack propagating velocity is studied. Dynamic energy release rate to static energy release rate is decreased with increasment of crack propagating velocity. The relationships between dynamic energy release rate and vertical strain have a similar pattern with those between static energy release rate and vertical strain. When normalized time(Cstla) is greater than or equal to 2, dynamic energy release rate approaches to a constant value.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.181-188
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• 2002

The objective of this study is to determine crack depth located under steel reinforcement in concrete specimens using ultrasonic method. Experimental studies were performed on concrete specimens containing vertical and inclined surface-opening cracks with known depths. The other studies were carried out on specimens with flexural crack. Experimental results have shown that the crack depth is effectually measured when the distance between the probes is less than the crack depth. The effect of steel on crack depth estimation is studied through a model by considering P-waves diffaction at the tip of crack and steel. In addition, experimental results show that the ultrasonic method is one of useful methods to evaluate the crack depth in reinforced concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.885-890
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• 2000

12 RC deep beams with a/d = 1.17 are reported. This paper is to study the effect of vertical and horizontal web reinforcement and web reinforcement arrangement on inclined cracking shear, ultimate shear strength, midspan deflection, and inclined crack width. Test results indicated that web reinforcement produces and arrangement seems to moderately affect inclined cracking shear, ultimate shear strength and crack width. However, addition of horizontal web reinforcement(pv = 0.0085) little or no influence on inclined cracking shear, ultimate shear strength and crack width. The member which vertical and horizontal web reinforcement concentrate on the center web considerably increases in load-carrying capacity.

• The korean journal of orthodontics
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• v.17 no.1
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• pp.85-91
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• 1987

The aim of this study was to clarify whether bonding/debonding procedure will affect the occurance of enamel crack. The frequency of enamel crack was compared between before-bonding and after-debonding on 200 human extracted teeth. Each facial surface of the tooth was divided in 9 fragments. A presence of crack, which was classified by its direction as vertical, horizontal and oblique crack, was surveyed in each fragment. Number of all cracks in facial surface was 1355 at before-bonding, and 1605 at after-debonding, so it revealed significant increase rate of $18.5\%$, but compared by fragment, cracks were significantly Increased in OC, OD, CC and GC fragments. All kinds of cracks were significantly increased, especially increase rate of oblique crack reached $54.9\%$. The increase rate of cracks was not superior at any fragment or region, but some evidence was seen in CC fragment. Judging from the above, increase of crack is unavoidable with bonding/debonding procedures.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.159-167
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• 2005

This work focuses on the effects of crack free friction on Mode II stress intensity factors, $K_{II}$, for a vertical surface crack in a two-dimensional finite element model of TiN/steel subject to rolling contact. Results indicate that maximum $K_{II}$ values, which occur when the load is adjacent to the crack, may be significantly reduced in the presence of crack face friction. The reduction is more significant for thick coatings than for thin. Crack extension and increased layer thickness result in increased $K_{II}$ values. The effect of crack face friction on compressive $K_I$ values appears negligible. Comparative results are presented for $MoS_2/steel$ and diamond-like carbon(DLC)/Ti systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.945-952
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• 1987

In this paper, Crack molding method called "Teflon crack Molding Method" is developed. With help of this method, we can mold a crack which is very similar to the natural crack, which has the tip radius of about 20.mu. the vertical and horizontal quality of crack excellent. In addition to these, by using this method in photoelastic experiment we can obtain the clear crack tip location and Isochromatic fringe pattern boundary, therefore the precise in the experimental data can be improved. improved.