• Journal of the Korean institute of surface engineering
• /
• v.25 no.4
• /
• pp.181-186
• /
• 1992

To investigate how to produce the crack free and chromium deposits, bath compositions, additives, electrolysis conditions and other electroplating parameters, such as cathodic current efficiency, surface hard-ness, crack density and corrosion rate of deposits were examined carefully. The crack free chrome deposits were well obtained using both wetting agents and two kind of additives. At 60 A/d$\m^2$, $60^{\circ}C$ electrolysis condition, crack free bright hard chromium deposits were well obtained to a thickness $300\mu\textrm{m}$ in Additive-I and Additive-II added solution.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.4
• /
• pp.593-599
• /
• 2022

In this study, a crack monitoring system capable of detecting cracks based on image processing techniques was developed to effectively check cracks, which are the main damage of concrete structures, and a program capable of imaging and analyzing cracks was developed using machine vision. This system provides objective and quantitative data by replacing the appearance inspection that checks cracks with the naked eye. The verification of the development system was applied to the construction site of a self-healing concrete water tank to monitor the crack and the amount of change in the crack width according to age. In the case of crack width detected by image analysis, the difference from the measured value using a digital microscope was up to 0.036 mm, and the crack healing effect of self-healing concrete could be confirmed through the reduction of crack width.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.381-388
• /
• 2004

We propose a 2D 'crack' element for the simulation of propagating crack with minimal remeshing. A regular finite element containing the crack tip is replaced with this novel crack element, while the elements which the crack has passed are split into two transition elements. Singular elements can easily be implemented into this crack element to represent the crack-tip singularity without enrichment. Both crack element and transition element proposed in our formulation are mapped from corresponding master elements which are commonly built using the moving least-square (MLS) approximation only in the natural coordinate. In numerical examples, the accuracy of stress intensity factor K/sub I/ is demonstrated and the crack propagation in a plate is simulated.

• Metals and materials international
• /
• v.24 no.6
• /
• pp.1412-1421
• /
• 2018

Cold-expanded austenitic high nitrogen steel (HNS) was subjected to investigate the effects of grain size on the stress-controlled high cycle fatigue (HCF) as well as the strain-controlled low cycle fatigue (LCF) properties. The austenitic HNSs with two different grain sizes (160 and $292{\mu}m$) were fabricated by the different hot forging strain. The fine-grained (FG) specimen exhibited longer LCF life and higher HCF limit than those of the coarse-grained (CG) specimen. Fatigue crack growth testing showed that crack propagation rate in the FG specimen was the same as that in the CG specimen, implying that crack propagation rate did not affect the discrepancy of LCF life and HCF limit between two cold-expanded HNSs. Therefore, it was estimated that superior LCF and HCF properties in the FG specimen resulted from the retardation of the fatigue crack initiation as compared with the CG specimen. Transmission electron microscopy showed that the effective grain size including twin boundaries are much finer in the FG specimen than that in the CG specimen, which can give favorable contributions to strengthening.

• Structural Engineering and Mechanics
• /
• v.12 no.4
• /
• pp.377-396
• /
• 2001

The excessive cracking of RC cantilever decks, which often requires special attention for structural engineers, is studied using a three-dimensional crack analysis model. The model is based on a fracture energy approach for analyzing cracks in concrete, and the numerical analysis is carried out using a modified load control method. The problem of excessive cracking is then studied with four different span-ratios. Based on the numerical results, the crack behavior with respect to the patterns of crack propagation, dissipation of the fracture energy, and effects on the structural integrity are discussed. The mechanisms which cause the excessive cracking are also explained.

• Journal of the Korea Concrete Institute
• /
• v.16 no.4 s.82
• /
• pp.511-520
• /
• 2004

The fracture energy evaluated from the previous experimental results can be simulated by using the modified singular fracture process zone (S-FPZ) model. The fracture model has two fracture properties of strain energy release rate for crack extension and crack close stress versus crack width relationship $f_{ccs}$ ( w ) for fracture process zone (FPZ) development. The $f_{ccs}$( w ) relationship is not sensitive to specimen geometry and crack velocity. The fracture energy rate in the FPZ increases linearly with crack extension until the FPZ is fully developed. The fracture criterion of the strain energy release rate depends on specimen geometry and crack velocity as a function of crack extension. The variation of strain energy release rate with crack extension can explain theoretically the micro-cracking, micro-crack localization and full development of the FPZ in concrete.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.6
• /
• pp.133-141
• /
• 2002

This paper describes a versatile finite element technique which has been used to investigate wide range of structural defects of practical importance. The procedure automatically remeshes the three-dimensional finite element model during the stages of crack growth. Problems include the surface cracks in leak-before-break situations, the shape development of multiple surface defects.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.551-556
• /
• 1997

Concrete can be defective for several reasons, including inadequate design, material selection or workmanship. Concrete and also dsteriorate or be damaged in use. Consequently existing reinforced concrete may not be functioning as originally intended and designed. So, the evaluate process to investigate initial crack is very important. It is the aim of this study to development and application for diagnosis method on the crack broker out of new constructions.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.2502-2507
• /
• 2003

In this paper, a crack sealing robot is developed. The crack sealing robot is built to detect, track, and seal the crack on the pavement. The sealing robot is required to brush all dirt in the crack out for preparing a better sealing job. Camera calibration has been done to get accurate crack position. In order to perform a cleaning job, the explicit force control method is used to regulate a specified desired force in order to maintain constant contact with the ground. Experimental studies of force tracking control are conducted under unknown environment stiffness and location. Crack tracking control is performed. Force tracking results are excellent and the robot finds and tracks the crack very well.

• Journal of the Korean Society for Heat Treatment
• /
• v.18 no.3
• /
• pp.164-171
• /
• 2005

Iodine-Induced Stress Corrosion Cracking (ISCC) properties of Zircaloy-4 and HANA4 developed in KAERI for the high burn-up nuclear fuel cladding were evaluated. To confirm the effect of final heat treatment on ISCC resistance of Zr-alloy, stress relieved and recrystallized specimens were prepared and tested. With the pre-cracked specimen at internal surface, ISCC crack propagation rates and threshold stress intensity factor ($K_{ISCC}$) based on the fracture mechanics were measured by internal pressurization test at $350^{\circ}C$ in iodine environment. $K_{ISCC}$ of Zircaloy-4 and HANA4 cladding were $3.3MPa{\cdot}m^{1/2}$ and $4.4MPa{\cdot}m^{1/2}$, respectively. Pitting corrosion at the crack surface was observed and it seemed that TG crack propagation was derived from the pitting.