• Journal of Korea Foundry Society
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• v.34 no.4
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• pp.136-142
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• 2014

Numerical solution of thermal stress by CAE analysis could be an effective method in product development stage of castings to predict and treat the problem of solidification cracking of castings. Quantitative stress-strain data are necessary, in this case. Tension type apparatus of a solidification crack test which can measure stress-strain relationship quantitatively was developed and the test procedure was established by this research. Solidification crack strength obtained from the following test procedure could be utilized to evaluate it in terms of effect factors on thermo-plastic characteristic of solidifying alloy such as grain size of solid, grain morphology, distribution of solid grain, etc. Proposed test procedure is as follow: Prediction of temperature at the failure site of solidification cracked specimen by computer simulation of solidification, Calculation of solid fraction of the failure site from thermodynamic solution of solidification under Scheil condition.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.369-376
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• 2001

As many studies have performed to reduce thermal cracking in mass concrete, it is already prepared against thermal cracking, we can find many plans against thermal cracking in several reference book. But it needs practical guidelines to be available in construction site. In this study to establish control method of thermal cracking in mass concrete, tests which have factors of placing thickness and curing method of concrete are performed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1089-1096
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• 1997

In this paper, Rancho Seco transient which is reported as a typical pressurized thermal shock event is postulated to be occuring in the Kori unit 1 plant, the oldest nuclear power plant in Korea. For the given material properties, transient history such as temperature and pressure, and postulated flaw, the stress distribution is obtained to calculate stress intensities for a wide range of assumed crack sizes. The stress intensities are compared with the fracture toughness, which is determined using the material properties and the distribution of the nil ductility transition temperature, to determine if cracking is expected to occur during the transient. The allowable operating year for the transient is determined and the evaluation results are discussed.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.657-663
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• 2006

By measuring concrete temperature and strains of concrete and reinforcing bars throughout gages embedded and also by observing the crack occurrence, this study aims at the characteristics of structural behavior of subway wall structure in associate with concrete ages. The length of 23.5m, thickness of 2.0m of real subway custody line was selected as a representative structure and 7 thermocouples and 6 strain gages were installed to measure the behavior of wall structure. The results were compared and verified with analytical results using MIDAS in order to show their usefulness. It was found that only attachment of strain gages on the surface of reinforcing bars can figure out the timing of crack occurrence and hydration heat program is useful to estimate comparatively exact magnitudes of temperature. Since estimated time of crack occurrence throughout thermal stress analysis depends on the period of transferred thermal stress from concrete to reinforcing bars, however, cracks from naked eyes were identified later than analytical results. Cracks were observed first at the center of wall line and then to the end of line symmetrically.

• Journal of Applied Reliability
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• v.8 no.4
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• pp.155-166
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• 2008

PTH cracks are caused by the mismatch of coefficient of thermal expansion(CTE) between polymer and laminated materials, and are one of the main failure mechanisms of multi layer boards. In spite of its importance, it is usually hard to measure or detect them because of its small size and invisibility. To detect PTH cracks more effectively, this paper proposes a theoretical model that can estimate the resistance value from crack size of PTHs. Using four-point probe resistance measurement method, the resistance value of test coupons is measured. Through measured data, we verify the validity of the proposed theoretical model and set up criteria of failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.807-812
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• 2001

This study is peformed for checking the limitation and application of each curing/heating methods on cold-weathering mat foundation construction, considering temperature control, early strength security and temperature declination range limit, by means of concrete material properties and thermal analysis technique that were published previously. In the result of this analysis, we checked the open air temperature and mat depth that are possible to apply each curing/heating methods on cold-weathering construction and found curing/heating time of each methods that is able to prevent early aged freezing damage and thermal crack

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.41-46
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• 2002

Recently, the design and construction of massive concrete structures are increased, But, the temperature rise within a large concrete mass makes the construction of massive concrete structures be very difficult. Therefore, various techniques of the thermal stress control of the mass concrete have been widely used. One of them is pipe-cooling which reduces the temperature of concrete with flowing water. It was shown to be possible to construct the massive concrete foundation of urban bridge successfully by application of pipe-cooling system with steel pipe and water circulation. It was also found to expected to make it possible to reduce the probability of thermal crack development in a massive concrete foundation of urban bridge by pipe-cooling system.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.44-55
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• 1994

This study is to apply the theory of fatigue fracture to solder joints under thermal cyclic loading and predict life of solder joint to failure. A 62Sn-36Pb-2Ag solder was used in this study. Tensile tests were preformed at temperatures of 15.dec. C, 50.dec. C and 85.dec. C in order to find terms of crack length "a". plastic strain range ""${\Delta}{\varepsilon}_p$" and temperature "T". Solder joint under thermal cyclic loading was analyzed by FEM. this FEM analysis together with the crack growth rate will provide the capability of the fatigue life prediction of solder joints and enhance the reliability od solder joint.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.139-146
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• 2006

Many concrete bridge decks develop transverse cracking shortly after construction. These cracks accelerate corrosion of reinforcing steel and lead to concrete deterioration, damage to components beneath the deck, unsightly appearance. These cracks shorten the service life and increase maintenance costs of bridge structures. In this study, VES-LMC overlay, which provides the same benefits as a conventional overlay, is designed to cure very quickly. Although the materials for VES overlays are more expensive, the cost is more than offset by the savings on traffic control and work zone safety measures. Otherwise, reaction of hydration occurs very rapidly in beginning step(concrete placing). As a results, thermal cracking can be occur by thermal stress in accordance with hydration-heat The purpose of this study was to estimate diagnosis of crack occurrence of VES-LMC through field tests at early-age.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1295-1300
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• 2008

During the manufacturing and the service life of Au-Al wire bonded electronic packages, the ball bonds experience elevated temperatures and hence accelerated thermal diffusion reactions that promote the transformation of the Au-Al phases and the IMC growth. In this paper, the IC under high temperature storage (HTS) tests at $175^{\circ}C,\;200^{\circ}C$, and $250^{\circ}C$ are meticulously investigated. Thermal exposure resulted in the IMC growth, Kirkendall void and the crack of the Au-Al phases. The crack propagation occurs resulting in the failure of the Au-Al ball bonds. As the IC was exposed at the high temperature, decreased in the lifetime.