• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.115-121
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• 2013

It is greatly expected that the technologies of durability enhancement and evaluation for the core structures of plant facilities, marine plant and bridge constructures will be greatly expanded in the plant industry fields. In this study, the actively ongoing applied cases were tried to be analyzed in the present domestic industry fields through the Ultrasonic Nanocrystalline Surface Modification (UNSM) and Ultrasonic Fatigue Test (UFT) technologies using ultrasonic elastic vibrational energy, and the new application technology to improve the durability of plant industry field, especially plant facilities, marine plant and core weld components of bridge constructures will be presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.22-27
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• 2007

Our environment is faced with serious problems related to the air pollution from automobiles in these days. In particular, the exhaust emissions of diesel engines are recognized as main causes of the air pollution. CRDI(common rail direct injection) diesel engine is widely used for the sake of minimization on exhaust emission. Because biodiesel fuel is a renewable and alternative fuel for diesel engine, its usability is expanded. In this study, a common rail diesel engine was run with 5% of biodiesel fuel(BDF 5%) more than 150 hours. Engine dynamometer testing was completed at regularly scheduled intervals to investigate the engine performance and exhaust emissions. The data of engine performance and exhaust emissions was sampled at 1 hour intervals for analysis. When a common rail diesel engine runs on BDF 5% for long time, power and energy consumption of the engine are similar to the case using diesel fuel. The smoke emission of BDF 5% was reduced in comparison with diesel fuel, that is, it was reduced approximately 15% at 4000rpm, and load of 90%. And, CO and $CO_2$ were reduced, too. On the other hand, NOx emission of biodiesel fuel was slightly increased about 2%, but it was almost same as a commercial diesel fuel.

• Structural Monitoring and Maintenance
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• v.2 no.1
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• pp.35-48
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• 2015

The main objective of this study is to evaluate the long-term performance of various concrete composites in natural marine environment prevailing in the Gulf region. Durability assessment studies of such nature are usually carried out under aggressive environments that constitute seawater, chloride and sulfate laden soils and wind, and groundwater conditions. These studies are very vital for sustainable development of marine and off shore reinforced concrete structures of industrial design such as petroleum installations. First round of testing and evaluation, which is presented in this paper, were performed by standard tests under laboratory conditions. Laboratory results presented in this paper will be corroborated with test outcome of ongoing three years field exposure conditions. The field study will include different parameters of investigation for high performance concrete including corrosion inhibitors, type of reinforcement, natural and industrial pozzolanic additives, water to cement ratio, water type, cover thickness, curing conditions, and concrete coatings. Like the laboratory specimens, samples in the field will be monitored for corrosion induced deterioration signs and for any signs of failureover initial period ofthree years. In this paper, laboratory results pertaining to microsilica (SF), ground granulated blast furnace slag (GGBS), epoxy coated rebars and calcium nitrite corrosion inhibitor are very conclusive. Results affirmed that the supplementary cementing materials such as GGBS and SF significantly impacted and enhanced concrete resistivity to chloride ions penetration and hence decrease the corrosion activities on steel bars protected by such concretes. As for epoxy coated rebars applications under high chloride laden conditions, results showed great concern to integrity of the epoxy coating layer on the bar and its stability. On the other hand corrosion inhibiting admixtures such as calcium nitrite proved to be more effective when used in combination with the pozzolanic additives such as GGBS and microsilica.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.689-692
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• 2008

HSC(High Strength Concrete) have superior properties well as improvement in durability compared with normal strength concrete. In spite of durability of HSC, explosive spalling of concrete is serious problem in structure safety. Therefore, Solving methods are required to control the explosive spalling. The properties of concrete are affected by changes of temperatures. Compressive strength and elasticity modulus were degraded depending on a rise of temperatures. Also, change in microstructure and dehydration of concrete subjected to high temperatures. This paper is concerned with change in microstructure and dehydration of the alumino silicate fire protection materials at high temperatures. The testing methods of fire protection materials in high temperature properties are make use of SEM, TG-DSC and XRD. From the experimental test results, influence of high temperatures on microstructure of alumino-silicate fire protection material was identified, including chemical dehydration of C-S-H and CH. The chemical dehydration of CH under various temperatures from to 450 to 600$^{\circ}$C has been measured using the TG-DSC. However, developed alumino silicate fire protection materials showed good stability in high Temperatures. Thus, the results indicate that it is possible to fireproof panels, fire protection of materials.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.79-86
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• 2007

The corrosion durability of steel bridge coatings, such as organic and metallic coatings, is often evaluated by field exposure tests, but such tests take from several years to decades to complete. As a potential method for fast corrosion testing, accelerated exposure tests were considered in this study. The S6-cycle accelerated exposure test, specified in the Japanese Industrial Standards (JIS K5621), was carried out on uncoated structural steels for 30, 60, 90, 120 and 150 days, and the resultant weight loss was determined. The weight loss was compared with that obtained from previous field exposure tests, and acceleration factors of the S6-cycle test to field exposure test sites were determined. The application of the S6-cycle accelerated exposure tests to field environments was presented based on the acceleration factor and the amount of flying salt.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.301-310
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• 2009

Steel has been widely used as a material in temporary structures. Corrosion attack often reduces the long-term durability of temporary steel members that are not protected from corrosion. In designing temporary steel structures, it is difficult to evaluate their long-term durability, since the thickness loss of steel members is not clear. In this study, laboratory and field exposure corrosion tests were performed on structural steel plate specimens, and the loss of thickness of specimens that were exposed to a subway construction site for 11 months and of specimens that were exposed to environments with controlled humidity and calcium chloride for six months were measured. Finally, a thickness loss equation was formulated based on the environmental conditions and the testing periods.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.129-137
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• 2017

PURPOSES : The purpose of this study is to develop bridge deck concrete materials based on ordinary Portland cement concrete, and to evaluate the applicability of the developed materials through material properties tests. METHODS : For field implementation, raw material (cement, fine aggregate, and coarse aggregate) properties, fresh concrete properties (slump and air content), strength (compressive, flexural and bond strength) gain, and durability (freeze-thaw resistance, scaling resistance, and rapid chloride penetrating resistance) performance were evaluated in the laboratory. RESULTS : For the selected binder content of $410kg/m^3$, W/B = 0.42, and S/a = 0.48, the following material performance results were obtained. Considering the capacity of the deck finisher, a minimum slump of 150 mm was required. At least 6 % of air content was obtained to resist freeze-thaw damage. In terms of strength, 51.28 MPa of compressive strength, 7.41 MPa of flexural strength, and 2.56 MPa of bond strength at 28 days after construction were obtained. A total of 94.9 % of the relative dynamic modulus of elasticity after 300 cycles of freeze-thaw resistance testing and $0.0056kg/m^2$ of weight loss in a scaling resistance test were measured. However, in a chloride ion penetration resistance test, the result of 3,356 Coulomb, which exceeds the threshold value of the standard specification (1000 Coulomb at 56 days) was observed. CONCLUSIONS : Instead of using high-performance modified bridge deck materials such as latex or silica fume, we developed an optimum mix design based on ordinary Portland cement concrete. A test construction was carried out at ramp bridge B (bridge length = 111 m) in Gim Jai City. Immediately after the concrete was poured, the curing compound was applied, and then wet mat curing was applied for 28 days. Considering the fact that cracks did not occur during the monitoring period, the applicability of the developed material is considered to be high.

• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.251-257
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• 2017

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner's Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.296-302
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• 2016

Studies aimed at reducing the occurrence of cracks by the shrinkage of concrete are in demand because the repair and reinforcement for cracks caused by declining concrete durability costs the user to maintain the concrete structure. In particular, in underground power facilities for power transmission, the cost is a heavy burden to repair and reinforce. For this reason, underground power facilities demanded effective methods for crack reduction at the engineering design step. This study, as a part of the development of shrinkage reducing agent for low shrinkage concrete on underground power facilities, investigated TEA to complement the shrinkage reducing agent to improve the early strength of concrete. In the case of TEA 3% as a shrinkage reducing agent, the early strength was improved significantly, and the shrinkage reducing effect was excellent. In addition, TEA 3.0 % and the shrinkage reducing agent 2.0 % showed excellent shrinkage property and compressive strength. On the other hand, more study of shrinkage reducing materials, including performance reviews on the shrinkage reducing materials with variable factors and type of materials, will be needed to generalize these results.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.337-343
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• 2010

Current need of weight reduction in automotive part increases the application for high strength steel (HSS). The various types of high strength steels have been used to produce chassis part, control arms and trailing arms for weight reduction and increasing of fatigue durability such as dual phase steel (DP) and ferrite bainite steel (FB). But, DP and FB steels have proven to show inferiority in durability as well as press formability. Edge cracking occurred often in flange forming and hole expansion processes is the major failure encountered. This paper discussed the behavior of edge stretchability of high strength steel of DP and FB steels. Experimental works have been conducted to study the effect of punch clearance and burr direction on hole expansion ratio (HER). Also finite element simulation (FEM) has been preformed to clarify the mechanism of flange crack and support the experimental results on HER of DP and FB steels. It was simulated the whole process of blanking process following by hole expansion process and ductile fracture criterion named the modified Cockcroft-Latham model which was used to capture the fracture initiation. From the hole expansion tests and FEM simulation studies it was concluded that ferrite bainite steel showed better stretch-flangeability than dual phase steel. It was attributed to the lower work hardening rate of ferrite bainite steel than dual phase steel at the sheared edge.