• 한국자동차공학회논문집
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• 제14권4호
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• pp.115-122
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• 2006

To evaluate the durability characteristics of in-direct injection diesel engine using BDF 20(a blend of 20% biodiesel fuel and 80% diesel fuel in volume), an IDI diesel engine used to commercial vehicle was operated on BDF 20 for 300 hours. Engine dynamometer testing was completed at regularly scheduled intervals to investigate the combustion characteristics, engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis. From the results, the combustion variations such as the combustion maximum pressure($P_{max}$) and the crank angle at which this maximum pressure occurs(${\Theta}_{Pmax}$) were not appeared during long-time dynamometer testing. Also, BSFC with BDF 20 resulted in lower than with diesel fuel. The peak pressure with BDF 20 was higher than that with diesel fuel due to the oxygen content in BDF. And, BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions with a little increase of oxides of nitrogen than diesel fuel. It was concluded that there was no unusual deterioration of the engine, or any unusual change in exhaust emissions during the durability test of an IDI diesel engine using BDF 20.

• Computers and Concrete
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• 제14권2호
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• pp.175-191
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• 2014

In recent years, the emergence of nanotechnology and nanomaterial has created hopes to improve various properties of concrete. Nano silica as one of these materials has been introduced as a cement replacement material for concrete mixture in construction applications. It can modify the properties of concrete, due to high pozzolanic reactions and also making a denser microstructure. On the other hand, it is well recognized that the use of mineral admixtures such as silica fume affects the mechanical properties and durability of cementitious materials. In addition, the superior performance of self-consolidating concrete (SCC) and self-consolidating mortars (SCM) over conventional concrete is generally related to their ingredients. This study investigates the effect of nano silica and silica fume on the compressive strength and chloride permeability of self-consolidating mortars. Tests include compressive strength, rapid chloride permeability test, water permeability, capillary water absorption, and surface electrical resistance, which carried out on twenty mortar mixtures containing zero to 6 percent of nano silica and silica fume. Results show that SCMs incorporating nano silica had higher compressive strength at various ages. In addition, results show that nano silica has enhanced the durability SCMs and reduced the chloride permeability.

• Geomechanics and Engineering
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• 제12권5호
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• pp.785-801
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• 2017

Biopolymer treatment of geomaterials to develop sustainable geotechnical systems is an important step towards the reduction of global warming. The cutting edge technology of biopolymer treatment is not only environment friendly but also has widespread application. This paper presents the strength and slake durability characteristics of biopolymer-treated sand sampled from Al-Sharqia Desert in Oman. The specimens were prepared by mixing sand at various proportions by weight of xanthan gum biopolymer. To make a comparison with conventional methods of ground improvement, cement treated sand specimens were also prepared. To demonstrate the effects of wetting and drying, standard slake durability tests were also conducted on the specimens. According to the results of strength tests, xanthan gum treatment increased the unconfined strength of sand, similar to the strengthening effect of mixing cement in sand. The slake durability test results indicated that the resistance of biopolymer-treated sand to disintegration upon interaction with water is stronger than that of cement treated sand. The percentage of xanthan gum to treat sand is proposed as 2-3% for optimal performance in terms of strength and durability. SEM analysis of biopolymer-treated sand specimens also confirms that the sand particles are linked through the biopolymer, which has increased shear resistance and durability. Results of this study imply xanthan gum biopolymer treatment as an eco-friendly technique to improve the mechanical properties of desert sand. However, the strengthening effect due to the biopolymer treatment of sand can be weakened upon interaction with water.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.76.1-76.1
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• 2010

Recently, many efforts to solve the durability problem of PEM fuel cell are carried on constantly. However, despite this attention, durability researches of gas diffusion layer (GDL) are not much reported yet. Generally, GDL of PEM fuel cell experiences three external attacks, which are dissolution of water, erosion of gas flow, corrosion of electric potential. In this study, among these degradation factors, carbon corrosion of electric potential was focused and investigated with accelerated carbon corrosion test. Through the test, it is confirmed that carbon corrosion occurred at GDL, and corroded GDL decreased a performance of operating fuel cell. The property changes of GDL were measured with various methods such as air permeability meter, pore distribution analyzer, thermo gravimetric analyzer, and tensile stress test to discover the effects of carbon corrosion. Carbon corrosion caused not only loss of weight and thickness, but also degradation of mechanical strength of GDL. In addition, to analysis the reason of GDL property changes, a surface and a cross section of GDL were observed with scanning electron microscope. After 100 hours test, the GDL showed serious damage in center of layer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1326-1330
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• 2008

The failure mode of steel road wheels in a vehicle is cracks from ventilation hole through to contact plane on steel wheel's disc plate. But a number of cracks of Cornering Fatigue Limit Test is on contact plane near to wheel nut mounting area, even though it's satisfied with specified cycles. So this paper searches out causes to improve durability and reliability of C.F.T by uni-axial bending moment test. The verified cause is a "fretting" on contact area of steel wheel. In result, this paper suggests a solution to prevent a fretting by inserting a damping shim, 0.7mm between steel wheel contact areas. Therefore this paper makes it possible to move crack position of C.F.T in steel wheel from contact plane to vehicle's failure mode.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.28-34
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• 2017

The vehicle stabilizer link is one of the suspension components that reduces the bumping and rolling during vehicle driving. However, this stabilizer link could be a source of the abnormal noises when its free gaps have higher than normal values. Therefore, the current study aims at investigating the quantitative relationships between the abnormal noises and free gaps of the vehicle stabilizer links, as well as the length of time that the vehicle stabilizer links could be used without generating abnormal noises. In this study, the abnormal noises were measured based on the magnitude of the stabilizer link vibration, while the free gaps were quantified through the force-displacement curves of the stabilizer links. Harsh durability tests were also conducted in order to quantify the operating cycles of the stabilizer links before generating the abnormal noises, along with the concomitant measurements of the free gaps. The current results showed that the abnormal noises of the stabilizer links were detected when its free gaps were larger than 0.12 mm. However, the free gaps of the stabilizer links, which are bigger than 0.1 mm, produced the abnormal noises at 1.5 million cycles under harsh durability test conditions. A parametric study in the future that would reflect the different shapes and sizes of the stabilizer links for diverse vehicles could determine more generalized relationships between the abnormal noises and free gaps of the vehicle stabilizer links.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.84-94
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• 2019

Aluminum substrates are irradiated with chromium ions and the steam condensation heat transfer performance on these surfaces is examined. Filmwise condensation is induced on the surface of aluminum specimens irradiated with chromium ion dose of less than $10^{16}ions/cm^2$ while dropwise condensation occurs on the specimens irradiated with chromium ion dose of $5{\times}10^{16}ions/cm^2$ in the range of ion energy from 70 to 100 keV. The heat transfer coefficient of the surfaces on which dropwise condensation occurs appeared to be approximately twice as much as the prediction by Nusselt's film theory. In a durability test, dropwise condensation lasts over six months and the heat transfer coefficient is also maintained.

• 한국정밀공학회지
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• 제31권12호
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• pp.1155-1159
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• 2014

Thermal barrier coating (TBC) which is used to protect the substrate of gas turbine is exposed to high temperature environment. Because of high temperature environment, thermally grown oxide (TGO) is grown at the interface of thermal barrier coating in operation of gas turbine. The growth of TGO critically affects to durability of TBC, so the evaluation about durability of TBC with TGOs of various thickness is needed. In this research, TGO was inserted by aging of TBC specimen to evaluate the effect of the TGO growth. Then thickness of TGO was defined by microstructure analysis, and thermal fatigue test was performed with these aging specimens. Finally, the relation between thermal fatigue life and the TGO growth according to aging time was obtained.

• 한국생산제조학회지
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• 제25권3호
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• pp.198-203
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• 2016

Computer-Aided Engineering (CAE) durability analysis and experiments of an aluminum alloy brake pedal were carried out for the car lighter by die casting method. In the CAE analysis, KS standards and criteria of the Volvo Car Corporation were applied, and in the experiment, KS standards were applied. The CAE analysis results show that aluminum alloy brake pedals are stronger than the conventional steel brakes pedals because the yield strength of the aluminum alloy increased by almost 97% over that of steel. Further, the structures of the cylinder and the frame were reinforced with increasing thickness of flame and were changed to suit the die-casting process. Through a durability test based on the KS standard, the strength of a prototype of the aluminum alloy brake pedal was confirmed to be sufficient.

• 한국군사과학기술학회지
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• 제22권3호
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• pp.341-352
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• 2019

LTV(Light Tactical vehicle) operating in our military requires higher levels of performance and durability to withstand harsher conditions than ordinary vehicles, as they must travel on both rough-train and off-road as well as on public roads. Recently, developed light tactical vehicle is developed by a variety of test evaluations in order to satisfy ROC(Required Operational Capability) by the requirement military group. However, there is no standardized driving test condition for satisfying the durability performance of Korean tactical vehicle. Therefore, this study aims to provide basic data to establish reliable driving test conditions by analyzing the maneuver conditions and the driving data in order to select the representative drive course required. To do this, we analyzed the future operational environment, the area of operation analysis and the driving information of light tactical vehicle.