• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.493-498
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• 2015

The fuel cell vehicle is a type of hydrogen vehicle which uses a fuel cell to produce electricity, powering its on-board electric motor. The fuel cell vehicle driving principle is completely different from the internal combustion engine vehicle. In order to ensure the durable quality of the fuel cell vehicle, durability test mode considering the characteristics of the fuel cell must be developed. In this study, we derived the durability test mode profile through collecting and analyzing fuel cell vehicle driving data. Then, the accelerated durability test mode is developed by adding degradation conditions and is experimentally validated to have an acceleration factor of 5~6.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.396-408
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• 2016

Rock fracture mechanics has been widely applied to various fields of rock and civil engineering. But most researches covered mode I behavior, though mode II behavior is dominant in rock engineering. Until now, there is only one ISRM suggested method for mode II toughness of rock. A new SCC (Short Core in Compression) mode II toughness test method was developed considering 1) application of confining pressure, 2) easiness of notch creation, 3) utilization of existing equipment, 4) simple test procedure. The stress intensity factors were determined by 3D finite element method considering line and distributed loading conditions. The tests with granite specimens were carried out using MTS 815 rock test system with a loading rate of 0.002 mm/s. The mean value of mode II fracture toughness of granite showed $2.33MPa{\sqrt{m}}$. Mode I toughness of the same granite was $1.12MPa{\sqrt{m}}$, determined by Brazilian disk test and $K_{IIC}/K_{IC}=2.08$. The smooth fracture surface with rock powder formation also supported mode II behavior of SCC method. The SCC method can be used for the determination of mode II fracture toughness of rocks based on the current results.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1127-1132
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• 2003

Suspension system of vehicle have enough endurance during its life time to protect passenger. Spring is one of major part of vehicle. Thus, a fatigue strength evaluation for leaf spring based on road load response was carried out. At first, strain of leaf spring is measured on the city condition and proving ground condition. And next, the damage analysis of road load response data was carried out. And fatigue test of leaf spring were also carried out. Based on -N life relation, fatigue life of leaf spring was evaluated at belgian mode, city mode and drawing test specification. After that, it is compared the design life of leaf spring and evaluated fatigue life by belgian mode, city mode and drawing test specification. From the above, the maximum load-fatigue life relation of leaf spring was defined by test. and new test target of belgian mode and city mode was proposed to accept design specification of leaf spring. It is expect that proposed test target can verify leaf spring fatigue endurance at specific road condition.

• Journal of ILASS-Korea
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• v.23 no.4
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• pp.234-243
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• 2018

Since September 2017, a small diesel vehicle certification test mode has been enhanced from NEDC to WLTC. The main reason for the change of the certification test mode is that the certification test mode of the emission control standard of the diesel vehicle does not sufficiently reflect various driving patterns of the actual roads. Several automakers have developed after-treatment systems such as LNT, SCR, and DPF to meet enhanced emissions regulations. In this study, four small diesel cars were selected for sale in Korea, and the exhaust gas measurement test was performed in the WLTC mode, which reflects the driving characteristics of the actual roads. As a result of test, LNT vehicle exceeded Euro 6 NOx regulation and SCR vehicle satisfied Euro 6 NOx regulation. In addition, both LNT and SCR systems showed high NOX emission characteristics due to speed, RPA and Vxa. For the PN, all test vehicles were fitted with a DPF and met the Euro 6 PN regulations, with similar PN emissions results in LNT and SCR system.

• Journal of the Korean Society of Safety
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• v.28 no.6
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• pp.36-41
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• 2013

Previous study showed that delamination region in concrete structures can be successfully visualized using mode shapes of delaminated concrete section. However, modal tests for this purpose to obtain mode shapes of the delaminated concrete section may not be applicable in practice since, to correctly obtain the mode shapes of the section, the location and the shape of the delamination region in a structure should be known in advance. Unfortunately those are normally unknown in a real structure. Therefore, a moving forward test method may be useful to obtain the mode shapes of the concrete section when the location and the shape of the delamination region are not known. In this study, impact-echo testing based mode shape estimation technique is proposed and experimentally validated for visualization of delamination region.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.62.2-62.2
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• 2011

To guarantee 20-25 years to the lifetime of the PV modules without failure, reliability test of the module is very important. Field-aged test of the outdoor environment is required. However, due to time constraints, accelerated testing is required to predict the lifetime of PV modules and find causes of failure. Failure is caused by many complex phenomena. In this study, we experimented two accelerated tests about corrosion and fatigue, respectively. First, temperature cycling test for fatigue were tested and Coffin-Manson equation was analyzed. Second, damp heat test for corrosion were tested and Eyring equation were analyzed. Finally, using two-mode failure model, we suggest a new lifetime model that analyze the phenomenon by combining two kinds of data.

• Journal of the Korean Society of Safety
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• v.33 no.4
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• pp.15-20
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• 2018

In this study, we have performed the Cone Calorimeter test and Smoke density test in accordance with ISO 5660-1 and ASTM E662 respectively to check the smoke production characteristics of rubber flooring materials for railway vehicle. Early in the ASTM E662 test, more smoke was produced in the flame mode test than non-flame mode test, but later more smoke was produced in non-flame mode test. The correlation($R^2$) between TSR(Total Smoke Release) by ISO 5660-1 and Ds(Specific Optical Density) by ASTM E662 Flame mode was 0.782. The $R^2$ between TSR by ISO 5660-1 and Ds by ASTM E662 Non-flame was 0.930.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.5
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• pp.614-622
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• 2018

Based on army operating road profile, the endurance test of military vehicle aims to reproduce the similar loading conditions with mixture of proving ground tracks. It is so called as endurance test mode and its optimal generation is important to meet high reliability of endurance test. In this paper, proving ground optimization is proposed to achieve a close match to the target profile. Several performance measures such as torque-revolution counts or transmission ratio for the powertrain system can be considered as one of the objective functions. However, the one-side optimal endurance test mode may give the poor solution in the whole system point of view. To incorporate several goals simultaneously, this paper employs multi-objective optimization technique to generate endurance test mode. One of the most widely used method, weighted-sum method is applied here and the case study is discussed.

• Smart Structures and Systems
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• v.13 no.5
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• pp.797-819
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• 2014

This paper presents a theoretical algorithm for constructing the mode shapes of a bridge from the dynamic responses of a test vehicle moving over the bridge. In comparison with those approaches that utilize a limited number of sensors deployed on the bridge, the present approach can offer much more spatial information, as well as higher resolution in mode shapes, since the test vehicle can receive the vibration characteristics of each point during its passage on the bridge. Basically only one or few sensors are required to be installed on the test vehicle. Factors that affect the accuracy of the present approach for constructing the bridge mode shapes are studied, including the vehicle speed, random traffic, and road surface roughness. Through numerical simulations, the present approach is verified to be feasible under the condition of constant and low vehicle speeds.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.64-75
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• 2003

This study presents a newly suggested test method of Mode II fracture toughness measurement called "Punch Through Shear Test" which was originally proposed by Backers and Stephansson in 2001. The purpose of this study is to check the validity of the suggested testing method by performing Mode II fracture toughness tests for Daejeon Granite. In addition, the optimal specimen geometry for the testing and the relation between Mode II fracture toughness and confining pressure were also investigated. Fractured surface was observed to be very smooth with lots of rock debris which came off fracture surface which obviously implies that the surface was sheared off. This confirms that Mode II fracturing actually occurred. In addition, numerical analyses including continuum analysis, particle flow code analysis and crack propagation simulations were performed. Results of these numerical analyses indicated that the cracks occurred in the specimen were predominantly in Mode II and these cracks led to failure of the test specimen. From this investigation, it can be concluded that the newly suggested "Punch Through Shear Test" method provides a reliable means of determining the Mode II fracture toughness. fracture toughness.