• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.81-90
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• 2008

It is of great importance to determine the optimum cutter spacing in TBM. In order to determine the optimum cutter spacing, a series of cutting tests by linear cutting machine (LCM) are performed with changing cutter space. This study showed that a numerical method for estimating the optimum cutter spacing could be developed by AUTODYN-3D in order to overcome the limitation of LCM test. By using this method, the optimum cutter spacing of Hwangdeung granite was estimated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.167-174
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• 2006

In this paper, the applicability of strain data to a strain-energy-based damage evaluation methodology in detecting damage in a beam-like structure is demonstrated. For the purpose of this study, one of the premier damage evaluation methodology based on modal amplitudes, the damage index method, is expanded to accomodate strain data, and the numerical and experimental verifications are conducted using numerical and experimental data. To compare the relative performance of damage detection, the damage evaluation using acceleration data is also performed for the same damage scenarios. The experimental strain and acceleration data are extracted from laboratory static and dynamic tests. The numerical and experimental studies show that the strain data as well as acceleration data can be utilized in detecting damage.

• Journal of Applied Reliability
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• v.11 no.1
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• pp.31-41
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• 2011

A strut mount is an important part of vehicles which reduces the vibration and the impact transmitted from the wheels while supporting a shock absorber and a coil spring. Rubber compounding, shape design, and process design technologies are important components to improve the functionality of a strut mount such as durability, static, dynamic, and torsional characteristics. Among them the rubber compounding technology is the key technology which dominates the quality of a strut mount. In this study a strut mount with high reliability has been developed by adopting new rubber compounding and improving the shape of the inner plate and the isolator. Through the tests for prototypes it has been shown that the durability has been improved more than 2.5 times, from about 60,000 cycles to about 160,000 cycles.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.726-733
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• 2005

It is very important to pay careful attention to construction of earthwork/tunnel transition zone for railway. The transition zone of the railway is the section which roadbed stiffness is suddenly varied. Differences in stiffness have dynamic effects and these increase the forces in the track and the extent of deformation. In this study, performance of transition zone was investigated through the field tests. The wheel loads and sleeper settlement were measured after installing field testing sections.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.534-539
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• 2001

This paper presents the critical speed analysis of geogrid-reinforced rail roadbeds on soft soil. A rail roadbed on soft ground must be designed to avoid intolerable stress in the underlying soil and to give sufficient support for the rail system. At high speeds, the deformation of rail systems will gain dynamic amplification, and reach excessive values as a certain speed, here termed critical speed is approached. The elastic Winkler foundation model was used to predict the critical speed of geogrid-reinforced rail roadbeds on soft soil and the model properties were determined by the in-situ cyclic plate load test. Based on the parametric study of elastic beam on Winkler foundation model, the critical speed increase with the increase of the flexural risidity of subgrade EI and the stiffness coefficient of Winkler foundation k. From the in-situ cyclic load tests and analysis of elastic beam on Winkler foundation model, the critical speed increase with increase in number of reinforced layer and non-dimensional value for depth of first geogrid layers and the thickness of reinforced rail roadbed u/d.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1297-1302
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• 2007

It is very important to evaluate the reliable deformational characteristics of soils not only in the analysis of geotechnical structures under working stress conditions as foundation in railroad or road system but also for the soil dynamic problems. Different testing techniques are likely to have different testing conditions as strain amplitude, stress level, loading frequency and number of loading cycles. The deformational characteristics of soils can be affected by these variables. In this paper, the effects on modulus of soils subjected to cyclic load were investigated. For the evaluation of deformational characteristics of soils subjected cyclic load, various testing such as TS, RC, TX, and FFRC tests were performed. It was shown that the modulus evaluated by various testing methods are comparable to each other fairly well when the effects of these factors were properly taken into account. For reliable evaluation, therefore, those effects on the modulus need to be considered, and measured values should be effectively adjusted to actual conditions where the soil is working.

• International Journal of Highway Engineering
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• v.14 no.5
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• pp.47-55
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• 2012

PURPOSES: SUPERPAVE binder grade tests including Multiple Stress Creep and Recovery(MSCR) test are applied to evaluate rheological properties of four polymer modified binders. METHODS: To evaluate grade of four modified binders, PG testing protocols, such as DSR, BBR and MSCR are employed. RESULTS: It is observed that MSCR test shows different performance grades especially on modified binders. Both DMP and EG binder show similar high temperature performance to SBS 5% modified binder. CONCLUSIONS: Binder Grading system in Korea need to be reviewed to properly reflect the performnace of modified binders. The binders modified with DMP and EG can be possible alternatives SBS 5% modified binder considering its performance and cost.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1144-1150
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• 2009

Appropriate vibration model is required to predict in advance the vibration level of a large vehicle which carries sensitive electronic/mechanical equipments and drives often on the unpaved and/or off-road conditions. Central tire inflation system(CTIS) is recently adopted to improve the mobile operation of military and bulletproof vehicles. In this paper, full vehicle model(FVM) having 11 degrees of freedom and equipped with CTIS has been developed for a large vehicle which has $8\times8$ wheels$\times$driving wheels. Usability of the developed model is validated via road tests for three different modes (i.e. highway, country, and mud/sand/snow modes) and for various velocity conditions. The developed FVM can be used to predict the vibration level of the large vehicle as well as to determine the driving velocity criterion for different road conditions.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.100-107
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• 2000

The hydraulic couplings have been widely used in industries, automobile, and power-station drives including ships. A mathematical analysis by which the design and application of hydraulic couplings are made is used in conventional design formulae and general roto-dynamic theories. The fluid flow of hydraulic couplings can be considered to have two component, one circumferentially about the coupling axis, and the other passing fluid from the pump to the turbine in the plane of the coupling axis. Tests have been carried out on the full-scale production coupling. The performance test consists of taking measurement of torque of the fluid coupling for three different amount of working fluid inside with various loads to the output shaft. The purpose of this research is to construct the experimental test equipments and to establish a series of performance test for the domestically developed hydraulic couplings, and to obtain experimental results which can be used to improve the performance of the hydraulic coupling and to solve the practical problems confronted in operation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.81-84
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• 1997

The hot deformation behavior of SiCp/AA2024 composites reinforced with different sizes of SiCp reinforcements (1, 8, 15, 36, and 44${\mu}{\textrm}{m}$) was investigated by hot torsion tests. The hot restoration of the composites depending on the SiCp reinforcements particle size was studied from the effective stress - strain curves. Dynamic recrystallization (DRX) was occurred in the SiCp/AA2024 composites during the hot deformation at 320 - 43$0^{\circ}C$ under a strain rate of 1.0/sec. Also, the critical strain for DRX decreased with decreasing the reinforcement size of SiCp from 44 to 8${\mu}{\textrm}{m}$. The composite reinforced with SiCp of 8${\mu}{\textrm}{m}$ showed the highest flow stress (265 MPa) and the work hardening rate at 32$0^{\circ}C$ under a strain rate of 1.0/sec.