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Rhee I.,Korea Railway Research Institute | Choi E.,Hongik University | Roh Y.-S.,Seoul National University of Science and Technology
KSCE Journal of Civil Engineering | Year: 2012

Approximately 35% of Korean railroad bridges are classified as steel plate girder bridges. Their connections in the vicinity of stiffeners and other secondary members toward the main girder can be progressively deteriorated owing to stress concentrations, residual stress, welding defects, and harsh environmental conditions. Most bridges of this type were built in the early 1900s, hence, they suffer from aging and progressive degradation of connection zones, and they require extensive maintenance. In accordance with these efforts, the objective of this study is to address the detailed analysis of thin steel plates with bolt connections in order to simulate a method for detecting damage due to loosening in mechanically fastened zones of steel plate girders. For simplicity, we confine this study to previous laboratory-scale experiments for bolt connection problems using PZT (Lead-Zirconate-Titanate) sensors, and we carry out a comparative study with the aid of stress wave transmission using the finite element method, signal processing using wavelets, and piezoelectricity. We carried out fundamental modal analysis and transient dynamic analysis with 3D piezoelectric elements as a sensor/actuator in an open circuit. The material deviation effect of the piezoelectric patch manufacturing process, poling directional properties, geometrical modeling of bolts (bolt pressure), waveform sensitivity, and phase/group velocity characteristics of generated Lamb waves are discussed in conjunction with time-frequency-scale domain analysis. © 2012 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. Source

Jeon K.W.,Hanbat National University | Shin K.B.,Hanbat National University | Kim J.S.,Korea Railway Research Institute
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

We describe the evaluation of the fatigue life and strength of a lightweight railway bogie frame made of glass fiber/epoxy 4-harness satin-woven composites. To obtain the S-N curve for the evaluation of the fatigue characteristics of the composite bogie frame, we performed a tension-compression fatigue test for composite specimens with different stacking sequences of the warp direction, fill direction, and 0°/90° direction. We used a stress ratio (R) of -1, a frequency of 5 Hz, and an endurance limit of 10 . The fatigue strength of the composite bogie frame was evaluated by a Goodman diagram according to JIS E 4207. The results show that the fatigue life and strength of the lightweight composite bogie satisfy the requirements of JIS E 4207. Given its weight, its performance was better than that of a conventional metal bogie frame based on an SM490A steel material. © 2011 The Korean Society of Mechanical Engineers. Source

Song K.Y.,Chung - Ang University | Yoon H.J.,Korea Railway Research Institute
Optics Letters | Year: 2010

We experimentally demonstrate that the reflection spectrum of a Brillouin dynamic grating in a polarizationmaintaining fiber can be much narrower than the intrinsic linewidth of the stimulated Brillouin scattering, matching well with the theory of a fiber Bragg grating in terms of the linewidth and the reflectivity. A 3 dB bandwidth as narrow as 10.5 MHz is observed with the Brillouin dynamic grating generated in a 9 m uniform fiber. © 2010 Optical Societv of America. Source

Lee Y.-H.,Korea Railway Research Institute
ICCAS 2010 - International Conference on Control, Automation and Systems | Year: 2010

The train control system (TCS) plays the core role to secure the safety and punctuality for railway train operation. There are various systems applied to urban transit lines which are developed differently and independently from other countries. The national standard specifications and guidelines have been established and maintained for the TCS in Korea. As the requirements of the high-efficient and economic operation of the urban transit system is getting higher, the unmanned operation of the train is moving to the limelight. Lots of systems supporting unmanned operation are being applied to the new lines such as Yongin, Busan (3rd line), Incheon (2nd line) and so on. The standard of the TCS for urban transit supports the system for unmanned operation as requirements. The function model of TCS has been established on the basis of the standard specification to analyze the requirements and behavior of the TCS. The model is also to support the test and evaluation of the system to be operated with the unmanned through the standard. ©ICROS. Source

Song K.Y.,Chung - Ang University | Yoon H.J.,Korea Railway Research Institute
Optics Letters | Year: 2010

We propose and experimentally demonstrate a high-resolution distributed measurement of the Brillouin gain spectrum in a polarization-maintaining fiber (PMF) using Brillouin dynamic grating. In our approach, acoustic waves which contain the information of the local Brillouin frequency are generated by a long pump pulse in one polarization along the PMF and are read out by a short probe pulse with an orthogonal polarization at a different optical frequency from the pump. In experiments, a distributed strain measurement with a 10 cm spatial resolution is demonstrated in a 105 m PMF. © 2009 Optical Society of America. Source

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