• Journal of the Korean Society for Railway
• /
• v.19 no.2
• /
• pp.204-212
• /
• 2016

The soils used as trackbed in Korea are selected using USCS utilizing basic soil properties such as Grain Size Distribution(GSD), % passing of #200 sieve ($P_{200}$), % passing of #4 sieve ($P_4$), Coefficient of uniformity ($C_u$), and Coefficient of curvature ($C_c$). Degree of compaction of the soils adapted in the code by KR should be evaluated by maximum dry density (${\gamma}_{d-max}$) and deformation modulus $E_{v2}$. The most important influencing factor that is critical to stability and deformation of the compacted soils used as trackbed is stiffness. Thus, it is necessary to construct a correlation between the modulus and the basic soil properties of trackbed soil in order to redefine a new soil classification system adaptable only to railway construction. To construct the relationship, basic soil test data is collected as a database, including GSD, maximum dry unit weight (${\gamma}_{d-max}$), OMC, $P_{200}$, $P_4$, $C_u$, $C_c$, etc.; deformation modulus $E_{v2}$ and $E_{vd}$ are obtained independently by performing a Repeated Plated Bearing Test (RPBT) and Light Weight Deflectometer Test (LWDT) for ten different railway construction sites. A linear regression analysis is performed using SPSS to obtain the relationship between the basic soil properties and the deformation modulus $E_{v2}$ and $E_v$. Based on the constructed relationship and the various obtained mechanical test data, a new soil classification system will be proposed later as a guideline for the design and construction of trackbed foundation in Korea.

• Journal of the Korean Society for Railway
• /
• v.8 no.4
• /
• pp.299-307
• /
• 2005

In general, structural integrity of rolling stock structures should last more than 25 years. During the lifetime corrosive degradation occurs. For structural design and diagnosis, quantitative relationship between corrosive degradation and variation of mechanical properties such as tensile strength and fatigue strength is needed. In this study, first of all we established the atmospheric corrosion test procedure. At regular intervals using specimens of SM490A and SS400 on the atmospheric corrosion test bed, we carried out tensile and fatigue tests. The fatigue strength decreases as the atmospheric corrosion period increases. In addition we studied the effect of post-weld heat treatment on the tensile and fatigue behaviour and performed electrochemical corrosion tests.

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.778-782
• /
• 2004

Floating floor structure, which is mainly adopted for reducing interior noise of railway vehicle, is known that it is superior to single wall in respect of sound transmission loss. The dynamic characteristic of the support in the floating floor that is one of the important design variables in floating floor structure can change the sound and vibration insulation properties of it. From excitation test, the dynamic stiffness and loss factor of the support are evaluated. They are used as input parameter for analyzing the sound transmission loss of floating floor. Predicted transmission loss is compared with the prototype-car test results.

• Proceedings of the KSR Conference
• /
• 2001.10a
• /
• pp.410-415
• /
• 2001

Conventional Korean tunnel portals require a lot of overburden as, fer static reasons, about 1.5 to 2.0 times the tunnel diameter is needed for the height in order to achieve a sufficient arching effect. Thus, considerable movement of earth and support constructions are required which lead to undesirably large changes of and damage to the environment. With a massively designed pipe roof, tunnels with little overburden can be built. For the effective construction of a pipe roof as an advancing safeguarding method, the following properties are indispensable： stability, insensitivity to settling and drilling accuracy. With the AT casing system a new pipe roof method has been developed which on the one hand entirely combines the properties mentioned last, and which on the other hand permits safe, economical and environmentally friendly construction of tunnels at low overburden heights of 3 to 6 m.

• Journal of the Korean Society for Railway
• /
• v.9 no.6 s.37
• /
• pp.695-700
• /
• 2006

This study investigates the effects of the material properties and the fatigue behavior in the SM490A material specimens due to the low-temperature atmosphere. In the fatigue behavior, the low-temperature affects the fatigue life. As the temperature get low, the fatigue limit increase, also As the yield strength and the tensile strength increase, the impact absorbed energy decrease. The difference of fatigue lift represents to normal distribution and it is larger between the room temperature and the low temperature, but in the result of the cumulative density function, the effect of temperature is not too large on it.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.2053-2058
• /
• 2008

Extruded aluminium panels have been widely used for railway vehicle structures because of their light specific weight and other merit. In the past, GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) were mainly used to join aluminium panels. But recently friction stir welding (FSW) is widely used. due to its lots of advantage. In this study aluminium A6005-T6 which are used for car body structures was chosen. The influence of main parameters such as : pin rotating speed, welding speed, shoulder diameter, pin length and tilting angle on mechanical properties was examined. Optical microscope observation, micro hardness test and tensile test were carried out. Tensile strength of the stir welded plates is 74% of that of the base material.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.601-605
• /
• 2004

Railway wheel is the important element of rolling-stock in the viewpoint of running safety. Thus, the material properties of strength, fatigue crack, durability are needed, and the standards for test and criteria of whee] are established to guarantee quality of wheel. In the meantime, the suppliers for wheel in domestic are varied from domestic monopolization to diverse company of China, Russia, Czech Republic, etc. The uniform quality of wheel is important from a maintenance point of view. We collected wheel samples of diverse vendors to analyze the uniformity of wheel on the basis of korea national standard. We tested material properties and analyzed the test data statistically.

• Proceedings of the KSR Conference
• /
• 2005.11a
• /
• pp.211-216
• /
• 2005

Resonance of railroad bridge can be broken out when natural frequency of the bridge coincides with exciting frequency of moving forces. In order to avoid aforementioned unpleasant response of the structure, exact determination of dynamic structural properties is important to understand dynamic behavior of the structure under moving train loads. In the present paper, a 25 meters long full scale IPC girder and 15m Precom girder models were fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios. In the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied to obtain frequency response functions more exactly and the modal parameters are evaluated varying with structural status.

• Proceedings of the KSR Conference
• /
• 2003.10c
• /
• pp.383-388
• /
• 2003

This study investigates the change of the temperature and mechanical properties of the braking disk for the railway vehicle. The average temperature is measured about $100^{\circ}C$ and the maximum temperature is measured over $200^{\circ}C$ by non-contact sensor from Seoul to Chunan. In the $20^{\circ}C-300^{\circ}C$, the $0.2\%$ offset yield strengths of the disk (GC25-30 material) are a little down to the reference value, but the linear relation of tensile test result is not find from the linear change of temperature. However, $J_{IC}$ values have the inverse proportion to the temperature, and the $J_{IC}$ value at $200^{\circ}C$ decrease $30.55\%$ from the $J_{IC}$. value of the room temperature. This result means that the crack length on the braking disk is rapidly increase at $200^{\circ}C$

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.104-111
• /
• 2006

The non-linear properties of rubber material which are described as strain energy function are important parameter to design and evaluate of rubber spring. These are determined by material tests which are uni-axial tension and bi-axial tension. The computer simulation using the nonlinear element analysis program executed to predict and evaluate the load capacity and stiffness for chevron spring. In order to investigate the heat-aging effects on the rubber material properties, the acceleration test were carried out. Compression set results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the compression set test, several useful life prediction for rubber material were proposed.