Jeong Guk Kim

Thermographic Investigation of Hot Spots in Railway Brake Discs

Damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method. A brake disc with gray cast iron, which is currently used in Korea, was employed for this investigation. A high-speed infrared camera was used to measure the surface temperature of brake disc as well as for in-situ monitoring of hot spot evolution. From the thermographic images, the observed hot spots and thermal damage of railway brake disc during braking operation were qualitatively analyzed. Moreover, in this investigation, the previous experimental and theoretical studies on hot spots phenomenon were reviewed, and the current experimental results were introduced and compared with theoretical prediction.

Damage Characterization of Ceramic Matrix Composites (CMCs) during Tensile Testing

Nondestructive evaluation (NDE) techniques were used for the tensile damage characterization in ceramic matrix composites (CMCs). Ultrasonic testing (UT) and infrared (IR) thermography were employed to assess defects and/or damage evolution before and during mechanical testing. Prior to tensile testing, a UT C-scan and a xenon flash method were performed to obtain initial defect information in light of UT C-scans and thermal diffusivity maps, respectively. An IR camera was used for in-situ monitoring of progressive damages. The IR camera measured temperature changes during tensile testing. This paper has presented the feasibility of using NDE techniques to interpret structural performance of CMCs.

A Study on the Structural Fracture of Body Structure in Railroad Car

An evaluation was carried out by applying a load to the underframe of the freight car to determine the structural strength of the carbody of a newly manufactured freight car for transportation. This study is aimed at evaluating the safety of the underframe of the freight car under the maximum load conditions. The freight car for use in rail freight was designed mainly with SM490A steel and ASTM A441 steel for production. The carbody for rolling stock is a principal structure supporting major underframe equipment and freight. Thus, strength evaluation of this structure is very important. Both structural analysis and loading test were performed under the loading condition. Prior to evaluating structural strength, finite element method software was used for structural analyses of stress distribution in a carbody of freight car. The strain gages were attached on the carbody based on the FEM results. A vertical load test, compressive load test, measurement of deflection amount and a natural frequency measurement test were conducted.

Evaluation of Structural Strength in Body Structure of Freight Car

To check the structural strength of the body of the newly–made container freight car, load was added to the underframe of the container freight car. The objective of this study is to evaluate whether or not the underframe of a freight car under the maximal strength is safe. A freight car for transporting railroad freight is usually designed and made of SM490YA steel and SM490Y steel. The carbody of rolling stock is a principal structure that supports major equipment of the underframe and the container freight. Therefore, the strength evaluation of this structure is important. Both structural analysis and loading test were performed under the loading condition. Prior to the evaluation of structural strength, finite element method software was used for structural analyses on stress distribution in a carbody of a freight car. The strain gauges were attached on the carbody based on FEM results. The actual vertical loading test and horizontal compression loading test were conducted

Structural Safety Assessment of Railway Freight Car during Static Loading

The structural strength during static loadings for a carbody of railway container freight car was evaluated to verify the structural strength of newly manufactured carbody. The carbody of freight car was designed with SM490YA steel and stainless steel for the general railway transportation. Prior to the assessment of structural strength, finite element method (FEM) characterization was used for the stress and structural analyses on stress distribution in a carbody of container freight car. The strain gages were attached on the carbody based on the FEM results in order to measure structural strength during static loadings such as vertical and compression loadings. The actual vertical loading test and horizontal compression loading test were conducted, and the results were compared with the previous FEM results. In this investigation, the evaluation method for the structural strength in a structural component has been introduced using several engineering techniques, and experimental and theoretical results were compared.

A Study on the Structural Analysis and Loading Test of the Bogie Frame

This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.

NDE Characterization and Mechanical Behavior in Ceramic Matrix Composites

Several nondestructive evaluation (NDE) techniques, including ultrasonic C-scan, X-ray computed tomography (CT), and infrared (IR) thermography, were employed on ceramic matrix composites (CMCs) to illustrate defect information that might effect mechanical behavior and to analyze structural performance of CMCs. Prior to tensile testing, through C-scan and CT analyses results, the qualitative relationship between the relative ultrasonic transmitted amplitude and porosity based on CT was exhibited. An IR camera was used for in-situ monitoring of progressive damages and to determine temperature changes during tensile testing. Moreover, scanning-electron microscopy characterization was used to perform microstructural failure analyses. This paper describes the use of nondestructive evaluation (NDE) techniques to facilitate the understanding of tension behavior of CMCs.

Safety Diagnosis of Collided Subway Electric Multiple Units (EMUs)

Engineering safety diagnosis of collided subway electric multiple units (EMUs) was conducted for safety assessment. Several advanced engineering analysis techniques including nondestructive evaluation (NDE) techniques and stress and structural analyses programs, were performed for better understandings and exploration of failure analysis and safety concerns. NDE techniques such as ultrasonic testing and magnetic particle testing, were used to detect manufactureinduced and/or in-service defects and collision-induced flaws, and measure the dimensions of deformed and non-deformed parts on damaged EMUs due to a rear-end collision. Moreover, stress and structural analyses using commercial I-DEAS software provided important information on stress distribution and load transfer mechanisms as well as the amount of damages during the crash. A good agreement has been found between structural analysis results and the results of actual damages in EMUs during crash. In this investigation, various advanced engineering analysis techniques for the safety analysis of subway EMUs have been introduced and the analysis results have been used to rovide the critical information for the safety assessment of collided EMUs.

Analysis of Hot Spots Evolution on Brake Disc Using High-Speed Infrared Camera

The hot spot generation has been considered as the main degradation mechanism in railway brake disc. Therefore, the understanding of hot spots, also called hot judder, which is undesirable low frequency vibrations developed by non-uniform contact area between brake pad material and brake disc, is important for a better understanding of material design as well as enhancement of materials properties in railway brake disc. Also, infrared (IR) thermography is a powerful NDE technique for the characterization of thermal phenomenon in engineering components and/or systems including engineering materials. The high-speed IR camera provides the measurement of temperature change during brake operation as well as the images of temperature contour on the brake disc surface. In this investigation, damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method. Moreover, based on obtained thermographic images of hot spots, the hot spots and thermal damage of railway brake disc during braking operation were qualitatively analyzed.

A Study on the Fatigue Test of Bogie Frame by Stress Measurement

This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.