Taek Yul Oh

Transfer matrix modelling for the 3-dimensional vibration analysis of piping system containing fluid flow

For three dimensional vibration analysis of piping system containing fluid flow, a transfer matrix formulation is presented. The fluid velocity and pressure were considered, that coupled to longitudinal and flexural vibrations. Transfer matrices were derived from direct solutions of the differential equations of motion of pipe conveying fluids, and the variations of natural frequency with flow velocities for straight and curved pipes were investigated. The results were confirmed to the corrections of known data. The scheme of this study can be easily applied to the related fields, using small size personal computers with core memory about 200kbytes.

A Study on the Evaluation Methods of Running Safety for Railway Vehicle

The important factor to evaluate the running safety of a railway vehicle would be the interaction force between wheel and rail(derailment coefficient), for which is one of important factors to check the running safety of a railway vehicle that may cause a tragic accident. Especially, a newly developed vehicle that first runs commercially requires necessarily the measurement and evaluation of derailment coefficient for securing the safety of a vehicle while measuring the derailment coefficient in view of securing running safety could be the more important factor than any other factors. In the meanwhile, it should be also measured the interaction force between wheel and rail in view of track maintenance as well as running safety because increased weight of a vehicle while it is running over a railway may cause damages or destruction on track components such as rails, sleepers and etc consisted of track and any rapid distortion of track. For the reason, the study was intended to evaluate the curving performance and the running safety from the analyses of dynamic running properties, manufacturing wheel axes to measure the working operation of wheels/rail, static load test, derailment coefficient calculated by running test on main track, ratio of wheel unloading, lateral force tolerance of the vehicle that is newly manufactured and commercially running on Gwangju Urban Railway and describe the results.

Effect of Osteoporosis on Natural Frequencies in Mouse Femur: Vibration Test and Micro-CT Based Finite Element Analysis

In this study, the change of the natural frequencies in mouse femurs with osteoporosis was investigated based on a vibration test and a finite element. Three groups of the femurs include the osteoporotic group, the treated group and the normal group. In the vibration test, the natural frequencies were measured by the mobility test. For the finite element analysis, the micro finite element model of the femur was reconstructed using the Micro-CT images and the Voxel mesh generation algorithm. From the results, the averaged natural frequencies in the osteoporotic group were the highest, followed by those in the treated group. The finite element models were validated within 15% errors by comparing the natural frequencies in the finite element analysis with those in the vibration test. The developed Micro-CT system, the Voxel mesh generation algorithm, the presented finite element analysis, and vibration test could be useful for the investigation of the structural change of the bone tissue, and the diagnosis and the treatment in the osteoporosis.

Running Safety Estimation of Korean Style High Speed Railway Vehicle

For the safety of railway, it should be evaluated for the running safety by measuring the derailment coefficient[1,2]. Although railway has run the fixed and maintained rail, some of railway is derailed. This report shows the results that performed the static load test, wheelset manufacturing for test, main line running test on the basis of the derailment theory and experience. It is executed main line test into more than 200km/h for estimating the running safety of korean style high speed railway vehicle. As the test results, could confirm the running safety of high speed railway vehicle from the results of the wheel unloading, lateral force, derailment coefficient etc. Derailment coefficient was less than 0.6, and lateral force allowance limit and wheel load reduction ratio were enough safe. Nomenclature P : Vertical force, Ton Q : Lateral force, Ton dP : Wheel unload, Ton α : Angle of contact between wheel and rail, rad μ : Friction coefficient Introduction Important factor checked by running safety of railway vehicle is derailment coefficient. Derailment coefficient in railway is very important item because it is directly concerned in big accident. Interaction force should be measured between wheel and rail. Namely, the relationship of wheel load and lateral load could secure the railway safety. The wheel load contains the weights of the carbody, luggage, people, equipments etc. The lateral load is varied by curvature of the rail. The railway is important transportation means which has many roles such as a safety and a regularity. That is a results from various confidential performance tests and evaluations of the system. The railway system consist of various subsystems vehicle, power supply, signal, communications, track structures, operations, etc. Among them, as an item of safety evaluation, there is a measurement of wheel/rail force, so called a measurement of derailment coefficient. This is a very important item because derailment of a railway will bring about a big accident. Especially it is more important in high speed railway which operation speed is over two times as fast as existing railway vehicle. this paper shows the wheelset manufacturing(strain gauge mounting, wheatston bridge connection etc.) Wheelset for test of the derailment coefficient Wheelset processing and selection of the gauge mounting points. Because motor cars wheel plate of the high speed trains are curved shape, it should be happened mutual interference between vertical load and horizontal load[3,4]. Left and right of the wheel should be manufactured symmetrically that the 20mm diameter angled 60 for measuring the derailment coefficient. The diameter of the wheel is Ø920mm. So we processed the Ø60mm holes 90° apart at the position of Ø538mm for the mounting Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 1989-1994 doi:10.4028/www.scientific.net/KEM.270-273.1989

P-09 THE MECHANICAL PROPERTIES OF TRABECULAR BONE IN KNEE JOINT

In this study, we performed the compressive strength test of trabecular bone in knee joint for measuring the elastic modulus and ultimate strength. The main knee joint is femorotibial articulation between the lateral and medial femorotibial condyle. In the case of osteoarthritis, some patients have only medial condylar osteoarthritis. We performed the mechanical test for comparison the difference of the each condylar strength. We used diamond core-drill and linear precision saw for making the specimens. Specimens were cored from both condyle in distal femur and proximal tibia in fresh cadaver (male 10, female 12), and tested by universal test machine with temperature control saline circulation system. Results of the test in distal femoral parts, averaged elastic modulus was for male, for female. Averaged ultimate strength was for male, for female. Male was 2.4 times stronger than female. In the proximal tibial parts, averaged elastic modulus was for male, for female. Averaged ultimate strength was for male, for female. Male was 1.5 times stronger than female. In the distal femoral condyle, medial condyle had more strength than lateral condyle at middle region. But lateral condyle had more strength than medial condyle at anterior & posterior regions (p

The Cause Examination of the Crack of the End Beam for Welding Structure Type Bogie

Bogie is the connection device between carbody and wheel in railway vehicles. It is the core part that exert a important effect on the passenger safety and running safety. Bogie largely consists of the bogie frame, suspension, air brake system and wheel set. A static and dynamic load have acted on it complexly. When the bogie is designed, a finite element method, static load test, fatigue test, running test should be considered. A welded structure type bogie was developed for high speed freight car. But some bogie frames have the problems in end beam. There were some cracks ine end beams. The crack situation of the end beam have a bad effect on the brake system. In that case, the cars would be in danger of derailment. This report shows the cause of end beam crack, improvement method. In order to clear the crack cause, many tests were tried. The test result concludes that the crack cause of the end beam is not the brake load but the vibration at the real line running on the track. It is estimated that the improved car which end beam was reinforced was safe enough within permitted life of the car (25years). On the basis of the results, the existing end beam was improved. The safe of the improved end beam was proved by real line test on the track. The operation of freight car have no problems any more.

Development of a Torsion-Free Brake Shoe Holder Hanger for the Bogie of Railway Freight Car

Among welded structure bogies used for high speed freight cars, failures in an end beam have been found in a number of bogies manufactured in between 1999 and 2000. A freight car suffers from a harsher loading condition and it uses a tread brake without a secondary suspension system. It is presumed that the cause of the failure on the end beam is not the vertical loading by the cargo and the vehicle but the force exerted by the brake. The failure at the end beam makes the brake system useless and can cause a derailment in the worst case. In this study, we propose a simple torsion-free brake shoe holder hanger to remove torsion of hanger bracket. Also performed are the finite element analysis and the on-board test for the developed part. Comparison tests verified the applicability of the torsion-free brake shoe holder hanger.