Tae-Soo Kwon

Evaluation of Crash Energy Absorption Capacity of a Tearing Tube

This paper deals with the numerical prediction of energy absorption capacity of a tearing tube, which can absorb the crash energy through expanding and axial splitting processes. It is important to consider the dynamic material behavior and fracture characteristics of tube material in order to simulate the deformation behavior of a tearing tube accurately. Uniaxial tensile tests are performed in order to obtain the flow stress curve and the fracture strain of a tube material according to the strain rate. Quasi-static tensile tests were carried out in the range of strain rates from 0.001/sec to 0.01/sec using a static tensile testing machine. Dynamic tensile tests were conducted at strain rates ranged from 0.1/sec to 300/sec using a high speed material testing machine. These dynamic material properties are utilized to finite element analysis through a user material subroutine of ABAQUS/Explicit. Especially, ductile fracture criteria are adopted in order to describe the fracture characteristics of a tube material during axial splitting process. Dynamic tearing cases are simulated and the reliability of numerical results is verified by comparing them with the experimental results in dynamic tearing tests. The simulated results accurately predict the onset of fracture in axial splitting process and the energy absorption capacity has a good agreement with experimental results.

Study on a 2-Dimensional Dynamic Modeling Technique to Analyze the Overriding Phenomena of Rollingstock

This paper proposed a new 2-D multi-body dynamic modeling technique to analyze overriding behaviors taking place during train collision. This dynamic model is composed of nonlinear springs, dampers and masses by considering the deformable characteristics of carbodies as well as energy absorbing structures and components. By solving this dynamic model for rollingstock, energy absorbing capacities of collision elements, accelerations of passenger sections, impact forces applied to interconnecting devices, and overriding displacements can be well estimated. For a case study, we chose KHST (Korean High Speed Train), obtained crush characteristic data of each carbody section from 3-D finite element analysis, and established a 2-D multi-body dynamic model. This 2-D dynamic model was simulated under the train-to-train collision scenarios, and evaluated with 3-D virtual testing model. It was founded from the simulation results that this 2-D dynamic model could well predict overriding behaviors, and the modeling technique of carbody deformation was very important in overriding estimation.

A Study on Design and Dynamic Characteristics of Tearing Tubes Applied in Tram

Abstract : The paper aims to design and verify tearing tube type energy absorption device applied in tram to ensure safety in case of collision accident. Energy capacity of tearing tube is determinated based on EN15227 and Standard Collision Scenarios Criterion in Detail in Republic of Korea. Tearing tube is designed based on theoretical model suggested by X.Huang et al. and assumption by T.Y. Reddy et al. Real scale collision tests are conducted to analyze the energy absorption characteristics and deformation mode. Bending of curl tips is absorbed collision energy when curl tips and tube body are contacted to each other from the tests and we suggest and include the formula on bending of curl tips in theoretical model. Key words :Tram(트램), Tearing tube( 테어링 튜브), EN15227(EN 규격), Collision test( 충돌 시험), Bending of curl tips(컬 끝의 굽힘) 1. 서 론 1) 본 논문은 국내에 새로 도입되는 트램이라는 교통수단의 충돌 사고 시 안전을 확보하기 위한 장치를 설계 및 검증하는 것을 목적으로 한다.Thin-wall 튜브는 에너지흡수부재의 한 종류로 많은 연구가 진행되었다. A. G. Olabi 등 1) 은 thin-wall 튜브의 다양한 에너지 흡수 매커니즘에 대하여 소개하였다. S. R. Reid

Characterization of dynamic tensile and shear strength of safety bolts in light collision safety devices of a train

This paper introduces design strategy to develop safety bolts in light collision safety devices under dynamic tensile and shear loading conditions. The light collision safety device is an energy absorbing one for low speed collision of a train. An energy absorbing scenario in the device has several sequential stages. Tension and shear bolts are the key components which make the sequential energy absorbing scenario operated by a series of failures at the specific collapse load. Exact failure loads of tension and shear bolts at crash conditions were determined in aid of finite element analysis considering the dynamic material properties of component materials. Failure loads of tension and shear bolts designed were verified with experiments using tension and shear type jig sets at quasi-static and dynamic loading conditions. Strain gages were attached to both the parallel section of tension bolts to measure the load response acting on tension bolts and the jig set to measure the load responses acting on shear bolts. The quasi-static and dynamic experiments as well as the numerical analysis explained above predicted the load capacities of tension and shear bolts accurately for the crashworthiness design.

Study on 3-D Simulation for Overriding Evaluation of Urban Train

In this paper, we propose a collision simulation technique the evaluation of urban trains. We perform simulation that include a dynamics bogie model which represents the dynamic behavior of bogies and a finite-element model that can model crash behavior. We perform simulation in accordance with the 40-mm vertical offset head-on scenario for overriding the evaluation of the EU and domestic crashworthiness regulations. We evaluate the overriding by the vertical displacement of the wheelset using the overriding evaluation standard. Finally, if proposed simulation technique is applied, we can evaluate the overriding for urban-train crashworthiness regulations.

Full-Scale Crash Testing Facilities for a Railway Vehicle

KRRI (Korea Railroad Research Institute) has successfully performed several tens of impact tests of crash parts for a railway vehicles. Full-scale crash testing facilities were newly established including a crash barrier, dynamic load cell, high speed DAS (Data Acquisition System), a laser displacement sensor, dummies, a motor car and etc. This paper introduces series of impact test results using full-scale crash testing facilities. The impact test for railway vehicles consists of three categories, i.e. single item tests, module tests and crash structure tests. For single item tests, expansion tubes, composite tubes, collapsible tubes and etc. were tested. For module tests, a crash test of a light collision safety device with an expansion tube and triggering mechanism was performed. For crash structure tests, several full-scale crash tests were performed including front-end and cab structures with or without dummies. The crash testing equipment developed will be able to evaluate the occupant safety as well as the structural crashworthiness of a train.Copyright