• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.568-573
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• 2006

In order to numerically evaluate automotive hydro-formed DP-steel tubes on crash performance considering welding heat effects, the finite element simulations of crash behavior were performed for hydro-formed tubes with and without heat treatment effects. This work involves the mechanical characterization of the base material and the HAG-welded zone as well as finite element simulations of the crash test of hydro-formed tubes with welded brackets and hydro-forming of tubes. The welding heat effects on the crash performance are evaluated in efforts to improve the process optimization procedure of the engine cradle in the design stage. In particular, FEM simulations on indentations have been performed and experimentally verified for material properties of weld zone and heat affected zone.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.1
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• pp.43-50
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• 2013

This paper aims to determine the optimal location of expressway patrol vehicle stations that minimizes additional troubles caused by the delay of crash treatments. To do this, we formulate a maximum covering problem and a p-center problem weighted by crash frequency, using the shortest distance as the criteria for allocating service district, and we employ the Lagrangian relaxation algorithm to solve the former and Daskin's heuristic algorithm to solve the latter, respectively. Based on crash data of Korean expressways, the results from the proposed models are compared with the current location of patrol vehicle stations by using several indices as the level of service for crash treatment, such as maximum crash-weighted distance, average crash-weighted distance, and average access distance. The results show that the proposed models improve average access distance and time by about 10km and 10min, respectively. When allocation for service district is changed only with the fixed current location, the level of service can be also improved. The models and results proposed in this paper can contribute to improving the level of service for crash treatment on expressways. They can also provide the theoretical basis on the location decision for other various emergency facilities, and the allocation decision for floating service districts according to time-period crash data.

• Korean Journal of Metals and Materials
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• v.50 no.12
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• pp.873-882
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• 2012

Dual Phase (DP) steel which has a soft ferrite phase and a hard martensite phase reveals both high strength and high ductility and has received increased attention for use in automotive applications. To conduct structural analysis to verify vehicle safety, highly credible experimental results are required. In this study, tensile tests were performed in a strain rate range from $10^{-4}/s$ to 300/s for Sink Roll-Less (SRL) hot-dip metal coated sheets. Collision properties were estimated through simulation by LS-DYNA using the stress-strain curve obtained from the tensile test. The simulation results were compared with the actual crash test results to confirm the credibility of the simulation. In addition, a tensile test and a crash test with 2% prestrain and a baking (PB) specimen were evaluated identically because automotive steel is used after forming and painting. The mechanical behaviors were improved with an increasing strain rate regardless of the PB treatment. Thus, plastic deformation with an appropriate strain rate is expected to result in better formability and crash characteristics than plastic deformation with a static strain rate. The ultimate tensile strength (UTS) and absorbed energy up to 10% strain were improved even though the total elongation decreased after PB treatment, The results of the experimental crash test and computer simulation were slightly different but generally, a similar propensity was seen.

• Journal of the Society of Disaster Information
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• v.12 no.3
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• pp.279-285
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• 2016

Road sides safety barrier system is the last safety during traffic accident. The structural performance of a roadside safety barrier should be kept above expectations. It is possible to protect the passenger's life. End treatment part is installed in the end of the barrier it prevents a phenomenon in which for the vehicle for the guardrail during a vehicle collision it is facility of the absorbing of car crashed impact. By repeated analysis through computer simulation for improving the vehicle crash it will be able to develop crash barriers to respond appropriately to various parameters.

• Transactions of Materials Processing
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• v.24 no.5
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• pp.354-360
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• 2015

AHSS (Advanced High Strength Steels) has been increasingly employed by global automotive OEMs in order to satisfy strengthened regulations and reduce weight for fuel efficiency. Hot stamping using boron steels in AHSS increases not only formability but also strength. The typical hot-stamped automotive part is the center pillar that is critical for vehicle side impact. However, the hot-stamped part can be risky for the passenger safety caused by brittle fracture under a vehicle collision. The high power diode laser is suitable for the heat treatment giving AHSS increased elongation that prevents brittle fracture in car crash. Therefore, local softening by laser heat treatment for energy absorption area on the hot-stamped part improves crash-worthiness.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.2
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• pp.12-19
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• 2011

Real-world accident cases were investigated to understand injury characteristics of the elderly driver. A total 10 cases of car-to-car frontal crash accidents from passenger car including SUV claimed to domestic car insurance company were reviewed. The injury characteristics of the elderly were analyzed from personal information (gender, age), medical treatment record (medical certificate, curative days), vehicle information (model, air-bag, seatbelt) and damage information. This study showed that elderly driver has higher possibility of thorax injury than non-elderly's. Moreover, Injury type and severity were more severe than non-elderly driver at similar type accident conditions. Also, elderly driver's medical treatment period needs 3 times more than non-elderly driver's.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1643-1651
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• 2012

Recently, with increasing standards of living and income, environmental pollution has attracted increased interest. On account of a revision to water pollution regulations, the improvement of sewage disposal efficiency was studied. One of the ways to improve the sewage disposal efficiency is to increase the dissolved oxygen content of water in the water treatment tank. In this study, we suggest a nozzle design using a spiral and a crash mode for generating micro bubbles and thus increasing the dissolved oxygen content of water. The micro bubbles through the spiral and crash flows are generated in the nozzle. In the design of the crash mode, the development goal with regard to the bubble size was not achieved. On the other hand, a bubble size of $0-50{\mu}m$ accounted for 79.3% of all bubbles in the spiral mode. This study should contribute toward increasing the sewage disposal efficiency.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.82-87
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• 2012

The purpose of this study is to produce a side impact beam with high tensile steel using a roll forming process. The door side impact beam plays an important roll in a car because it protects passengers from external crash. The roll forming process is a continuous bending process wherein a long metal sheet is bended as it continuously passes several rolls. The characteristic of this study is that an impact beam is produced by a continuous process using a ultra high strength steel without a hardening heat treatment. A model was determined by analysing plasticity of a cross section shape considering high strength. Design parameters of the impact beam was determined by crash-analysing the model. Workpiece products were manufactured by designing dies for roll forming and setting them up in a following process line. Results of a bending test and a FEM analysis was considered and reviewed.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.141-148
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• 2002

Repair were made for front pillar, center pillar and side-step panel for lightweight vehicles with head-on and 40% off-set collision of 15 km/h in a RCAR standard. The salt dilution was sprayed and the compression tests were performed for vehicles with and without anti-corrosional treatment after repair. After 764 hours of salt-dilt sprayed test without using anti-corrosion, the mean penetration depth fur corrosion was shown to be 58% of the thickness. The resulyed decrease in bending stiffness by 10∼20% can cause reduction of the residual life and crash-absorption capability for damaged vehicles. The corrosoin safety tests showed that the anti-corrosional treatment should be made to improve the safety characteristics for a or damaged car.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.406-411
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• 2003

This paper deals with the effect of laser material processing on the EMU production technique. Material processing with lasers takes advantage of all the characteristics of laser light. The high energy density and directionality achieved with lasers permits strong localized heat- or photo-treatment of materials with spatial resolution below one micrometer. The pulsed and mono-chromatic light allows the control of depth of heat treatment or selective excitation. The laser beam can be moved to process large areas, is a sterile tool and is no subject to wear and tear. Using laser processing have taken more interests in EMU production for improving the rigidity, weight reduction, crash durability, and cost savings so that their application to auto-bodies has been increased.