• 한국도로학회논문집
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• 제15권2호
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• pp.139-147
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• 2013

PURPOSES : This study aims to draw differences between primary and secondary crashes by comparing crash characteristics and to identify the unique characteristics of secondary crashes for making better effective countermeasures to reduce secondary crashes. METHODS : The characteristics of secondary crashes were compared to those of primary crashes through a two sample proportional test (z-test). RESULTS : The results showed that vehicle-to-vehicle crashes and vehicle-to-person crashes are dominant crash types in secondary crashes. Compared to primary crashes, secondary crashes were likely to occur during nighttime. With respect to season and weather, the proportion of secondary crashes occurred during winter and in snowy weather is relatively higher than that of primary crashes. The main causes of primary crashes were found to be drowsiness, speeding, and exaggerated steering control, whereas main factors affecting the occurrence of secondary crashes were negligence of keeping eyes forward and no keeping a safe distance as expected. CONCLUSIONS : The characteristics affecting the occurrence of secondary crashes are different from those of primary crashes, indicating that proper countermeasures should be established to prevent the occurrence of secondary crashes on highways.

• Steel and Composite Structures
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• 제28권2호
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• pp.179-194
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• 2018

Reliable and accurate method of computationally aided design processes of advanced thin walled structures in automotive industries are much essential for the efficient usage of smart materials, that possess higher energy absorption in dynamic compression loading. In this paper, most versatile components i.e., thin walled crash tubes with different geometrical profiles are introduced in view of mitigating the impact of varying cross section in crash behavior and energy absorption characteristics. Apart from the geometrical parameters such as length, diameter and thickness, the non-dimensionalized parameters of average forces which control the plastic bending moment for varying thickness has explored in view of quantifying its impact on the crashworthiness of the structure. The explicit finite element code ABAQUS is utilized to conduct the numerical studies to examine the effect of parametric modifications in crash behavior and energy absorption. Also the simulation results are experimentally validated. It is evident that the circular cross-sectional tubes are preferable as high collision impact shock absorbers due to their ability in withstanding axial and oblique impact loads effectively. Furthermore, the specific energy absorption (SEA), crash force efficiency (CFE), plastic bending moment, peak force responses and its impact for optimally tailoring a design to cater the crashworthiness requirements are investigated. The primary outcome of the study is to provide sufficient information on circular tubes for the use of energy absorbers where impact oblique loading is expected.

• Structural Engineering and Mechanics
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• 제70권2호
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• pp.153-168
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• 2019

In this paper, energy absorption characteristics of circular windowed tubes with different section shapes (circular, ellipse, square, hexagon, polygon and pentagon) are investigated numerically and experimentally. The tube possesses the same material, thickness, height, volume and average cross sectional area which are subjected under axial and oblique quasi-static loading conditions. Numerical model was constructed with FE code ABAQUS/Explicit, the obtained outcome of simulation is in good matching with the experimental data. The energy absorbed, specific energy absorption, crash force efficiency, peak and mean loads along with the collapse modes with their initiation point of simple and windowed tubes were evaluated. The technique for order of preference by similarity ideal solution (TOPSIS) approach was employed for assessing their overall crushing performances. The obtained results confirm that efficacy of crash force indicators have improved by introducing windows and tubes with pentagonal and circular windows achieves the maximum ranking about 0.528 and 0.517, it clearly reveals the above are best window shapes.

• Journal of Welding and Joining
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• 제29권5호
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• pp.72-81
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• 2011

In the present day, the needs of new steel for lightweight car-body have been increased in the automotive industry. however, the resistance spot welding is difficult to apply to the new steel because of the narrow weld current range and defects. As the solutions to these problems, adhesive bonding process is proposed. Adhesive bonding which reduce noise and vibration can be applied to joining the new steel. In this study, crash tests of b-pillar applied the resistance spot welding, structural adhesive bonding, the mixture of the structural adhesives and resistance spot welding were performed. And FEM crash model for b-pillar applied the structural adhesive bonding was developed. The results of experiment and analysis on b-pillar crash test were compared to verify the validity.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.135-141
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• 2005

Currently many safety assessment tests are conducted by crashing a vehicle against a rigid or deformable barrier. It is quite rational to evaluate crash performance of a vehicle in a barrier test in terms of vehicle stiffness and strength. However, there has been a lot of debate on whether barrier testing is a duplicate of real world crash collisions. One of the issues is car to car compatability. There are two essential subjects in compatability. One is partner-protection when crashing into another vehicle and the other is self-protection when struck by another vehicle. When considering a car to car frontal crash between a mini car and a large heavy car, it is necessary to evaluate human body stiffness of each vehicle. In this study, in order to evaluate the compatability of cars in car-to-car crashes, four tests were conducted. Test speed of each car is 48.3km/h, and the overlap of the mini and large car is $40\%$, and the overlap of the small cars is $100\%$. In all tests, only a drive dummy is used. The test results of the car to car crash test show that vehicle safety standard of mini car is not satisfied compared with large heavy car and HIC value of mini car is higher than large car. In this case observed that the relatively lower stiffness and weight of the mini car resulted in absorbing a large share of the total input energy of the system when crashed into the large heavy car.

• 대한토목학회논문집
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• 제40권2호
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• pp.167-175
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• 2020

1979년 Herman과 Prigogine에 의해 제안된 Two-fluid Model은 도시부 네트워크의 운영성을 설명하는 거시적인 모형으로서 네트워크 내 정지차량 비율과 평균 주행속도의 관계에 기초하고 있다. 이러한 Two-fluid Model의 파라미터는 교통류 특성에 따라 변화하므로 파라미터를 통한 운영성 분석 시 교통류 상태 변화를 규명하는 단계가 수반되어야 한다. 이에 본 연구는 Two-fluid Model의 파라미터를 활용하여 강우에 따른 교통사고 위험도를 비교하였고, 이로 인한 주행 행태가 도시부 네트워크의 운영성에 영향을 미침을 확인하였다. 먼저 Two-fluid Model 파라미터 추정결과, 맑은 날 대비 비가 온 날의 네트워크 운영성이 저하된 것으로 나타났다. 이후 운전자의 교통사고 위험인지 모형 계수를 산출하고 강우 여부에 따른 교통사고 위험도와 그에 따른 주행 행태 변화를 분석하였다. 오전·오후 시간대 모두 운전자는 맑은 날과 동일한 속도를 유지하였을 때 비가 온 날의 교통사고 위험도가 높을 수 있기 때문에, 위험도를 낮추기 위해 주행속도를 감속하는 경향을 보였다. 그러나 맑은 날 보다 비가 온 날의 위험도는 여전히 높은 것으로 파악되었다. 향후에는 도시부 교통망의 거시적 운영성과 사고 위험도 간의 관계를 보다 다양한 네트워크에서 분석하고 동시에 개선할 수 있는 방안을 연구해볼 필요가 있겠다.

• 한국도로학회논문집
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• 제11권1호
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• pp.153-164
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• 2009

본 연구에서는 경찰청에서 제공한 2006년 전국 37,589개의 보행자 사고 자료에서 나타난 보행자 사고 심각도를 분석했다. 이를 위해 본 연구에서는 보행자사고 심각도에 영향을 미칠 것으로 예상되는 주요 요인을 미리 선정하여, 그 영향을 순서형 로짓 모형(Ordered Logit Model)을 통해 분석했다. 이모형은 사고 심각도와 같이 종속변수가 순서형으로 표시되는 경우 매우 유용한 결과를 제시하는 것으로 알려져 있어서 본 연구에서 사용했다. 본 연구는 다음과 같은 결과를 나타냈다. 첫째, 우리나라 보행자 사고 심각도는 운전자와 보행자로 나타나는 인적요인에서 성별, 나이, 음주여부에 영향을 많이 받는다. 둘째, 기타 요인에는 차량, 도로기하구조, 날씨, 시간대가 포함된다. 셋째, 보행자 사고 심각도는 계절요인과 무관하다. 끝으로, 보행자 사고 심각도 분석을 위해 순서형 로짓 모형을 적용하면 매우 적절한 분석결과를 얻을 수 있다. 결론적으로 본 연구는 우리나라 보행자 사고 심각도는 사람들이 전통적으로 생각하는 것과 같은 방식인 것으로 확인했다. 이 결론은 본 연구에서 사용한 사고자료에 국한한 것이며, 이 결론을 일반화시키려면 추후 연구가 필요하다.

• 대한교통학회지
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• 제29권4호
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• pp.43-51
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• 2011

교통사고는 단일요인에 의해 발생하기도 하지만 대부분 다양한 요인이 복합적으로 작용하여 교통사고의 사후분석시 명확한 인과관계를 규명하는데 어려움이 있다. 본 연구에서는 초보운전자에 의한 교통사고를 대상으로 교통사고의 심각도에 영향을 주는 요인들에 대해 분석하였다. 사고발생 시 인명피해가 큰 보행자-차량 교통사고의 사고 심각도를 종속변수로 설정하고 사고 심각도의 증가에 유의한 영향을 미칠 것으로 판단되는 성별, 연령, 교통법규위반 횟수, 교통사고위치 등의 운전자 특성에 관련된 각종 변수들을 독립변수로 설정하여 운전자 운전 경력에 따라 분류하였다. 이항 로지스틱 회귀분석(BLR)을 적용하여 운전경력별 사고심각도 영향 요인을 도출하였다. 분석결과, 운전경력 그룹에 관계없이 운전자 연령, 교통법규위반 횟수, 교통사고위치가 보행자-차량 교통사고 심각도 증가에 영향을 미치는 것으로 나타났다. 본 연구에서 제시한 교통사고 심각도에 영향을 미치는 운전자 특성은 향후 운전자 인적 특성과 더불어 도로환경 및 차량관련 요소에 관련된 교통사고 심각도에 영향을 미치는 요인 분석에 효과적으로 사용될 것으로 기대된다.

• 대한금속재료학회지
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• 제50권12호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.21-24
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• 2007

This paper deals with introduction of testing equipments for the evaluation of dynamic tensile characteristics of auto-body steel sheets and the crashworthiness of auto-body members. The servo-hydraulic high speed material testing machine was developed for tensile tests at the intermediate strain rate to obtain the tensile material properties at the strain rate under 500/sec. The split Hopkinson bar apparatus using the elastic wave was developed for dynamic material characteristics at the high strain rate ranged from 1,000 to 10,000/sec. The servo-hydraulic high speed crash testing machine is the equipment for the evaluation of the collapse load and crashworthiness of auto-body members. High speed carrying truck crashes to specimen with the maximum velocity of 17 m/sec.