Crashworthiness Standards Research Articles

Recentadvances inthe collision passive safety of trains andimpact biological damage of drivers and passengers

Despite a series of active safety precautions have been adopted by railway passenger trains, train collision accident cannot be completely eliminated in service,resulting in serious casualties and huge economic losses once it happened. With the continuous increase of train speed, the train collision safety and relevant impact protections have been paid more attention, and numerous related explorations have been carried out by domestic and foreign scholars. This paper reviews recent advances in the passive safety of train collisions and impact biological damage of drivers and passengers. First, the train collision accidents at home and abroad in recent years are summarized, and the biological damage distributions of survivals in a certain train collision accident are analyzed. Secondly, the main research approaches of collision passive safety of trains are illustrated, including numerical simulation, experimental investigation, and theoretical analysis, while the response attitudes and derailment mechanisms during the train collision process are outlined. Thirdly, the research progress of the collision passive safety of trains are elaborated, in terms of the design and evaluation standards of vehicle crashworthiness, energy-absorbing structural design based on multistage energy dissipation, train structural crashworthiness design based on collision energy management. Finally, the impact biological damage of drivers and passengers in train collisions are emphasized, and the related protective measures of reducing the biological damage of drivers and passengers are presented. Through the above overview, some suggestions are put forward for further studies: i) the applicability of the existing crashworthiness standards for trains needs to be further explored under the increased train speed; ii) the theoretical study on train collision is still scarce, and the collision theory of high-speed train should be further developed; iii) how to effectively learn from and refer to the mature experience of the automobile collision still needs systematic and in-depth investigation; and iv) the design and evaluation method of train passive safety based on the impact biological damage of drivers and passengers should be explored.

Rail vehicle crashworthiness based on collision energy management: an overview

ABSTRACT This paper summarizes the research on passive safety of rail vehicles from the perspective of Crash Energy Management (CEM) in recent decades, which covers the analysis of main crashworthiness standards, as well as the latest research progress in theoretical methods, numerical simulation, and experimental technology of rail vehicles crashworthiness. According to the research status of each subject, some weak links and potential research suggestions are pointed out, such as the requirements of CEM in standards, the influence mechanism of the coupler under different collision speeds, structural compatibility and standardization of anti-climbers, the establishment of vehicle structure crashworthiness design method in design-simulation-test closed-loop system, etc. In the future, under the support of mature CEM theory, more detailed and reliable numerical simulation models, more comprehensive vehicle crash test data, and higher computer computing efficiency, the passive safety of rail vehicles will be guaranteed to the maximum extent.

Dealing with existing theory: national fatality rates, vehicle standards and personal safety

In this paper we discuss some of the weaknesses in exiting theories and understandings behind road safety interventions and policy making. The paper deals with four main issues: road traffic fatality rates and per capita income of countries, vehicle crashworthiness standards, role of pedestrian and powered two-wheeler share in traffic on fatalities, and safety standards for vehicles other than cars. Recent data indicate that there may not be a strong relationship between income and road safety performance and it is possible for low and middle-income countries (LMIC) to decrease death rates at present income levels. Safer cars have had a major role in reducing fatality rates, but, gains in traffic safety in high income countries may be partly due to reducing exposure of vulnerable road users. Small lightweight vehicles (like tuk-tuks, three-wheeled scooter taxis) operating in many LMIC appear to have low fatality rates though they do not follow any crashworthiness standards. Very different crashworthiness standards need to be developed for low mass vehicles incapable of operating speeds greater than 50 km/h. LMIC may not be able to reduce fatality rates below about 7 per 100,000 population unless there are innovative developments in road design and all vehicle safety standards.

Occupant Injury Severity and Accident Causes in Helicopter Emergency Medical Services (1983-2014).

Helicopter emergency medical services (HEMS) transport critically ill patients to/between emergency care facilities and operate in a hazardous environment: the destination site is often encumbered with obstacles, difficult to visualize at night, and lack instrument approaches for degraded visibility. The study objectives were to determine 1) HEMS accident rates and causes; 2) occupant injury severity profiles; and 3) whether accident aircraft were certified to the more stringent crashworthiness standards implemented two decades ago. The National Transportation Safety Board (NTSB) aviation accident database was used to identify HEMS mishaps for the years spanning 1983-2014. Contingency tables (Pearson Chi-square or Fisher's exact test) were used to determine differences in proportions. A generalized linear model (Poisson distribution) was used to determine if accident rates differed over time. While the HEMS accident rate decreased by 71% across the study period, the fraction of fatal accidents (36-50%) and the injury severity profiles were unchanged. None of the accident aircraft fully satisfied the current crashworthiness standards. Failure to clear obstacles and visual-to-instrument flight, the most frequent accident causes (37 and 26%, respectively), showed a downward trend, whereas accidents ascribed to aircraft malfunction showed an upward trend over time. HEMS operators should consider updating their fleet to the current, more stringent crashworthiness standards in an attempt to reduce injury severity. Additionally, toward further mitigating accidents ascribed to inadvertent visual-to-instrument conditions, HEMS aircraft should be avionics-equipped for instrument flight rules flight.

Occupant injury and fatality in general aviation aircraft for which dynamic crash testing is certification-mandated

Towards further improving general aviation aircraft crashworthiness, multi-axis dynamic tests have been required for aircraft certification (14CFR23.562) since 1985. The objective of this study was to determine if occupants in aircraft certified to these higher crashworthiness standards show a mitigated fraction of fatal accidents and/or injury severity.The NTSB aviation database was queried for accidents occurring between 2002 and 2012 involving aircraft certified to, or immune from, dynamic crash testing and manufactured after 1999. Only operations conducted under 14CFR Part 91 were considered. Statistical analysis employed proportion tests and logistic regression.Off-airport landings are associated with high decelerative forces; however for off-airport landings, the fraction of fatal accidents for aircraft subject to, or exempt from, dynamic crash testing was similar (0.53 and 0.60, respectively). Unexpectedly, for on-airport landings a higher fraction of fatalities was evident for aircraft whose certification mandated dynamic crash testing. Improved crashworthiness standards would be expected to translate into a reduced severity of accident injuries. For all accidents, as well as for those deemed survivable, the fraction of minor and serious injuries was reduced for occupants in aircraft certified to the higher crashworthiness standards. Surprisingly, the fraction of occupants fatally injured was not decreased for aircraft subject to dynamic crash tests. To shed light on this unexpected finding flight history, airman demographics and post-impact fires for aircraft for which dynamic crash testing is mandatory or exempt was examined. For the former cohort the median distance of the accident flight was nearly 44% higher. Aircraft subject to dynamic crash testing were also involved in a greater fraction (0.25 versus 0.12, respectively) of post-impact fires.Our data suggest that while the more stringent crashworthiness standards have mitigated minor and serious injuries, surprisingly the fraction of occupants fatally injured is unaltered. The unchanged fraction of fatal injuries may reflect partly (a) fatigue associated with longer flight distances and (b) a greater proportion of post-impact fires.

Virtual Design Method for Controlled Failure in Foldcore Sandwich Panels

For certification, novel fuselage concepts have to prove equivalent crashworthiness standards compared to the existing metal reference design. Due to the brittle failure behaviour of CFRP this requirement can only be fulfilled by a controlled progressive crash kinematics. Experiments showed that the failure of a twin-walled fuselage panel can be controlled by a local modification of the core through-thickness compression strength. For folded cores the required change in core properties can be integrated by a modification of the fold pattern. However, the complexity of folded cores requires a virtual design methodology for tailoring the fold pattern according to all static and crash relevant requirements. In this context a foldcore micromodel simulation method is presented to identify the structural response of a twin-walled fuselage panels with folded core under crash relevant loading condition. The simulations showed that a high degree of correlation is required before simulation can replace expensive testing. In the presented studies, the necessary correlation quality could only be obtained by including imperfections of the core material in the micromodel simulation approach.

Failure of CFRP airframe sandwich panels under crash-relevant loading conditions

New aircraft fuselage concepts have to prove equivalent crashworthiness standards compared to conventional metallic fuselages for certification. Brittle failure mechanisms of CFRP structures make the verification of equivalent crashworthiness for novel CFRP fuselage concepts challenging since conventional metal fuselages absorb a significant part of the kinetic energy by plasticization. In this context, the damage initiation and failure of twin-walled fuselage panels were investigated under crash relevant bending–compression loads. Since the sandwich failure is initiated by core failure, a trigger concept for CFRP composite sandwich panels was developed based on local modifications in the fold pattern of the core for controlled failure initiation. By locally adjusting the collapse strength of the core in normal direction, the failure position and failure load can be adapted according to the defined kinematic hinge requirements. The core trigger concept was validated in experiments with triggered and untriggered sandwich panels under identical loading conditions.

Multi-objective optimisation and sensitivity analysis of a paratransit bus structure for rollover and side impact tests

Paratransit buses are heavily used in the United States. A paratransit bus consists of custom passenger compartments mounted onto separate cutaway chassis. The lack of dedicated national crashworthiness standards, along with different construction methods used by paratransit fleet manufacturers, can result in a wide variance of passenger compartment structural strength. In August 2007, the Florida Department of Transportation (FDOT), to ensure adequate crashworthiness performance, introduced a standard stipulating that newly acquired buses must be tested for rollover and side impact conditions. The rollover test is performed using a tilt table test according to UN-ECE Regulation 66. The side impact test involves the impact of a bus by a common sport utility vehicle or pickup truck. In the current study, an original finite element model of a paratransit bus was used in LS-DYNA® simulations of both the rollover and the side impact testing procedures per FDOT standard. Using LS-OPT®, a metamodel-based approach was used to perform multi-objective optimisation of the bus structure for the rollover and the side impact tests. The linear ANOVA and the Sobol's indices approach were used for sensitivity analysis. The structural components of the bus having the greatest influence on the bus performance in the simulated test scenarios were identified. The simulation results show that the original bus design would pass the FDOT testing procedure. However, appropriate redistribution of the mass can noticeably increase its strength for the side impact case.

Severe-to-fatal head injuries in motor vehicle impacts

Severe-to-fatal head injuries in motor vehicle environments were analyzed using the United States Crash Injury Research and Engineering Network database for the years 1997–2006. Medical evaluations included details and photographs of injury, and on-scene, trauma bay, emergency room, intensive care unit, radiological, operating room, in-patient, and rehabilitation records. Data were synthesized on a case-by-case basis. X-rays, computed tomography scans, and magnetic resonance images were reviewed along with field evaluations of scene and photographs for the analyses of brain injuries and skull fractures. Injuries to the parenchyma, arteries, brainstem, cerebellum, cerebrum, and loss of consciousness were included. In addition to the analyses of severe-to-fatal (AIS4+) injuries, cervical spine, face, and scalp trauma were used to determine the potential for head contact. Fatalities and survivors were compared using nonparametric tests and confidence intervals for medians. Results were categorized based on the mode of impact with a focus on head contact. Out of the 3178 medical cases and 169 occupants sustaining head injuries, 132 adults were in frontal (54), side (75), and rear (3) crashes. Head contact locations are presented for each mode. A majority of cases clustered around the mid-size anthropometry and normal body mass index (BMI). Injuries occurred at change in velocities (Δ V) representative of US regulations. Statistically significant differences in Δ V between fatalities and survivors were found for side but not for frontal impacts. Independent of the impact mode and survivorship, contact locations were found to be superior to the center of gravity of the head, suggesting a greater role for angular than translational head kinematics. However, contact locations were biased to the impact mode: anterior aspects of the frontal bone and face were involved in frontal impacts while temporal–parietal regions were involved in side impacts. Because head injuries occur at regulatory Δ V in modern vehicles and angular accelerations are not directly incorporated in crashworthiness standards, these findings from the largest dataset in literature, offer a field-based rationale for including rotational kinematics in injury assessments. In addition, it may be necessary to develop injury criteria and evaluate dummy biofidelity based on contact locations as this parameter depended on the impact mode. The current field-based analysis has identified the importance of both angular acceleration and contact location in head injury assessment and mitigation.

229: Prototype “Safety Concept” Ambulances: Are They Actually Safe?

In the USA, ambulances have a safety record below that of passenger vehicles and a crash fatality rate greater than 10 times worse than large trucks per mile traveled, a rear compartment exempt from crashworthiness standards, and are essentially designed without automotive and crashworthiness technical expertise.

Structural response of paratransit buses in rollover accidents

Existing crashworthiness standards in the United States are focused primarily on passenger cars and school buses, while paratransit buses are not required to meet these codes. The main objective of this research was to develop a finite element (FE) model of the Champion Challenger paratransit bus in order to perform the crashworthiness evaluation during the rollover test using computational mechanics. The FE model was developed based on technical description and AutoCAD files of the bus structure supplied by Champion, the producer of the Challenger bus. In the absence of U.S. crashworthiness standards applicable to paratransit buses, the FE model of Champion Challenger bus was used for computational mechanics study of the rollover test according to ECE Regulation 66. All numerical analyses were carried out using LS-DYNA, a nonlinear, explicit code. Experimental validation of assumed material models, mesh density, and contact definition was performed through a simple pendulum impact test of the bus sidewall panels [1].

Compatibility of Vehicles with Safety Barriers: Head Ejection Through Side Windows

The safety performance of roadside features may depend not only on barrier but also on vehicle behavior. Best results require efficient synergy of barrier and vehicle, or compatibility. Examples of problems where such compatibility may be needed are discussed. One of these problems—head ejection in collisions with high-containment barriers—was investigated with an accident survey, full-scale tests, and laboratory sled tests. One of the conclusions is that, with high-containment barriers suitable for narrow medians, partial head ejection occurs systematically and may represent a high risk. Head containment in such collisions should be mandatory for crashworthy vehicles. This can be easily obtained with laminated glass, without window frame reinforcement. The conclusion is that vehicle and barrier crashworthiness standards should be linked. Collisions with safety barriers are statistically significant events and should be considered among vehicle passive safety items.

US rail equipment crashworthiness standards

In 1999 the US Department of Transportation's Federal Railroad Administration (FRA) issued new regulations and the American Public Transportation Association (APTA) issued new standards for rail passenger equipment crashworthiness. These new regulations and standards include conventional strength-based requirements for equipment used below 200km/h (125 mile/h), crashenergy management for equipment used above 200km/h (125 mile/h) and dynamic sled testing of occupant seats.

Application of Computer-Aided analysis tools for aircraft occupant and seat crashworthiness problems

This paper describes some applications of the computer-aided analysis tools typically used in the studies of the crash responses of aircraft seats and occupants. The methodology used incorporates a combination of non linear finite element analysis and multibody modeling of the seat and the occupant as well as component testing in early design stages, and sled and/or full-scale testing in later stages of design evaluations. The nature of the current crashworthiness standards is first discussed. The systems approach utilised for the aircraft seat design process is briefly described. Examples of this systems approach methodology for some of the current crash safety issues are then presented and the importance of the CAE tools in these crashworthiness problems is demonstrated. These crashworthiness problems include the head impact protection for seats facing the bulkhead, the solution to the proposed 32G commuter seat, and the certification criteria for side-facing aircraft seats. Using this methodology and the CAE tools, solutions to these crashworthiness problems are arrived at.

Technology, behavior, and safety: An empirical study of automobile occupant-protection regulation

Technology and human behavior can influence the effectiveness of safety policies. In the field of traffic safety, rational-choice theorists postulate that automobile safety devices induce increased driver risk taking. Such behavioral responses could partly or totally nullify the lifesaving potential of governmental safety rules for new cars, such as the crashworthiness standards adopted by the United States in the late 1960s and early 1970s. This study explores the behavioral-response hypothesis in the context of a car-vintage model of U.S. car occupant death rates. Results from the model imply that U.S. standards have reduced the occupant death rate by roughly 30 percent, a finding consistent with minimal driver response to safety devices. The study provides support for the technological approach to safety policy and suggests that policymakers might consider adopting additional crashworthiness regulations, such as some form of passive-restraint program.