Methods to mitigate injury to toddlers in near-side impact crashes

This research focuses on the injury potential of children seated in forward-facing child safety seats during side impact crashes in a near-side seated position. Side impact dynamic sled tests were conducted by NHTSA at Transportation Research Center Inc. (TRC) using a Hybrid III 3-year-old child dummy seated in a convertible forward/rearward child safety seat. The seat was equipped with a LATCH and a top tether and the dummy was positioned in forward-facing/near-side configuration. The test was completed using an acceleration pulse with a closing speed of 24.1 km/h, in the presence of a rigid wall and absence of a vehicle body. A fully deformable finite element model of a child restraint seat, for side impact crash investigations, has been developed which has also been previously validated for frontal and far side impacts. A numerical model utilizing a Hybrid III 3-year-old dummy, employing a similar set-up as the experimental sled test was generated and simulated using LS DYNA. The numerical model was validated by comparing the head and the chest accelerations, resultant upper and lower neck forces and moments from the experimental and numerical tests. The simulation results were observed to be in good agreement to the experimental observations. A numerical model of the near-side laboratory tests, utilizing a Q3s child dummy, was also created for parametric studies regarding different ISOFIX configurations. Further, numerical simulations were completed for both the dummy models with rectangular and cross-shaped sections of rigid ISOFIX systems. In addition, studies were conducted to confine lateral movement of the dummy's head by adding energy absorbing foam on the side wings in the vicinity of the contact region of the CRS. It was observed that the use of rigid ISOFIX system reduced the lateral displacement of the CRS and different injury parameters. Addition of energy absorbing foam blocks was effective in further reducing the lateral displacement of the dummy's head. The lateral displacement of the head was reduced by 68 mm by using cross-shaped section ISOFIX with energy absorbing foam near the vicinity of the head of the Hybrid III 3-year-old dummy compared to the flexible LATCH configuration without foam. For the Q3s dummy, the lateral displacement of the head was reduced by 48 mm by utilizing a cross-shaped section rigid ISOFIX system with the addition of energy absorbing foam compared to the flexible LATCH configuration.     

A numerical investigation into the effect of CRS misuse on the injury potential of children in frontal and side impact crashes

This research focuses on an investigation into the head and neck injuries sustained by toddlers due to CRS misuse under frontal and side impact crashes. A fully deformable FE model incorporating a Hybrid III 3-year-old dummy was developed which has been previously validated for frontal impacts under CMVSS 208 and FMVSS 213 testing conditions. Furthermore, this model has also been validated under near-side impact conditions in accordance to crash tests carried out by NHTSA. In addition, numerical models incorporating a Q3/Q3s prototype child crash test dummies were developed. The objective of this research was to study the effect of seatbelt slack and the absence of the top tether strap on the head and neck injuries sustained by toddlers in a vehicle crash. Numerical simulations were conducted under full frontal and near side impact crash testing conditions in accordance with FMVSS 213 for the Hybrid III 3-year-old dummy and Q3/Q3s dummies in the absence and presence of slack in the seatbelt webbing, and in the absence and presence of the top tether strap. In addition, the effect of using a cross-shaped rigid ISOFIX system was also investigated. An analysis of the head and chest accelerations, neck loads and moments was completed to investigate the potential of injury due to CRS misuse. An increase in HIC₁₅ by approximately 30–40% for the frontal impact and 10–20% for the near-side impact respectively was observed for the Q3 child dummy due to both forms of CRS misuse. In the absence of the top tether strap the forward head excursions were observed to be increased by approximately 70% for the Hybrid III 3-year-old dummy and 40% for the Q3 dummy, respectively. Use of the cross-shaped rigid ISOFIX system illustrated a reduction in head and neck injury parameters, for both frontal and side impact conditions, in the absence and presence of CRS misuse. CRS misuse results in a significant increase in injury parameters and potential for contact related head injuries. Use of a rigid ISOFIX system to restrain a CRS provides better CRS and dummy confinement and reduced injury potential than a flexible ISOFIX system.     

Finite element comparison of human and Hybrid III responses in a frontal impact

The improvement of finite element (FE) Human Body Models (HBMs) has made them valuable tools for investigating restraint interactions compared to anthropomorphic test devices (ATDs). The objective of this study was to evaluate the effect of various combinations of safety restraint systems on the sensitivity of thoracic injury criteria using matched ATD and Human Body Model (HBM) simulations at two crash severities. A total of seven (7) variables were investigated: 3-point belt with two (2) load limits, frontal airbag, knee bolster airbag, a buckle pretensioner, and two (2) delta-v's – 40 kph and 50 kph. Twenty four (24) simulations were conducted for the Hybrid III ATD FE model and repeated with a validated HBM for 48 total simulations. Metrics tested in these conditions included sternum deflection, chest acceleration, chest excursion, Viscous Criteria (V*C) criteria, pelvis acceleration, pelvis excursion, and femur forces. Additionally, chest band deflection and rib strain distribution were measured in the HBM for additional restraint condition discrimination. The addition of a frontal airbag had the largest effect on the occupant chest metrics with an increase in chest compression and acceleration but a decrease in excursion. While the THUMS and Hybrid III occupants demonstrated the same trend in the chest compression measurements, there were conflicting results in the V*C, acceleration, and displacement metrics. Similarly, the knee bolster airbag had the largest effect on the pelvis with a decrease in acceleration and excursion. With a knee bolster airbag the simulated occupants gave conflicting results, the THUMS had a decrease in femur force and the ATD had an increase. Preferential use of dummies or HBM's is not debated; however, this study highlights the ability of HBM metrics to capture additional chest response metrics.     

Investigating occupant safety through simulating the interaction between side curtain airbag deployment and an out-of-position occupant

The objective of this research is to elucidate the effect of side curtain airbag deployment on occupant injuries and safety when the occupant is either in-position or out-of-position (OOP). We used side impact vehicle collision simulations with a 1996 Dodge Neon model, which was further modified to include a side curtain airbag, a seatbelt, and a 50th percentile Hybrid III dummy. The airbag used in the study was inflated using both the uniform pressure (UP) and smooth particle hydrodynamics (SPH) methods. In-position and OOP simulations were performed to assess and establish guidelines for airbag aggressivity thresholds and occupant position versus risk of injury. Three different OOP scenarios (OOP1, OOP2, OOP3) were initially setup following the work of Lund (2003), then modified such that the dummy's head was closer to the airbag, increasing the chance of injury caused by the airbag. The resultant head acceleration as a function of time for in-position and OOP simulations shows that both UP and SPH methods produce similar peak accelerations in cases where the airbag is fully inflated prior to impact. In all cases, the head peak accelerations and the head injury criteria for simulations with an airbag were significantly lower when compared with the no airbag case, which would typically indicate that the use of an airbag results in improved occupant protection during side impact. However, in the case of OOP2 and OOP3, the neck flexion forces actually increase significantly when compared with the no airbag case. This finding indicates that the HIC and neck flexion forces criterion are in conflict and that there may be a tradeoff in terms of occupant injury/safety with a side curtain airbag that is strongly correlated to the occupant position. Consequently, this study shows that safety devices result in a significant effect on occupant injury/safety when the occupant is in OOP conditions. Moreover, in some cases, simulation results show that the side curtain airbag may not make the occupant safer. This study requires further investigation of the vehicle-specific airbag and its interaction with an occupant in various OOP conditions.     

Influence of standing or seated pelvis on dummy responses in rear impacts

Objective

There is a question whether the standing or seated pelvis should be used in Hybrid III dummy evaluations of seats and belt restraint systems in severe rear impacts. This study compares the standing and seated Hybrid III pelvis in matched rear sled tests.

Methods

Sixteen sled tests were found at 10, 16 and 24 km/h rear delta V in Ford's archives where matched tests were run with the standing and seated pelvis in a belted Hybrid III dummy. Two new tests were conducted at 40 km/h rear delta V to extend the severity range. The head, chest and pelvis were instrumented with triaxial accelerometers and the upper and lower neck, thoracic spine and lumbar spine had transducers measuring triaxial loads and moments. Belt Loads were measured. High-speed video recorded different views of the dummy motion. Dummy kinematics and biomechanical responses were compared for all of the data with the two different Hybrid III pelvic designs.

Results

In the 40 km/h sled tests, the dummy motion and excursion were essentially similar with the standing and seated pelvis. The similarities included the lap belt interaction with the pelvis and the leg movement upward flexing the hip joint. Overall, similar biomechanic and kinematic responses were found, including the pelvic acceleration, spinal forces and moments. For the lower speed tests at 10, 16 and 24 km/h, the motion sequence was also similar with the two different pelvises, including the upward movement of the legs as the seat was loaded and rebound kinematics. The biomechanical responses were similar. The seated pelvis involves only a small portion of the upper leg molded into the vinyl skin of the pelvis and does not limit leg rotation at the hip joint. Furthermore, lap belt loads were minimal during the rearward movement of the dummy.

Conclusions

The matched testing showed no significant difference in occupant kinematics or biomechanical responses between the standing and seated pelvis in rear sled tests. The Hybrid III dummy with the seated pelvis is suitable for FMVSS 301 and other testing of seats and belt restraint systems in severe rear impacts.     

儿童乘员约束系统研究现状与展望

儿童乘员约束系统也称儿童安全座椅，是一项新兴的研究领域。随着儿童乘员数量的上升，对于能够有效地保护儿童乘员安全的约束系统的研究具有特殊的重要意义。介绍了儿童乘员约束系统与成人乘员约束系统在分类和组成上的区别，以及相应的发展和健全的安全法规；展望了先进的设计理论、计算机仿真技术应用和系统型研究策略给儿童乘员约束系统研究开辟的前景。     

基于小偏置碰的乘员二次碰撞分析及约束系统仿真优化

研究64 km/h小偏置碰的乘员动态响应及约束系统参数影响.通过建立50 km/h全正碰与64 km/h小偏置碰的约束系统模型,比对两种工况中的乘员二次碰撞运动姿态与损伤特点.仿真结果表明小偏置碰中乘员上躯干相对车体产生较大的横向加速度,导致头部和颈部等部位损伤加剧.基于上述损伤特点,导入侧气帘模块并分析其对乘员损伤的...     

Parents’ attitudes,knowledge and behaviours relating to safe child occupant travel

This study investigated parents’ attitudes, knowledge and behaviours relating to safe child occupant travel following new Australian legislation regarding child restraint system (CRS) and motor vehicle restraint use for children aged 7 years and under. A questionnaire exploring attitudes, knowledge and behaviours regarding general road safety, as well as safe child occupant travel, was completed by 272 participants with at least one child aged between 3 and 10 years residing in the Australian state of Victoria. Responses to the questionnaire revealed that participants’ attitudes, knowledge and behaviours towards road safety in general were fairly positive, with most participants reporting that they restrict their alcohol consumption or do not drink at all while driving (87%), drive at or below the speed limit (85%) and ‘always’ wear their seatbelts (98%). However, more than half of the participants reported engaging in distracting behaviours ‘sometimes’ or ‘often’ (54%) and a small proportion of participants indicated that they ‘sometimes’ engaged in aggressive driving (14%). Regarding their attitudes, knowledge and behaviours relating to safe child occupant travel, most participants reported that they ‘always’ restrain their children (99%). However, there was a surprisingly high proportion of participants who did not know the appropriate age thresholds’ to transition their child from a booster seat to an adult seatbelt (53%) or the age for which it is appropriate for their child to sit in the front passenger seat of the vehicle (20%). Logistic regression analyses revealed that parents’ knowledge regarding safe child occupant travel was significantly related to their attitudes, knowledge and behaviours towards road safety in general, such as drinking habits while driving and CRS safety knowledge. Based on the findings of this study, a number of recommendations are made for strategies to enhance parents’ attitudes, knowledge and behaviours relating to safe child occupant travel, as well as for future research.     

The effect of collision pulse properties on seven proposed whiplash injury criteria

Recent epidemiological and biomechanical studies have suggested that whiplash injury is related to a vehicle's average acceleration rather than its speed change during a rear-end collision. To further explore this phenomenon, the effect of various kinematic properties of the collision pulse on seven proposed whiplash injury criteria was quantified. A BioRID II rear-impact dummy was seated on a programmable sled and exposed six times to each of 15 different collision pulses. Five properties of the collision pulse were varied: peak acceleration (1.3-4.4 g), speed change (3-11 km/h), duration (52-180 ms), displacement (2-26 cm) and shape (square, sine and triangular). Linear and angular accelerations and displacements of the head, and linear accelerations of the T1 and pelvis were measured in the sagittal-plane. Upper neck loads in the sagittal-plane were also measured. Variations within the proposed injury criteria between the different pulses were compared using analyses of variance. Six criteria--peak upper neck shear force, peak upper neck moment, peak retraction, the neck injury criterion (NIC) and two normalized neck injury criteria (Nij and Nkm)--exhibited graded responses that were most sensitive to the average acceleration of the collision pulse. Peak extension angle between the head and T1 decreased with both increasing speed change and peak acceleration, and was, therefore, deemed unsuitable as a whiplash injury criterion for the BioRID dummy. Of the seven criteria, Nij and Nkm were best able to distinguish between the 15 pulses. If the six graded injury criteria are related to the risk of whiplash injury, then the results of this study indicate that the risk of whiplash injury can be reduced by bumper and seat designs that prolong the collision pulse and thereby reduce the average vehicle and occupant accelerations for a given speed change.     

Injury prediction in a side impact crash using human body model simulation

Background

Improved understanding of the occupant loading conditions in real world crashes is critical for injury prevention and new vehicle design. The purpose of this study was to develop a robust methodology to reconstruct injuries sustained in real world crashes using vehicle and human body finite element models.

Methods

A real world near-side impact crash was selected from the Crash Injury Research and Engineering Network (CIREN) database. An average sedan was struck at approximately the B-pillar with a 290 degree principal direction of force by a lightweight pickup truck, resulting in a maximum crush of 45 cm and a crash reconstruction derived Delta-V of 28 kph. The belted 73-year-old midsized female driver sustained severe thoracic injuries, serious brain injuries, moderate abdominal injuries, and no pelvic injury. Vehicle finite element models were selected to reconstruct the crash. The bullet vehicle parameters were heuristically optimized to match the crush profile of the simulated struck vehicle and the case vehicle. The Total Human Model for Safety (THUMS) midsized male finite element model of the human body was used to represent the case occupant and reconstruct her injuries using the head injury criterion (HIC), half deflection, thoracic trauma index (TTI), and pelvic force to predict injury risk. A variation study was conducted to evaluate the robustness of the injury predictions by varying the bullet vehicle parameters.

Results

The THUMS thoracic injury metrics resulted in a calculated risk exceeding 90% for AIS3+ injuries and 70% risk of AIS4+ injuries, consistent with her thoracic injury outcome. The THUMS model predicted seven rib fractures compared to the case occupant's 11 rib fractures, which are both AIS3 injuries. The pelvic injury risk for AIS2+ and AIS3+ injuries were 37% and 2.6%, respectively, consistent with the absence of pelvic injury. The THUMS injury prediction metrics were most sensitive to bullet vehicle location. The maximum 95% confidence interval width for the mean injury metrics was only 5% demonstrating high confidence in the THUMS injury prediction.

Conclusions

This study demonstrates a variation study methodology in which human body models can be reliably used to robustly predict injury probability consistent with real world crash injury outcome.