Series Of Sled Tests Research Articles

Optimizing Seat Belt and Airbag Designs for Rear Seat Occupant Protection in Frontal Crashes.

Recent field data have shown that the occupant protection in vehicle rear seats failed to keep pace with advances in the front seats likely due to the lack of advanced safety technologies. The objective of this study was to optimize advanced restraint systems for protecting rear seat occupants with a range of body sizes under different frontal crash pulses. Three series of sled tests (baseline tests, advanced restraint trial tests, and final tests), MADYMO model validations against a subset of the sled tests, and design optimizations using the validated models were conducted to investigate rear seat occupant protection with 4 Anthropomorphic Test Devices (ATDs) and 2 crash pulses. The sled tests and computer simulations were conducted with a variety of restraint systems including the baseline rear-seat 3-point belt, 3-point belts with a pre-tensioner, load limiter, dynamic locking tongue, 4-point belts, inflatable belts, Bag in Roof (BiR) concept, and Self Conforming Rear seat Air Bag (SCaRAB) concept. The results of the first two sled series demonstrated that the baseline 3-point belt system are associated with many injury measures exceeding injury assessment reference values (IARVs); showed the significance of crash pulse and occupant size in predicting injury risks; and verified the potential need of advanced restraint features for better protecting the rear-seat occupants. Good correlations between the tests and simulations were achieved through a combination of optimization and manual fine-tuning, as determined by a correlation method. Parametric simulations showed that optimized belt-only designs (3-point belt with pre-tensioner and load limiter) met all of the IARVs under the soft crash pulse but not the severe crash pulse, while the optimized belt and SCaRAB design met all the IARVs under both the soft and severe crash pulses. Two physical prototype restraint systems, namely an "advanced-belt only" design and an "advanced-belt and SCaRAB" design, were then tested in the final sled series. With the soft crash pulse, both advanced restraint systems were able to reduce all the injury measures below the IARVs for all four ATDs. Both advanced restraint systems also effectively reduced almost all the injury measures for all ATDs under the severe crash pulse, except for the THOR. The design with the advanced-belt and SCaRAB generally provided lower injury measures than those using the advanced belt-only design. This study highlighted the potential benefit of using advanced seatbelt and airbag systems for rear-seat occupant protection in frontal crashes.

A Novel Approach to Measuring Muscle Mechanics in Vehicle Collision Conditions.

The aim of the study was to evaluate a novel approach to measuring neck muscle load and activity in vehicle collision conditions. A series of sled tests were performed on 10 healthy volunteers at three severity levels to simulate low-severity frontal impacts. Electrical activity—electromyography (EMG)—and muscle mechanical tension was measured bilaterally on the upper trapezius. A novel mechanical contraction (MC) sensor was used to measure the tension on the muscle surface. The neck extensor loads were estimated based on the inverse dynamics approach. The results showed strong linear correlation (Pearson’s coefficient = 0.821) between the estimated neck muscle load and the muscle tension measured with the MC sensor. The peak of the estimated neck muscle force delayed 0.2 ± 30.6 ms on average vs. the peak MC sensor signal compared to the average delay of 61.8 ± 37.4 ms vs. the peak EMG signal. The observed differences in EMG and MC sensor collected signals indicate that the MC sensor offers an additional insight into the analysis of the neck muscle load and activity in impact conditions. This approach enables a more detailed assessment of the muscle-tendon complex load of a vehicle occupant in pre-impact and impact conditions.

Thoracic Injury Risk Curves for Rib Deflections of the SID-IIs Build Level D.

Injury risk curves for SID-IIs thorax and abdomen rib deflections proposed for future NCAP side impact evaluations were developed from tests conducted with the SID-IIs FRG. Since the floating rib guide is known to reduce the magnitude of the peak rib deflections, injury risk curves developed from SID-IIs FRG data are not appropriate for use with SID-IIs build level D. PMHS injury data from three series of sled tests and one series of whole-body drop tests are paired with thoracic rib deflections from equivalent tests with SID-IIs build level D. Where possible, the rib deflections of SID-IIs build level D were scaled to adjust for differences in impact velocity between the PMHS and SID-IIs tests. Injury risk curves developed by the Mertz-Weber modified median rank method are presented and compared to risk curves developed by other parametric and non-parametric methods.

Kinematics of Pediatric Crash Dummies Seated on Vehicle Seats with Realistic Belt Geometry

Objective: A series of sled tests was performed using vehicle seats and Hybrid-III 6-year-old (6YO) and 10YO anthropomorphic test devices (ATDs) to explore possibilities for improving occupant protection for children who are not using belt-positioning booster seats.Methods: Cushion length was varied from production length of 450 mm to a shorter length of 350 mm. Lap belt geometry was set to rear, mid, and forward anchorage locations that span the range of lap belt angles found in vehicles. Six tests each were performed with the 6YO and 10YO Hybrid III ATDs. One additional test was performed using a booster seat with the 6YO. The ATDs were positioned using an updated version of the University of Michigan Transportation Research Institute (UMTRI) seating procedure that positions the ATD hips further forward with longer seat cushions to reflect the effect of cushion length on posture that has been measured with child volunteers. ATD kinematics were evaluated using peak head excursion, peak knee excursion, the difference between peak head and peak knee excursion, and the maximum torso angle.Results: Shortening the seat cushion improved kinematic outcomes, particularly for the 10YO. Lap belt geometry had a greater effect on kinematics with the longer cushion length, with mid or forward belt geometries producing better kinematics than the rearward belt geometry. The worst kinematics for both ATDs occurred with the long cushion length and rearward lap belt geometry. The improvements in kinematics from shorter cushion length or more forward belt geometry are smaller than those provided by a booster seat.Conclusions: The results show potential benefits in occupant protection from shortening cushion length and increasing lap belt angles, particularly for children the size of the 10YO ATD.

The necessity of evaluating child neck injury in frontal collision of school bus for transportation safety

The frequent school bus accidents and resulting injuries accelerated the formulation and revision of the school bus regulations. In the school bus regulations, the injury criteria and evaluation procedures of head, chest, and femur were included, however, neck injury evaluation has not been incorporated. Thus, the neck protection was often ignored and no relevant studies were found to specially focus on this topic. In this study, the child body region injuries, especially the neck under compartmentalization (without seatbelt), lap belt, and lap/shoulder belt restraint strategies in school bus frontal impact were particularly evaluated through a series of sled tests in laboratory environment. Results showed that most of the injury metrics of head, chest, and femur were below their threshold limits, but, on the contrary, most neck injury metrics did not meet the requirement of the regulations, which indicated that neck was one of the most easily injured regions in frontal impact. This study also pointed out that the lap/shoulder belt can provide good protections for all the body regions involved in this study, whereas traditional compartmentalization and only lap belt can protect head, chest, and femur well, but cannot effectively protect the neck, thus some countermeasures on redesigning the traditional seatback were proposed. According to the conclusions drawn in this study, neck injury evaluation are strongly recommended to incorporate into the regulations, meanwhile, lap/shoulder belt is also suggested to equip with the current school bus seats.

Evaluation of the adequacy of neck injury indicators on bioridii in a lower-rear impact sled test

The BioRIDII (Biofidelic Rear-Impact Dummy II) is regarded as possessing similar characteristics to human volunteers and PMHS (post-mortem human subjects) in terms of its response to low-speed rear-impact tests. The biofidelity of the RID 2 (Rear-Impact Dummy 2) does not yield satisfactory results in comparison to the BioRIDII. Although a great deal of research on the repeatability and reproducibility of the BioRIDII has been conducted, the research results to date do not directly suggest the neck injury criteria and limit values that should be set in safety regulations. The purpose of this research is to evaluate neck injury indicators for the BioRIDII using low-speed rear-impact sled tests on three sets of BioRIDII ver-g. A series of sled tests was conducted to assess the adequacy of neck injury indicators in terms of the repeatability and reproducibility of the results obtained for the three BioRIDII dummies tested. The sled tests were performed according to the test procedure proposed by K-NCAP (the Korea New Car Assessment Program). Several neck injury indicators, namely, NIC, Nkm, upper- and lower-neck Fx, upper- and lower-neck Fz and My, T1 X acc and Head X acc, were analyzed for each dummy. The results show that for some criteria, such as the lower-neck shear force and moment and T1 acceleration, the BioRIDII could be considered adequate.

Development and Testing of a More Realistic Pelvis for the Hybrid III 6-Year-Old ATD

Objective: Design and test a new pelvis for the Hybrid III 6-year-old (6YO) anthropometric test device (ATD) with a more humanlike bone structure, flesh contour, and flesh stiffness intended to provide more realistic interaction with belt restraints. Methods: Target geometry for the new pelvis bone was based on a 3D model of the skeletal pelvis derived from statistical analysis of pediatric computed tomography (CT) scans. The current pelvis bone was reshaped to better match the target geometry, with a particular emphasis on the contour in the areas of belt interaction. The prominence representing the anterior–superior iliac spine (ASIS) was lowered by 15 mm. The pelvis flesh was molded using softer vinyl while maintaining a 10-mm flesh margin over the ASIS. A series of 20 sled tests was conducted to compare the performance of the modified pelvis with the current Hybrid III pelvis. Results: In a series of sled tests using a range of belt anchorage locations, a dummy equipped with the new pelvis did not submarine in conditions where the lap belt was positioned below the ASIS. Tests run with the lap belt initially positioned over the ASIS resulted in submarining, unlike tests performed with the standard dummy pelvis. Conclusions: The new pelvis for the 6YO Hybrid III ATD better represents the skeletal and flesh geometry of similar-sized children. The ATD equipped with the new pelvis is more sensitive to lap belt geometry than the standard ATD. The modified ATD may provide an improved assessment of booster seats and belt restraints intended for child occupants.

Motorcycle Rider Trajectory in Pitch-Over Brake Applications and Impacts

This paper describes how pitch-over events are common in motorcycle accidents, and can be caused by impact to the front wheel and occasionally by hard brake application. In either case, the rider of the motorcycle can be propelled over the handlebars as the motorcycle pitches rear-end up. In accidents caused by pitch-over braking, the accident investigator may be faced with limited evidence and then must rely on analyzing the throw distance of the rider in attempting to reconstruct the pre-accident speed of the motorcycle. This analysis can be complicated by the presence of a second rider (the passenger) on the motorcycle. Pitch over caused by front wheel impact can be similarly complex. Although motorcycle deformation as a result of front wheel impact has been studied, circumstances surrounding the nature of the deformation, or the impact itself, may require that the trajectory of the rider be analyzed in order to determine the pre-impact motorcycle speed. A series of sled tests was conducted to analyze rider and passenger motion during pitch-over events to develop a more complete understanding of how deceleration and initial speed affect the occupant trajectory and velocity. Brake stops were simulated on the sled as well as front wheel impacts. A full-scale crash test was also conducted and compared against the results of the sled simulations. High-speed video footage was analyzed to develop an understanding of the pitch-over dynamics as well as rider/passenger trajectories and velocities. This paper presents the results of this study and offers a method for accident reconstructionists to employ as they examine motorcycle accidents that involve pitch-over events.

Integration of Scientific Visualization With Physical and Digital Modeling for Improved Child Restraint System Safety

Computational modeling continues to play an increasingly significant role in the design of more effective vehicle crash safety systems. Researchers now frequently exercise models formulated with sophisticated computer analyses to supplement empirically generated results and conduct extensive what-if exploratory studies for information formerly available solely from costly and time-consuming physical testing. Our research team is developing a modeling and analysis capability that features a scientific visualization toolkit called NYSCEDII CRS visualization module (NCVM). NCVM post-processes conventional crash simulation imagery, enabling modelers to visualize aspects of both the digital model and the sled-test simulation in an immersive visual environment. This paper describes NCVM’s design and development in detail and illustrates its application to a series of sled tests conducted with a recent-production child restraint system and dummy occupant.

A parametric study of a side airbag system to meet deflection based criteria.

A side airbag system comprising of 12 liter bag to cover the BioSid chest and the abdomen down to the arm rest level, and 75 mm of padding to cover the pelvic/thigh area was evaluated by a series of sled tests at two different velocities, 10 m/s and 12 m/s. The initial bag (over) pressure was varied from 0 to 80 kPa and the bag ventilation area was varied from zero to 1500 mm2. Compressed air was used to fill the bag. It was found that the ventilation of the bag reduced the maximum chest deflection by 30 percent and the maximum viscous criterion, VC, by 50 percent (comparison was made with the same bag without ventilation). A suitable initial bag (over) pressure was found to be about 50 kPa, when the loading of the abdomen was also taken into consideration. The results indicate that the chest deflection is proportioned to the door average velocity (during the first 20 ms of deflection) to the power of about 2 and that the VC is proportional to the same velocity to the power of about 4. It was also found that a 12 liter ventilated side airbag resulted in 30-40 percent lower chest deflection and about 60 percent lower VC than 50 mm of chest padding (Ethafoam 220).