Stephanie M. Beeman

Occupant kinematics in low-speed frontal sled tests: Human volunteers, Hybrid III ATD, and PMHS.

A total of 34 dynamic matched frontal sled tests were performed, 17 low (2.5g, Δv=4.8kph) and 17 medium (5.0g, Δv=9.7kph), with five male human volunteers of approximately 50th percentile height and weight, a Hybrid III 50th percentile male ATD, and three male PMHS. Each volunteer was exposed to two impulses at each severity, one relaxed and one braced prior to the impulse. A total of four tests were performed at each severity with the ATD and one trial was performed at each severity with each PMHS. A Vicon motion analysis system, 12 MX-T20 2 megapixel cameras, was used to quantify subject 3D kinematics (±1mm) (1kHz). Excursions of select anatomical regions were normalized to their respective initial positions and compared by test condition and between subject types. The forward excursions of the select anatomical regions generally increased with increasing severity. The forward excursions of relaxed human volunteers were significantly larger than those of the ATD for nearly every region at both severities. The forward excursions of the upper body regions of the braced volunteers were generally significantly smaller than those of the ATD at both severities. Forward excursions of the relaxed human volunteers and PMHSs were fairly similar except the head CG response at both severities and the right knee and C7 at the medium severity. The forward excursions of the upper body of the PMHS were generally significantly larger than those of the braced volunteers at both severities. Forward excursions of the PMHSs exceeded those of the ATD for all regions at both severities with significant differences within the upper body regions. Overall human volunteers, ATD, and PMHSs do not have identical biomechanical responses in low-speed frontal sled tests but all contribute valuable data that can be used to refine and validate computational models and ATDs used to assess injury risk in automotive collisions.

Mechanisms of eye injuries from fireworks

Injuries from fireworks are prevalent among youth. The eye is the most frequently injured body part and accounts for more than 2000 injuries annually. Although it is suggested the pressure wave caused by explosions (i.e. blast overpressure) can cause serious eye injuries, there is no clear evidence to support this. The purpose of this research is to assess whether blast overpressure or projected material from fireworks causes eye injury. This study evaluates the response of six human cadaver eyes to charges at distances of 22 cm, 12 cm, and 7 cm from the cornea. Due to variability in consumer fireworks, 10 g charges of Pyrodex gunpowder were used to simulate fireworks in a controlled, repeatable manner. A pressure sensor inserted in the vitreous measured intraocular pressure, and four pressure sensors mounted around the eye measured total and static pressures. Pressure measurements were used to calculate rise time, positive duration, impulse, and wave velocity. The charges produced survivable peak overpressures (Average maximum pressure = 51.15 kPa) which correspond to detonating 0.45 kg TNT at approximately 3.0 m. Minor grain-sized corneal abrasions were the only injuries observed. The abrasion size and pattern suggested unspent gunpowder was projected onto the eye, which was confirmed with high speed video. Increasing proximity to the eye resulted in more abrasions. Intraocular pressure was used to calculate injury risk, which was less than or equal to 0.01% for hyphema, lens damage, retinal damage, and globe rupture. The low calculated injury risk further supports the lack of major injuries observed. The combined presence of injuries caused by projected material and lack of injuries directly caused by the blast overpressure indicated serious eye injuries could be caused by projectiles, but not blast overpressure, at these energy levels.

Kinetic and kinematic responses of post mortem human surrogates and the Hybrid III ATD in high-speed frontal sled tests

Despite improvements in vehicle design and safety technologies, frontal automotive collisions continue to result in a substantial number of injuries and fatalities each year. Although a considerable amount of research has been performed on PMHSs and ATDs, matched dynamic whole-body frontal testing with PMHSs and the current ATD aimed at quantifying both kinetic and kinematic data in a single controlled study is lacking in the literature. Therefore, a total of 4 dynamic matched frontal sled tests were performed with three male PMHSs and a Hybrid III 50th percentile male ATD (28.6g, Δv=40 kph). Each subject was restrained using a 4 kN load limiting, driver-side, 3-point seatbelt. Belt force was measured for the lap belt and shoulder belt. Reaction forces were measured at the seat pan, seat back, independent foot plates, and steering column. Linear head acceleration, angular head acceleration, and pelvic acceleration were measured for all subjects. Acceleration of C7, T7, T12, both femurs, and both tibias were also measured for the PMHSs. A Vicon motion analysis system, consisting of 12 MX-T20 2 megapixel cameras, was used to quantify subject 3D motion (±1 mm) at a rate of 1 kHz. Excursions of select anatomical regions were normalized to their respective initial positions and compared by test condition and between subject types. Notable discrepancies were observed in the responses of the PMHSs and the ATD. The reaction forces and belt loading for the ATD, particularly foot plate, seat back, steering column, and lap belt forces, were not in agreement with those of the PMHSs. The forward excursions of the ATD were consistently within those of the PMHSs with the exception of the left upper extremity. This could potentially be due to the known limitations of the Hybrid III ATD shoulder and chest. The results presented herein demonstrate that there are some limitations to the current Hybrid III ATD under the loading conditions evaluated in the current study. Overall, this study presents a comprehensive data set of belt forces, reaction forces, accelerations, and bilateral displacement data that can be used to evaluate the performance of ATDs and validate computational models.

Human Occupants in Low-Speed Frontal Sled Tests: Effects of Pre-Impact Bracing on Chest Compression, Reaction Forces, and Subject Acceleration

Objectives: The purpose of this study was to investigate the effects of pre-impact bracing on the chest compression, reaction forces, and accelerations experienced by human occupants during low-speed frontal sled tests. Methods: A total of twenty low-speed frontal sled tests, ten low severity (∼2.5g, Δv = 5kph) and ten medium severity (∼5g, Δv = 10kph), were performed on five 50th-percentile male human volunteers. Each volunteer was exposed to two impulses at each severity, one relaxed and the other braced prior to the impulse. A 59-channel chestband, aligned at the nipple line, was used to quantify the chest contour and anterior-posterior sternum deflection. Three-axis accelerometer cubes were attached to the sternum, 7th cervical vertebra, and sacrum of each subject. In addition, three linear accelerometers and a three-axis angular rate sensor were mounted to a metal mouthpiece worn by each subject. Seatbelt tension load cells were attached to the retractor, shoulder, and lap portions of the standard three-point driver-side seatbelt. In addition, multi-axis load cells were mounted to each interface between the subject and the test buck to quantify reaction forces. Results: For relaxed tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, all belt forces, and three resultant reaction forces (right foot, seatpan, and seatback). For braced tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, and two resultant reaction forces (right foot and seatpan). Bracing did not have a significant effect on the occupant accelerations during the low severity tests, but did result in a significant decrease in peak resultant sacrum linear acceleration during the medium severity tests. Bracing was also found to significantly reduce peak shoulder and retractor belt forces for both test severities, and peak lap belt force for the medium test severity. In contrast, bracing resulted in a significant increase in the peak resultant reaction force for the right foot and steering column at both test severities. Chest compression due to belt loading was observed for all relaxed subjects at both test severities, and was found to increase significantly with increasing severity. Conversely, chest compression due to belt loading was essentially eliminated during the braced tests for all but one subject, who sustained minor chest compression due to belt loading during the medium severity braced test. Conclusions: Overall, the data from this study illustrate that muscle activation has a significant effect on the biomechanical response of human occupants in low-speed frontal impacts.

Non-censored rib fracture data during frontal PMHS sled tests

ABSTRACT Objective: The purpose of this study was to obtain non-censored rib fracture data due to three-point belt loading during dynamic frontal post-mortem human surrogate (PMHS) sled tests. The PMHS responses were then compared to matched tests performed using the Hybrid-III 50th percentile male ATD. Methods: Matched dynamic frontal sled tests were performed on two male PMHSs, which were approximately 50th percentile height and weight, and the Hybrid-III 50th percentile male ATD. The sled pulse was designed to match the vehicle acceleration of a standard sedan during a FMVSS-208 40 kph test. Each subject was restrained with a 4 kN load limiting, driver-side, three-point seatbelt. A 59-channel chestband, aligned at the nipple line, was used to quantify the chest contour, anterior-posterior sternum deflection, and maximum anterior-posterior chest deflection for all test subjects. The internal sternum deflection of the ATD was quantified with the sternum potentiometer. For the PMHS tests, a total of 23 single-axis strain gages were attached to the bony structures of the thorax, including the ribs, sternum, and clavicle. In order to create a non-censored data set, the time history of each strain gage was analyzed to determine the timing of each rib fracture and corresponding timing of each AIS level (AIS = 1, 2, 3, etc.) with respect to chest deflection. Results: Peak sternum deflection for PMHS 1 and PMHS 2 were 48.7 mm (19.0%) and 36.7 mm (12.2%), respectively. The peak sternum deflection for the ATD was 20.8 mm when measured by the chest potentiometer and 34.4 mm (12.0%) when measured by the chestband. Although the measured ATD sternum deflections were found to be well below the current thoracic injury criterion (63 mm) specified for the ATD in FMVSS-208, both PMHSs sustained AIS 3+ thoracic injuries. For all subjects, the maximum chest deflection measured by the chestband occurred to the right of the sternum and was found to be 83.0 mm (36.0%) for PMHS 1, 60.6 mm (23.9%) for PMHS 2, and 56.3 mm (20.0%) for the ATD. The non-censored rib fracture data in the current study (n = 2 PMHS) in conjunction with the non-censored rib fracture data from two previous table-top studies (n = 4 PMHS) show that AIS 3+ injury timing occurs prior to peak sternum compression, prior to peak maximum chest compression, and at lower compressions than might be suggested by current PMHS thoracic injury criteria developed using censored rib fracture data. In addition, the maximum chest deflection results showed a more reasonable correlation between deflection, rib fracture timing, and injury severity than sternum deflection. Conclusions: Overall, these data provide compelling empirical evidence that suggests a more conservative thoracic injury criterion could potentially be developed based on non-censored rib fracture data with additional testing performed over a wider range of subjects and loading conditions.

Upper Body Kinematics of Relaxed Volunteers, Braced Volunteers, Hybrid III ATD, and PMHS in Low-Speed Frontal Sled Tests

Human occupant responses in motor vehicle collisions (MVCs) are commonly predicted and evaluated in a laboratory using surrogates including human volunteers, anthropomorphic test devices (ATDs), and post mortem human surrogates (PMHSs) [1]. The ultimate goal of these surrogates is to demonstrate a similar response to humans in MVCs that can be used to evaluate human tolerance and enhance vehicle design and safety. The distinguishing attribute of human volunteers that non-human surrogates do not currently possess is the combination of identical human anthropometry, anatomy, and physiologic response of the target population, including resting muscle tone and active bracing capabilities. All human volunteer laboratory testing must be performed at sub-injurious levels due to ethical constraints, while non-human surrogates can be used to examine injurious or traumatic events. Given the capabilities and shortcomings of each surrogate in automobile safety research, performing matched tests with these surrogates can aid in the understanding of the biomechanical response of humans in an impact environment, leading to improvements in ATD design and increased efficacy of safety devices. Therefore, the purpose of this study was to investigate volunteer, ATD, and PMHS occupant kinematic responses in matched low-speed frontal sled tests.Copyright

Human Eye Response to Blast Overpressure

Each year, approximately two million people in the United States suffer eye injuries that require treatment [1]. Although it is suggested that blast overpressure can cause serious eye injuries, there is no clear evidence in the literature to support this injury mechanism. Conversely, projectile impacts have been shown to cause serious eye injuries [2, 3]. The critical question is whether blast overpressure alone can cause eye injury or if injuries are caused solely by projected material. Therefore, the purpose of the current study is to measure the intraocular pressure (IOP) of postmortem human eyes during blasts and assess injuries sustained in order to more fully understand the effect of blast overpressure on the eye.Copyright