This paper describes the injuries generated during dynamic belt loading to a porcine model of the 6-year-old human abdomen, and correlates injury outcomes with measurable parameters. The test fixture produced transverse, dynamic belt loading on the abdomen of 47 immediately post-mortem juvenile swine at two locations (upper/lower), with penetration magnitudes ranging from 23% - 65% of the undeformed abdominal depth, with and without muscle tensing, and over a belt penetration rate range of 2.9 m/s - 7.8 m/s. All thoracoabdominal injuries were documented in detail and then coded according to the Abbreviated Injury Scale (AIS). Observed injuries ranged from AIS 1 to AIS 4. The injury distribution matched well the pattern of injuries observed in a large sample of children exposed to seatbelt loading in the field, with most of the injuries in the lower abdomen. Univariate and multiple regression models were used to assess mechanical predictors as injury criteria for maximum AIS 2+ and 3+ outcomes, including peak belt tension and posterior reaction force, abdominal penetration, penetration rate, the viscous criterion, and a newly proposed criterion, FCmax, which is the maximum of the instantaneous product of loading rate and normalized penetration. The Goodman-Kruskal Gamma (gamma) was used to assess each parameter's ability to discriminate between injurious and non-injurious tests. Injury risk functions were generated for both outcomes by fitting a 2-parameter Weibull distribution to the injury data using survival analysis. The best discriminators were peak belt tension (gamma = 0.86 and 0.83, p < 0.01), the work done by the deforming thorax (gamma = 0.86 and 0.74, p < 0.01), and abdominal penetration (gamma = 0.89 and 0.66, p < 0.02). Penetration rate was not a good discriminator (gamma = 0.34 and 0.52), and the consideration of penetration rate decreased the discrimination of the viscous criterion (gamma = 0.67 and 0.58) relative to penetration alone. FCmax was a better discriminator of injury than the viscous criterion (gamma = 0.70 and 0.76, p < 0.01), indicating that the loading rate may be more related to injury outcome than the penetration rate.

Rupture of the thoracic aorta is a leading cause of rapid fatality in automobile crashes, but the exact mechanisms of this injury remain unidentified. One commonly postulated mechanism is a differential motion of the aortic arch relative to the heart and its neighboring vessels caused by high-magnitude acceleration of the thorax. This paper investigates acceleration as an aortic injury mechanism using nine impact-sled tests with human cadaver thoraces. The test system utilized generates very high posteriorly directed thoracic accelerations with minimal compression of the chest. The sled tests resulted in peak mid-spine accelerations of 169±35.0g (mean±standard deviation) with sustained mid-spine accelerations of up to 80g for 20ms in most cases. The tests resulted in maximum chest compressions of 7±3.1% of the total chest depth, and maximum recorded increases in intra-aortic, tracheal, and esophageal pressure of 177, 112, and 156kPa, respectively. No macroscopic injuries to the thoracic aorta resulted from these tests, though other limited visceral injury was observed. The results suggest that posteriorly directed acceleration alone (up to the magnitudes studied here) is not sufficient to cause gross aortic injury. Furthermore, the observed transient increases in intra-aortic and extra-aortic pressure indicate that complex pressure distributions are present during dynamic thoracic deceleration events. This suggests that any attempt to model traumatic aortic injury should include consideration for both the intra-aortic fluid pressure and the extra-aortic, intra-thoracic pressure present during the event.

To better understand the biomechanical response of pediatric occupants undergoing abdominal belt loading, a porcine model (sus scrofa domestica) was developed to represent the abdomen of a 6-year-old human. A custom test fixture was designed to replicate two-point transverse belt loading across the anterior abdomen at rates up to 7 m/s. Five independent parameters were varied—abdominal compression, belt loading velocity, location of belt loading, loading waveform (ramp-hold vs. ramp-release), and the presence of abdominal muscle stimulation—for a total of 21 unique conditions and 47 total dynamic tests. The upper abdomen tests directly loaded the lower ribs, liver, spleen, and stomach, while lower abdomen tests involved direct loading of the small and large intestines. Quasi-static compression tests were also performed to model the force-deflection response of the abdomen with and without active muscle tensing. The effect of loading location, loading velocity, and the presence of muscle stimulation on the force-deflection response was compared between the quasi-static and the dynamic tests. The upper abdomen produced a stiffer response than the lower abdomen in the quasi-static tests, but this effect was muted at dynamic rates. The effect of active muscle stimulation was similarly noticeable only in quasi-static tests, due to the lower reaction forces. Injury risk functions were created to evaluate the robustness of various predictive criteria, and the Goodman-Kruskal gamma was calculated for each criterion to assess its predictive ability. Forceand compression-based criteria, such as maximum posterior reaction force, maximum belt force, and maximum abdominal deflection, proved to more predictive than velocity or viscous criteria such as (V*C)max. The most common injuries associated with the upper abdomen tests were rib fractures, liver lacerations, splenic lacerations, and kidney contusions. The lower abdomen tests tended to produce mesenteric lacerations and contusions of the small intestine, and ruptures of the large intestine. These findings will later be used to develop a reusable, biofidelic abdominal insert for the 6-year-old Hybrid III ATD.

Injury to the thorax is the predominant cause of fatalities in crash-involved automobile occupants over the age of 65, and many elderly-occupant automobile fatalities occur in crashes below compliance or consumer information test speeds. As the average age of the automotive population increases, thoracic injury prevention in lower severity crashes will play an increasingly important role in automobile safety. This study presents the results of a series of sled tests to investigate the thoracic deformation, kinematic, and injury responses of belted post mortem human surrogates (PMHS, average age 44 years) and frontal anthropomorphic test devices (ATDs) in low-speed frontal crashes. Nine 29 km/h (three PMHS, three Hybrid III 50th% male ATD, three THOR-NT ATD) and three 38 km/h (one PMHS, two Hybrid III) frontal sled tests were performed to simulate an occupant seated in the right font passenger seat of a mid-sized sedan restrained with a standard (not force-limited) 3-point seatbelt. All occupants were instrumented to record deformation contours and accelerations of the thorax at multiple locations. The ATD subjects were also instrumented to record the internal deformation of the thorax via multi-point tracking systems. For the 29 km/h tests, PMHS maximum chest deflections ranged from 10% to 19% of the undeformed chest depth, and peak mid-spine accelerations ranged from 21 to 24 g. The average peak internal mid-sternal (sternum slider) deflections for the Hybrid III were 23 mm (29 km/h tests) and 30 mm (38 km/h tests). The average maximum Hybrid III sternal deflection of 23 mm measured in the 29 km/h tests corresponds to an AIS 3+ thoracic injury risk of 14% or greater for people 70 years and older. This result suggests that three-point belted elderly occupants without shoulder-belt force limiters could experience non-trivial thoracic injuries in frontal crashes that are below NHTSA's compliance and/or consumer information test severities.

Rupture of the thoracic aorta is a leading cause of rapid fatality in automobile crashes, but the mechanism of this injury remains unknown. One commonly postulated mechanism is a differential motion of the aortic arch relative to the heart and its neighboring vessels caused by high-magnitude acceleration of the thorax. Recent Indy car crash data show, however, that humans can withstand accelerations exceeding 100 g with no injury to the thoracic vasculature. This paper presents a method to investigate the efficacy of acceleration as an aortic injury mechanism using high-acceleration, low chest deflection sled tests. The repeatability and predictability of the test method was evaluated using two Hybrid III tests and two tests with cadaver subjects. The cadaver tests resulted in sustained mid-spine accelerations of up to 80 g for 20 ms with peak mid-spine accelerations of up to 175 g, and maximum chest deflections lower than 11% of the total chest depth. Transient increases in intra-aortic pressure up to 177 kPa were measured. No macroscopic injuries to the thoracic aorta resulted from these tests. The method employed proved consistent and repeatable. This method may be appropriate for future investigation of the efficacy of acceleration as a predictor of aortic injury.

This study presents the development of a porcine (sus scrofa domestica) model to represent the abdomen of a 6-year-old human for biomechanical testing, and utilizes this model to quantify the mechanical response and injury tolerance of the pediatric abdomen to seatbelt loading. The long term goal of this study is to develop a biofidelic abdominal insert for the 6-year-old Hybrid III crash test dummy which will provide automotive design engineers with a tool to quantify the response of the abdomen during belt loading in order to mitigate abdominal injuries in pediatric occupants. Five loading parameters were controlled independently (abdominal deflection, loading rate, loading waveform, active abdominal muscle tensing, and belt location) to yield 47 distinct, repeated tests on 47 subjects. A custom-built loading frame was used to generate forced displacements using a two-point, transversely oriented seatbelt over the anterior abdomen. The injuries produced under the test conditions are the same types of seatbelt-induced abdominal injuries that are observed in pediatric occupants in real world automobile crashes. Specifically, the belt location is highly correlated to the type of injury seen, with upper abdominal tests resulting in more frequent liver, and spleen injuries, while lower abdominal tests more frequently generate injury to the large and small intestines. Preliminary examination of the data indicates that belt force, posterior reaction force, and maximum abdominal compression are predictive of abdominal injury. However, belt velocity was not predictive of abdominal injury, and the inclusion of velocity in a mathematical injury criterion (such as V*C) was not an improvement over belt force or maximum abdominal compression alone.