Stapp car crash journal最新文献

The objective of this study was to generate biomechanical corridors from post-mortem human subjects (PMHS) in two different seatback recline angles in 56 km/h sled tests simulating a rear-facing occupant during a frontal vehicle impact. PMHS were placed in a production seat which included an integrated seat belt. To achieve a repeatable configuration, the seat was rigidized in the rearward direction using a reinforcing frame that allowed for adjustability in both seatback recline angle and head restraint position. The frame contained instrumentation to measure occupant loads applied to the head restraint and seatback. To measure PMHS kinematics, the head, spine, pelvis, and lower extremities were instrumented with accelerometers and angular rate sensors. Strain gages were attached to anterior and posterior aspects of the ribs, as well as the mid-shaft of the femora and tibiae, to determine fracture timing. A chestband was installed at the mid sternum to quantify chest deformation. Biomechanical corridors for each body and seat location were generated for each recline angle to provide data for quantitatively evaluating the biofidelity of ATDs and HBMs. Injuries included upper extremity injuries, rib fractures, pelvis fractures, and lower extremity injuries. More injuries were documented in the 45-degree recline case than in the 25-degree recline case. These injuries are likely due to the excessive ramping up and corresponding kinematics of the PMHS. Biomechanical corridors and injury information presented in this study could guide the design of HBMs and ATDs in rigid, reclined, rear-facing seating configurations during a high-speed frontal impact.

This paper examines how vehicle backing technologies affect driver performance during backing maneuvers. We conducted experiments using sport utility vehicles (SUV) with four technological variations: a baseline vehicle (B-L), a vehicle equipped with a parking sensor (PS-V), a vehicle equipped with a backup camera (hereafter BC-V), and a vehicle equipped with both technologies (BCPS-V). Two reverse parking maneuvers were tested: backing straight and backing diagonally into a parking space. For each vehicle, we measured the parameters of the driver's gaze, vehicle speed, the distance between the stopped vehicle and an object behind it, and the presence or absence of contact with the object. Fifteen drivers participated in the experiment. For backing straight, the B-L and PS-V drivers gazed at the driver-side mirror the longest; BC-V and BCPS-V drivers gazed at the monitor the longest. There was no significant difference in maximum speed among the four backing technology conditions. The PS-V was the farthest from the object when stopped, followed by the BCPS-V, the BC-V, and the B-L. Regarding the rate of noncontact, the BCPS-V ranked highest (67%, 95% confidence of interval [CI] [38%, 88%]), followed by the PS-V (60%, 95% CI [32%, 84%]), the BC-V (53%, 95% CI [27%, 79%]), and the B-L (20%, 95% CI [4%, 48%]). For backing diagonally, the B-L and PS-V drivers gazed at the passenger-side mirror the longest; BC-V and BCPS-V drivers gazed at the monitor the longest. The vehicles' maximum speed showed no significant difference between the four backing technologies. However, the presence of backing technologies significantly reduced the vehicle speed at the object location. Once stopped, the BCPS-V had the longest distance from the object behind it, followed by the PS-V, the BC-V, and the B-L. The rate of non-contact was the highest for the PS-V (73%, 95% CI [45%, 92%]), followed by the BCPS-V (67%, 95% CI [38%, 88%]), the BC-V (60%, 95% CI [32%, 84%]), and the B-L (20%, 95% CI [4%, 48%]). These results indicate that the backing technologies in this study reduced the probability of direct impact with objects situated behind the vehicles. However, focusing on backing diagonally, which requires more complicated driving, vehicles equipped with a sonar backing system appear, in this study, to perform better in terms of stopping distance than those that did not have sonar.

Obese vehicle occupants sustain specific injury patterns in case of accidents in which the interaction between the seat belt and the abdomen may play a role. This study aimed to collect geometrical characteristics and to investigate the mechanical responses of the abdomen of obese subjects. Four Post Mortem Human Subjects (PMHS) with BMI ranging from 31 to 46 kg/m² were collected. CT-scans performed in the seated position revealed that the antero-posterior depth of the abdominal fold (from the inguinal region to the most anterior point of the abdominal surface) was much greater (170 mm max., 127 mm average) than the thickness of subcutaneous adipose tissues (85 max., 38 mm in average). Each PMHS was subjected to three infra-injurious antero-posterior belt pulls in a seated posture with a lap belt positioned (C1) superior to the umbilicus, (C2) inferior to the umbilicus, (C3) inside the abdominal fold between the abdomen and the thigh. During the C1 and C2 tests, the belt moved cranially, and the abdominal fold opened widely especially in C2. Forces remained below 1800 N, for maximum applied displacements ranging from 89 to 151 mm for C1 and C2, and 37 to 66 mm for C3. Finally, sled tests were conducted on two PMHS seated on a semi-rigid seat and restrained by a three-point belt equipped with pretensioners and a 3.5 kN force limitation at the shoulder. The first PMHS (BMI 39 kg/m²) was tested at 49 km/h (39 g peak) and sustained severe injuries (AIS 4 pelvis dislocation, AIS 3 bilateral femur fractures) attributed to the combined loading of the seat and lap belt force (about 11 kN and 7 kN, respectively). The second PMHS (BMI 46 kg/m²) was subjected to a 29 km/h test (8 g plateau) and sustained no injury. The lap belt slid inside the abdominal fold in the first case and deformed the lower abdomen in the second, providing limited restraint forces during that interaction and leading to a large body excursion for the first test. The results highlight the possible relevance of the abdominal fold at the abdomen thigh junction to model and study the restraint conditions of obese occupants using Human Body Models (HBM).

Frontal impacts with reclined occupants are rare but severe, and they are anticipated to become more common with the introduction of vehicles with automated driving capabilities. Computational and physical human surrogates are needed to design and evaluate injury countermeasures for reclined occupants, but the validity of such surrogates in a reclined posture is unknown. Experiments with post-mortem human subjects (PMHS) in a recline posture are needed both to define biofidelity targets for other surrogates and to describe the biomechanical response of reclined occupants in restrained frontal impacts. The goal of this study was to evaluate the kinematic and injury response of reclined PMHS in 30 g, 50 km/h frontal sled tests. Five midsize adult male PMHS were tested. A simplified semi-rigid seat with an anti-submarining pan and a non-production threepoint seatbelt (pre-tensioned, force-limited, seat-integrated) were used. Global motions and local accelerations of the head, pelvis, and multiple vertebrae were measured. Seat and seatbelt forces were also measured. Injuries were assessed via post-test dissection. The initial reclined posture aligned body regions (pelvis, lumbar spine, and ribcage) in a way that reduced the likelihood of effective restraint by the seat and seatbelt: the occupant's pelvis was initially rotated posteriorly, priming the occupant for submarining, and the lumbar spine was loaded in combined compression and bending due to the inertia of the upper torso during forward excursion. Coupled with the high restraining forces of the seat and seatbelt, the unfavorable kinematics resulted in injuries of the sacrum/coccyx (four of five PMHS injured), iliac wing (two of five PMHS injured), lumbar spine (three of five PMHS injured), and ribcage (all five PMHS suffered sternal fractures, and three of five PMHS suffered seven or more rib fractures). The kinematic and injury outcomes strongly motivate the development of injury criteria for the lumbar spine and pelvis, the inclusion of intrinsic variability (e.g., abdomen depth and pelvis shape) in computational simulations of frontal impacts with reclined occupants, and the adaptation of comprehensive restraint paradigms to predicted variability of occupant posture.

The CORA rating metric is frequently used in the field of injury biomechanics to compare the similarity of response time histories. However, subjectivity exists within the CORA metric in the form of user-customizable parameters that give the metric the flexibility to be used for a variety of applications. How these parameters are customized is not always reported in the literature, and it is unknown how these customizations affect the CORA scores. Therefore, the purpose of this study was to evaluate how variations in the CORA parameters affect the resulting similarity scores. A literature review was conducted to determine how the CORA parameters are commonly customized within the literature. Then, CORA scores for two datasets were calculated using the most common parameter customizations and the default parameters. Differences between the CORA scores using customized and default parameters were statistically significant for all customizations. Furthermore, most customizations produced score increases relative to the default settings. The use of standard deviation corridors and exclusion of the corridor component were found to produce the largest score differences. The observed differences demonstrated the need for researchers to exercise transparency when using customized parameters in CORA analyses.

Naturalistic driving studies have shown that pediatric occupants do not assume ideal seating positions in real-world scenarios. Current vehicle assessment programs and child restraint system (CRS) sled tests, such as FMVSS No. 213, do not account for a wide range of seating postures that are typically observed during real-world trips. Therefore, this study aims to analyze the kinematic and kinetic response of a pediatric human body model in various naturalistic seating positions in booster seats when subjected to a frontal offset impact in a full-vehicle environment, with and without the application of pre-crash automatic emergency braking (AEB). A 6YO (seated on a lowback and highback booster) and a 10YO (seated in no-CRS and on a lowback booster) PIPER pediatric human body model's response was explored in a reference, and two most commonly observed seating postures: forward-leaning and forward-inboard-leaning. The vehicle environment with a side-curtain airbag (SCAB) was subjected to a small offset barrier impact (25% overlap at 40MPH), with and without the application of a pre-crash automatic emergency braking (AEB). 24 conditions were simulated using finite element analysis. Cases with a pre-crash AEB resulted in relatively lower kinematic and kinetic values due to the occupant being in a more flexed position before impact compared to without-AEB cases, coupled with the increased ride-down effect due to AEB. Moreover, different seating postures resulted in substantially different kinematics and kinetics, the injury metrics crossing the injury assessment reference values in some cases. Therefore, to design a passive safety standard test for pediatric occupants, it is important to consider the possible postural changes that may occur.

Motor vehicle crashes remain the leading cause of death for children. Traditionally, restraint design has focused on the crash phase of the impact with an optimally seated occupant. In order to optimize restrain design for real-world scenarios, research has recently expanded its focus to non-traditional loading conditions including pre-crash positioning and lower speed impacts. The goal of this study was to evaluate the biofidelity of the large omni-directional child (LODC) ATD in non-traditional loading conditions by comparing its response to pediatric volunteer data in low-speed sled tests. Low-speed (2-4 g, 1.9-3.0 m/s) frontal (0°), far-side oblique (60°), and far-side lateral (90º) sled tests, as well as lateral swerving (0.72 g, 0.5 Hz) tests, were conducted using the LODC. The LODC was restrained using a 3-point-belt with an electromechanical motorized seat belt retractor, or pre-pretensioner. Motion capture markers were placed on the head, torso, and belt. The LODC was compared to previously collected pediatric volunteer data as well as the HIII 10 and Q10. Significant difference between the pediatric volunteers and ATDs were identified by comparing the mean ATD response to the pediatric volunteer 95% CI. The LODC exhibited lower forward head excursion (262 mm) compared to pediatric volunteers (263 - 333 mm) in low-speed frontal sled tests (p<0.05), but was closer to the pediatric volunteers than the HIII 10 (179 mm) and Q10 (171 mm). In lateral swerving, the LODC (429 mm) exhibited greater lateral head excursion (p<0.05) compared to pediatric volunteers (115 - 171 mm). The LODC exhibited a greater reduction in kinematics compared to the pediatric volunteers in all loading conditions with a pre-pretensioner. These data provide valuable insight into the biofidelity of the LODC in non-traditional loading conditions, such as evaluating pre-crash maneuvers on occupant response.

Lower extremity injuries caused by floor plate impacts through the axis of the lower leg are a major source of injury and disability for civilian and military vehicle occupants. A collection of PMHS pendulum impacts was revisited to obtain data for paired booted/unbooted test on the same leg. Five sets of paired pendulum impacts (10 experiments in total) were found using four lower legs from two PMHS. The PMHS size and age was representative of an average young adult male. In these tests, a PMHS leg was impacted by a 3.4 or 5.8 kg pendulum with an initial velocity of 5, 7, or 10 m/s (42-288 J). A matching LS-DYNA finite element model was developed to replicate the experiments and provide additional energy, strain, and stress data. Simulation results matched the PMHS data using peak values and CORA curve correlations. Experimental forces ranged between 1.9 and 12.1 kN experimentally and 2.0 and 11.7 kN in simulation. Combat boot usage reduced the peak force by 36% experimentally (32% in simulation) by compressing the sole and insole with similar mitigations for calcaneus strain. The simulated Von Mises stress contours showed the boot both mitigating and shifting stress concentrations from the calcaneus in unbooted impacts to the talus-tibia joint in the booted impacts, which may explain why some previous studies have observed shifts to tibia injuries with boot or padding usage.

Several studies, available in the literature, were conducted to establish the most relevant criterion for predicting the thoracic injury risk on the THOR dummy. The criteria, such as the maximum deflection or a combination of parameters including the difference between the chest right and left deflections, were all developed based on given samples of Post Mortem Human Subject (PMHS). However, they were not validated against independent data and they are not always consistent with the observations from field data analysis. For this reason, 8 additional PMHS and matching THOR tests were carried out to assess the ability of the criteria to predict risks. Accident investigations showed that a reduction of the belt loads reduces the risk of rib fractures. Two configurations with different levels of force limitation were therefore chosen. A configuration representing an average European vehicle was chosen as a reference. It consists of a 3-point belt with a 3.5 kN and then 2 kN digressive limiter, combined with a 54-liter airbag. For better reproducibility and durability, the tests were performed with a pre-inflated bag and a semi-rigid seat. In this first configuration, the THOR dummy had a maximum resulting deflection of 43 mm. To differentiate the criteria, the second configuration was chosen such that it resulted in about the same deflection on the THOR dummy, but with a 5 kN belt force limitation combined with a lower pressure airbag. To reach this target of 43 mm, the pulse severity was lowered. Some criteria were higher in this second configuration, which allows them to be distinguished from the maximum deflection criterion. Four tests on four PMHS were performed in each configuration. The injury assessments showed that the total number of fractures was almost the same in both configurations, but that the number of separated fractures was greater in the 5 kN configuration. 25% of the subjects sustained AIS >3 injuries related to the number of displaced fractures in the 3.5/2 kN load limitation configuration. The result increased to 75% in the 5kN configuration. In total, 8 PMHS and the matching THOR tests were performed and used to assess the ability of the thoracic criteria to predict rib fractures in 2 types of chest loading configurations. The test results did not allow to conclude on the relevance of the criteria measured on the THOR dummy for the total number of rib fractures identified at autopsy (NFR). However, clearly different assessments for separated rib fractures (NSFR), make it possible to differentiate the criteria. The maximum resultant deflection failed to properly predict separated rib fractures while other criteria that include the left-to-right rib deflection difference did.