Anthropomorphic Test Device Research Articles

Foot force models of crowd dynamics on a wobbly bridge.

Modern pedestrian and suspension bridges are designed using industry standard packages, yet disastrous resonant vibrations are observed, necessitating multimillion dollar repairs. Recent examples include pedestrian-induced vibrations during the opening of the Solférino Bridge in Paris in 1999 and the increased bouncing of the Squibb Park Bridge in Brooklyn in 2014. The most prominent example of an unstable lively bridge is the London Millennium Bridge, which started wobbling as a result of pedestrian-bridge interactions. Pedestrian phase locking due to footstep phase adjustment is suspected to be the main cause of its large lateral vibrations; however, its role in the initiation of wobbling was debated. We develop foot force models of pedestrians' response to bridge motion and detailed, yet analytically tractable, models of crowd phase locking. We use biomechanically inspired models of crowd lateral movement to investigate to what degree pedestrian synchrony must be present for a bridge to wobble significantly and what is a critical crowd size. Our results can be used as a safety guideline for designing pedestrian bridges or limiting the maximum occupancy of an existing bridge. The pedestrian models can be used as "crash test dummies" when numerically probing a specific bridge design. This is particularly important because the U.S. code for designing pedestrian bridges does not contain explicit guidelines that account for the collective pedestrian behavior.

Rotational and linear head accelerations from taekwondo kicks and punches

ABSTRACTThe purpose was to compare rotational and linear head accelerations as a result of taekwondo kicks and punches. Taekwondo athletes executed five repetitions of the turning kick, spinning hook kick, hook punch, straight punch, and jab punch to a Hybrid III Crash Test Dummy head-neck complex. A tri-axial accelerometer and an angular rate sensor were mounted inside the Hybrid III head to measure resultant linear (RLA) and rotational accelerations. The Hybrid III was fixed to a height-adjustable frame and fitted with protective taekwondo headgear. Dummy head height was positioned to each participant’s standing height. Acceleration data were processed in accordance with SAE J211-1.There was no significant multivariate difference in RLA but the effect was not clear. Univariate follow-up analysis showed a significant difference in RLA but the effect was also not clear. There was no difference in rotational acceleration. The highest RLA and rotational acceleration were produced, in order, by the turning kick, hook kick, hook punch, straight punch, and jab. These data are clinically important as they provide a better understanding of the biomechanical injury measures and support for improved headgear testing methodology.

DEVELOPMENT AND BIOFIDELITY EVALUATION OF AN OCCUPANT BIOMECHANICAL MODEL OF A CHINESE 50TH PERCENTILE MALE FOR SIDE IMPACT

Finite element modeling has played a significant role in the study of human body biomechanical responses and injury mechanisms during vehicle impacts. However, there are very few reports on similar studies conducted in China for the Chinese population. In this study, a high-precision human body finite element model of the Chinese 50th percentile male was developed. The anatomical structures and mechanical characteristics of real human body were replicated as precise as possible. In order to analyze the model’s biofidelity in side-impact injury prediction, a global technical standard, ISO/TR 9790, was used that specifically assesses the lateral impact biofidelity of anthropomorphic test devices (ATDs) and computational models. A series of model simulations, focusing on different body parts, were carried out against the tests outlined in ISO/TR 9790. Then, the biofidelity ratings of the full human body model and different body parts were evaluated using the ISO/TR 9790 rating method. In a 0–10 rating scale, the resulting rating for the full human body model developed is 8.57, which means a good biofidelity. As to different body parts, the biofidelity ratings of the head and shoulder are excellent, while those of the neck, thorax, abdomen and pelvis are good. The resulting ratings indicate that the human body model developed in this study is capable of investigating the side-impact responses of and injuries to occupants’ different body parts. In addition, the rating of the model was compared with those of the other human body finite element models and several side-impact dummy models. This allows us to assess the robustness of our model and to identify necessary improvements.

Crash-test dummy and pendulum impact tests of ice hockey boards: greater displacement does not reduce impact

BackgroundOne injury mechanism in ice hockey is impact with the boards. We investigated whether more flexible hockey boards would provide less biomechanical loading on impact than did existing (reference) boards.MethodsWe...

Automated recognition of rear seat occupants' head position using Kinect™ 3D point cloud

IntroductionChild occupant safety in motor-vehicle crashes is evaluated using Anthropomorphic Test Devices (ATD) seated in optimal positions. However, child occupants often assume suboptimal positions during real-world driving trips. Head impact to the seat back has been identified as one important injury causation scenario for seat belt restrained, head-injured children (Bohman et al., 2011). There is therefore a need to understand the interaction of children with the Child Restraint System to optimize protection. MethodNaturalistic driving studies (NDS) will improve understanding of out-of-position (OOP) trends. To quantify OOP positions, an NDS was conducted. Families used a study vehicle for two weeks during their everyday driving trips. The positions of rear-seated child occupants, representing 22 families, were evaluated. The study vehicle – instrumented with data acquisition systems, including Microsoft Kinect™ V1 – recorded rear seat occupants in 1120 driving 26 trips. Three novel analytical methods were used to analyze data. To assess skeletal tracking accuracy, analysts recorded occurrences where Kinect™ exhibited invalid head recognition among a randomly-selected subset (81 trips). Errors included incorrect target detection (e.g., vehicle headrest) or environmental interference (e.g., sunlight). When head data was present, Kinect™ was correct 41% of the time; two other algorithms – filtering for extreme motion, and background subtraction/head-based depth detection are described in this paper and preliminary results are presented. Accuracy estimates were not possible because of their experimental nature and the difficulty to use a ground truth for this large database. This NDS tested methods to quantify the frequency and magnitude of head positions for rear-seated child occupants utilizing Kinect™ motion-tracking. ResultsThis study's results informed recent ATD sled tests that replicated observed positions (most common and most extreme), and assessed the validity of child occupant protection on these typical CRS uses. SummaryOptimal protection in vehicles requires an understanding of how child occupants use the rear seat space. This study explored the feasibility of using Kinect™ to log positions of rear seated child occupants. Initial analysis used the Kinect™ system’s skeleton recognition and two novel analytical algorithms to log head location. Practical applicationsThis research will lead to further analysis leveraging Kinect™ raw data – and other NDS data – to quantify the frequency/magnitude of OOP situations, ATD sled tests that replicate observed positions, and advances in the design and testing of child occupant protection technology.

Evaluation of the effectiveness of toe board energy-absorbing material for foot, ankle, and lower leg injury reduction

ABSTRACTObjective: Since 2000, numerous improvements have been made to the National Association for Stock Car Auto Racing, Incorporated (NASCAR®) driver restraint system, resulting in improved crash protection for motorsports drivers. Advancements have included seats, head and neck restraints (HNRs), seat belt restraint systems, driver helmets, and others. These enhancements have increased protection for drivers from severe crash loading. Extending protection to the driver's extremities remains challenging. Though the drivers’ legs are well contained for lateral and vertical crashes, they remain largely unrestrained in frontal and frontal oblique crashes.Method: Sled testing was conducted for the evaluation of an energy-absorbing (EA) toe board material to be used as a countermeasure for leg and foot injuries. Testing included baseline rigid toe boards, tests with EA material–covered toe boards, and pretest positioning of the 50th percentile male frontal Hybrid III anthropomorphic test device (ATD) lower extremities. ATD leg and foot instrumentation included foot acceleration and tibia forces and moments.Results: The sled test data were evaluated using established injury criteria for tibial plateau fractures, leg shaft fractures, and calcaneus, talus, ankle, and midfoot fractures.Conclusion: A polyurethane EA foam was found to be effective in limiting axial tibia force and foot accelerations when subjected to frontal impacts using the NASCAR motorsport restraint system.

The Effect of Anthropomorphic Test Device Lower Leg Surrogate Selection on Impact Mitigating System Evaluation in Low- and High-Rate Loading Conditions.

The lower legs are at risk of substantial injury during events such as frontal automotive crashes and antivehicular mine blasts. Loading to occupants can be assessed using an instrumented anthropomorphic test device (ATD), whose measurements can be compared to established injury criteria. NATO's AEP-55 STANAG 4569 recognizes two surrogates for lower leg injury assessments from impacts with intruding floor pans resulting from underbelly blast loads; (1) the rigid Hybrid III instrumented lower leg, and; (2) the compliant MILitary Lower eXtremity (MIL-LX). The established injury criterion for the Hybrid III leg specifies a maximum lower tibia compressive load of 5.4 kN, whereas the MIL-LX limit is 2.6 kN measured at the upper tibia for similar injury severity levels. The difference in compliance between the two legs could affect the evaluation of protection levels, resulting in an over- or under-estimation of the force attenuation of energy attenuating (EA) floor mats. The responses of the two lower leg surrogates were evaluated at impact velocities up to 12 m/s, representing floor intrusions during antivehicle mine blasts. An air cannon was used to accelerate a rigid or padded floor plate into the sole of the surrogate lower legs, loading them axially, in order to assess the protective capability of commercial EA floor mats. The peak load from the lower and upper load cells in the Hybrid III and MIL-LX legs were compared to identify at what point their respective injury criteria would be exceeded in both the padded and unpadded conditions. Comparisons of the surrogate legs' responses resulted in different evaluations of risk, with the Hybrid III leg exceeding its limit at an impact speed of 6.0 m/s, and the MIL-LX exceeding its limit at 5.5 m/s (for tests including an EA product). Furthermore, the inclusion of an EA mat had a greater relative protective effect on the Hybrid III than the MIL-LX leg, with padding reducing the force to 17 to 34% of the unpadded condition for the Hybrid III, versus 67 to 89% of the unpadded condition for the MIL-LX. The load reduction was found to be velocity dependent for both surrogates. These results indicate that the two surrogates are not equivalent in their assessment of protective capability. Therefore, the selection of ATD leg for testing of EA mats (and other protective devices) will influence the evaluation of these systems, and more robust metrics are required to identify which is the most appropriate surrogate for evaluating injury to the lower limb.

Comparison of response variation of THOR and Hybrid III dummy Models in a controlled rollover impact model

ABSTRACTSeveral dynamic rollover test procedures have been developed over the years; however, the repeatability of test results is often questioned. Also, there can be sensitivity of test and simulation results to small variations in the initial conditions. The objective of this study is to evaluate the response variation of three different crash dummy finite element (FE) models (two versions of a 50th percentile male Hybrid III (HIII) and a Test Device for Human Occupant Restraint (THOR) dummy) in a simulation of a controlled rollover test, using a late model vehicle FE model. A baseline model was established with each dummy, and then a global sensitivity analysis was performed for each dummy varying vehicle design and crash parameters. The simplified HIII dummy model was very sensitive to small variations in the initial conditions of the test. Both the THOR and detailed HIII models gave very consistent results presenting similar trends in the sensitivity analysis.

Effects of Lumbar Spine Assemblies and Body-Borne Equipment Mass on Anthropomorphic Test Device Responses During Drop Tests.

When simulating or conducting land mine blast tests on armored vehicles to assess potential occupant injury, the preference is to use the Hybrid III anthropomorphic test device (ATD). In land blast events, neither the effect of body-borne equipment (BBE) on the ATD response nor the dynamic response index (DRI) is well understood. An experimental study was carried out using a drop tower test rig, with a rigid seat mounted on a carriage table undergoing average accelerations of 161 g and 232 g over 3 ms. A key aspect of the work looked at the various lumbar spine assemblies available for a Hybrid III ATD. These can result in different load cell orientations for the ATD which in turn can affect the load measurement in the vertical and horizontal planes. Thirty-two tests were carried out using two BBE mass conditions and three variations of ATDs. The latter were the Hybrid III with the curved (conventional) spine, the Hybrid III with the pedestrian (straight) spine, and the Federal Aviation Administration (FAA) Hybrid III which also has a straight spine. The results showed that the straight lumbar spine assemblies produced similar ATD responses in drop tower tests using a rigid seat. In contrast, the curved lumbar spine assembly generated a lower pelvis acceleration and a higher lumbar load than the straight lumbar spine assemblies. The maximum relative displacement of the lumbar spine occurred after the peak loading event, suggesting that the DRI is not suitable for assessing injury when the impact duration is short and an ATD is seated on a rigid seat on a drop tower. The peak vertical lumbar loads did not change with increasing BBE mass because the equipment mass effects did not become a factor during the peak loading event.

Differences in the kinematics of booster-seated pediatric occupants using two different car seats

ABSTRACTObjective: The objective of this article is to compare the performance of forward-facing child restraint systems (CRS) mounted on 2 different seats.Methods: Two different anthropomorphic test device (ATD) sizes (P3 and P6), using the same child restraint system (a non-ISOFIX high-back booster seat), were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Two different seats (seat A, seat B) were used. Three repetitions per ATD and mounting seat were done, resulting in a total of 12 sled crashes. Dummy sensors measured the head tri-axial acceleration and angular rate and the thorax tri-axial acceleration, all acquired at 10,000 Hz. A high-speed video camera recorded the impact at 1,000 frames per second. The 3D kinematics of the head and torso of the ATDs were captured using a high-speed motion capture system (1,000 Hz). A pair-matched statistical analysis compared the outcomes of the tests using the 2 different seats.Results: Statistically significant differences in the kinematic response of the ATDs associated with the type of seat were observed. The maximum 3 ms peak of the resultant head acceleration was higher on seat A for the P3 dummy (54.5 ± 1.9 g vs. 44.2 ± 0.5 g; P =.012) and for the P6 dummy (56.0 ± 0.8 g vs. 51.7 ± 1.2 g; P =.015). The peak belt force was higher on seat A than on seat B for the P3 dummy (5,488.0 ± 198.0 N vs. 4,160.6 ± 63.6 N; P =.008) and for the P6 dummy (7,014.0 ± 271.0 N vs. 5,719.3 ± 37.4 N; P =.015). The trajectory of the ATD head was different between the 2 seats in the sagittal, transverse, and frontal planes.Conclusion: The results suggest that the overall response of the booster-seated occupant exposed to the same impact conditions was different depending on the seat used regardless of the size of the ATD. The differences observed in the response of the occupants between the 2 seats can be attributed to the differences in cushion stiffness, seat pan geometry, and belt geometry. However, these results were obtained for 2 particular seat models and a specific CRS and therefore cannot be directly extrapolated to the generality of vehicle seats and CRS.

Comparison of Q-series child dummy and human model restrained in shield CRS in frontal impact

ABSTRACTChild Restraint System (CRS) can effectively protect child occupants from severe injury in vehicle collision; thus, the Q-series anthropomorphic test devices (ATD or dummy) are necessary for testing the performance of CRSs. In this study, complementary approaches (sled testing with a Q1.5 dummy, computer simulation with a Q1.5 dummy model and 1.5 YO human model) are developed to study the difference of the Q-series child dummy and human model while restrained in shield CRS. The results suggest that in frontal sled impact, the differences in the dynamic response of the Q-series dummy and human model are mainly due to the stiffer thoracic spine and lumbar spine. The implications of these differences for the evaluation and design of Q-series child ATD will be discussed. Also, some suggestions about the improvement of the Q-series child ATD are provided.

Kinetic and kinematic analysis of stamping impacts during simulated rucking in rugby union

ABSTRACTLaceration injuries account for up to 23% of injuries in rugby union. They are frequently caused by studded footwear as a result of a player stamping onto another player during the ruck. Little is known about the kinetics and kinematics of rugby stamping impacts; current test methods assessing laceration injury risk of stud designs therefore lack informed test parameters. In this study, twelve participants stamped on an anthropomorphic test device in a one-on-one simulated ruck setting. Velocity and inclination angle of the foot prior to impact was determined from high-speed video footage. Total stamping force and individual stud force were measured using pressure sensors. Mean foot inbound velocity was 4.3 m ∙ s−1 (range 2.1–6.3 m ∙ s−1). Mean peak total force was 1246 N and mean peak stud force was 214 N. The total mean effective mass during stamping was 6.6 kg (range: 1.6–13.5 kg) and stud effective mass was 1.2 kg (range: 0.5–2.9 kg). These results provide representative test parameters for mechanical test devices designed to assess laceration injury risk of studded footwear for rugby union.

Mechanical characterization and finite element implementation of the soft materials used in a novel anthropometric test device for simulating underbody blast loading

Soft materials (e.g. polymers) are widely used in biomechanical devices to represent the nonlinear viscoelastic properties inherent in biological soft tissues. Knowledge of their mechanical properties is used to inform design choices and develop accurate finite element (FE) models of human surrogates. The goal of this study was to characterize the behavior of eight polymeric materials used in the design of a novel anthropomorphic test device (ATD) and implement these materials in an FE model of the ATD.Tensile and compressive tests at strain rates ranging from 0.01s−1 to 1000s−1 were conducted on specimens from each material. Stress-strain relationships at discrete strain rates were used to define strain rate-dependent hyper-elastic material models in a commercial finite element solver. Then, the material models were implemented into an FE model of the ATD. The performance of the material models in the FE model was evaluated by simulating experiments that were conducted on the ATD lower limb.The material characterization tests revealed viscoelastic strain rate-dependent properties in the flesh and compliant elements of the ATD. Higher modulus polymers exhibited rate-dependent, strain-hardening properties. A strong agreement was seen between the material model simulations and corresponding experiments. In component simulations, the materials performed well and the model reasonably predicted the forces observed in experiments.

An automated method to morph finite element whole-body human models with a wide range of stature and body shape for both men and women

Field data analyses have shown that small female, obese, and/or older occupants are at increased risks of death and serious injury in motor-vehicle crashes compared with mid-size young men. The current adult finite element (FE) human models represent occupants in the same three body sizes (large male, mid-size male, and small female) as those for the contemporary adult crash dummies. Further, the time needed to develop an FE human model using the traditional method is measured in months or even years. In the current study, an improved regional mesh morphing method based on landmark-based radial basis function (RBF) interpolation was developed to rapidly morph a mid-size male FE human model into different geometry targets. A total of 100 human models with a wide range of human attributes were generated. A pendulum chest impact condition was applied to each model as an initial assessment of the resulting variability in response. The morphed models demonstrated mesh quality similar to the baseline model. The peak impact forces and chest deflections in the chest pendulum impacts varied substantially with different models, supportive of consideration of population variation in evaluating the occupant injury risks. The method developed in this study will enable future safety design optimizations targeting at various vulnerable populations that cannot be considered with the current models.

Average male and female virtual dummy model (BioRID and EvaRID) simulations with two seat concepts in the Euro NCAP low severity rear impact test configuration

Soft tissue neck injuries, also referred to as whiplash injuries, which can lead to long term suffering accounts for more than 60% of the cost of all injuries leading to permanent medical impairment for the insurance companies, with respect to injuries sustained in vehicle crashes. These injuries are sustained in all impact directions, however they are most common in rear impacts. Injury statistics have since the mid-1960s consistently shown that females are subject to a higher risk of sustaining this type of injury than males, on average twice the risk of injury. Furthermore, some recently developed anti-whiplash systems have revealed they provide less protection for females than males. The protection of both males and females should be addresses equally when designing and evaluating vehicle safety systems to ensure maximum safety for everyone. This is currently not the case. The norm for crash test dummies representing humans in crash test laboratories is an average male. The female part of the population is not represented in tests performed by consumer information organisations such as NCAP or in regulatory tests due to the absence of a physical dummy representing an average female.Recently, the world first virtual model of an average female crash test dummy was developed. In this study, simulations were run with both this model and an average male dummy model, seated in a simplified model of a vehicle seat. The results of the simulations were compared to earlier published results from simulations run in the same test set-up with a vehicle concepts seat. The three crash pulse severities of the Euro NCAP low severity rear impact test were applied. The motion of the neck, head and upper torso were analysed in addition to the accelerations and the Neck Injury Criterion (NIC). Furthermore, the response of the virtual models was compared to the response of volunteers as well as the average male model, to that of the response of a physical dummy model. Simulations with the virtual male and female dummy models revealed differences in dynamic response related to the crash severity, as well as between the two dummies in the two different seat models. For the comparison of the response of the virtual models to the response of the volunteers and the physical dummy model, the peak angular motion of the first thoracic vertebra as found in the volunteer tests and mimicked by the physical dummy were not of the same magnitude in the virtual models.The results of the study highlight the need for an extended test matrix that includes an average female dummy model to evaluate the level of occupant protection different seats provide in vehicle crashes. This would provide developers with an additional tool to ensure that both male and female occupants receive satisfactory protection and promote seat concepts that provide the best possible protection for the whole adult population. This study shows that using the mathematical models available today can provide insights suitable for future testing.

Development of thoracic injury risk functions for the THOR ATD

The Test Device for Human Occupant Restraint (THOR) 50th percentile male anthropomorphic test device (ATD) aims to improve the ability to predict the risk of chest injury to restrained automobile occupants by measuring dynamic chest deflection at multiple locations. This research aimed to describe the methods for developing a thoracic injury risk function (IRF) using the multi-point chest deflection metrics from the 50th percentile male THOR Metric ATD with the SD-3 shoulder and associating to post-mortem human subjects (PMHS) outcomes that were matched on identical frontal and frontal-oblique impact sled testing conditions. Several deflection metrics were assessed as potential predictor variables for AIS 3+ injury risk, including a combined metric, called PC Score, which was generated from a principal component analysis. A parametric survival analysis (specifically, accelerated failure time (AFT) with Weibull distribution) was assessed in the development of the IRF. Model fit was assessed using various modeling diagnostics, including the area under the receiver operating characteristic curve (AUC). Models based on resultant deflection consistently exhibited improved fit compared to models based on x-axis deflection or chord deflection. Risk functions for the THOR PC Score and Cmax (maximum resultant deflection) were qualitatively equivalent, producing AUCs of 0.857 and 0.861, respectively. Adjusting for the potential confounding effects of age, AFT survival models with Cmax or PC Score as the primary deflection metric resulted in the THOR injury risk models with the best combination of biomechanical appropriateness, potential utility and model fit, and may be recommended as injury predictors.

Evaluation of a coplanar 6a3ω configuration in the Hybrid III 50th percentile male head

ABSTRACTObjectives: In order to understand the mechanisms of traumatic brain injury (TBI) and develop proper safety measures, it is essential that accurate instrumentation methods are utilized. The brain injury criterion (BrIC) has been developed and validated to predict brain injuries in combination with the head injury criterion (Takhounts et al. 2011, 2013). Because the validated BrIC is heavily dependent on angular motion, the accuracy of any head instrumentation technique should be judged in part by its ability to measure angular motion. The main objective of this study was to evaluate a method of accurately measuring 6-degree-of-freedom (DOF) anthropomorphic test device (ATD) head kinematics using a coplanar 6 accelerometers and 3 angular rate sensors (6a3ω) configuration.Methods: A coplanar 6a3ω configuration (c6a3ω) was implemented via a newly designed fixture. The c6a3ω fixture was placed at the center of gravity (CG) of a Hybrid III 50th percentile ATD (HIII 50) head. In addition, a tetrahedron fixture with 9 installed accelerometers (tNAAP) was externally mounted on the posterior surface of the HIII 50 skull cap. The c6a3ω setup also allowed for comparison to the 3a3ω configuration (i3a3ω) by subsequently treating the c6a3ω fixture as an i3a3ω fixture by only using accelerations and angular rates from select sensors. A total of 63 tests were conducted by impacting the head–neck apparatus at various high speeds and directions by a pneumatic ram. Normalized root mean square deviation (NRMSD), peak differences, and uncertainty were used for quantitative evaluation of the 3 configurations (e.g., c6a3ω, i3a3ω, and tNAAP).Results: The average NRMSD and peak differences between the calculated angular accelerations were less than 5% between the tNAAP and the c6a3ω with 5.6% of uncertainty but greater than 18% for NRMSD and 20% for the peak differences between the tNAAP and i3a3ω with 58.2% uncertainty. Average NRMSD and peak differences between transformed resultant linear accelerations and gold standards (accelerations directly measured by accelerometers at the origin of tNAAP or c6a3ω fixtures) were also calculated. The c6a3ω had both NRMSD and peak differences less than 3% (uncertainty of 2.5%), and i3a3ω had NRMSD, peak values, and uncertainty on the order of 20% and higher. The tNAAP was slightly less accurate than the c6a3ω for transformed accelerations (NRMSD and peak differences <6%, uncertainty of 4.6%) and showed NRMSD and peak differences in the 7–8% range for angular velocity and rotation (uncertainty of 4.3 and 6.7%, respectively).Conclusions: The c6a3ω configuration exhibited much better accuracy for calculating angular acceleration and transformed linear acceleration than the i3a3ω configuration. The tNAAP showed slightly less accurate transformed linear acceleration than the c6a3ω and was demonstrated to have less accuracy than c6a3ω and i3a3ω for calculating angular velocity and rotation. The c6a3ω configuration could be a potential alternative to specialized NAAP ATD heads because all kinematics can be measured near the head CG, and 6a3ω instrumentation provides the most comprehensive 6DOF kinematics (i.e., accelerations, velocities, and displacements) with accuracy.

Repeatability testing of a new Hybrid III 6-year-old ATD lower extremity

ABSTRACTObjective: Vehicle safety is improving, thus decreasing the number of life-threatening injuries and increasing the need for research in other areas of the body. The current child anthropomorphic test device (ATD) does not have the capabilities or instrumentation to measure many of the potential interactions between the lower extremity and the vehicle interior. A prototype Hybrid III 6-year-old ATD lower extremity (ATD-LE) was developed and contains a tibia load cell and a more biofidelic ankle. The repeatability of the device has not yet been assessed; thus, the objective was to evaluate the repeatability of the ATD-LE. Additionally, a dynamic assessment was conducted to quantify injury threshold values.Methods: A pneumatic ram impactor was used at 2 velocities to evaluate repeatability. The ATD-LE was fixed to a table and impacted on the plantar aspect of the forefoot. Three repeated trials at 1.3 and 2.3 m/s without shoes and 2.3 m/s with shoes were conducted. The consistency of tibia force (N), bending moment (Nm), ankle range of motion (ROM, °), and stiffness (Nm/°) were quantified. A dynamic assessment using knee bolster airbag (KBA) tests was also conducted. The ATD-LE was positioned to mimic 3 worst-case scenarios: toes touching the mid-dashboard, touching the lower dashboard, and flat on the floor prior to airbag deployment. The impact responses in the femur and tibia were directly collected and compared with published injury threshold values.Results: Ram impact testing indicated primarily excellent repeatability for the variables tested. For all 3 conditions the coefficients of variance (CV) were as follows: tibia force, 1.9–2.7%; tibia moment, 1.0–2.2%; ROM, 1.3–1.4%; ankle stiffness, 4.8–15.6%. The shoe-on condition resulted in a 25% reduction in tibia force and a 56% reduction in tibia bending moment. The KBA tests indicate that the highest injury risk may be when the toes touch the lower dashboard, due to the high bending moments recorded in the tibia at 76.2 Nm, which was above the injury threshold.Conclusions: The above work has demonstrated that the repeatability of the ATD-LE was excellent for tibia force, bending moment, and ankle ROM. The ATD-LE has the ability to provide new information to engineers and researchers due to its ability to directly evaluate the crash response of the ankle and leg. New information on injury mechanism and injury tolerance may lead to injury reduction and thus help advance the safety of children.

Validation of a railway inline seating model for occupants injury biomechanics

ABSTRACTThis paper presents the validation of a finite element model in LS-DYNA of the interior inline seating layout simulating a frontal rail impact event for which the experimental test results provide the reference for the injury biomechanics of the occupants. The representative layout consists in two rows of seats and its supporting structures modelled with nonlinear finite elements and the crash acceleration pulse that represents the impact of the railway vehicle structure is imposed in the floor of the coach. For the appropriate identification of the injury mechanisms to the occupant associated to the frontal crash analysis is used the Hybrid III 50th percentile Anthropomorphic Testing Device, being the interaction between the occupant model and the structure characterised via penalty contact force models. The validity of the numerical model is discussed to ensure the representativeness of the analysis procedure and to identify the most relevant injury indices of the occupants. In particular, the head injury criterion is the most critical injury index for the inline seating layout, with a relative deviation of 6.2% of the simulation result with respect to the experimental test.

Does unbelted safety requirement affect protection for belted occupants?

ABSTRACTObjective: Federal regulations in the United States require vehicles to meet occupant performance requirements with unbelted test dummies. Removing the test requirements with unbelted occupants might encourage the deployment of seat belt interlocks and allow restraint optimization to focus on belted occupants. The objective of this study is to compare the performance of restraint systems optimized for belted-only occupants with those optimized for both belted and unbelted occupants using computer simulations and field crash data analyses.Methods: In this study, 2 validated finite element (FE) vehicle/occupant models (a midsize sedan and a midsize SUV) were selected. Restraint design optimizations under standardized crash conditions (U.S.-NCAP and FMVSS 208) with and without unbelted requirements were conducted using Hybrid III (HIII) small female and midsize male anthropomorphic test devices (ATDs) in both vehicles on both driver and right front passenger positions. A total of 10 to 12 design parameters were varied in each optimization using a combination of response surface method (RSM) and genetic algorithm. To evaluate the field performance of restraints optimized with and without unbelted requirements, 55 frontal crash conditions covering a greater variety of crash types than those in the standardized crashes were selected. A total of 1,760 FE simulations were conducted for the field performance evaluation. Frontal crashes in the NASS-CDS database from 2002 to 2012 were used to develop injury risk curves and to provide the baseline performance of current restraint system and estimate the injury risk change by removing the unbelted requirement.Results: Unbelted requirements do not affect the optimal seat belt and airbag design parameters in 3 out of 4 vehicle/occupant position conditions, except for the SUV passenger side. Overall, compared to the optimal designs with unbelted requirements, optimal designs without unbelted requirements generated the same or lower total injury risks for belted occupants depending on statistical methods used for the analysis, but they could also increase the total injury risks for unbelted occupants.Conclusions: This study demonstrated potential for reducing injury risks to belted occupants if the unbelted requirements are eliminated. Further investigations are necessary to confirm these findings.