Oblique Side Impact Research Articles

COMPARISON OF DIFFERENT MATERIAL CONSTITUTIVE MODELS FOR PREDICTING AORTIC BIOMECHANICAL RESPONSE AND INJURY IN BLUNT SIDE IMPACTS

Traumatic rupture of the aorta (TRA) is highly lethal in motor vehicle collisions (MVCs). Human body biomechanical models (HUBMs) show promise as useful tools for better comprehension of the mechanical response and injury mechanism of TRA. However, the prediction accuracy largely depends on its material modeling. This study investigated the performance of the isotropic elastic material constitutive model (Mat_001) and the orthotropic elastic material constitutive model (Mat_002) for predicting aortic dynamic response and injury in blunt side impacts, via simulations against vertical and oblique side impact cadaver tests with previously developed HUBM. The aortic strain response, peak intraluminal pressure, thoracic deflections and injury distributions were compared. It was found that both Mat_001 and Mat_002 could be used to model aortic tissue, but Mat_002 presented more sensitivity to blunt side impacts in terms of strain responses. The thoracic rib cage and internal organs sustained more severe injuries under the oblique left side impact (AIS 5+) than those under the vertical left side impact (AIS 4+), whereas the aortic peri-isthmus exhibited a higher TRA risk in the vertical side impact than that in the oblique side impact, with regard to the peak longitudinal strain. The TRA could result from the aorta’s sudden stretch, and the peak longitudinal strain could be regarded as a main contributing factor to it. This study enhances our understanding of the aortic material modeling and injury mechanisms.

Characterization of far-side occupant chest injuries in oblique side impact considering uncertainty

Purpose Oblique side impact is a common form of impact in life, and the far-side occupant’s chest is highly susceptible to injury in the impact process. This study analyzed the effects of different factors on the chest response of far-side occupants in oblique side impacts. Methods In this study, a simplified sled model was developed. After that, five factors, namely, impact velocity, impact angle, seat friction coefficient, seatbelt friction coefficient, and seatbelt force-limiting were considered as uncertain variables and randomly sampled. Sixteen sets of impact simulations with different parameters were performed using the sampled results to evaluate the farside occupant chest response. Results Results showed that the impact velocity was positively correlated with the chest deflection and chest acceleration, with correlation coefficients 0.77 and 0.92, respectively, and the impact angle was negatively correlated with the chest deflection and chest acceleration, with correlation coefficients -0.83 and -0.54, respectively. The seatbelt friction coefficient and force limiting value were positively and negatively correlated with the occupant’s chest response, respectively. Conclusions The results suggested that multiple variables collectively influenced occupant injury, and random combinations of different variables may play a critical role in impact outcomes. This study provides a reference for the study of occupant injury in far-side impacts.

Design Loads and Pier Responses for Oblique Side Barge Impacts on Bridges

For bridges susceptible to barge collision, design provisions are typically utilized in determining collision scenarios and impact loading. Provisions in the United States require that bridges be designed to withstand two distinct collision events: direct (head-on) and glancing (e.g., oblique side). Head-on impact scenarios are represented using empirically determined static loads, and perpendicular impact loads are applied with magnitudes assumed equal to 50% of head-on impact loads. Subsequent to the formation of these provisions, numerous studies have identified the need to account for dynamic phenomena when designing bridges to resist vessel collision loads. Further, design-oriented computational techniques have been developed to characterize representative vessel–bridge collision scenarios, quantify dynamic barge impact loads, and compute time-varying bridge responses. While previous studies focused on head-on barge–bridge collision, the current study characterizes oblique side barge impact loading and resulting bridge response. Parameters such as barge flotilla configuration, impact angle, and location of impact initiation are investigated across a range of bridge models, leading to the identification of design-relevant oblique side impact scenarios. An alternative to the 50% design approach for oblique side impact scenarios involving the corners of barge bows is then proposed for assessing overall stability. The proposed approach incorporates dynamic phenomena and maintains agreement relative to more detailed analyses.

Analysis of characteristics about far-side occupant’s chest injury during oblique side impact

The chest is one of the most frequently injured body parts during a side impact. In this study, the effects of impact angle, impact speed, and D-ring position on the occupant’s chest injury in the far-side crash were analyzed. First, a model with a sled and a Test Human Occupant Restraint (THOR) dummy was established. Second, the acceleration curves with peaks of 6.6 and 9.0 g were applied to the sled. Then 12 sets of simulations with different impact angles and D-ring positions were conducted to evaluate the occupant’s chest responses. Results indicate that the peak chest deflection at Lower Left (LL) decreased by 11.6% on average, and that at Lower Right (LR) increased by 11.7% on average when the D-ring position moved backward. Meanwhile, with the D-ring position moving upward, the peak chest deflection at LL grew by 24.8% on average, while it decreased by 14.7% at LR.

Crashworthiness among side pole testing

This research presents results from measurement data analysis of 47 oblique side impact pole crash tests conducted for the New Car Assessment Program (NCAP). Integrating measured acceleration data allowed to calculate changes of velocity and other key parameter like coefficient of restitution of the impacts. An objective of this work was, to obtain parameters for the side crash, which can be useful for vehicular accident reconstruction. Despite of identical test velocity, we can observe a wide range of kinetic energy induced due to the to some extent tremendously differing masses of the vehicles. In addition, the part of this energy, which is dissipated into deformation energy, differs enormously. In some cases, the kinetic energy after impact is unexpected high, which in this case is equal to a comparatively large change of velocity (Δv). Analysing the dummy measurements of the considered side pole tests, we cannot observe a relationship between velocity change of the vehicle and load of the dummy. Resultant restrictions for the use of delta-V as crash severity metric or predictor for the risk of injury are discussed.

Protection of children in forward-facing child restraint systems during oblique side impact sled tests: Intrusion and tether effects

ABSTRACTObjective: Testing was conducted to quantify the kinematics, potential for head impact, and influence on head injury metrics for a center-seated Q3s in a forward-facing child restraint system (FFCRS) in oblique impacts. The influences of a tether and intruded door on these measures were explored.Methods: Nine lateral oblique sled tests were conducted on a convertible forward-facing child restraint seat (FFCRS). The FFCRSs were secured to a bench seat from a popular production small SUV at the center seating position utilizing the lower anchor and tether for children (LATCH). The vehicle seat was fixed on the sled carriage at 60° and 80° from full frontal (30° and 10° forward rotation from pure lateral) providing an oblique lateral acceleration to the Q3s and FFCRS. A structure simulating an intruded door was mounted to the near (left) side of vehicle seat. The sled input acceleration was the proposed FMVSS 213 lateral pulse scaled to a 35 km/h delta-V. Tests were conducted with and without the tether attached to the FFCRS.Results: Results indicate the influence of the tether on kinematics and injury measures in oblique side impact crashes for a center- or far-side-seated child occupant. All tests without a tether resulted in head contact with the simulated door, and 2 tests at the less oblique angle (80°) with a tether also resulted in head contact. No head-to-door contact was observed in 2 tests utilizing a tether. High-speed video analysis showed that the head moved beyond the CRS head side wings and made contact with the simulated intruded door. Head injury criterion (HIC) 15 median values were 589 without the tether vs. 332 with the tether attached. Tests utilizing a tether had less lateral head excursion than tests without a tether (median 400 vs. 442 mm).Conclusion: These tests demonstrate the important role of the tether in controlling head excursion for center- or far-side-seated child occupants in oblique side impact crashes and limiting the head injury potential with an intruded door. The tether may not influence the kinematics of a near-side-seated occupant as strongly where the vehicle door or side structure interacts with the CRS and influences its motion. The results indicate that there may be an opportunity to improve child head kinematics and head protection in oblique side impacts through different CRS attachment methods and/or alternative vehicle side structure protection or padding.

The Influence of Enhanced Side Impact Protection on Kinematics and Injury Measures of Far- or Center-Seated Children in Forward-Facing Child Restraints

Objective: To evaluate the influence of forward-facing child restraint systems’ (FFCRSs) side impact structure, such as side wings, on the head kinematics and response of a restrained, far- or center-seated 3-year-old anthropomorphic test device (ATD) in oblique sled tests.Methods: Sled tests were conducted utilizing an FFCRS with large side wings and with the side wings removed. The CRS were attached via LATCH on 2 different vehicle seat fixtures—a small SUV rear bench seat and minivan rear bucket seat—secured to the sled carriage at 20° from lateral. Four tests were conducted on each vehicle seat fixture, 2 for each FFCRS configuration. A Q3s dummy was positioned in FFCRS according to the CRS owner's manual and FMVSS 213 procedures. The tests were conducted using the proposed FMVSS 213 side impact pulse. Three-dimensional motion cameras collected head excursion data. Relevant data collected during testing included the ATD head excursions, head accelerations, LATCH belt loads, and neck loads.Results: Results indicate that side wings have little influence on head excursions and ATD response. The median lateral head excursion was 435 mm with side wings and 443 mm without side wings. The primary differences in head response were observed between the 2 vehicle seat fixtures due to the vehicle seat head restraint design. The bench seat integrated head restraint forced a tether routing path over the head restraint. Due to the lateral crash forces, the tether moved laterally off the head restraint reducing tension and increasing head excursion (477 mm median). In contrast, when the tether was routed through the bucket seat's adjustable head restraint, it maintained a tight attachment and helped control head excursion (393 mm median).Conclusion: This testing illustrated relevant side impact crash circumstances where side wings do not provide the desired head containment for a 3-year-old ATD seated far-side or center in FFCRS. The head appears to roll out of the FFCRS even in the presence of side wings, which may expose the occupant to potential head impact injuries. We postulate that in a center or far-side seating configuration, the absence of door structure immediately adjacent to the CRS facilitates the rotation and tipping of the FFCRS toward the impact side and the roll-out of the head around the side wing structure. Results suggest that other prevention measures, in the form of alternative side impact structure design, FFCRS vehicle attachment, or shared protection between the FFCRS and the vehicle, may be necessary to protect children in oblique side impact crashes.

Parametric study for head injury criteria response of three-year olds in a child restraint system in oblique and lateral intrusive side impact

A parametric study is undertaken to ascertain the sensitivity of the child restraint system (CRS) design, with respect to oblique side impact at standard velocities in consideration of intrusion. A hybrid model is constructed using a combination of both finite elements and multi-body ellipsoids where a three-year-old Hybrid III child dummy is placed inside a CRS and restrained with a harness system. A prescribed structural motion simulation of a side-impact crash is carried out based on experimental data. Validation is performed and the model is shown to be acceptable for common standard injury responses as well as being greatly economical in terms of computational processing time. A plan of experiments is prepared based on the Latin hypercube sampling for six parameters involving two different crash velocities. The head injury criterion (HIC) is considered as the response in this study. The model is adapted for intrusion and oblique impact. Response surface models are shown to be suitable for the mathematical modelling of the problem and Student's t-test is used to assess the parameter sensitivity both qualitatively and quantitatively. Most of the parameters are seen to have greater significance for wider principle direction of force (PDOF) angles above 60°. In general, a gradual decrease in significance is observed for parameters with increasing impact velocity, with the notable exception of the impact angle. The impact angle is shown to most notably affect the HIC especially from PDOF angles 45°–75°, identified as the critical impact angle range. The far side shoulder harness slack parameter is also found to be significant in reducing the HIC.

Response Surface Approach for Sensitivity Study of Neck Forces in Restrained Child Occupant during Side-Impact Crash

A study is undertaken to characterize the Neck Force (NF) of a CRS restrained 3 year old child occupant involved in lateral and oblique side impact. The Response Surface Method is used to map the parameter sensitivity upon the NF for impact speed of 32.2 km/h (20 mph) both individually as well as cross interactively. Design of Experiments is used with Latin Hypercube Sampling involving six predictors. A study of the response plots and statistical data obtained provide insights on the characteristic of each predictor with respect to the neck forces sustained. Greater parameter significance affecting neck forces is seen for narrow impact angles (φ ≤ 60°). Singularly, the impact angle parameter is revealed to be largely the most sensitive parameter to affect neck force especially at narrow angles. The critical range for this is identified to be between angles 50° and 70° while a secondary critical range is observed for angles below 34°.

Force Corridors of Post Mortem Human Surrogates in Oblique Side Impacts from Sled Tests

To develop region-specific force corridors in side impacts under oblique loadings using post mortem human surrogates (PMHS). Unembalmed PMHS were positioned on a sled. Surrogates contacted a segmented, modular/ scalable load-wall to isolate region-specific forces (shoulder, thorax, abdomen, pelvis). Heights and widths of segmented load-wall plates were adjustable in sagittal and coronal planes to accommodate anthropometry variations. Load cells were used to gather region-specific forces. Tests were conducted at 6.7m/s. Peak forces and times of attainments, and standard corridors (mean±1 SD) are given for the four torso regions and summated forces. The mean age, stature, and total body mass of the five male PMHS were: 56.6±4.4years, 183±3.5cm and 70.6±9.0kg. Peak pelvis forces were the greatest, followed by thorax, abdomen and shoulder. Sequence of times of attainments of peak forces initiating from pelvis increased rostrally to abdomen to thorax and shoulder regions. Corridors were tight in all regions, except shoulder. As previous force corridors were based solely on pure-lateral impacts and region-specific forces were not extracted, the present oblique responses using anthropometry-specific load-wall design can be used to develop injury criteria and evaluate the biofidelity of dummies.