Tanya Kapoor

Methods to mitigate injury to toddlers in near-side impact crashes

This research focuses on the injury potential of children seated in forward-facing child safety seats during side impact crashes in a near-side seated position. Side impact dynamic sled tests were conducted by NHTSA at Transportation Research Center Inc. (TRC) using a Hybrid III 3-year-old child dummy seated in a convertible forward/rearward child safety seat. The seat was equipped with a LATCH and a top tether and the dummy was positioned in forward-facing/near-side configuration. The test was completed using an acceleration pulse with a closing speed of 24.1 km/h, in the presence of a rigid wall and absence of a vehicle body. A fully deformable finite element model of a child restraint seat, for side impact crash investigations, has been developed which has also been previously validated for frontal and far side impacts. A numerical model utilizing a Hybrid III 3-year-old dummy, employing a similar set-up as the experimental sled test was generated and simulated using LS DYNA. The numerical model was validated by comparing the head and the chest accelerations, resultant upper and lower neck forces and moments from the experimental and numerical tests. The simulation results were observed to be in good agreement to the experimental observations. A numerical model of the near-side laboratory tests, utilizing a Q3s child dummy, was also created for parametric studies regarding different ISOFIX configurations. Further, numerical simulations were completed for both the dummy models with rectangular and cross-shaped sections of rigid ISOFIX systems. In addition, studies were conducted to confine lateral movement of the dummys head by adding energy absorbing foam on the side wings in the vicinity of the contact region of the CRS. It was observed that the use of rigid ISOFIX system reduced the lateral displacement of the CRS and different injury parameters. Addition of energy absorbing foam blocks was effective in further reducing the lateral displacement of the dummys head. The lateral displacement of the head was reduced by 68 mm by using cross-shaped section ISOFIX with energy absorbing foam near the vicinity of the head of the Hybrid III 3-year-old dummy compared to the flexible LATCH configuration without foam. For the Q3s dummy, the lateral displacement of the head was reduced by 48 mm by utilizing a cross-shaped section rigid ISOFIX system with the addition of energy absorbing foam compared to the flexible LATCH configuration.

An investigation into the head and neck injury potential of three-year-old children in forward and rearward facing child safety seats

Abstract This research focuses on the injury potential of children in forward and rearward facing child restraint seats in frontal collisions. Experimental sled tests were completed following the guidelines outlined in the Federal Motor Vehicle Safety Standard 213 using a Hybrid III 3-year-old dummy in a convertible forward/rearward facing child restraint seat. The seat was equipped with a five point child safety belt and the experimental test was completed in the forward facing configuration. The Hybrid III 3-year-old dummy was equipped with three uniaxial accelerometers arranged in mutually perpendicular directions in the head and chest. A numerical model employing a subset of the apparatus used in the forward facing experimental sled test was developed and numerically simulated using LSDYNA. To verify the numerical simulations, the head and chest accelerations were compared to the experimental findings and it was observed that a reasonable correlation between the data existed. Further numerical simulations were completed to investigate the influence of positioning the 3-year-old dummy in the rearward configuration on the head and neck injury potential during frontal crash. Through an analysis of injury criteria, using neck loads and head accelerations, it was observed that the rearward facing child dummy sustained significantly lower levels of neck injury criteria while exhibiting similar levels of the head injury criteria as the forward facing child dummy.

A numerical investigation into the effect of CRS misuse on the injury potential of children in frontal and side impact crashes

This research focuses on an investigation into the head and neck injuries sustained by toddlers due to CRS misuse under frontal and side impact crashes. A fully deformable FE model incorporating a Hybrid III 3-year-old dummy was developed which has been previously validated for frontal impacts under CMVSS 208 and FMVSS 213 testing conditions. Furthermore, this model has also been validated under near-side impact conditions in accordance to crash tests carried out by NHTSA. In addition, numerical models incorporating a Q3/Q3s prototype child crash test dummies were developed. The objective of this research was to study the effect of seatbelt slack and the absence of the top tether strap on the head and neck injuries sustained by toddlers in a vehicle crash. Numerical simulations were conducted under full frontal and near side impact crash testing conditions in accordance with FMVSS 213 for the Hybrid III 3-year-old dummy and Q3/Q3s dummies in the absence and presence of slack in the seatbelt webbing, and in the absence and presence of the top tether strap. In addition, the effect of using a cross-shaped rigid ISOFIX system was also investigated. An analysis of the head and chest accelerations, neck loads and moments was completed to investigate the potential of injury due to CRS misuse. An increase in HIC(15) by approximately 30-40% for the frontal impact and 10-20% for the near-side impact respectively was observed for the Q3 child dummy due to both forms of CRS misuse. In the absence of the top tether strap the forward head excursions were observed to be increased by approximately 70% for the Hybrid III 3-year-old dummy and 40% for the Q3 dummy, respectively. Use of the cross-shaped rigid ISOFIX system illustrated a reduction in head and neck injury parameters, for both frontal and side impact conditions, in the absence and presence of CRS misuse. CRS misuse results in a significant increase in injury parameters and potential for contact related head injuries. Use of a rigid ISOFIX system to restrain a CRS provides better CRS and dummy confinement and reduced injury potential than a flexible ISOFIX system.

Load Limiting Behavior in CRS Tether Anchors as a Method to Mitigate Head and Neck Injuries Sustained by Children in Frontal Crash

Objective. This study focuses on methods to reduce injuries, specifically in the head and neck region, sustained by children seated in forward-facing child restraint system during a frontal vehicle crash. The main objective of this research was to implement load-limiting behavior into the upper tether and lower LATCH anchors of the CRS in order to reduce the neck injury criteria by increasing forward head excursion. Methods. Federal Motor Vehicle Safety Standard 213 outlines that the maximum limit for head excursion of the child dummy should be 720 mm, and the neck injury criteria should be less than 0.33 beyond the first 30 ms of the impact. Working within these limits, a fully deformable finite element model of a child restraint seat incorporating a Hybrid III 3-year-old dummy has been previously developed that has been validated for frontal impacts under CMVSS 208 and FMVSS 213 testing conditions. Observations from this previous work have illustrated that despite the head excursion being significantly less than the proposed limit of 720 mm, values of the neck injury criteria exceeded the protection reference values. Values of the load limits for both upper tether and lower LATCH anchors were calculated based on two approaches, initially based upon neck injury criteria and then an energy-based approach. Three numerical models were developed incorporating a Hybrid III 3-year-old dummy, Q3 child dummy, and a child finite element model. Numerical simulations, utilizing the identical 213 testing conditions, were completed incorporating load-limiting capabilities of the upper tether and lower LATCH anchors. Results. Evaluation of injury criteria based on the quantitative analysis of the simulations yielded that the implementation of load-limiting behavior in the upper tether and lower LATCH anchors was effective in reducing the head injury criteria by approximately 60 to 70%. Conclusion. Implementation of load-limiting behavior in the upper tether and lower LATCH anchors of the child restraint system effectively reduces the head and neck injuries sustained by toddlers in a frontal vehicle crash while controlling forward head excursion within the limits as defined by NHTSA.

Child Restraint Seat Design Considerations to Mitigate Injuries to Three-Year-Old Children in Side Impact Crashes

Abstract This research focuses on the injury potential of children seated in forward-facing child safety seats during side impact crashes in a far-side seated position. Side impact dynamic sled tests were conducted by Transportation Research Center Inc. (TRC) using two Hybrid III 3-year-old child dummies in convertible forward/rearward child safety seats. The seats were equipped with a LATCH and a top tether and the dummies were positioned in forward-facing/far-side configuration. The tests were completed using an acceleration pulse with a closing speed of 32.8 km/h, and the seat fixture with vehicle body oriented at 270° relative to the motion of the sled. A fully deformable finite element model of a child restraint seat, for side impact crash investigations, has been developed which has also been previously validated for frontal impacts. A numerical model employing a similar set-up as the experimental sled test was generated and simulated using LSDYNA. The numerical model was validated by comparing the head and the chest accelerations, resultant upper and lower neck forces and moments from the experimental and numerical tests. The simulation results were observed to be in good agreement to the experimental observations. Further studies were conducted to confine lateral movement of the dummys head by adding energy absorbing foam on the side wings in the vicinity of the contact region of the CRS. It was observed from the simulation results that the addition of foam padding and foam blocks was effective in reducing the head injury criteria of the Hybrid III 3-year-old dummy by approximately 30%, and the upper neck lateral shear and lateral bending by approximately 45%.

The effect of using universal anchorages in child restraint seats on the injury potential for children in frontal crash

Abstract This paper focuses on the efficacy of various methods used for anchoring child safety seats in vehicles. An experimental vehicle crash test was conducted incorporating two three-year-old Hybrid III crash test dummies, restrained in a five-point child restraint seats, in accordance to Canadian Motor Vehicle Safety Standard 208. One Child Restraint Seat was affixed to the vehicle seat using the car seat belt and the second was anchored using the lower anchorages provided in the vehicle for child seats. A top tether was used in addition to both the anchoring techniques to provide additional support to the child safety seat. The vehicle crash test was completed to investigate the head, neck, and thoracic injury potential of the Hybrid III crash test dummies due to change in anchoring methods. Similarities and differences were noted in the response of the two dummies to the same crash conditions. Peak values of the neck injury criteria, calculated from the observations obtained from the lower neck loads cell ranged from 1.7 to 1.9. The head injury criteria calculated over a 15 ms evaluation period were observed to lie between 250 and 350, and the values computed over a 36 ms evaluation period ranged between 450 and 600. Percentage reduction of approximately 10% to 20% was observed in the neck forces and moments and head accelerations by using the adult seat belt instead of the ISOFIX for CRS anchoring. A high probability of neck and cervical injuries was estimated for both child restraining configurations.

Countermeasures to mitigate head and neck injuries to toddlers in frontal and lateral vehicle crash conditions

This study focuses on methods to reduce injuries, specifically in the head and neck region, sustained by children seated in forward-facing child safety seats during a vehicle crash. A fully deformable finite element model (FEM) of a child restraint seat incorporating a Hybrid III 3-year-old dummy has previously been developed which has been validated for frontal impacts under CMVSS 208 and FMVSS 213 testing conditions, and near-side impacts under ANPRM (FMVSS 213) norms. Observations from this previous work have illustrated higher values of neck forces and moments sustained by the dummys neck. The main objective of this research was to develop a head and neck restraining device in order to limit the forward and lateral head movement/rotation of the child. The head and neck safety device comprised two parts, namely the collar and the tether. The collar was restrained to the dummys torso with the seatbelt and the tether was constrained to the dummys head. In addition, the effect of using a cross-shaped rigid ISOFIX system was also investigated. Three numerical models were developed incorporating a Hybrid III 3-year-old dummy, Q3/Q3s child dummies and a child FEM. Numerical simulations were completed in frontal, near-side and a 45° impact situation in accordance with the FMVSS 213 norms in the absence and presence of the head and neck safety device, for both the flexible LATCH and the cross-shaped rigid ISOFIX system. Evaluation of injury criteria based on the quantitative analysis of the simulations yielded that the head and neck device in conjunction with the rigid ISOFIX system was effective in reducing the resultant upper neck forces by approximately 40 to 75% for all the child models under different impact conditions. In addition, the head injury criterion was observed to be reduced by approximately 45 to 65% for all the impact conditions. Presence of the head and neck device effectively reduced the head excursions for all the impact conditions. In addition, the cross-shaped rigid ISOFIX further decreased the CRS displacement in both the forward and lateral directions. The forward and lateral displacement of the centre of mass of the head was observed to be reduced by approximately 30 to 50% for different impact conditions. Greater amount of bending in both the lateral and forward directions was observed for the Q3/Q3s dummies and the child FE model. This can be attributed to lower degree of stiffness and geometrical differences in the Q3/Q3s dummys neck, which make the neck more flexible.

Crash analysis of a three-year-old human child model in side impacts considering normal and incorrect CRS usage

The majority of child crash analyses have been evaluated using child dummies. Due to structural simplifications in modelling human anatomy in crash testing dummies, the predictive capabilities of dummies for injuries are limited. In previous studies, a three-year-old human child model was modified by implementing the child neck biomechanical behaviour. The altered biofidelity of the cervical spine was validated with paediatric cadaver head/neck tests reported in the literature. This study focuses on the crash evaluation of the modified three-year-old human child model, by comparing kinematic and biomechanical responses to those of the unmodified human child model and the Q3s dummy model in simulated side impacts. Four different restraint conditions, namely near-side, far-side, near-side misuse (without top tether) and far-side misuse, were selected for comparison in terms of the Head Injury Criteria, head acceleration, head excursion, head contact force, neck force and chest acceleration, under a forward-facing configuration.

A comparison of the head and neck injury parameters on a TNO P3 and a three-year-old hybrid III child dummies from numerical simulations

This study focuses on the behaviour of child dummies, namely a 3-year-old Hybrid III and a TNO P3, in terms of head and neck injury potential in forward and rearward facing child safety seats in frontal vehicle crash. Numerical simulations were conducted using a moderate acceleration pulse acquired from the National Transportation Biomechanics Research Center database with a closing speed of 41 km/h. A finite element model incorporating a three-year-old Hybrid III dummy, in a five-point convertible child safety seat was developed and the prescribed acceleration pulse was simulated using LS-DYNA. A multi-body dynamic simulation, utilizing the identical acceleration pulse, was completed for the three-year-old P3 dummy in a four-point convertible child safety seat using MADYMO. Similarities and differences were noted in the numerical observations for both the P3 and Hybrid III dummies which are presented within the paper. Peak values of the neck injury criteria, calculated from observations from the upper neck load cell in the forward facing configurations, for both the Hybrid III and P3 dummies were approximately 0.5. Values of the head injury criteria, calculated using a window of 15 ms, ranged from 20 to 70. For both the child dummies, neck and head injury criteria values were substantially reduced for the rearward facing configurations when compared with the forward facing results.