| 1. |
- Brynskog, Erik, 1989, et al.
(author)
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Population Variance in Pelvic Response to Lateral Impacts - A Global Sensitivity Analysis
- 2022
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In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2022-September, s. 173-196
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Conference paper (peer-reviewed)abstract
- Pelvic fracture remains the third most common moderate to severe injury in motor vehicle crashes, and the dominating lower extremity injury in lateral impacts. An essential tool for analysis of injury, and real-world occupant protection, are finite element human body models. However, today's state-of-the-art pelvis models do not adequately consider the variability in shape and size naturally occurring in human populations. In this study, we developed a new detailed pelvis finite element model, morphable to enable representation of the population shape variance. The model was validated using force-displacement data from post-mortem human subjects, in lateral loading of the denuded pelvis, followed by a global sensitivity analysis. The results suggests that in lateral impacts to the pelvis, pelvic shape contributes to the model response variance by the same magnitude as pelvic bone material stiffness, and that each of these contributions are approximately twice that of the cortical bone thickness. Hence, to model pelvic response for a general population accurately, future studies must consider both pelvic shape and the material properties in the analysis. Increased knowledge about population variability, and inclusion in safety evaluations, can result in more robust systems that reduce the risk of pelvic injuries in real-world accidents.
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| 2. |
- Corrales, M. A., et al.
(author)
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Explaining and predicting the increased thorax injury in aged females: age and subject-specific thorax geometry coupled with improved bone constitutive models and age-specific material properties evaluated in side impact conditions
- 2024
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In: Frontiers in Public Health. - 2296-2565. ; 12
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Journal article (peer-reviewed)abstract
- Predicting and understanding thorax injury is fundamental for the assessment and development of safety systems to mitigate injury risk to the increasing and vulnerable aged population. While computational human models have contributed to the understanding of injury biomechanics, contemporary human body models have struggled to predict rib fractures and explain the increased incidence of injury in the aged population. The present study enhanced young and aged human body models (HBMs) by integrating a biofidelic cortical bone constitutive model and population-based bone material properties. The HBMs were evaluated using side impact sled tests assessed using chest compression and number of rib fractures. The increase in thoracic kyphosis and the associated change in rib angle with increasing age, led to increased rib torsional moment increasing the rib shear stress. Coupled with and improved cortical bone constitutive model and aged material properties, the higher resulting shear stress led to an increased number of rib fractures in the aged model. The importance of shear stress resulting from torsional load was further investigated using an isolated rib model. In contrast, HBM chest compression, a common thorax injury-associated metric, was insensitive to the aging factors studied. This study proposes an explanation for the increased incidence of thorax injury with increasing age reported in epidemiological data, and provides an enhanced understanding of human rib mechanics that will benefit assessment and design of future safety systems.
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| 3. |
- Corrales, M. A., et al.
(author)
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Methodology to geometrically age human body models to average and subject-specific anthropometrics, demonstrated using a small stature female model assessed in a side impact
- 2023
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In: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1476-8259 .- 1025-5842. ; 26:10, s. 1208-1219
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Journal article (peer-reviewed)abstract
- The aged population has been associated with an increased risk of injury in car-crash, creating a critical need for improved assessment of safety systems. Finite element human body models (HBMs) have been proposed, but require representative geometry of the aged population and high mesh quality. A new hybrid Morphing-CAD methodology was applied to a 26-year-old (YO) 5th percentile female model to create average 75YO and subject-specific 86YO HBMs. The method achieved accurate morphing targets while retaining high mesh quality. The three HBMs were integrated into a side sled impact test demonstrating similar kinematic response but differing rib fracture patterns.
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| 4. |
- Forman, Jason, et al.
(author)
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Variability in Body Shape, Superficial Soft Tissue Geometry, and Seatbelt Fit Relative to the Pelvis in Automotive Postures—Methods for Volunteer Data Collection With Open Magnetic Resonance Imaging
- 2024
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In: Journal of Biomechanical Engineering. - 0148-0731 .- 1528-8951. ; 146:3
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Journal article (peer-reviewed)abstract
- Variability in body shape and soft tissue geometry have the potential to affect the body’s interaction with automotive safety systems. In this study, we developed a methodology to capture information on body shape, superficial soft tissue geometry, skeletal geometry, and seatbelt fit relative to the skeleton—in automotive postures—using Open Magnetic Resonance Imaging (MRI). Volunteer posture and belt fit were first measured in a vehicle and then reproduced in a custom MRI-safe seat (with an MR-visible seatbelt) placed in an Open MR scanner. Overlapping scans were performed to create registered three-dimensional reconstructions spanning from the thigh to the clavicles. Data were collected with ten volunteers (5 female, 5 male), each in their self-selected driving posture and in a reclined posture. Examination of the MRIs showed that in the males with substantial anterior abdominal adipose tissue, the abdominal adipose tissue tended to overhang the pelvis, narrowing in the region of the Anterior Superior Iliac Spine (ASIS). For the females, the adipose tissue depth around the lower abdomen and pelvis was more uniform, with a more continuous layer superficial to the ASIS. Across the volunteers, the pelvis rotated rearward by an average of 62% of the change in seatback angle during recline. In some cases, the lap belt drew nearer to the pelvis as the volunteer reclined (as the overhanging folds of adipose tissue stretched). In others, the belt-to-pelvis distance increased as the volunteer reclined. These observations highlight the importance of considering both interdemographic and intrademographic variability when developing tools to assess safety system robustness.
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| 5. |
- Genzel, Jonny, et al.
(author)
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An Open-Source Finite Element Model of a Generic Car Seat: Development and Validation for Low-Severity Rear Impact Evaluations
- 2022
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In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - : IRCOBI. - 2235-3151. ; 2022-September, s. 229-242, s. 229-242
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Conference paper (peer-reviewed)abstract
- A Finite Element model of a generic Laboratory Seat was developed to replicate a physical counterpart used in rear-impact volunteer tests. The Laboratory Seat has a simplified design, developed to facilitate replication in computational models. The seat has a flat rigid base and the seatback consists of four horizontal panels attached to side posts by coil springs. The seat model was validated with results from component tests and sled tests, including the Anthropomorphic Test Device, BioRID II. An initial test series was carried out to generate data for component validation: the first set of tests to characterise the coil spring properties; and the second set comprising Impactor Tests on Head Restraint Foam to assess the head restraint material properties. For system level validation, sled tests were conducted both with the empty Laboratory Seat and with the BioRID II. The BioRID II tests were conducted in conjunction with an earlier volunteer test study. Both the component and the sled tests were reproduced in a virtual environment. Good agreement was achieved between the mechanical tests and the computational simulations. The seat model is freely available to use: https://openvt.eu/fem/open-access-laboratory-seat-model.
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| 6. |
- Gepner, B. D., et al.
(author)
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Evaluation of GHBMC, THUMS and SAFER Human Body Models in Frontal Impacts in Reclined Postures
- 2022
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In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2022-September, s. 116-143
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Conference paper (peer-reviewed)abstract
- Virtual tools, such as human body models (HBMs), can support advances in vehicle development and restraint system design. The goal of this study is to evaluate selected HBMs against data from recent reclined post-mortem human subject (PMHS) tests. Three HBMs - the Global Human Body Modelling Consortium detailed model v.6.0, Total Human Model for Safety v.6.0, and SAFER HBM v.10 - were used in this study. The models were positioned with respect to the average PMHS position and utlised a previously developed environment model. The HBMs were evaluated comparing belt engagement, boundary forces and displacements (in the seat and belt), and the trajectories of the head, T1, T8, T11, L1, L3, and pelvis. The HBMs' belt engagement, boundary forces and displacements, and X-direction (fore-aft) trajectories were all generally consistent with the PMHS. All HBMs predicted more downward motion of the head and T1 compared to the PMHS. The HBMs also showed rearward pelvis pitch at peak lap belt force, opposite to the PMHS. Some of these differences were associated with differences in flexion of the lumbar spine. This is the first study to provide an in-depth evaluation of multiple reclined HBMs in frontal crashes compared to reclined PMHS.
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| 7. |
- Iraeus, Johan, 1973, et al.
(author)
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Generic finite element models of human ribs, developed and validated for stiffness and strain prediction - To be used in rib fracture risk evaluation for the human population in vehicle crashes
- 2020
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In: Journal of the Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 106
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Journal article (peer-reviewed)abstract
- To enable analysis of the risk of occupants sustaining rib fractures in a crash, generic finite element models of human ribs, one through twelve, were developed. The generic ribs representing an average sized male, were created based on data from several sources and publications. The generic ribs were validated for stiffness and strain predictions in anterior-posterior bending. Essentially, both predicted rib stiffness and rib strain, measured at six locations, were within one standard deviation of the average result in the physical tests. These generic finite elements ribs are suitable for strain-based rib fracture risk predictions, when loaded in anterior-posterior bending. To ensure that human variability is accounted for in future studies, a rib parametric study was conducted. This study shows that the rib cross-sectional height, i.e., the smallest of the cross-sectional dimensions, accounted for most of the strain variance during anterior-posterior loading of the ribs. Therefore, for future rib fracture risk predictions with morphed models of the human thorax, it is important to accurately address rib cross-sectional height.
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| 8. |
- Jakobsson, Lotta, 1967, et al.
(author)
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ASSESSMENT OF PASSENGER SAFETY IN FUTURE CARS - IDENTIFYING THE REAL-WORLD NEEDS TOWARDS SAFETY SYSTEM DEVELOPMENT
- 2023
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In: 27th ESV Conference Proceedings.
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Conference paper (peer-reviewed)abstract
- Future cars will likely include further collision mitigation systems, seat positions and seating configurations compared to current cars, in addition to an increased degree of shared mobility solutions. At the same time the population is becoming older and the diversity in car passenger dimensions is growing. This calls for assessment tools and evaluation methods beyond the current standardized crash test methods. This paper summarizes the results of a Swedish research project on how to assess the protection of the heterogeneous population of passengers (i.e., nondrivers) in future car crashes, focusing on restraint interaction. With the overall purpose of further improving passenger protection, the specific aims were to achieve method developments based on the enhancement of tools (physical and virtual human substitutes) as well as to create knowledge on passenger protection needs. This comprehensive research project combined multiple competencies and international collaborations, and a large number of studies have been performed using different methods. The applied methods include real-world crash data analyses to identify scenarios and situations, crash testing and simulation, and additionally user-studies conducted in cars to evaluate sitting posture, beltfit, kinematics, comfort, experiences and attitudes. Furthermore, the project included studies on crash test dummies (ATDs) and Human Body Models (HBM). Moreover, adult morphed HBMs were developed in various sizes, ages and sexes, for investigating various protection principles. In novel studies, crash interventions strategies were applied to predicted residual crash configurations. User-studies provided evidence of self-selected passenger postures in real car settings and, thus, deviations from standardized ATD positions. The importance of body shape was highlighted in a beltfit user-study including older adults. Essential booster design parameters were identified for children in upright and reclined seat positions. Restraint principles were investigated for adults in reclined seat positions and with the seat in rearward positions, away from the frontal airbag and knee bolster, along with an evaluation of the capabilities of the assessment tools. The adult HBM morphed to various sizes, ages and sexes were validated for prediction of in-crash kinematics in different impact scenarios, and provided enhanced insights in passenger protection assessment compared to the three standardized sizes of ATDs. Simulations with PIPER6y, a child-sized HBM, emphasized the importance of vehiclebooster-user system interaction. The results from the research project provided input to safety system development, ATD/HBM design, assessment methods development, and a number of identified research challenges for future work. Specifically, there is a need to further explore car passenger interaction with the restraint system in terms of seat positions and variations in body sizes, shapes and postures. The inclusions of the heterogeneous population into more advanced tools such as HBMs are essential, acknowledging that when moving closer to “zero injuries”, the situations to address are more unique and specific. Although a large range of studies using different methods was conducted, many challenges still remain to cover the entire scope of passenger safety in future cars.
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| 9. |
- Larsson, Emma, 1991, et al.
(author)
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Predicting occupant head displacements in evasive maneuvers; tuning and comparison of a rotational based and a translational based neck muscle controller
- 2023
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In: Frontiers in Bioengineering and Biotechnology. - 2296-4185. ; 11
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Journal article (peer-reviewed)abstract
- Objective : Real-life car crashes are often preceded by an evasive maneuver, which can alter the occupant posture and muscle state. To simulate the occupant response in such maneuvers, human body models (HBMs) with active muscles have been developed. The aim of this study was to implement an omni-directional rotational head-neck muscle controller in the SAFER HBM and compare the bio-fidelity of the HBM with a rotational controller to the HBM with a translational controller, in simulations of evasive maneuvers. Methods : The rotational controller was developed using an axis-angle representation of head rotations, with x, y, and z components in the axis. Muscle load sharing was based on rotational direction in the simulation and muscle activity recorded in three volunteer experiments in these directions. The gains of the rotational and translational controller were tuned to minimize differences between translational and rotational head displacements of the HBM and volunteers in braking and lane change maneuvers using multi-objective optimizations. Bio-fidelity of the model with tuned controllers was evaluated objectively using CORrelation and Analysis (CORA). Results : The results indicated comparable performance for both controllers after tuning, with somewhat higher bio-fidelity for rotational kinematics with the translational controller. After tuning, good or excellent bio-fidelity was indicated for both controllers in the loading direction (forward in braking, and lateral in lane change), with CORA scores of 0.86−0.99 and 0.93−0.98 for the rotational and translational controllers, respectively. For rotational displacements, and translational displacements in the other directions, bio-fidelity ranged from poor to excellent, with slightly higher average CORA scores for the HBM with the translational controller in both braking and lane changing. Time-averaged muscle activity was within one standard deviation of time-averaged muscle activity from volunteers. Conclusion : Overall, the results show that when tuned, both the translational and rotational controllers can be used to predict the occupant response to an evasive maneuver, allowing for the inclusion of evasive maneuvers prior to a crash in evaluation of vehicle safety. The rotational controller shows potential in controlling omni-directional head displacements, but the translational controller outperformed the rotational controller. Thus, for now, the recommendation is to use the translational controller with tuned gains.
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| 10. |
- Larsson, Karl-Johan, 1985, et al.
(author)
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A First Step Toward a Family of Morphed Human Body Models Enabling Prediction of Population Injury Outcomes
- 2024
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In: Journal of Biomechanical Engineering. - 0148-0731 .- 1528-8951. ; 146:3
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Journal article (peer-reviewed)abstract
- The injury risk in a vehicle crash can depend on occupant specific factors. Virtual crash testing using finite element human body models (HBMs) to represent occupant variability can enable the development of vehicles with improved safety for all occupants. In this study, it was investigated how many HBMs of different sizes that are needed to represent a population crash outcome through a metamodel. Rib fracture risk was used as an example occupant injury outcome. Morphed HBMs representing variability in sex, height, and weight within defined population ranges were used to calculate population variability in rib fracture risk in a frontal and a side crash. Two regression methods, regularized linear regression with second-order terms and Gaussian process regression (GPR), were used to metamodel rib fracture risk due to occupant variability. By studying metamodel predictive performance as a function of training data, it was found that constructing GPR metamodels using 25 individuals of each sex appears sufficient to model the population rib fracture risk outcome in a general crash scenario. Further, by utilizing the known outcomes in the two crashes, an optimization method selected individuals representative for population outcomes across both crash scenarios. The optimization results showed that 5–7 individuals of each sex were sufficient to create predictive GPR metamodels. The optimization method can be extended for more crashes and vehicles, which can be used to identify a family of HBMs that are generally representative of population injury outcomes in future work.
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