Raed E. El-Jawahri

Finite-Element-Based Transfer Equations: Post-Mortem Human Subjects versus Hybrid III Test Dummy in Blunt Impact

In the present study, transfer equations relating the responses of post-mortem human subjects (PMHS) to the mid-sized male Hybrid III test dummy (HIII50) under matched, or nearly-identical, loading conditions were developed via math modeling. Specifically, validated finite element (FE) models of the Ford Human Body Model (FHBM) and the HIII50 were used to generate sets of matched cases (i.e., 256 frontal impact cases involving different impact speeds, severities, and PMHS age). Regression analyses were subsequently performed on the resulting age-dependent FHBM- and HIII50-based responses. This approach was conducted for five different body regions: head, neck, chest, femur, and tibia. All of the resulting regression equations, correlation coefficients, and response ratios (PHMS relative to HIII50) were consistent with the limited available test-based results. Language: en

Fracture Modeling Inputs for a Human Body Model via Inference from a Risk Curve: Application for Skull Fracture Potential

A three-step process was developed to estimate fracture criteria for a human body model. The process was illustrated via example wherein skull fracture criteria were estimated for the Ford Human Body Model (FHBM) - a finite element model of a mid-sized human male. The studied loading condition was anterior-to-posterior, blunt (circular/planar) cylinder impact to the frontal bone. In Step 1, a conditional reference risk curve was derived via statistical analysis of the tests involving fractures in a recently-reported dataset (Cormier et al. 2011a). Therein, Cormier et al. authors reported results for anterior-to-posterior dynamic loading of the frontal bone of rigidly-supported heads of male post mortem human subjects, and fracture forces were measured in 22 cases. In Step 2, the FHBM head was used to conduct some underlying model validations relative to the Cormier tests. The model-based Force-at-Peak Stress was found to approximate the test-based Fracture Force. In Step 3, models of Cormiers setup with assumed fracture criteria were made such that they produced the experimentally-observed spread of fracture forces. Moreover, iteration was conducted on the model-based stress and strain fracture criteria (viz., σult and eult). The outcomes were analyzed via the same statistical approach applied in Step 1, and subject to σult ≈ 125 MPa and eult ≈ 2.2%, the model-based risk curve nearly identically recovered the reference test-based risk curve (i.e., PFE-based ≈ 1.03 Preference and R2=0.99). Language: en

Further Validation of the Head in the Ford Human Body FE Model

The head in the Ford human body model (FHBM) was previously validated against impact test data involving post mortem human subjects (PMHS). The objective of the current study was to further validate the head model against more PMHS tests. The data included the following published tests: rigid bar impact to the forehead, zygoma, and maxilla (2.5–4.2 m/s), lateral pendulum impact (5.7 m/s), and front pendulum impact to the frontal bone, nasal bone, and maxilla (2.2 m/s). The responses from the model were compared to available published cadaveric response corridors and to various cadaveric responses. When compared to the cadaveric response corridors, the responses from the model were within those corridors. In addition, the model responses demonstrated acceptable fidelity with respect to the test data. The head injury criterion (HIC15 ), strain, and stress values from the model were also reported.Copyright

Development and Validation of a 50th Percentile Male Pedestrian FE Model

The objective of this study was to develop and validate a finite element (FE) human model that represents a 50th percentile adult pedestrian male. The geometry of the previously developed and well validated Ford Human Body (FHB) model was modified to change the posture from driving to standing. The femur, tibia, and fibula were validated against published test data of human bone specimens in different dynamic loading scenarios. The leg model was validated against dynamic, three-point bending test data of human legs from Post Mortem Human Subjects (PMHS). The kinematics and dynamics of the full pedestrian model was validated against PMHS car-pedestrian impact test data under different levels of severity. The model responses were compared with the corresponding published generalized response corridors. In all the component level and full body model simulations the responses from the model correlated well with both the generalized response corridors and the responses from the individual cadavers.© 2010 ASME

Chest Deflection vs. Chest Acceleration as Injury Indicator in Front Impact Simulations Using Full Human Body Finite Element Model

The Ford Motor Company Human Body Finite Element Model (FHBM) was validated against rib dynamic tension and 3-point bending tests. The stress-strain and moment-strain data from the tension and bending simulations respectively were compared with human rib specimen test data. The model used represented a 50th percentile adult male. It was used to compare chest deflection and chest acceleration as thoracic injury indicator in blunt impact and belted occupants in front sled impact simulations. A 150 mm diameter of 23.4 kg impactor was used in the blunt impact simulations with impact speeds of 2, 4, and 8 m/s. In the Front sled impact simulations, single-step acceleration pulses with peaks of 10, 20, and 30 g were used. The occupants were restrained by 3-point belt system, however neither pretensioner nor shoulder belt force limiter were used. The external force, head acceleration, chest deflection, chest acceleration, and the maximum values of Von Mises stress and plastic strain were the model outputs. The results showed that the external contact force, head acceleration, chest deflection, and chest acceleration in the blunt impact simulations varied between 1.5–7 kN, 5–28 g, 18–80 mm, and 8–40 g respectively. The same responses varied between 7–24 kN, 13–40 g, 15–50 mm, and 16–46 g respectively in the front sled impact simulations. The maximum Von Mises stress and plastic strain were 50–127 MPa, and 0.04–2% respectively in the blunt impact simulations and 72–134 MPa, and 0.13–3% respectively in the sled impact simulations.Copyright

Further Validation of the Ford Human Body FE Model and Use of the Model to Investigate the Effects of Shoulder Belt Force Limiting of 3-Point and 4-Point Restraints in Frontal Impact

Ford Motor Company human body FE model was validated against 3-point & 4-point belted PMHS tests in frontal impact and PMHS knee impact. The chest deflection, chest acceleration, and belt force in frontal impact simulations were compared with the PMHS test data, while the impact force, femur acceleration, pelvis acceleration, and sacrum acceleration of the knee impact simulations were compared with the respective corridors from PMHS tests. The model used represents a 50th percentile adult male. It was used to study the effects of shoulder belt force limit on 3-point and 4-point restrained occupants in frontal impacts without airbags. A 25 g pulse and a shoulder belt load limit of 1, 2, 3, 4, 6, and 8 kN were used for the 3-point and 4-point restraint systems with a rigid steering wheel, front header, and windshield of a stiffer larger vehicle structure. The results showed that the head acceleration and the chest deflection of the 4-point belt system are less than the respective cases of the 3-point system while the chest acceleration levels were about the same in 3-point and 4-point belt. The mid-shaft femur forces were always higher in the 4-point belt than those of the 3-point belt.Copyright