Jeff Crandall

Limiting performance analysis of toepan padding for mitigating lower limb injuries

Abstract The potential application of using toepan padding for the prevention and reduction of lower limb injuries is investigated computationally in this paper. A two-mass lower limb injury model is developed on the basis of impact tests using post-mortem human surrogates. A limiting performance analysis is used to find the best possible physical performance and characteristics of passive and active padding for the minimization of peak tibia force. Computational results indicate that, for the prevention and reduction of lower limb injuries, the active padding is superior to the passive padding.

Fracture tolerance of the male forearm: The effect of pronation versus supination

Abstract This paper presents the dynamic injury tolerance of the male forearm, derived from dynamic three-point bending tests using ten male cadaver upper extremities. The impact loading conditions were chosen to be representative of those observed during upper extremity interaction with frontal air bags. Using matched forearm pairs, it was determined that the forearm is significantly (p = 0.01) stronger in the supinated position, 126±13 N m, than in the pronated position, 108 ± 8 N m. Two distinct fracture patterns were seen for the pronated and supinated groups. In the supinated position the average difference in fracture time between the radius and ulna was not significantly different (p = 0.24); however, the pronated tests yielded an average difference in fracture time that was significantly different (p = 0.05), with the ulna breaking before the radius in every test. This trend implies that in the pronated position the ulna and radius are loaded independently, while in the supinated position the ulna and radius are loaded together as a combined structure. To produce a conservative injury criterion, only the data from the pronated tests were included for an average failure tolerance of 108 N m. It is anticipated that these data will provide injury reference values for the male forearm during driver air bag loading.

Comparison and evaluation of contemporary restraint systems in the driver and front-passenger environments

Abstract Restrained driver and passenger kinematics and injury outcome in frontal collisions are compared using US fatality field data and post-mortem human surrogate sled tests. The fatality data indicate that a frontal airbag may provide greater benefit for a passenger than for a driver. The thoracic injuries sustained by passenger-side surrogates restrained by a force-limited, pre-tensioned belt and airbag are evaluated, and kinematics are compared with driver-side subjects exposed to a similar impact. Driver and passenger kinematic differences are identified and the implications are discussed with respect to the injury-predictive ability of existing thoracic injury criteria. The chest acceleration of the passenger-side subjects exhibited a bimodal profile with an initial (and global) maximum before the subject loaded the airbag. A second acceleration peak occurred as the subject loaded both the belt and the airbag. A similarly restrained driver-side subject loaded the belt and airbag concurrently at the time of peak chest acceleration and therefore did not exhibit this biomodal chest acceleration. While the injury-causing or injury-mitigating significance of this bimodal response is not known, its significance with respect to thoracic injury prediction is discussed.

Comparison of the Q3 and Hybrid III 3-year-old dummy head and neck response during side air bag loading

Abstract This paper presents the results of 20 tests designed to compare the head and neck response of the Q3 dummy and the Hybrid III 3-year-old dummy subject to loading by a deploying side air bag. In a static test environment, experiments were conducted in two positions using three seat-mounted thoracic side air bags that varied only in the level of inflator output. Substantial kinematic and kinetic differences were observed owing to differences in head geometry and mass, and neck stiffness between the two dummies. The Hybrid III head is 18 per cent heavier than the Q3 and resulted in peak head centre of gravity accelerations significantly lower (p = 0.01) than those observed in the Q3. The stiffer Hybrid III neck resulted in 41 ± 29 per cent higher neck flexion moment compared with the Q3. While the stiffness properties for the Q3 neck are similar in all directions, the Hybrid III neck has preferred anterior-posterior stiffness properties. This difference was observed in tests where lateral loading of the head forced lateral bending in which the Hybrid III recorded a 101 ± 80 per cent higher lateral bending moment compared with the Q3. Although there is considerable uncertainty as to the validity of published injury criteria owing to the lack of child biomechanical data, these tests suggest that separate injury criteria are needed for each dummy.

Dynamic response of the Hybrid III three year old dummy head and neck during side air bag loading

Abstract This paper presents the results from 14 tests designed to evaluate the response and injury potential of a Hybrid III three year old dummy subject to loading by a deploying seat mounted side air bag. An instrumented Hybrid III three year old dummy was used for tests in two different occupant positions chosen to maximize head and neck loading. Four seat mounted thoracic side air bags were used that varied only in the level of inflator output. The National Highway Traffic Safety Administrations neck injury criteria for complex loading were modified to include moment values for both anterioposterior and lateral directions. The results indicate that side air bags may be designed so that the forces and moments in the child dummys neck are below injury threshold values during a side air bag deployment. While there is considerable uncertainty as to the validity of published injury criteria owing to the lack of child biomechanical data, this study demonstrates the sensitivity of child response to initial position which provides insight into placement and geometry of side airbag systems. Furthermore, the data indicate a relationship between airbag inflator properties and child dummy response for a given airbag geometry.

Comparison of upper extremity test devices for the evaluation of frontal air bags

Abstract This study examines the response of two upper extremity test devices under driver-side air bag deployment to contribute to the development of dummy surrogates for the investigation of primary contact forearm injuries during air bag deployments. The first of these test devices, the SAE 5th Percentile Female Arm (SAE arm), is an anthropomorphic representation of a small female forearm and upper arm that is instrumented with load cells, accelerometers and potentiometers to enable the determination of upper extremity kinematics and dynamics. The second, the Research Arm Injury Device (RAID), is a simple beam test device designed for detailed investigation of moments and accelerations resulting from close contact in the initial stages of air bag deployment. It includes strain gauges distributed along its length to measure the distribution of moment applied by the air bag deployment. The study used four air bags representing a wide range of aggressivities in the current automobile fleet. Logistic risk functions for forearm fracture were developed using existing cadaver studies and the moment response of each test device. These risk functions indicate that, for 50 per cent risk of ulna or ulna/radius fractures, the SAE arm peak forearm moment is 67 N m while the RAID peak forearm moment is 373 N m.

Fifth percentile female dummy upper extremity interaction with a deploying side air bag

Abstract This paper presents the results from experiments designed to characterize the upper extremity response of the small female during side air bag loading. A seat-mounted thoracic side air bag was deployed statically using three different inflators. The aggressivity of the inflators varied in peak pressure and pressure onset rate. The fifth percentile female HIII dummy was utilized in three positions, which were chosen to maximize loading of the humerus and elbow joint. Two had the dummy positioned outboard with the forearm on the armrest, and the third had the dummy inboard such that the humerus was positioned horizontally in front of the air bag module with the forearm supported above the armrest. Instrumentation for the fifth percentile female dummy included the fully instrumented SAE upper extremity with six axis load cells in the humerus and forearm as well as accelerometers and angular rate sensors attached to each segment. All inflators produced resultant humerus moments below published injury tolerance values for the small female, with the more aggressive air bags producing higher responses. The upper extremity proved useful in evaluating injury risk relative to side air bag design.