Harold J. Mertz

The position of the United States delegation to the ISO working group 6 on the use of HIC in the automotive environment

A review and analysis of existing cadaver head impact data has been conducted in this paper. The association of the Head Injury Criterion with experimental cadaver skull fracture and brain damage has been investigated, and risk curves of HIC versus skull fracture and brain damage have been developed. Limitation of the search for the maximum HIC duration to 15ms has been recommended for the proper use of HIC in the automotive crash environment.

Biomechanical basis for the CRABI and Hybrid III child dummies

A family of adult and child size dummies was developed under the direction of two task groups of the SAE Mechanical Human Simulation Subcommittee of the Human Biomechanics and Simulation Standards Committee. These new child size dummies represent fiftieth percentile children who are 6 months, 12 months, 18 months, 3 years, and 6 years old. The sizes and total body weights of the dummies were based on detailed anthropometry studies of children of these ages. The techniques used to establish the segment masses and the resulting design goals are detailed. Appropriate impact response requirements were scaled from the biofidelity response requirements of the Hybrid III, taking into account the differences in size, mass and elastic modulus of bone between adults and children. The techniques used to establish the biomechanical impact response requirements for the child dummies are discussed and the resulting biomechanical impact response requirements are given.

Injury Risk Curves for Children and Adults in Frontal and Rear Collisions

This paper describes the development of injury risk curves for measurements made with the CRABI and Hybrid III family of biofidelic child and adult dummies that are used to evaluate restraint systems in frontal and rear-end collision simulations. Injury tolerance data are normalized for size and strength considerations. These data are analyzed to give normalized injury risk curves for neck tension, neck extension moment, combined neck tension and extension moment, sternal compression, the rate of sternal compression, and the rate of abdominal compression for children and adults. Using these injury risk curves dummy response limits can be defined for prescribed injury risk levels. The injury risk levels associated with the various injury assessment reference values currently used with the CRABI and Hybrid III family of dummies are noted.

Prediction of thoracic injury from dummy responses

Currently used criteria based on functions of spinal acceleration obtained from crash test dummies are shown to be invalid indicators of chest injury in blunt frontal impacts. Cadaver impact data are analyzed; and injury is found to be a statistically significant function of chest deflection, chest depth, and cadaver age at death. Based on the resulting regression equations, injury-limiting chest deflections are recommended for various size test dummies. The recommendations apply only to test dummies that have significant thoracic biofidelity for blunt frontal impact. They are valid for environments which include significant blunt frontal impact. Their extension to other environments has not been validated.

Performance Requirements and Characteristics of Mechanical Necks

A short history of the development of mechanical necks for anthropomorphic dummies is given. The response envelopes recommended by Mertz and Patrick are reviewed. A modified performance requirement for mechanical necks based on this data, but emphasizing loading corridors, is set forth. Autogenous and dynamic neck trajectories for the volunteer LMP are presented, and the difficulties of establishing a trajectory performance requirement are discussed.

Hybrid III sternal deflection associated with thoracic injury severities of occupants restrained with force-limiting shoulder belts

A relationship between the risk of significant thoracic injury (AIS is greater than or equal to 3) and Hybrid III dummy sternal deflection for shoulder belt loading is developed. This relationship is based on an analysis of the Association Peugeot-Renault accident data of 386 occupants who were restrained by three-point belt systems that used a shoulder belt with a force-limiting element. For 342 of these occupants, the magnitude of the shoulder belt force could be estimated with various degrees of certainty from the amount of force-limiting band ripping. Hyge sled tests were conducted with a Hybrid III dummy to reproduce the various degrees of band rearing. The resulting Hybrid III sternal deflections were correlated to the frequencies of AIS greater than or equal to 3 thoracic injury observed for similar and tearing in the field accident data. This analysis indicates that for shoulder belt loading a Hybrid III sternal deflection of 50 mm corresponds to a 40 to 50 percent risk of an AIS greater than or equal to 3 thoracic injury.

Thoracic Injury Assessment of Belt Restraint Systems Based on Hybrid III Chest Compression

Chest compression is one of the vital responses for development of occupant restraint systems. This study conducted an analysis of two published crash reconstruction studies that involved belted occupants. The aim of the analysis was to provide a basis for comparing occupant injury risks with Hybrid III chest compression in similar exposures. Results from both studies were similar and indicate that belt loading resulting in 40 mm Hybrid III chest compression represents a 20-25% risk of an AIS 3 thoracic injury for car occupants. Additionally, the field experience of APR (Association Peugeot/Renault) and Volvo indicate that crashes severe enough to result in greater than 40 mm of Hybrid III chest compression are infrequent and that injuries in these classic field studies are mostly associated with crash severities which would result in less than 40 mm of hybrid III chest compression.

The Effect of Limiting Shoulder Belt Load with Air Bag Restraint

The dilemma of using a shoulder belt force limiter with a three point belt system is selecting a limit load that will balance the reduced risk of significant thoracic injury due to the shoulder belt loading of the chest against the increased risk of significant head injury due to the greater upper torse motion allowed by the shoulder belt load limiter. However, with the use of air bags, this dilemma is more mangeable since it only occurs for non-deploy accidents where the risk of significant head injury is low even for the unbelted occupant. A study was done using a validated occupant dynamics model of the Hybrid III dummy to investigate the effects of a prescribed set of shoulder belt force limits had on head and thoracic responses for 48 and 56 km/h barrier simulations with driver air bag deployment and for threshold crash severity simulations with no air bag deployment.(A) For the covering abstract of the conference see IRRD 875168.

Correlation of field injuries and GM hybrid III dummy responses for lap-shoulder belt restraint

Simulated frontal, lap-shoulder belted, barrier impact tests were performed using a Volvo sedan and General Motors Hybrid III anthropomorphic test dummy. Swedish field accident injury data for this vehicle are available from another published study. For the purpose of this program, the injuries were logically subdivided into four body regions: head, neck, thorax, and lower torso. The Hybrid III has instrumentation in each of these regions. The results of three replicated tests at barrier equivalent velocities of nominally 32 and 48 km/h are discussed in terms of the field injuries, thereby providing a basis for more intelligent interpretation of future Hybrid III test results.

Biofidelity of the Hybrid III Head

An analysis was done of published forehead head impact data from cadaver specimens. Only data that were sufficiently documented to allow duplication of the impact environment were used in the analysis. A Hybrid III head, a Part 572 head, a Repeatable Pete head and two WSU heads were subjected to the same impact environments as the cadavers. A comparison of peak resultant head accelerations indicated that the Hybrid III response was the most representative of the cadaver data. The Part 572 head produced accelerations which were greater than the responses of the cadavers. These results support the claim that the Hybrid III heads response is humanlike for forehead impacts.