Biomechanical and Scaling Basis for Frontal and Side Impact Injury Assessment Reference Values.

In 1983, General Motors Corporation (GM) petitioned the National Highway Traffic Safety Administration (NHTSA) to allow the use of the biofidelic Hybrid III midsize adult male dummy as an alternate test device for FMVSS 208 compliance testing of frontal impact, passive restraint systems. To support their petition, GM made public to the international automotive community the limit values that they imposed on the Hybrid III measurements, which were called Injury Assessment Reference Values (IARVs). During the past 20 years, these IARVs have been updated based on relevant biomechanical studies that have been published and scaled to provide IARVs for the Hybrid III and CRABI families of frontal impact dummies. Limit values have also been developed for the biofidelic side impact dummies, BioSID, ES-2 and SID-IIs. The purpose of the original publication was to provide in a single document: 1) a listing of the IARVs for measurements made with the Hybrid III and CRABI families of frontal impact dummies, and for the biofidelic side impact dummies, 2) the biomechanical and/or scaling bases for these IARVs, and 3) a comparison of IARVs and regulatory compliance limits and how they affect restraint design. The purpose for republication is to correct errors in the original publication and update the regulatory compliance limits.

Age-Specific Injury Risk Curves for Distributed, Anterior Thoracic Loading of Various Sizes of Adults Based on Sternal Deflections.

Injury Risk Curves are developed from cadaver data for sternal deflections produced by anterior, distributed chest loads for a 25, 45, 55, 65 and 75 year-old Small Female, Mid-Size Male and Large Male based on the variations of bone strengths with age. These curves show that the risk of AIS ≥ 3 thoracic injury increases with the age of the person. This observation is consistent with NASS data of frontal accidents which shows that older unbelted drivers have a higher risk of AIS ≥ 3 chest injury than younger drivers.

Morphomics of the Talus.

Previous studies of frontal crash databases reported that ankle fractures are among the most common lower extremity fractures. While not generally life threatening, these injuries can be debilitating. Laboratory research into the mechanisms of ankle fractures has linked dorsiflexion with an increased risk of tibia and fibula malleolus fractures. However, talus fractures were not produced in the laboratory tests and appear to be caused by more complex loading of the joint. In this study, an analysis of the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) for the years 2004-2013 was conducted to investigate foot-ankle injury rates in front seat occupants involved in frontal impact crashes. A logistic regression model was developed indicating occupant weight, impact delta velocity and gender to be significant predictors of talus fracture (p<0.05). Separately, a specific set of Computed Tomography (CT) scans from the International Center for Automotive Medicine (ICAM) scan database was used to characterize the talar dome. This control population consisted of 207 adults aged 18 to 84, with no foot or ankle trauma, and scans that had suitable coverage of the talus. Size of the talus was determined using medial-to-lateral width and anterior-to-posterior depth measurements. Geometry was assessed by evaluating the radius of the articulating talus and strength was assessed using a combination of cross sectional area and density. Demographics were studied to investigate correlation with talus measurements from the CT scan database. A multi-variable linear regression model of the morphomics showed gender to be statistically significant (p<0.05) for talus depth, width, cross-sectional area, radius and strength. Body Mass Index (BMI) was significant for depth and radius. Weight was significant for depth, width, density and strength. Stature was significant for depth, cross-sectional area, radius and strength. Age was significant for radius and density.

Thoracic Injury Risk Curves for Rib Deflections of the SID-IIs Build Level D.

Injury risk curves for SID-IIs thorax and abdomen rib deflections proposed for future NCAP side impact evaluations were developed from tests conducted with the SID-IIs FRG. Since the floating rib guide is known to reduce the magnitude of the peak rib deflections, injury risk curves developed from SID-IIs FRG data are not appropriate for use with SID-IIs build level D. PMHS injury data from three series of sled tests and one series of whole-body drop tests are paired with thoracic rib deflections from equivalent tests with SID-IIs build level D. Where possible, the rib deflections of SID-IIs build level D were scaled to adjust for differences in impact velocity between the PMHS and SID-IIs tests. Injury risk curves developed by the Mertz-Weber modified median rank method are presented and compared to risk curves developed by other parametric and non-parametric methods.

Rationale for and dimensions of impact surfaces for biofidelity tests of different sizes of frontal and side impact dummies.

The biofidelity impact response corridors that were used to develop the Hybrid III family of dummies were established by scaling the various biofidelity corridors that were defined for the Hybrid III mid-size, adult male dummy. Scaling ratios for the responses of force, moment, acceleration, velocity, deflection, angle, stiffness and time were developed using dimensions and masses that were prescribed for the dummies. In addition, an elastic modulus ratio for bone was used to account for the differences between child and adult bone elastic properties. A similar method is being used by ISO/TC22/SC12/WG 5 to develop biofidelity guidelines for a family of side impact dummies based on scaling the biofidelity impact response corridors that are prescribed for WorldSID, a mid-size, adult male dummy. While the various biomechanical impact response requirements for the Hybrid III family of dummies and the WorldSID are documented in the literature, the scaling used to prescribe the dimensions of the impact surfaces that are used for the various biofidelity tests for various sizes of dummies are not documented. This paper describes the rationale for how these impact surfaces should be scaled, gives the scaling equations, and gives the dimensions of the impact surfaces that should be used for the various biofidelity tests of the different sizes of adult and child dummies. For future PMHS and human volunteer tests that are conducted to define impact biofidelity guidelines, it is recommended that the impact surfaces be scaled for the test subject size so that the data can be appropriately normalized to any size subject.

Side Impact Response Corridors for the Rigid Flat-Wall and Offset-Wall Side Impact Tests of NHTSA Using the ISO Method of Corridor Development.

The purpose of this paper is to compare the biofidelity rating schemes of ISO/TR9790 and the NHTSA Bio Rank System. This paper describes the development of new impact response corridors being proposed for ISO/TR9790 from the results of a recent series of side-impact sled tests. The response data were analyzed by methods consistent with ISO/TR9790, including normalization by impulse-momentum analysis and the elimination of subjects that sustained six or more rib fractures. Unlike ISO/TR9790, this paper proposes the elimination of the data from tests in which the timing and the sequence of loading of the individual impact plates were inconsistent compared to other tests conducted with the same impact wall configuration. As a result of differences in the analysis methods, data selection criteria, and the method of corridor construction, the impact response corridors proposed here are different from those developed by NHTSA, despite the fact that both sets of corridors were developed from the same series of sled tests. Responses of the ES-2 and ES-2re side impact dummies are compared to both sets of corridors. The response corridors developed in this paper are proposed as an addition to and not a replacement for those given in the 1999 revision of ISO/TR9790.

Biomechanical and scaling bases for frontal and side impact injury assessment reference values.

In 1983, General Motors Corporation (GM) petitioned the National Highway Traffic Safety Administration (NHTSA) to allow the use of the biofidelic Hybrid III midsize adult male dummy as an alternate test device for FMVSS 208 compliance testing of frontal impact, passive restraint systems. To support their petition, GM made public to the international automotive community the limit values that they imposed on the Hybrid III measurements, which were called Injury Assessment Reference Values (IARVs). During the past 20 years, these IARVs have been updated based on relevant biomechanical studies that have been published and scaled to provide IARVs for the Hybrid III and CRABI families of frontal impact dummies. Limit values have also been developed for the biofidelic side impact dummies, BioSID, EuroSID2 and SID-IIs. The purpose of this paper is to provide in a single document: 1) a listing of the IARVs for measurements made with the Hybrid III and CRABI families of frontal impact dummies, and for the biofidelic side impact dummies, 2) the biomechanical and/or scaling bases for these IARVs, and 3) a comparison of IARVs and regulatory compliance limits and how they affect restraint design.

Guidelines for assessing the biofidelity of side impact dummies of various sizes and ages.

The Human Mechanical Simulation Subcommittee of the Human Biomechanics and Simulation Standards Committee of the Society of Automotive Engineers took on the task of defining test procedures and associated response guidelines to be used to assess the level of biofidelity of side impact dummies that are being developed. This paper describes the results of their efforts. Guidelines are provided for assessing the levels of biofidelity of dummies that represent 6-, 12-, and 18-month-old infants, 3-, 6-, and 10-year-old children, and of dummies that represent a small female, midsize male and large male adults. These guidelines were developed by normalizing the side impact biofidelity guidelines that were established by the International Standards Organization for the head, neck, shoulder, thorax, abdomen and pelvis of the midsize adult male. The ISO guidelines can be used to define biofidelity guidelines for any size or age of dummy provided pertinent geometric, inertial and tissue properties are specified.