Joseph M. Cormier

Comparison of risk factors for cervical spine, head, serious, and fatal injury in rollover crashes

Previous epidemiological studies of rollover crashes have focused primarily on serious and fatal injuries in general, while rollover crash testing has focused almost exclusively on cervical spine injury. The purpose of this study was to examine and compare the risk factors for cervical spine, head, serious, and fatal injury in real world rollover crashes. Rollover crashes from 1995-2008 in the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) were investigated. A large data set of 6015 raw cases (2.5 million weighted) was generated. Nonparametric univariate analyses, univariate logistic regression, and multivariate logistic regression were conducted. Complete or partial ejection, a lack of seatbelt use, a greater number of roof inversions, and older occupant age significantly increased the risk of all types of injuries studied (p<0.05). Far side seating position increased the risk of fatal, head, and cervical spine injury (p<0.05), but not serious injury in general. Higher BMI was associated with an increased risk of fatal, serious, and cervical spine injury (p<0.05), but not head injury. Greater roof crush was associated with a higher rate of fatal and cervical spine injury (p<0.05). Vehicle type, occupant height, and occupant gender had inconsistent and generally non-significant effects on injury. This study demonstrates both common and unique risk factors for different types of injuries in rollover crashes.

The tolerance of the frontal bone to blunt impact

The current understanding of the tolerance of the frontal bone to blunt impact is limited. Previous studies have utilized vastly different methods, which limits the use of statistical analyses to determine the tolerance of the frontal bone. The purpose of this study is to determine the tolerance of the frontal bone to blunt impact. Acoustic emission sensors were used to provide a noncensored measure of the frontal bone tolerance and were essential due to the increase in impactor force after fracture onset. In this study, risk functions for fracture were developed using parametric and nonparametric techniques. The results of the statistical analyses suggest that a 50% risk of frontal bone fracture occurs at a force between 1885 N and 2405 N. Subjects that were found to have a frontal sinus present within the impacted region had a significantly higher risk of sustaining a fracture. There was no association between subject age and fracture force. The results of the current study suggest that utilizing peak force as an estimate of fracture tolerance will overestimate the force necessary to create a frontal bone fracture.

The influence of body mass index on thoracic injuries in frontal impacts

For this study, a comprehensive analysis was performed to assess the influence of body mass index on thoracic injury potential. The data for this study were obtained from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) database for years 1993-2005. Obese occupants had a 26 and 33% higher risk of AIS > or = 2 and AIS > or = 3 thoracic injury when compared to lean occupants. The increased risk of AIS > or = 3 injury due to obesity was slightly higher for older occupants, but the influence of age was greater than that of obesity. The increase in injury potential was higher for unbelted obese occupants than unbelted. Non-parametric and parametric risk curves were developed to estimate the risk of thoracic injury based on occupant BMI, belt use and delta-V. Overall, increase in thoracic injury risk due to obesity is more prominent in males and older occupants and for occupants sustaining AIS > or = 3 thoracic injuries.

The tolerance of the maxilla to blunt impact

This study reports the results of 38 infraorbital maxilla impacts performed on male cadavers. Impacts were performed using an unpadded, cylindrical impactor (3.2 kg) at velocities between 1 and 5 m/s. The peak force and acoustic emission data were used to develop a statistical relationship of fracture risk as a function of impact force. Acoustic emission sensors were used to provide a noncensored measure of the maxilla tolerance and were essential due to the increase in impactor force after fracture onset. Parametric and nonparametric techniques were used to estimate the risk of fracture tolerance. The nonparametric technique produced an estimated 50% risk of fracture between 970 and 1223 N. The results obtained from the parametric and nonparametric techniques were in good agreement. Peak force values achieved in this study were similar to those of previous work and were unaffected by impactor velocity. The results of this study suggest that an impact to the infraorbital maxilla is a load-limited event due to compromise of structural integrity.

Validation and Application of a Methodology to Calculate Head Accelerations and Neck Loading in Soccer Ball Impacts

Calculating head accelerations and neck loading is essential for understanding and predicting head and neck injury. Most of the desired information cannot be directly measured in experiments with human volunteers. Achieving accurate results after applying the necessary transformations from remote measurements is difficult, particularly in the case of a head impact. The objective of this study was to develop a methodology for accurately calculating the accelerations at the center of gravity of the head and the loads and moments at the occipital condyles. To validate this methodology in a challenging test condition, twenty (20) human volunteers and a Hybrid III dummy were subjected to forehead impacts from a soccer ball traveling horizontally at speeds up to 11.5 m/s. The human subjects and the Hybrid III were instrumented with linear accelerometers and an angular rate sensor inside the mouth. The dummy was also equipped with accelerometers at the center of gravity of the head and load cells in the upper and lower neck. The force applied to the head by the soccer ball was calculated by double differentiating the ball displacement measured from high speed video. Standard mechanics equations were used to transform mouth accelerations to the head center of gravity and to calculate loads and moments at the occipital condyles. Accurate angular acceleration data were obtained by rigidly mounting a small angular rate sensor inside the mouth on a bite block. The neck loads calculated using inverse dynamics required filtering to a cutoff frequency of 50 Hz in order to reduce the noise to an acceptable level and achieve a good match with the neck load cell data. Noise was a particular problem in the calculated occipital condyle sagittal plane bending moment. Although some differences in the results of the human and dummy tests were observed, The Hybrid III dummy head and neck appeared to be reasonably biofidelic in this loading scenario.

A new methodology for investigating airbag-induced skin abrasions

Although airbags have been shown to reduce the incidence of life-threatening injuries, they have increased the risk of minor injuries such as those to the skin. Based on the distribution of injuries that can be directly attributed to the airbag itself, it is believed that shear loading exists as a mechanism for these skin injuries. The purpose of this study was to develop a new methodology designed to assess the injury potential from different types of airbag with respect to shear loading. This new methodology utilized a high-speed impactor to accelerate the airbag fabric past a sample of skin. Contact normal forces were monitored by the use of pressure sensors, and fabric velocity was determined from a high-speed video. The abraded skin samples were analysed using light microscopic analysis and ultraviolet light source photography. A new abrasion rating method was developed called the total abrasion score, which allows for quantifiable differentiation between the abrasions caused by different airbag fabric and seam types.

Analytical Model for Investigating Low-Speed Sideswipe Collisions

Vehicle dynamics in sideswipe collisions are markedly different from other types of collisions. Sideswipe collisions are characterized by prolonged sliding contact, often with very little structural deformation. An analytical model was developed to investigate the vehicle dynamics of sideswipe collisions. The vehicles were modeled as rigid bodies, and lateral interaction between the vehicles was modeled with a linear elastic spring. This linear spring was meant to represent the combined lateral stiffness of both vehicles before significant crush develops. Longitudinal interaction between the vehicles was modeled as frictional contact. In order to validate the model, seven (7) low speed (3 – 10 kph), shallow angle (15°) sideswipe collisions were staged with instrumented vehicles. These sideswipe collisions were characterized by long contact durations (~ 1 s) and low accelerations (< 0.4 g’s). The experimental collisions were also simulated with EDSMAC. EDSMAC overpredicted peak longitudinal vehicle acceleration by an average of 83% and underpredicted the length of contact damage by an average of 50%. In contrast, the linear spring model accurately predicted the peak longitudinal vehicle acceleration (5% error) when the stiffness parameter was tuned to match the length of contact damage. These results suggest that a noncrush-based linear spring model for calculating intervehicular force could significantly improve the accuracy of reconstructions of low speed sideswipe collisions compared to existing methods such as SMAC.

Characterization of Force Deflection Properties for Vehicular Bumper-to-Bumper Interactions

This is the complete manuscript and replacement for SAE paper 2014-01-0482, which was retracted due to incomplete content. This paper reports on 76 quasi-static tests conducted to investigate the behavior of road vehicle bumper systems. The tests are a quasi-static replication of real world low speed collisions. The tests represented front to rear impacts between various vehicles. Force and deflection were captured in order to quantify the stiffness characteristics of the bumper-tobumper system. A specialized test apparatus was constructed to position and load bumper systems into each other. The purpose was to replicate or exceed damage that occurred in actual collisions. The fixture is capable of positioning the bumpers in various orientations and generates forces up to 50 kips. Various bumper-to-bumper alignments were tested including full overlap, lateral offset, and override/underride configurations. Force and displacement were recorded and the data was analyzed to develop system stiffness and crush parameters. These parameters can be used in a collision-based model to calculate vehicle delta-v (ΔV) and acceleration. The simulation uses an impact mechanics-based numerical algorithm published by Scott [6]. The paper reports on the test results of various combinations of vehicle categories. Vehicle type includes passenger, light transport and heavy vehicle bumper systems. Language: en

Experimental Analysis of Airbag Seam Design: High-Rate Shear Testing for Skin Abrasions

Approximately 66 per cent of all airbag deployments in the USA result in at least one skin injury, with 47 per cent of these skin injuries attributed directly to the airbag deployment. The purpose of the present study was to evaluate the risk of skin abrasions from the airbag fabric seam design by using a new shear testing methodology. High-rate shear loading was performed with a pneumatic impactor that propelled a section of airbag fabric across porcine skin at 85 m/s. Twenty-seven tests (three control and 24 with fabric) were performed using eight different seam designs. A 40 cm × 10 cm section of airbag fabric with each seam was forced across a 5 cm × 5 cm section of fresh porcine skin that was acquired within 2 h post-mortem. No abrasions were observed in the three control tests, but abrasions were observed in all 24 of the tests conducted using airbag fabric. The unturned, sewn seam orientation resulted in significantly more severe abrasions than the woven, unturned seam orientation (P = 0.01). This new system and results illustrate that different seam designs can result in different skin abrasion risk. Moreover, the data show that severe abrasions can be caused by normal pressures well below the 1.75 MPa injury threshold previously published.

Kinematics and Kinetics of Vigorous Head Shaking

Previous studies on neck muscle strength and motion have assumed or imposed varying constraints on the heads and bodies of the subjects. In this study, we asked 20 subjects to vigorously shake their heads 5-10 times in a completely unconstrained manner. The kinematics and kinetics of the head and neck were measured from video analysis and instrumentation mounted inside the mouth. Subjects shook their heads at self-selected tempos ranging from 1.9-4.7 Hz over a 20-91° range of motion. The motion of each subjects head could be approximated by a fixed center of rotation that was typically located in the midcervical spine, but varied widely among subjects. Significant differences between men and women were observed. Peak head accelerations were low (4.3 ± 1.1 g and 250 ± 103 rad/s2 for men, 3.0 ± 0.9 g and 182 ± 58 rad/s2 for women) and estimated peak generated neck moments at C7/T1 were comparable to values reported in isometric neck strength studies (47 ± 14 N·m in extension and 22 ± 9 N·m in flexion for men, 25 ± 8 N·m in extension and 9 ± 7 N·m in flexion for women).