Biomedical subjects

Stephen W Rouhana

Publications and source records attributed to Stephen W Rouhana.

9 recordsLinked to original sources

PubMed2006

Worldsid assessment of far side impact countermeasures.

Far side impact trauma has been demonstrated as a significant portion of the total trauma in side impacts. The objective of the study was to assess the potential usefulness of countermeasures and assess the trade-offs associated with generic countermeasure design. Because the WorldSID dummy has demonstrated promise as a potential far side impact dummy, it was chosen to assess countermeasures in this mode. A unique far side impact buck was designed for a sled test system that included, as a standard configuration, a center console and outboard three-point belt system. This configuration assumed a left side driver with a right side impact. The buck allowed for additional options of generic restraints including shoulder or thorax plates or an inboard shoulder belt. The entire buck could be mounted on the sled in either a 90-degree (3-o'clock PDOF) or a 60-degree (2-o'clock PDOF) orientation. A total of 19 WorldSID tests were completed. The inboard shoulder belt configuration produced high shear forces in the lower neck (2430 N) when the belt position was placed over the mid portion of the neck. Shear forces were reduced and of opposite sign when the inboard belt position was horizontal and over the shoulder; forces were similar to the standard outboard belt configuration (830 - 1100 N). A shoulder or thorax restraint was effective in limiting the head excursion, but each caused significant displacement at the corresponding region on the dummy. A shoulder restraint resulted in shoulder displacements of 30 - 43 mm. A thorax restraint caused thorax deflections of 39 - 64 mm. Inboard restraints for far side impacts can be effective in reducing head excursion but the specific design and placement of these restraints determine their overall injury mitigating characteristics.

Accidents, Traffic↗

PubMed2005

Shoulder injury and response due to lateral glenohumeral joint impact: an analysis of combined data.

To date, several lateral impact studies (Bolte et al., 2000, 2003, Marth, 2002 and Compigne et al., 2004) have been performed on the shoulder to determine the response characteristics and injury threshold of the shoulder complex. Our understanding of the biomechanical response and injury tolerance of the shoulder would be improved if the results of these tests were combined. From a larger data base shoulder injury tolerance criteria can be developed as well as corridors for side impact dummies. Data from the study by Marth (2002, 12 tests) was combined with data from the previous studies. Twenty-two low speed tests (4.5 +/- 0.7 m/s) and 9 high speed tests (6.7 +/- 0.7 m/s) were selected from the combined data for developing corridors. Shoulder force, deflection and T1y acceleration corridors were developed using a minimization of cumulative variance technique. The reduction in impact speed and the addition of padding reduced the magnitude and increased the time to peak of shoulder forces and T1y accelerations. Logistic analyses were performed on the combined data sets to determine the best predictors of MAIS-2 shoulder injuries. Maximum normalized shoulder deflection and Cmax had p values of 0.0000 and were the best predictors of shoulder injuries. For the 50(th)-percentile male, a shoulder deflection of 40 mm and a Cmax of 20% corresponded to a 50 % risk of MAIS-2 shoulder injury. In linear regression analysis, maximum normalized medial scapula X acceleration and maximum normalized sternum X acceleration were best related with the shoulder deflection and confirmed the forward movement of the sternum and rearward movement of the scapula.

Journal Article↗

PubMed2005

Characteristics of PMHS Lumbar Motion Segments in Lateral Shear.

The purpose of this study was to determine the characteristics of eighteen lumbar spine motion segments subjected to lateral shear forces under quasi-static (0.5 mm/s) and dynamic (500 mm/s) test conditions. The quasi-static test was also performed on the lumbar spine of a side impact anthropomorphic test device, the EuroSID-2 (ES-2). In the quasi-static tests, the maximum force before disc-endplate separation in the PMHS lumbar motion segments was 1850 +/- 612 N, while the average linear stiffness of PMHS lumbar motion segments was 323 +/- 126 N/mm. There was a statistically significant difference between the quasi-static (1850 +/- 612 N) and dynamic (2616 +/- 1151 N) maximum shear forces. The ES-2 lumbar spine (149 N/mm) was more compliant than the PMHS lumbar segments under the quasi-static test condition.

Journal Article↗

PubMed2005

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.

Journal Article↗

PubMed2005

Evaluation of the ES-2re Dummy in Biofidelity, Component, and Full Vehicle Crash Tests.

This technical paper presents the results from tests conducted with the ES-2re, a version of the ES-2 side impact dummy that was modified by the National Highway Traffic Safety Administration (NHTSA) to improve its performance in crash tests. Through the series of biofidelity tests conducted on the ES-2re, described in International Standards Organization (ISO) Technical Report (TR)9790 (1999), the OSRP observed a final overall biofidelity ranking of 4.1 for the ES-2re, which corresponds to an ISO classification of "marginal." The biofidelity of the ES-2re is compared to that of the ES-2 and the WorldSID. Repeatability was also evaluated on the ES-2re based on the biofidelity test data. Additional pendulum tests were performed to assess the response of the dummy in oblique loading conditions, and results indicate that oblique loading from the front leads to significantly reduced rib deflections. To evaluate inconsistencies observed in the response of the ES-2, the OSRP analyzed the shoulder biofidelity via additional sled and drop tests. Due to the shoulder design of the ES-2 and ES-2re, the dummies appear to have significant sensitivity to initial conditions, potentially increasing variability in full vehicle tests. Finally, the responses of the ES-2re in full vehicle tests are compared to those of the ES-2 and the WorldSID.

Journal Article↗

PubMed2005

Development and Evaluation of a Proposed Neck Shield for the 5 Percentile Hybrid III Female Dummy.

Frontal airbag interaction with the head and neck of the Hybrid III family of dummies may involve a non-biofidelic interaction. Researchers have found that the deploying airbag may become entrapped in the hollow cavity behind the dummy chin. This study evaluated a prototype neck shield design, the Flap Neck Shield, for biofidelic response and the ability to prevent airbag entrapment in the chin/jaw cavity. Neck pendulum calibration tests were conducted for biofidelity evaluation. Static and dynamic airbag deployments were conducted to evaluate neck shield performance. Tests showed that the Flap Neck Shield behaved in a biofidelic manner with neck loads and head motion within established biofidelic limits. The Flap Neck Shield did not alter the neck loads during static or dynamic airbag interactions, but it did consistently prevent the airbag from penetrating the chin/jaw cavity. Use of the Flap Neck Shield with the 5(th) percentile Hybrid III female dummy is recommended for frontal airbag deployments given its acceptable biofidelic response and repeatable performance.

Journal Article↗

PubMed2004

Mechanical Properties of the Shoulder Ligaments under Dynamic Loading.

Thirty-three fresh human cadaver shoulders were harvested and bone-ligament-bone specimens of acromioclavicular joint, coracoclavicular joint and sternoclavicular joint were obtained. A test fixture and clamps specifically designed for this ligament study and a high-speed Instron machine were used. One quasi-static rate (nominally 0.1 %/sec) and two high rates (nominally, high rate 1 = 40,000 %/sec and high rate 2 = 15,000 %/sec) were used in this study. In the acromioclavicular joint tests, ligament failure was the most common failure mode. Bone fractures occurred most often at the clavicle rather than acromion. In the coracoclavicular joint tests, the majority of specimens failed at the ligament and bone fractures occurred at the coracoid. In the sternoclavicular joint tests, the specimen failed at the bone in most cases. In the acromioclavicular joint and coracoclavicular joint tests, high rate 2 tests and quasi-static tests had more bone fracture cases than high rate 1 tests. Cross sectional area, deflection at failure, load at failure, strain at failure, stress at failure and Young's modulus of these three shoulder joints were found. The Young's modulus, ultimate stress and ultimate load of the three joints were found to be significantly lower in the quasi-static rate tests compared to the high rate 2 tests but not significantly different between high rate 1 and high rate 2 tests. There are no significant relationships between cross-sectional area and age, height or weight, nor between the mechanical properties of the shoulder joint and age, height or weight.

Journal Article↗

PubMed2003

Biomechanics of 4-point seat belt systems in frontal impacts.

The biomechanical behavior of 4-point seat belt systems was investigated through MADYMO modeling, dummy tests and post mortem human subject tests. This study was conducted to assess the effect of 4-point seat belts on the risk of thoracic injury in frontal impacts, to evaluate the ability to prevent submarining under the lap belt using 4-point seat belts, and to examine whether 4-point belts may induce injuries not typically observed with 3-point seat belts. The performance of two types of 4-point seat belts was compared with that of a pretensioned, load-limited, 3-point seat belt. A 3-point belt with an extra shoulder belt that "crisscrossed" the chest (X4) appeared to add constraint to the torso and increased chest deflection and injury risk. Harness style shoulder belts (V4) loaded the body in a different biomechanical manner than 3-point and X4 belts. The V4 belt appeared to shift load to the clavicles and pelvis and to reduce traction of the shoulder belt across the chest, resulting in a reduction in chest deflection by a factor of two. This is associated with a 5 to 500-fold reduction in thoracic injury risk, depending on whether one assumes 4-point belts apply concentrated or distributed load. In four of six post mortem human subjects restrained by V4 belts during 40 km/h sled tests, chest compression was zero or negative and rib fractures were nearly eliminated. Submarining was not observed in any test with post mortem human subjects. Though lumbar, sacral and pelvic injuries were noted, they are believed to be due to the artificial restraint environment (no knee bolsters, instrument panels, steering systems or airbags). While they show significant potential to reduce thoracic injury risk, there are still many issues to be resolved before 4-point belts can be considered for production vehicles. These issues include, among others, potential effects on hard and soft neck tissues, of interaction with inboard shoulder belts in farside impacts and potential effects on the fetus of latch/buckle junctions at the centerline of pregnant occupants. Work continues at Ford Motor Company to resolve these issues.

Journal Article↗

PubMed2002

ES-2 Dummy Biomechanical Responses.

This technical paper presents the results of biomechanical testing conducted on the ES-2 dummy by the Occupant Safety Research Partnership and Transport Canada. The ES-2 is a production dummy, based on the EuroSID-1 dummy, that was modified to further improve testing capabilities as recommended by users of the EuroSID-1 dummy. Biomechanical response data were obtained by completing a series of drop, pendulum, and sled tests that are outlined in the International Organization of Standardization Technical Report 9790 that describes biofidelity requirements for the midsize adult male side impact dummy. A few of the biofidelity tests were conducted on both sides of the dummy to evaluate the symmetry of its responses. Full vehicle crash tests were conducted to verify if the changes in the EuroSID-1, resulting in the ES-2 design, did improve the dummy's testing capability. In addition to the biofidelity testing, the ES-2 dummy repeatability, reproducibility and durability are discussed. Finally, this technical paper will compare the biofidelity ratings of the current adult side impact dummies with the ES-2 dummy, which received an overall dummy biofidelity rating of 4.6.

Journal Article↗