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Technical Paper

Cadaver and Dummy Knee Impact Response

Knee impacts along the femoral axis of unembalmed male cadavers and Part 572 dummies were made with rigid pendulum impactors at Wayne State University. The dummy exhibited significantly higher knee impact forces than the cadaver subjects. This difference of response is shown to be due to differences of effective leg mass and knee padding. The dummy with its heavy rigid metal skeleton is not like its human counterpart, where the majority of the leg weight is composed of loosely coupled flesh. The knee impacts of the dummy subjects showed that the dummy femur transducer force was consistently less than the corresponding dummy knee impact force by a constant ratio of 0.8. We recommend that the “skeletal” weight of the Part 572 dummy leg should be substantially reduced, with the weight difference being added to a properly simulated leg flesh. Also, the simulated flesh covering of the knee should be modified to reduce the peak force resulting from rigid body impacts.
Technical Paper

Safety Comparison of Laminated Glass and Acrylic Glazing in Front Camper Windows

Children riding on the bed over the cab in campers can be injured in forward force collisions from striking the glazing material and/or being ejected through the opening. The two types of glazing commonly used are acrylic and laminated. A comparison of the performance of the two types of glazing in simulated forward force collisions at velocities up to 30 mph showed the acrylic material to pose threats of neck and back injury and the laminated material to result in lacerations. Ejections occurred with the acrylic that were not present with the laminated windshields when correct glazing techniques were used. With poor installation procedures, ejections occurred in both types of glazing materials. It is concluded that the best way to avoid injury is to prevent the child from riding in the over-the-cab bunk. If the child does ride there, his body axis should be positioned at an angle to the longitudinal axis of the vehicle.
Technical Paper

Passive and Active Restraint Systems-Performance and Benefit/Cost Comparison

Five different restraint systems-mandatory harness, airbag + 20% lap belt usage, airbag, passive three point harness, and torso and knee bar-are analyzed for fatality and injury reduction, benefit/cost ratio, and cost-effectiveness. The mandatory harness is superior to the others in all comparisons with approximately 100,000 lives saved over the first 10 years which is about twice as many as would be saved by the other systems. A major advantage of the mandatory harness is that practically all of the vehicles are equipped while the other systems will require 10 years for complete installation.
Technical Paper

Dynamic Response of the Spine During +Gx Acceleration

A review of the existing mathematical models of a car occupant in a rear-end crash reveals that existing models inadequately describe the kinematics of the occupant and cannot demonstrate the injury mechanisms involved. Most models concentrate on head and neck motion and have neglected to study the interaction of the occupant with the seat back, seat cushion, and restraint systems. Major deficiencies are the inability to simulate the torso sliding up the seat back and the absence of the thoracic and lumbar spine as deformable, load transmitting members. The paper shows the results of a 78 degree-of-freedom model of the spine, head, and pelvis which has already been validated in +Gz and -Gx acceleration directions. It considers automotive-type restraint systems, seat back, and seat cushions, and the torso is free to slide up the seat back.
Technical Paper

Injury to Unembalmed Belted Cadavers in Simulated Collisions

Unembalmed cadavers restrained with a three point harness were exposed to a deceleration environment of 20, 30 and 40 mph BEV.* Injuries were tabulated from detailed autopsies. The results Indicate an AIS-1 injury at 25.5 mph, an AIS-2 injury at 31.5 mph and an AIS-3 injury at 34.5 mph. The AIS-3 injury level is recommended as the maximum acceptable injury. The cadavers sustained the same types of injury that have been reported in medical literature including bruises, abrasions, lacerations, fractures and viscera ruptures, but injury severities were greater in the cadavers than in living humans at a given collision severity. Also, there is a wide spread in the degree of injury between cadavers due to differences in age and physical condition. The threshold of cadaver rib fracture is 30 mph and the threshold of cadaver vertebral fracture is between 30 and 40 mph for the environment utilized. More numerous and severe abdominal injuries were observed.
Technical Paper

Improved Laminated Windshield with Reduced Laceration Properties

A new laminated automobile windshield called Triplex “Ten-Twenty,” fabricated from two thermally stressed glass plies of 2.3 mm soda-lime float glass laminated with a 0.76 mm HPR polyvinyl butyral interlayer, has been biomechanically evaluated by Triplex Safety Glass Co., Ltd., using a dropping headform and a skull impactor, and by Wayne State University, using a 50th percentile anthropomorphic dummy on the WHAM III sled test facility. The results of these evaluations at velocities up to 60 km/h are expressed in terms of Gadd index, head injury criterion, and various laceration scales including the new Triplex laceration index (TLI). Some details are also given of other properties of the windshield. The results of the evaluations indicate that the Ten-Twenty windshield offers a reduction of about two units on the TLI scale equivalent to one of the following: 1. A 99% reduction in the number of cuts when the length and depth of cuts remain unaltered. 2.
Technical Paper

Strength and Response of the Human Neck*

Human volunteers were subjected to static and dynamic environments which produced noninjurious neck responses for neck extension and flexion. Cadavers were used to extend this data into the injury region. Analysis of the data from volunteer and cadaver experiments indicates that equivalent moment at the occipital condyles is the critical injury parameter in extension and in flexion. Static voluntary levels of 17.5 ft lb in extension and 26 ft lb in flexion were attained. A maximum dynamic value of 35 ft lb in extension was reached without injury. In hyperflexion, the chin-chest reaction changes the loading condition at the occipital condyles which resulted in a maximum equivalent moment of 65 ft lb without injury. Noninjurious neck shear and axial forces of 190 lb and 250 lb are recommended based on the static strength data obtained on the volunteers. Neck response envelopes for performance of mechanical necks are given for the extension and flexion modes of the neck.
Technical Paper

Living Human Dynamic Response to —Gx Impact Acceleration II—Accelerations Measured on the Head and Neck

A methodical investigation and measurement of human dynamic response to impact acceleration is being conducted as a Joint Army-Navy-Wayne State University investigation. Details of the experimental design were presented at the Twelfth Stapp Car Crash Conference in October 1968. Linear accelerations are being measured on the top of the head, at the mouth, and at the base of the neck. Angular velocity is also being measured at the base of the neck and at the mouth. A redundant photographic system is being used for validation. All data are collected in computer compatible format and data processing is by digital computer. Selected data in a stage of interim analysis on 18 representative human runs of the 236 human runs completed to date are presented. Review of the data indicates that peak accelerations measured at the mouth are higher than previous estimates.
Technical Paper

Dynamic Response of the Human Cadaver Head Compared to a Simple Mathematical Model

It is shown that the response of the occiput of a cadaver to sinusoidal vibration input to the frontal bone corresponds closely to that of a simple damped spring-mass system having a natural frequency equal to the first mode frequency of the skull, 0.17 damping factor. The first and third bending mode of the skull occurred near 300 and 900 Hz for both the cadaver preparation with silicon gel filled cranial cavity and the live human head. A second mode was found near 600 Hz in the live human. Head acceleration levels at which opposite pole pressure reached near —1 atm were 170 g and 500–600 g in the human cadaver and live monkey head, respectively, which values are roughly inversely proportional to major intracranial diameters. A method is derived for comparing the impact response of a simple system to a general shaped pulse to that of the cadaver head.
Technical Paper

Investigation of the Kinematics and Kinetics of Whiplash

The kinematics of rear-end collisions based on published acceleration pulses of actual car-to-car collisions (10 and 23 mph) were reproduced on a crash simulator using anthropomorphic dummies, human cadavers, and a volunteer. Comparison of the responses of subjects without head support were based on the reactions developed at the base of the skull (occipital condyles). The cadavers gave responses which were representative of persons unaware of an impending collision. The responses of both dummies used were not comparable with those of the cadavers or volunteer, or to each other. An index based on voluntary human tolerance limits to statically applied head loads was developed and used to determine the severity of the simulations for the unsupported head cases. Results indicated that head torque rather than neck shear or axial forces is the major factor in producing neck injury.
Technical Paper

Cadaver Knee, Chest and Head Impact Loads

Human tolerance to knee, chest, and head impacts based upon skeletal fracture of cadavers is reported. The results are based upon unrestrained cadaver impacts in a normal seated position in simulated frontal force accidents at velocities between 10 and 20 mph and stopping distances of 6-8 in. The head target was covered with 15/16 in. of padding. No skull or facial fractures were observed at loads up to 2640 lb. Extensive facial fractures and a linear skull fracture occurred during the application of the maximum head force of 4350 lb. The chest target was 6 in. in diameter with 15/16 in.of padding. The padding was rolled over the edge of the target to minimize localized high force areas on the ribs. A 1/8 in. diameter rod was inserted through the chest and fastened through a ball joint and flange to the soft tissue at the sternum.
Technical Paper

Impact Dynamics of Unrestrained, Lap Belted, and Lap and Diagonal Chest Belted Vehicle Occupants*

A comparison is presented of the forces, accelerations, and kinematics of an anthropomorphic dummy for identical sled impacts for unrestrained, lap belted, and lap and diagonal chest restrained conditions. Biaxial accelerometers were mounted in the head, chest, and on the proximal end of the femur to obtain the accelerations during the impacts. Seat belt load cells were put in series with the belts at each anchor point. Biaxial load cells were positioned to be impacted by the head, chest, and each knee for the unrestrained condition and by the head and chest for the lap belted configuration. For the lap and diagonal chest restrained condition these load cells were not used. Impacts of 10 and 20 miles per hour were made with sled stopping distance of 4 and 9 inches, respectively. At 20 miles per hour the head struck with a force of 1580 pounds in the unrestrained mode, 600 pounds with the lap belt, and did not hit with the lap and shoulder harness.