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A parameter study is performed involving several analytical vehicle occupant models in current use, with investigation of neck representations a primary goal. Side, oblique, and rear impact situations are investigated. Attention is given to the effects of varying head-neck mass and moments of inertia, anthropometry, muscle strength, and location, as well as well as strength, of motion-limiting “stops.” A model that replaces the conventional simple ball-joint neck with a two-joint, extensible neck is studied. This model also makes use of joint-stop ellipses to approximate the anatomical range for relatively free angular motion at a joint. Allowance is made for the effect of muscle contraction on occupant dynamics as a function of the degree of voluntary or involuntary tightening of the muscles, based upon experimental findings. A discrete parameter neck model that treats the cervical spine as a linkage of rigid vertebrae and massless, deformable discs is discussed briefly.

This paper describes the development of an improved neck simulation that can be adapted to current anthropometric dummies. The primary goal of the neck design is to provide a reasonable simulation of human motion during impact while maintaining a simple, rugged structure. A synthesis of the current literature on cervical spine mechanics was incorporated with the results of x-ray studies of cervical spine mobility in human volunteers and with the analysis of head-neck motions in human volunteer sled tests to provide a background for the design and evaluation of neck models. Development tests on neck simulations were carried out using a small impact sled. Tests on the final prototype simulation were also performed with a dummy on a large impact sled. Both accelerometers and high-speed movies were used for performance evaluation.

Blunt abdominal trauma is a major cause of death in the United States. However, little experimental work has been done to clarify the mechanism of blunt abdominal injury and to quantify tolerance parameters for the abdominal organs. This paper describes a joint study by the Highway Safety Research Institute and the Section of General Surgery of The University of Michigan in which direct impacts were applied to livers and kidneys. The tests were performed in a high-speed testing machine at a controlled ram velocity and stroke limit. The organ was surgically mobilized in anesthesized Rhesus monkeys and then placed on a load cell while still being perfused in the living animal. Tests were performed at ram speeds of 120, 6000, and 12000 in/min (5, 250,and 500 cm/s). The resulting load-deflection data were normalized and average stress-strain curves plotted for each test. In addition, the resulting injury severity was estimated immediately after impact using an injury scale of 1 to 5.

The object of this research program has been to extend the scope of earlier work to include long-duration head impacts and to develop new scaling relationships to allow extrapolation of impact data from infrahuman primates to living humans. A series of living primate side impacts to the head and torso was conducted in parallel with a series of impacts to human cadavers. Dimensional analysis techniques were employed to estimate in vivo human tolerance to side injury. The threshold of closed brain injury to humans was found to be 76 g for a pulse duration of 20 ms and an impact velocity of 43 ft/s (13.2 m/s). The maximum tolerable penetration to the chest was found to be 2.65 in (6.72 cm) for both the left and right sides. Scaling of abdominal injuries to humans was accomplished by employing a factor that relates impact contact area, animal mass, impact force, and pulse duration to injury severity.

A study has been conducted as an initial step in determining the differences observed between the motions of a living human impact sled test subject and a dummy test subject. The mechanism which is proposed for accomplishing this is the HSRI Two-Dimensional Mathematical Crash Victim Simulator. A series of measurements were taken on human test subjects, including classical and nonclassical anthropometric measurements, range of motion measurements for the joints, and maximum foot force measurements. A series of mathematical expressions has been used to predict body segment weight, centers of gravity, and moments of inertia using the results of the various body measurements. It was then possible to prepare a data set for use with the mathematical model.

This paper presents the various features and operational properties of a two-dimensional mathematical model of crash victim motions. The earliest forms of this model can be traced to the early 1960s. Developmental work on two-dimensional models then continued both within the automotive industry and in independent organizations such as the Highway Safety Research Institute (HSRI). The most recent product of this activity is the MVMA two-dimensional mathematical crash victim simulation developed at HSRI for the Motor Vehicle Manufacturers Association. The features of this model include: 1. An eight mass representation of the human body where contact between the crash victim and the vehicle is represented in terms of independent force-deformation properties of the victim and the vehicle. 2. An extensible multi-joint neck and a realistically flexible shoulder joint. 3. A real-line representation of the vehicle interior or exterior where shape is given as a network of points. 4.

Serious injuries are caused to the chest and thoracic organs both in front and side automobile collisions, and statistical surveys indicate that overall chest injuries are the third most frequent after head and the lower limbs. For safer design of restraint systems and vehicle interiors experimental data has to be obtained to establish chest injury criteria. Unembalmed human cadavers were used to conduct nine frontal and fourteen lateral impacts including four with a simulated arm rest. All impacts used a six inch (15.2 cm) diameter impactor with impact velocities ranging from 12 mph (19.3 kph) to 20 mph (32.2 kph). Chest impacts were also conducted on rhesus monkeys and baboons to establish primate-human injury scaling criteria. Four human volunteers were used to obtain static load deflection curves in the lateral and frontal directions. The results of the above experiments and those conducted by other investigators are presented and analyzed.

A study of the biomechanical factors concerned with the design of side structures and doors for crashworthiness has been made. Questions regarding optimum stiffness, location of reinforcing members, effect of armrests, and padding have been answered within the framework of injury criteria models. Results of animal studies, cadaver studies, and anthropometric dummies have been combined to produce injury criteria for lateral impacts to the head, thorax, and abdomen. Impacts were applied utilizing a specially designed “air gun” in a laboratory environment emphasizing reproducibility and control. Full-scale crash simulations were performed on an impact sled to verify the results of the more specialized tests and analyses. Scaled models of current production doors were used in the animal series. Scaling relationships for various species of animals have been developed and extrapolated to man. Significant differences in right and left side tolerances to impact were noted and detailed.

A variety of mechanical head forms is used today in the evaluation of the crashworthiness of automotive interiors and the effectiveness of helmet designs. Most head forms are of a very rigid metallic construction, although frangible head forms that indicate skull fracture are presently available. None of the existing head forms can be considered a complete mechanical analog to the human head in terms of mechanical response. This paper describes the initial phases of the development of such a head form. The first step in the development of the model was the determination of the pertinent mechanical properties of the tissues of the human head (scalp, skull bone, dura mater, and brain). A testing program which determined these properties at both static and dynamic strain rates is described and the results are summarized. The second phase of the program was to find and develop synthetic materials which duplicated the mechanical properties of the human tissues.

Basic physical characteristics of the neck have been defined which have application to the design of biomechanical models, anthropometric dummies, and occupant crash protection devices. The study was performed using a group of 180 volunteers chosen on the basis of sex, age (18-74 years), and stature. Measurements from each subject included anthropometry, cervical range-of-motion (observed with both x-rays and photographs), the dynamic response of the cervical flexor and extensor muscles to a controlled jerk, and the maximum voluntary strength of the cervical muscles. Data are presented in tabular and graphic form for total range-of-motion, cervical muscle reflex time, decelerations of the head, muscle activation time, and cervical muscle strength. The range-of-motion of females was found to average 1-12 deg greater than that of males, depending upon age, and a definite degradation in range-of-motion was observed with increasing age.

This paper reviews the state of theoretical and experimental technology relative to the dynamic performance of articulated highway vehicles. The review contains three major sections, corresponding to the traditional breakdown of vehicle performance: directional performance, braking performance, and combined directional and braking performance. An attempt is made to take a frankly evaluative point of view and to point out knowledge gaps and unanswered questions, in addition to documenting previous accomplishments and progress. The paper concludes with some recommendations for future research consistent with the findings of the review.