Search Results

Empirical models are presented which predict the threespace position of the torso when responding to reaches with the right arm. Models were derived which specify torso position in terms of the spacial location of 10 surface markers. These markers were positioned over palpable skeletal points of the spine and shoulder girdle. The necessary data were obtained through photogrammetric procedures utilizing four orthogonal cameras. The independent (input) variables to these models are the coordinates of the reach target. A supplementary, slightly more accurate, set of models was also derived in which the set of independent variables was enlarged to include the anthropometric dimensions of the subject. The second, concurrent phase of the analysis resulted in the derivation of a set of models which describes the configuration of the internal, torso skeletal system.

Advanced crash-impact protective equipment and techniques which have application to crew and passenger crash safety in jet transport aircraft have been evaluated. Thirty-two state-of-the-art concepts have been analyzed from a systems engineering viewpoint with respect to several engineering, psychological, and medical disciplines. In order to provide a framework to determine the function level of each concept, an event-oriented flow chart of the crash and escape event has been prepared. The 17 events occurring during a crash are included, beginning with system installation and concluding with emergency evacuation of a disabled aircraft. Performance with respect to the events on the flow chart are rated in terms of hazards of system use, maintainability, reliability, human factors, and other technological considerations.

Cyclical stepping (gait) has been studied extensively. Some of these results are reflected in the straight and curved path step-following algorithms in commercial digital human modeling (DHM) implementations. With the aid of these algorithms, DHM users define start, intermediate, and end path points and the software generates a walking-like motion along the path. Most of these algorithms have substantial limitations, among them that the figures exhibit “foot skate,” meaning that the kinematic constraint of foot contact with the ground is not respected. Turning is accomplished by pivoting the entire figure, rather than through realistic lower-extremity motions. The simulation of the non-cyclical stepping motions accompanying manual material handling pickup and delivery tasks requires manual manikin manipulation. This paper proposes a paradigm for the simulation of stepping behavior in digital human models based on a model of foot placements and motions.

This report presents the results of a three-year study designed to collect analyze, and reduce selected anthropometric data on 4027 infants and children representative of the current U.S. population ranging in age from newborn to 12 years of age. Since the major purpose was to provide basic measurement data most useful and critical to consumer product design, regulatory consideration, or other direct applications, 12 of the 41 measurements taken were applied measurements which have not been previously available. As an example of the direct application to product design, measurement of buttock depth on 3-to 6-month-old infants provided an objective basis for establishment of crib interslat distances. A substantial portion of the study involved the design, fabrication, development, and testing of a new generation of anthropometric measuring devices which transmit measurement signals to a portable mini-computer data acquisition system or to a set of readout meters.

In many task analyses using digital human figure models, only the terminal or apparently most stressful posture is analyzed. For reaches from a seated position, this is generally the posture with the hand or hands at the target. However, depending on the characteristics of the tasks and the people performing them, analyzing only the terminal posture could be misleading. This possibility was examined using data from a study of the reaching behavior of people with spinal cord injury. Participants performed two-handed forward reaching tasks. These reaches were to three targets located in the sagittal plane. The terminal postures did not differ significantly between those with spinal cord injury and those without. However, motion analysis demonstrated that they employed distinct strategies, particularly in the initial phase of motion.

Aircraft used for business (executive corporate transportation or personal business) and utility purposes now represent about one-third of the total United States aircraft inventory. Data from accident investigation of business aircraft involved in survivable accidents indicate serious injuries and fatality to the occupants occur most frequently as a result of the unprotected head and neck or chest flailing in contact with aircraft controls, instrument panel, or structure. Improvement of current aircraft to provide increased occupant safety and survival during crash impacts is both necessary and feasible. Design considerations include folding seat back locks to prevent collapse, increased seat tie-down to structure, instrument panels and glare shields designed to absorb energy through structural design and padding, stronger seat structure, lateral protection, design and packaging of knobs and projections to minimize injury in contact, and installation of upper torso restraint.

This paper presents an analysis of 67 neck injuries incurred in diving and sliding accidents in swimming pools. The accidents were investigated to establish the appropriate medical and mechanical factors involved. A mathematical model was developed to allow the prediction of the trajectory and velocity of the subjects prior to their injury. Nine of the accidents were selected for real life simulation. The simulation included the selection of test subjects of similar physical build to the accident victims who then performed the maneuvers leading to the injury, but in deeper water. High speed movies (200 frames per second) were taken, above and below the water, to measure the motion. A frame by frame analysis provided data to determine the trajectory and velocity profiles of the test subject. The maneuvers studied included diving from the pool edge, diving from various board types and sliding down various sliding board configurations.

Head injury is a serious threat to lives of people working around farm machinery. The consequence of head injuries are costly, paralytic, and often fatal. Clinical and biomechanical data on head injuries are reviewed and their application in the analysis of head injury risk associated with farm tractor discussed. A significant proportion of tractor-related injuries and deaths to adults, as well as children, is due directly or indirectly to head injury. An improved injury reporting program and biomechanical studies of human response to tractor rollover, runover, and falls, are needed to understand mechanisms of the associated head injury.

In a crash, impact against the steering assembly can be a major cause of serious and fatal injury to drivers. But the interrelationship between injury protection and factors of surface area, configuration, padding, relative position of the spokes, and number and stiffness of spokes and rim is not clear. This paper reports a series of high-G sled tests conducted with anesthetized animal subjects in 30 mph impacts at 30 G peaks. A total of eight tests were conducted, five utilizing pig subjects, one a female chimpanzee, one an anthropomorphic dummy, and one test with no subject. Instrumentation included closed circuit TV, a tri-axial load cell mounted between the steering wheel and column, seat belt load measurement, six Photo-Sonics 1000 fps motion picture cameras, and poloroid photography. Medical monitoring pre, during and post-impact was followed by gross and microscopic tissue examination.

Properties of the human neck which may influence a person's susceptibility to “whiplash” injury during lateral impact have been studied in 96 normal subjects. Subjects were chosen on the basis of age, sex, and stature and data were grouped into six primary categories based on sex (F, M) and age (18-24, 35-44, 62-74). The data include: measures of head, neck and body anthropometry in standing and simulated automotive seating positions, three-dimensional range of motion of the head and neck, head/neck response to low-level acceleration, and both stretch reflex time and voluntary isometric muscle force in the lateral direction. Reflex times are found to vary from about 30 to 70 ms with young and middle aged persons having faster times than older persons, and females having faster times than males. Muscle strength decreases with age and males are, on the average, stronger than females.

The objective of the study was to investigate the biomechanical response of the intact cranium. Unembalmed human cadavers were used in the study. The specimens were transected at the base of the skull leaving the intracranial contents intact; x-ray and computed tomography (CT) scans were obtained. They were fixed in a specially designed frame at the auditory meatus level and placed on the platform of an electrohydraulic testing device via a six-axis load cell. Following radiography, quasistatic loading to failure was applied to one of the following sites: frontal, vertex, parietal, temporal, or occipital. Retroreflective targets were placed in two mutually orthogonal planes to record the localized temporal kinematics. Applied load and piston displacement, and the output generalized force (and moment) histories were recorded using a modular digital data acquisition system. After the test, x-ray and CT images were obtained, and defleshing was done.

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.

The importance of crashworthiness and the role of restraint systems in occupant impact protection in U.S. civil aircraft design is being increasingly recognized. Current estimates of the number of fatalities which could be prevented annually in survivable accidents range from 33 to 94%. This study reviews the development of existing Federal Aviation Administration restraint system standards from the first requirement for safety belts in the Air Commerce Regulations of 1926 to present 14 CFR 1.1. The FAA and industry standards are critically evaluated for Parts 23 (small airplanes), 25 (air transports), 27 (rotorcraft), and 29 (transport category rotorcraft). State-of-the-art developments, including an overview of previous accident experience, results of experimental studies, comparison with other standards, and primary data sources are provided.

Business and executive aviation represent a combined total of over 40% of the general aviation fleet, but (1977) accounted for only 8.37% of all general aviation accidents recorded. During the period 1964-1977 some 7,351 aircraft engaged in business flying, and 883 in corporate/executive operations, were involved in accidents reported by the NTSB. These accidents were reviewed utilizing the University of Michigan Computerized Accident Files to provide an overall view of the incidence and nature of business/executive aircraft accidents relative to occupant crash injuries. In addition more detailed case studies of selected accidents investigated including a Lear Jet 25B, Cessna 421, Beech Volpar Model 18, and Ted Smith Aerostar 601, are provided to illustrate specific types of crashworthiness, occupant protection, or post-crash emergency egress findings applicable to business/executive operations. Post-crash fire was reported in 29 cases (16.3%) during the 3-year period (1975-1977).

General aviation accident investigations can provide valuable data to the design engineer concerning the crash performance of current models and can indicate needed improvements for occupant protection in future aircraft. Current statistics and the historical background of major investigations during the past 65 years are provided. A five-year study of general aviation accidents occurring in the State of Michigan is used as a basis to illustrate recent findings relative to occupant injury mechanisms, relative crash protection, and crashworthiness performance of current models of aircraft. Results indicate that the degree of structural damage may not relate to the degree of occupant injury when the cabin area remains relatively intact. A primary requirement is documented for adequate upper-torso restraint for all occupants, and the excellent crash performance of such a system is described.

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.

Workers who must perform manual operations with the hands above shoulder level have increased risk of developing painful disorders of the neck and shoulder. This is a special problem in automobile assembly because of the trend toward unit body construction. Parts that operators formerly attached to a frame must now be assembled to the underbody structure. Using a special conveyor system to tilt the vehicle has been considered as a way to minimize musculoskeletal stress. Experimental trials of chassis assembly operations using a 30 degree tilt are described here. Tilting was not effective in reducing stress of overhead work. The 30 degree angle was insufficient to significantly reduce work height, and tilting frequently obscured, rather than improved, visibility. In order for tilting to be effective, it appears that a full 90 degree rotation is required, and the vehicle needs to be designed to take advantage of body tilting.

Occupational populations have become increasingly diverse, requiring novel accommodation technologies for inclusive design. Hence, further attention is required to identify potential differences in work perception between workers with varying physical limitations. The major aim of this study was to identify differences in shoulder loading and perception of effort between a control population (C) and populations affected by chronic back pain (LBP) and spinal cord injury (SCI) in one-handed seated transfer tasks to targets. The effects of the injuries, and associated pain, are likely to produce variations in movement patterns, muscle loading and perceived effort.

This study begins the exploration of the relationship between shoulder external moments and perceived exertion levels for submaximal delivery tasks. Twenty subjects were recorded while performing hand load movement tasks to specified targets. After each exertion, subjects were asked to rate the effort required to perform the task. The recorded motion profiles were processed using a biomechanical upper extremity model, from which resultant external shoulder moments were calculated. Average resultant shoulder moments, stratified by exertion level, were also calculated. Several individual subject moment/exertion profiles showed identifiable trends. It was demonstrated that while no strong relationships exist for individual task exertion effort prediction based on resultant shoulder moments, there is a general trend in the overall data sample, as is shown by a high correlation between mean integrated resultant shoulder moment by exertion level and exertion levels.

Both the inverted-Y yoke torso harness with inertia reel and the air bag restraint system have had extensive independent development for some time by several engineering and research organizations for both aviation and ground vehicle occupant protection. The research reported in this paper consists of the first biomechanical primate evaluation of these concepts as experimentally adapted for possible automotive use. These tests are a continuation of a study involving the relative impact protection and effectiveness of major restraint systems utilized in general aviation aircraft and in limited automotive use. The objective of this test series was to determine how much protection those advanced restraint concepts provided; to obtain preliminary biomechanical and physiological data; to identify problems of technique and applications in occupant protection; and to provide an initial basis for direction of future test requirements.