Neck and body loads--"All the data is needed".
Over the past few years, it has become apparent that multiaxis accelerations to the human head and body have become a more important problem to aviators. Fortunately, there are mechanical models and testing facilities to obtain the dynamic motions of the head and body resulting from frontal impacts as well as lateral and oblique impacts. Compact six-component balance systems, to measure the dynamic forces and moments the head applies to the neck and those applied to the lumbar spine from the upper body segments, have been developed by the Robert A. Denton Corporation, and are starting to be used extensively in manikins to measure the dynamic loads applied to these critical parts of the body. While it is important to be able to measure the absolute loadings accurately, the measurement accuracy becomes critical when evaluating the comparative effects of various head encumbrances on the loads applied to the human neck. Changes in loadings of 5 to 10 percent can be critical, and accurate measurements of the applied loads is very important if the comparative difference of the effects of applied loading are to be evaluated. Unfortunately, it is believed that the balance systems are simplistically calibrated to obtain a measure of the axial or moment loadings. This paper will discuss the design and fabrication of a test apparatus that was developed by Systems Research Laboratories, Inc. (SRL), under the sponsorship of the Air Force Harry G. Armstrong Aerospace Medical Laboratory at Wright-Patterson Air Force Base to conduct a complete calibration of the different manikin load cells. A 6 x 6 calibration matrix that properly relates the forces and moments about and along three orthogonal axes is obtained through the use of this apparatus. The technique that was developed to calibrate the manikin load cells was based on utilizing the procedures that are commonly used to calibrate the complete interaction associated with six-component wind tunnel balance systems. The value of the calibration fixture and procedure developed will be demonstrated by comparing results obtained by this technique with those obtained using the simplistic procedure most widely used at the present time during manikin testing as well as those obtained using the manufacturer's 6 x 6 calibration matrix. The results presented will demonstrate the difference in the measurements obtained by use of the different calibration procedures and the need to utilize the complete calibration matrix, if accurate multiaxis loading information is to be recorded.
White
R P
RP
Research and Experimental Simulation Department, Systems Research Laboratories, Inc., Dayton, OH 45440, USA.
Bartol
A M
AM
D000054:Acceleration; D002138:Calibration; D004738:Engineering; D004867:Equipment Design; D005269:Femur; D006257:Head; D019416:Head Movements; D006801:Humans; D008159:Lumbar Vertebrae; D008348:Manikins; D009333:Neck; D004856:Postural Balance