Analysis of the Range of Motion of the Shoulder During Static Loading

Abstract

When developing new and safer vehicles, crash test dummies are important tools. The crash test dummy used in offset frontal collision tests today (Hybrid III), in e.g. EuroNCAP consumer testing is, to our knowledge, poorly validated for that type of testing. Volvo Car Corporation, Autoliv Research and Chalmers University of Technology have found a need for a tool that more accurately predicts the protective effects of safety systems in real life oblique and offset frontal crashes. This will be solved by designing a more humanlike dummy. The intention is to further develop the crash test dummy, THOR Alpha, to obtain a crash test dummy with more human-like movement in oblique and offset frontal collisions. The crash test dummy shoulder design of today is not very like that of a human. It is our belief that the human shoulder complex will move both superiorly, medially and further anterior than do the shoulder of the Hybrid III and the THOR Alpha dummy. This may influence the kinematics of the dummy when its movement is oblique and/or offset. It also influences the shoulder/belt interaction when using, for example, a three point belt. In order to construct a crash test dummy shoulder with more human-like kinematics there is a great need for information concerning the human shoulder complex. Range of movement and stiffness are especially important properties. In this thesis five volunteers were tested to obtain data on the kinematics and stiffness of human shoulders. Repetitive tests were conducted in a specially built test device in which the volunteer s arms were loaded with up to 40 kg in three directions in the sagittal plane and the displacement of the shoulders were recorded. When loading the shoulders, in any of the three directions, the movement of the shoulder is combined by anterior, medial and superior movement. The results from the tests show similar translation distance in medial and superior direction even though the direction of the force differs by 35. The values obtained on the stiffness of the shoulder in our study are very much dependant on the muscle tonus of the volunteers but it provides a useful estimate. The data acquired in this study will enable improvements to the shoulder of the present dummies which will lead to improved vehicle safety.