Study of human simultaneous exposition to strikes and mechanical vibrations
Janusz Szopa Ph.D. (Eng.)
On the basis of measurement the energetic vibroacoustic indicator, which characterise the simultaneous human exposition to mechanical vibration and strikes, was elaborated. The main assumption to calculate this indicator is, that reaction of human organism to strikes and vibration is proportional to energy, which is dissipated into heat in human organism. This energy is a result of a power VEA (called Vibration Energy Absorption) and time. This power is calculated from force-velocity cross spectrum, as a real part of it. Imaginary part of this spectrum is called Vibration Energy Stored - VES . Force and velocity are measured at the junction human with vibrating surface, and specially designed for this purpose measurement platform and adapter are used. To establish the differences in hand-arm exposition to strikes and mechanical vibration, 37 test signals (vibration and strikes signals generated in a shaker and real signals in work stands) were used in measurements. For whole-body expositions measurements were performed for five test signals. In measurements three person participated as operators. On the basis of measurement results was stated, that VEA is correlated with square velocity in a linear way. The ratio VEA/V2 given in a function of frequency is a quantity specific for type of signals (strike, shock, vibration), way of operating (feed force, grip force, body position) and properties connected with operator's body. This ratio is a base for calculation of the energetic vibroacoustic indicator.
Department of Vibroacoustic Hazards