Life safety. Mechanical vibrations (most important)

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Life safety. Mechanical vibrations (most important)

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14. MECHANICAL VIBRATIONS

Mechanical vibrations - These are periodically repeating movements, rotational or reciprocating. Any process of mechanical oscillations can be reduced to one or more harmonic sinusoidal oscillations, which are characterized by an amplitude equal to the maximum deviation from the equilibrium position; oscillation speed; acceleration; an oscillation period equal to the time of one complete oscillation; frequency of oscillations, equal to the number of complete oscillations per unit of time.

A variety of mechanical vibrations is vibration - these are small mechanical vibrations that occur in elastic bodies under the influence of variable forces, which are practically impossible to balance perfectly. For example, vibration on the ground propagates in the form of elastic waves and causes vibrations of buildings and structures.

Machine vibration can lead to malfunction of equipment and cause serious accidents. It is the cause of 80% of accidents in cars, as it leads to the accumulation of fatigue effects in metals and the appearance of cracks.

When exposed to vibration on a person the most significant is that the human body in this case is a complex dynamic system that changes depending on the posture of the person, his state (relaxation or tension) and other factors. For such a system, there are dangerous, resonant frequencies, and if external forces act on a person with frequencies close to or equal to the resonant ones, then the amplitude of oscillations of both the whole body and its individual organs increases sharply. For the human body in a sitting position, resonance occurs at a frequency of 4-6 Hz, for the head - at 20-30 Hz, for the eyeballs - at 60-90 Hz. At these frequencies intense vibration can cause traumatization of the spine and bone tissue, visual impairment, in pregnant women cause premature birth.

Fluctuations cause variable mechanical stresses in the tissues of the body, which are captured by many receptors and transformed into the energy of bioelectrical and biochemical processes. Information about the vibration acting on a person is perceived by the vestibular apparatus, which is located in the temporal bone of the skull and consists of the vestibule and semicircular canals located in mutually perpendicular planes. The vestibular apparatus provides an analysis of the positions and movements of the head in space, the activation of muscle tone and the maintenance of body balance.

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