Page 301 - Biomedical Engineering and Design Handbook Volume 1, Fundamentals

278 BIOMECHANICS OF THE HUMAN BODY

11.4 COUNTERMEASURES

Reducing the effects of vibration, shock, and impact on humans is effected in several ways: (1) by
isolation, to reduce the transmission of dynamic forces and accelerations to the body; (2) by personal
protective equipment, to distribute the dynamic forces over as large a surface area as possible and
provide vibration isolation, and absorption; and (3) by redesign, to reduce the source’s vibration
intensity. These subjects are considered after summarizing the occurrence of health effects from
exposure to vibration, shock, and impact, which establishes the performance required of ameliorative
measures.

11.4.1 Occurrence of Health Effects and Injury
There is extensive literature on the occurrence of health effects and injury from exposure to vibra-
tion, shock, and impact, which has been reviewed recently (Brammer, in press) and serves as the
basis for the present discussion. Estimates of exposures necessary for common human responses and
health effects are summarized in Table 11.2 for healthy adults; the interested reader is directed to the
references given in the table for more complete information, or to the recent review article cited.

TABLE 11.2 Estimates of Health and Injury Criteria for Healthy Adults

Frequency,
Human response Metric weighting or model Value Source
Perception (population mean, threshold):
Whole body (vertical) RMS accel. W 0.015 m/s 2 ISO 2631-1, 1997
k
Fingertip (selected frequencies) RMS accel. 4 Hz 0.0075 m/s 2 ISO 13091-2, 2003
RMS accel. 31 Hz M—0.10 m/s 2 ISO 13091-2, 2003
RMS accel. 31 Hz F—0.12 m/s 2 ISO 13091-2, 2003
RMS accel. 125 Hz M—0.25 m/s 2 ISO 13091-2, 2003
RMS accel. 125 Hz F—0.32 m/s 2 ISO 13091-2, 2003
Health effects (threshold):
Hand (HAVS) a W 1 m/s 2 ISO 5349-1, 2001
WAS(8) h
Whole body
Z direction VDV W 8.5 m/s 1.75 ISO 2631-1, 1997
k
X and Y directions VDV W 6.1 m/s 1.75 ISO 2631-1, 1997
d
Risk of injury (5–10% probability) from
vibration:
Hand (HAVS) a W 3 m/s 2 ISO 5349-1, 2001
WAS(8) h
Whole-body, Z (direction) VDV W 17 m/s 1.75 ISO 2631-1, 1997
k
Risk of injury (5–10% probability) from
2
shocks and impacts (up to 40 m/s ):
Many shocks, any direction E(∑apeak)6.6⇒ Neural network
compress model (Z); simple >0.5 MPa ISO 2631-5, 2004
spine model of Sec. 11.3.1
(X, Y)
Survivable single shock or impact:
To body (headward) ∗ DRI DRI model 18 After von Gierke, 1970
To head (manikin) HIC None 1000 NHTSA FMVSS 208 †
M—male
F—female
∗ When body is restrained.
† U.S. National Highway Traffic Safety Administration Federal Motor Vehicle Safety Standard 208.