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Study on Discomfort of Vertical Whole-body Shock Vibration Having Various Magnitudes, Frequencies and Damping  

Ahn, Se-Jin (Research Institute of MechanicalTechnology, Pusan National University)
Griffin, Michael J. (Institute of Sound and Vibration Research, University of Southampton)
Yoo, Wan-Suk (School of Mechanical Engineering, Pusan National University)
Jeong, Weui-Bong (School of Mechanical Engineering, Pusan National University)
Publication Information
Transactions of the Korean Society of Automotive Engineers / v.15, no.2, 2007 , pp. 50-57 More about this Journal
Abstract
Shocks are excited by impulsive forces and cause discomfort in vehicles. Current standards define means of evaluating shocks and predicting their discomfort, but the methods are based on research with a restricted range of shocks. This experimental study was designed to investigate the discomfort of seated subjects exposed to a wide range of vertical shocks. Shocks were produced from the responses of one degree-of-freedom models, with 16 natural frequencies (from 0.5 to 16 Hz) and four damping ratios (0.05 0.1, 0.2 and 0.4), to a hanning-windowed half-sine force inputs. Each type of shock was presented at five vibration dose values in the range $0.35\;ms^{-1.75}$ to $2.89\;ms^{-1.75}$. Fifteen subjects used magnitude estimation method to judge the discomfort of all shocks. The exponent in Stevens' power law, indicating the rate of growth in discomfort with shock magnitude, decreased with increasing fundamental frequency of the shocks. At all magnitudes, the equivalent comfort contours showed greatest sensitivity to shocks having fundamental frequencies in the range 4 to 12.5 Hz. At low magnitudes the variations in discomfort with the shock fundamental frequency were similar to the frequency weighting $W_b$ in BS 6841, but low frequency high magnitudes shocks produced greater discomfort than predicted by this weighting. At some frequencies, for the same unweighted vibration dose value, there were small but significant differences in discomfort caused by shocks having different damping ratios. The rate of increase in discomfort with increasing shock magnitude depends on the fundamental frequency of the shock. In consequence, the frequency-dependence of discomfort produced by vertical shocks depends on shock magnitude. For shocks of low and moderate discomfort, the current methods seem reasonable, but the response to higher magnitude shocks needs further investigation.
Keywords
Discomfort; Frequency weighting function; Equivalent comfort contour; Transient vibration; Whole-body vibration; Vibration dose value;
Citations & Related Records
Times Cited By KSCI : 1  (Citation Analysis)
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