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„^.Sn*kiv
H. P. Bruns - 2 - November 11, 1969
Duplication of data was required to provide some assurance that no gross variations
existed between test runs; however, the statistical sample is still so small that a
broad tolerance must be associated with this data. Further, it should be noted that
the acceleration levels in test #21 were slightly higher in the 1 - 5 Hz frequency range
than the levels presented; Figures 2, 3, and 4, from test #19.
The data analysis requested and received from Defense Engineering is in the
form of power spectral density (PSD) since this form is directly related to the power
or energy content of the system at any given frequency, i0eo, g^/Hz for acceleration
levels and in^/Hz for displacement levels. This data format is necessary for any
analytical work directed toward alleviating the vibration environment although it is
still not directly comparable with existing criteria. Reference 3 provides among
other things a study of random vibration inputs versus sinusoidal inputs 0 Results of
this study indicate that for human response the two types of excitation may be equated;
hence the PSD!s were converted to the peak acceleration levels for comparison in
Figure 1 by taking the square root and multiplying by 1.4.
Talladega data presented in Figure 1 as curves 19-1, 19-2, and 19-s graph
ically depicts the driver input vibration environment during turns 1,2 and the straight
away respectively. Comparing these curves with the vibration criteria for human toler
ance in Figure 1 it is noted that the vibration always exceeds the maximum environment
for a one hour duration up to 6 Hz 0 Remembering that the accelerometer used attenuates
the signal above 5 1/2 Hz and observing the irregularities in the apparent environmental
decay above 5 1/2 Hz it is reasonable to assume that the actual vibration environment
exceeds the one hour criteria in this frequency range also. Therefore, symptoms as
noted in the following table from Reference 4 should be anticipated:
{Each cross indicates a decided comment from one of the ten human subjects used in this study
as to his experiencing the symptom listed.)
Symp Abdom Chest Testic Head General
tom inal pain ular symp Dyspnea Anxiety discom
--> pain pain toms fort
Freq. 1
xxxxx XXX
1 cps XXX
xxxxx XXXX
2 cps
XXX
3 cps XX XX xxxxx X xxxxx
4 cps XX XX XX XXX XX xxxxx
xxxx X xxxxx
5 cps
X
6 cps XXX xxxx X xxxx
7 cps XX xxxxx X X X
8 cps X xxxx X XX XXX
9 cps XX xxxx X xxxxx
10 cps X X XXX XX X
xxxxx
15 cps
XXX
