This is a little different from Deepak's version. It appears in my new text on random vibration and shock testing, Section 25.27.
25.27 A few thoughts on fatigue failures
This questionable but typical equation:
[darn, the equation did not copy. Send me an e-mail and I'll try e-mailing the equation. However, perhaps you have MIL-STD-810.]
came from Method 514.4, Section I-4.7 of MIL-STD-810E, page 514.4-45. In -810F, it is in Annex B.
W = vibration levels (acceleration spectral density)
T = time (hours)
M = material constant (slope of Figure 25-62,commonly 4).
For sine testing, W represents peak g and M = 6, generally but 2.5 for electronic boards. These M and W numbers are “guesstimates”.
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