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|  MIL-D-18641F(SH)
analysis, the experimental proof test (see 3.14.28.1.1 .5.1) shall utilize stress coat (or its equivalent)
or photostress (molded birefringent coatings) techniques as deemed suitable, in order to determine
the location of maximum strain. Quantitative measurement of the magnitude of maximum principal
strain in the water box shall be obtained from strain gauges of 1/8 inch gauge length or smaller.
Water box loading (that load which produces the highest stress) shall be comprised of a
combination of design submergence pressure in conjunction with piping reaction loading applied
to the nozzles. The nozzle loads shall be calculated as specified in 3.14.28.1.1.4. A loading jig
incorporating mechanical or hydraulic jacks shall be provided to apply external loads on the nozzle
flanges. The following combinations of loads shall be applied.
Internal pressure equipment to 100 percent depth and external piping load (that piping
a.
reaction load which produces the highest stress) applied to one flange
b. Internal pressure equivalent to 100 percent depth and equal external piping load (that
piping reaction load which produces the highest stress) applied to both flanges.
43.5.1 Angular orientations. Experimental proof test shall be as follows. Since the angular
orientations of the applied moments to give the maximum stress for each load combination are
unknown, and the location of maximum stress is also unkonown the angular orientations of the
applied moments for load combinations (a) and (b) shall correspond to increments of 45 degrees
around the nozzles from O to 360 degrees in the first run, and a minimum of 9-degree increments
shall be used in the 45 degrees maximum stress sector in the second run. The location, magnitude
and direction of the maximum principal strain (stress) can be determined by brittle coating or
photostress, but must be checked with electric resistance strain gauges. Determine the maximum
value of principal strain (stress) in the water box (by either load combination (a) or (b)).
Determine the number of allowable cycles (corresponding to above stress) from the fatigue curve
for the particular material involved. Call these cycles as N1. Form a ratio of design cycles (nl) to
allowable cycles (Nl). Take half of the maximum value of principal strain (stress) in the water
box. Determine the number of allowable cycles (corresponding to this stress) from the fatigue
curve for the material involved. Call these cycles as N2. Form a ratio of design cycles (n2) to
allowable cycles (N2). If the sum of
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