MIL-DTL-17191E(SH)
Kmeasured = C(F/X)(cos(θ + δ))
Where "C" and "δ" are minor adjustment factors, if necessary, to account for system calibration (see 4.4.2.1.1).
In order to obtain mount stiffness (Kmount) to determine compliance with 3.4.2, the measured stiffness (Kmeasured)
may likely require adjustment to account for test apparatus flexibility (see 4.4.2.1.1).
(Kapparatus)(Kmeasured)
Kmount =
(Kapparatus) - (Kmeasured)
4.4.2.2 Static strength test.
4.4.2.2.1 Test system. A suitable test system capable of loading the mounts at a constant rate of deflection
while measuring load and deflection shall be used. A commonly used type of equipment for measuring
load-deflection is a Universal Testing Machine. The sampling rate of measured load and deflection shall provide a
sufficient number of samples to furnish smooth load-deflection plots without discontinuities. Deflection shall be
measured to the nearest 0.001 inch. Flexibility of the test apparatus (load frame, force gauge, fixtures, etc.) shall be
accounted for via correction of measured mount data. All sensors used for measurement (force and displacement
transducer) shall be calibrated at regular intervals.
4.4.2.2.2 Test in the axial direction (parallel to center bolt axis). A single mount shall be secured in a fixture
and subjected to four loading and unloading cycles at a constant deflection rate not exceeding 0.3 inch per minute.
For the first three loading cycles, loads shall be applied up to the peak static test load specified in Curve 2 on
figure 2 for the upper load rating of the mount. For the fourth loading cycle, the mount shall be loaded up to the
peak load specified in Curve 1 on figure 2 for the upper load rating of the mount. Load-deflection data shall be
recorded during the fourth loading cycle and shall be reported as the static load-deflection curve for the mount. The
mount shall be inspected during and after testing to determine compliance with 3.4.3.
FIGURE 2. Minimum static strength loads for resilient mounts.
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