MIL-STD-167-1A
5.1.2.4.1 Equipment operation. Except as noted below, equipment shall be energized or operated to perform its normal functions (see 6.2.f(6)). Equipment that is difficult to operate on the testing machine shall be energized and subjected to operating conditions during the test. The equipment shall then be operated after the test to demonstrate that there is no damage from the test (see 6.2.f(1)).
5.1.2.4.2 Exploratory vibration test. To determine the presence of response prominences (see 3.19) in the equipment under test, the equipment shall be secured to the vibration table and vibrated at frequencies from 4 Hz to
33 Hz, at a table vibratory single amplitude of 0.010 ± 0.002 inch (see 5.1.2.4.4 and 5.1.2.4.5 for exceptions). The change in frequency shall be made in discrete frequency intervals of 1 Hz and maintained at each frequency for
about 15 seconds. Alternately, a continuous frequency sweep with a rate of change of frequency not to exceed 0.067
Hz/second can be used. The frequencies at which functional or structural requirements are affected or violated and frequencies and locations at which response prominences occur shall be recorded, and these frequencies (rounded to the nearest integer frequency if discrete frequency intervals were not used) shall be considered as candidates for endurance testing (see Appendix A).
5.1.2.4.3 Variable frequency test. The equipment shall be vibrated from 4 Hz to 33 Hz in discrete frequency intervals of 1 Hz at the amplitudes shown in Table I (see 5.1.2.4.4 and 5.1.2.4.5 for exceptions). At each integral frequency, the vibration shall be maintained for 5 minutes. The frequencies at which functional or structural requirements are affected or violated and frequencies and locations at which response prominences occur shall be recorded. Note that because of increased amplitudes compared to those mandated by 5.1.2.4.2, response prominences and effects on or violations of functional or structural requirements may show up in this test that were not uncovered in the exploratory vibration test. Therefore, the frequencies at which these response prominences and effects on or violations of functional or structural requirements occur shall also be considered as candidates for endurance testing (see Appendix A).
5.1.2.4.4 Exception. Equipment intended for installation solely on a particular ship class need only be vibrated in the exploratory and variable frequency tests from 4 Hz to (1.15 x maximum design rpm x number of propeller blades/60) rounded up to the nearest integer frequency or the maximum test frequency as specified (see 6.2.f(7)).
5.1.2.4.5 Alternative test amplitudes. For equipment installed on ships with advanced isolation systems or low vibration propellers, alternative test amplitudes from Table I shall be used when specified (see 6.2.f(8)).
5.1.2.4.6 Endurance test. Endurance test frequencies are selected from the candidate list of endurance test frequencies developed during exploratory and variable frequency testing (see 5.1.2.4.2 and 5.1.2.4.3). When specified (see 6.2.f(9)), selection of these frequencies is subject to approval. The equipment shall be vibrated for a total period of at least 2 hours at the frequency determined to most seriously affect the functional or structural integrity of the equipment. Guidance for selecting response prominences from exploratory or variable frequency testing, for determining whether a response prominence is significant, and if the more serious response prominences can be identified, is given in Appendix A. In cases where there are multiple response prominence frequencies selected, the duration of vibration testing at each frequency shall be in accordance with Table II. If neither response prominences nor effects on equipment structural/functional performance are observed, this test shall be performed at
33 Hz or at the upper frequency as specified in 5.1.2.4.4. The amplitudes of vibration shall be in accordance with Table I, unless otherwise specified (see 5.1.2.4.5). See Figure 1 for a graphical representation of the amplitudes in Table I.
TABLE I. Vibratory displacement of environmental vibration.
Frequency range (Hz) |
Table single amplitude (inch) |
4 to 15 16 to 25 26 to 33 |
0.030 ±0.006 0.020 ±0.004 0.010 ±0.002 |
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