Материал: Стандарт MIL-STD-202G
MIL-STD-202G
2.9 Test condition H (80g peak). The specimens, while de-energized or operating under the load conditions specified, shall be subjected to the vibration amplitude, frequency range, and duration specified in 2.9.1, 2.9.2, and 2.9.3, respectively (see figure 204-1).
2.9.1Amplitude. The specimens shall be subjected to a simple harmonic motion having a constant amplitude of either 0.06-inch double amplitude (maximum total excursion) or 80g (peak), whichever is less. The tolerance on vibration amplitude shall be ±10 percent.
2.9.2Frequency range. The vibration frequency shall be varied logarithmically between the limits of 10 and 2,000 Hz (see 2.10), except that the procedure of method 201 of this standard may be applied during the 10 to 55 Hz band of the vibration frequency range.
2.9.3Sweep time and duration. The entire frequency range of 10 to 2,000 Hz and return to 10 Hz shall be traversed in 20 minutes. This cycle shall be performed 12 times in each of three mutually perpendicular directions (total of 36 times), so that the motion shall be applied for a total period of approximately 12 hours. Interruptions are permitted provided the requirements for rate of change and test duration are met. Completion of cycling within any separate band is permissible before going to the next band. When the procedure of method 201 of this standard is used for the 10 to 55 Hz band, the duration of this portion shall be the same as the duration for this band using logarithmic cycling (approximately) 1-1/3 hours in each of three mutually perpendicular directions.
2.10 Alternate procedure for use of linear in place of logarithmic change of frequency. Linear rate of change of frequency is permissible under the following conditions:
a.The frequency range above 55 Hz shall be subdivided into not less than three bands. The ratio of the maximum frequency to the minimum frequency in each band shall be not less than two.
b.The rate of change of frequency in hertz per minute (Hz/min) shall be constant for any one band.
c.The ratios of the rate of change of frequency of each band to the maximum frequency of that band shall be approximately equal.
2.10.1Example of alternate procedure. As an example of the computation of rates of change, assume that the frequency spectrum has been divided into three bands, 55 to 125 Hz, 125 to 500 Hz, and 500 to 2,000 Hz, in accordance with 2.10a. Let the (constant) ratio of rate of frequency change in Hz/min, to maximum frequency in Hz be k for each band. Then the rates of change for the three bands will be 125k, 500k, and 2,000k, respectively. The times, in minutes, to traverse the three frequency bands will therefore be respectively:
125 − 55 , 500 − 125 , 2000 − 500 55k 500k 2,000k
Since the minimum total sweep time is 30 minutes,
= 70 + 375 + 1,500
30
125k 500k 2,000k
from which: k = 0.0687
The required maximum constant rates of frequency change for the three bands are therefore 8.54, 34.4, and 136.6 Hz/min, respectively. The minimum times of traverse of the bands are 8.2, 10.9, and 10.9 minutes, respectively.
METHOD 204D
1 April 1980
5
MIL-STD-202G
3.MEASUREMENTS. Measurements shall be made as specified.
4.SUMMARY. The following details are to be specified in the individual specification:
a.Mounting of specimens (see 2.1).
b.Electrical-load conditions, if applicable (see 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, and 2.9).
c.Test condition letter (see figure 204-1).
d.Method of determining resonance, if applicable (see 2.4.3).
e.Measurements (see 3).
METHOD 204D
1 April 1980
6
MIL-STD-202G
METHOD 205E
SHOCK, MEDIUM IMPACT (CANCELED)
When method 205 is specified |
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Use test method 213 |
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Test condition |
g (peak values) |
Test condition |
g (peak values) |
Waveform |
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A |
15g (pk) |
K |
30g (pk) |
Sawtooth |
B |
30g (pk) |
H |
75g (pk) |
Sawtooth |
C |
50g (pk) |
I |
100g (pk) |
Sawtooth |
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METHOD 205E 16 April 1973
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MIL-STD-202G
METHOD 206
LIFE (ROTATIONAL)
1.PURPOSE. This test is performed for the purpose of determining the effects of subjecting electronic and electrical parts, which are actuated by rotational motion, to a number of operations approximating the life of the part. Total resistance, contact resistance, and dielectric strength are samples of measurements which may be made prior to, during, or after test, and which would show the effects of rotational actuation. Measurements prior to and after test are generally made for comparison purposes and would indicate the amount of change that results from this test. Parts with sealed shafts and bushings might have the effectiveness of the seal disturbed by rotation; a sealing test performed after this test would disclose this inadequacy. A switch-life test may be performed in conjunction with this test method.
2.PROCEDURE.
2.1Mounting. Specimens shall be mounted in their normal operating position by the intended means. Normal care shall be taken in the mounting procedure to prevent the binding of shafts during rotation. Figure 206-1 shows a suggested means of preventing this condition, when applicable. Mechanisms such as slip clutches may be used to prevent damage from the application of excessive torque to the specimens. When this test is conducted at an elevated temperature (see 2.6), the spacing between a group of like specimens shall be as specified.
2.2Test potential and load. The test potential and load applied to the specimens during rotation shall be as specified.
2.3Cycle. A cycle shall consist of a rotation of the shaft from one stop position to the other stop position (passing through detent positions, if any), and return to the original position. For specimens not having stops, a cycle shall
consist of a rotation of the shaft 360° and return, unless otherwise specified. Specimens with adjustable stops shall have the stops so placed as to permit maximum rotation. Specimens that are rotated by means other than a shaft shall meet the requirements of this paragraph by rotation 360° and return, unless otherwise specified, or from stop to stop.
2.4Cycle rate. The cycle rate shall be expressed in cycles per minute (cpm), and shall be as specified.
2.5Number of cycles. Specimens shall be subjected to one of the following test conditions, as specified:
Test condition |
Number of cycles |
A -------------------- |
500 |
B -------------------- |
2,000 |
C -------------------- |
5,000 |
D -------------------- |
10,000 |
E -------------------- |
15,000 |
F -------------------- |
25,000 |
G ------------------- |
50,000 |
H -------------------- |
100,000 |
J -------------------- |
200,000 |
K -------------------- |
300,000 |
L -------------------- |
500,000 |
M ------------------- |
1,000,000 |
N -------------------- |
2,000,000 |
METHOD 206
12 September 1963
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