MIL-STD-202H.pdf - 第203页

MI L - S TD - 202 -2 1 4 M E TH O D 21 4 RA NDO M V I B RA T I O N 1. SCOPE 1. 1 P urpose . T his test i s c on duc t ed f or t he pur p os e of d et e r m i ni ng t he a bi l i t y of c om pon e nt part s to withstan d …

MIL-STD-202-214

CONTENTS

PARAGRAPH PAGE

FOREWORD…………………………………………………………. ii

1. SCOPE 1

1.1 Purpose………………………………………….……..…………. 1

2. APPLICABLE DOCUMENTS 1

3. DEFINTIONS 1

4. GENERAL REQUIREMENTS 1

4.1 Apparatus………………………………………….….........……. 1

4.1.1 Vibration system....................................................................... 1

4.1.1.1 Control and analysis of vibration………………………………. 2

4.1.2 Monitoring………….…….………………….………...…………. 2

4.1.2.1 Vibration input..………………..…….………………..…………. 2

4.2. Method of mounting…………………………..….….………….. 2

4.3. Procedure………………………………………..……..…………. 3

5. DETAILED REQUIREMENTS 5

5.1 Measurements ……………………………………..……………. 5

5.2. Summary…………………………………………..…..…………. 5

6. NOTES 6

6.1 Supersession data………………………………………………. 6

FIGURES PAGE

1. Test condition I, random vibration test-curve envelope(see table I)….. 3

2. Test condition II, random vibration test-curve envelope (see table II)... 4

TABLES PAGE

I. Values for test-condition I……………….…………………………….…… 4

II. Values for test-condition II…………….……………………..……….…… 5

iii

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MIL-STD-202-214

METHOD 214

RANDOM VIBRATION

1. SCOPE

1.1 Purpose. This test is conducted for the purpose of determining the ability of component parts to withstand the

dynamic stress exerted by random vibration applied between upper and lower frequency limits to simulate the

vibration experienced in various service field environments. Random vibration is characteristic of modern field

environments produced by missiles, high-thrust jets and rocket engines. In these types of environments, the random

vibration provides a more realistic test. For design purposes, however, a swept frequency sinusoidal test may yield

more pertinent design information.

2. APPLICABLE DOCUMENTS

This section not applicable to this standard.

3. DEFINTIONS

This section not applicable to this standard.

4. GENERAL REQUIREMENTS

4.1. Appartaus.

4.1.1 Vibration system. The vibration system, consisting of the vibration machine, together with its auxiliary

equipment shall be capable of generating a random vibration for which the magnitude has a gaussian (normal)

amplitude distribution, except that the acceleration magnitudes of the peak values may be limited to a minimum of

three times the rms (three-sigma (σ) limits). The machine shall be capable of being equalized so that the magnitude

of its spectral density curve will be between specified limits (for example, see figures 1 and 2) when the test item, or a

substitute equivalent mass, is appropriately secured to the vibration machine. The equalization of an electro-dynamic

vibration machine system is the adjustment of the gain of the electrical amplifier and control system so that the ratio

of the output vibration amplitude to the input signal amplitude is of a constant value (or given values) throughout the

required frequency spectrum.

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MIL-STD-202-214

4.1.1.1 Control and analysis of vibration.

a. Spectral density curves. The output of the vibration machine shall be presented graphically as power

spectral density versus frequency. 1/ The spectral density values shall be within +40 and -30 percent (±1.5

dB) of the specified values between a lower specified frequency and 1,000 Hz, and within +100 and -50

percent (±3 dB) of the specified values between 1,000 and 2,000 Hz. A filter bandwidth will be a maximum

of 1/3 octave or a frequency of 25 Hz, whichever is greater.

b. Distribution curves. A probability density distribution curve may be obtained and compared with a gaussian

distribution curve. The experimentally obtained curve should not differ from the gaussian curve by more

than ±10 percent of the maximum value.

4.1.2 Monitoring. Monitoring involves measurements of the vibration excitation and of the test item performance.

When required in the individual specification, the specimen may be monitored during the test. The details of the

monitoring circuit, including the method and points of connection to the specimen, shall be specified.

4.1.2.1 Vibration input. The vibration magnitude shall be monitored on a vibration machine, on mounting fixtures,

at locations that are as near as practical to the test item mounting points. When the vibration input is measured at

more than one point, the minimum input vibration shall normally be made to correspond to the specified test curve

(see figures 1 and 2). For massive test items and fixtures, and for large force exciters or multiple vibration exciters,

the input-control value may be an average of the average magnitudes of three or more inputs. Accelerations in the

transverse direction, measured at the test item attachment points, shall be limited to 100 percent of the applied

vibration. The individual specification shall specify the number and location of the test points.

4.2 Method of mounting. The specimens shall be mounted in accordance with the instructions in the individual

specifications. The orientation of the specimen or direction(s) of the applied vibration motion shall be as specified.

Any special test fixtures or jigs required to run the test shall be as specified in sufficient detail in the individual

specification to assure reproducibility of the input motion applied to the specimen. These details shall include the

dimensions, the materials, temper, etc., as applicable.

1/ Power spectral density is the mean square value of an oscillation passed by a narrow-band filter per unit filter

bandwidth. For this application it is expressed as G

/f where G

/f is the mean square value of acceleration

expressed in gravitational units per number of cycles of filter bandwidth. The spectral density curves are usually

plotted either on a logarithmic scale, or in units of decibels (dB). The number of decibels is defined by the

equation:

frG

log20

log

The rms value of acceleration within a frequency band between f

and f

is:

1/2













∫

dff

Grms

Where G

r/f is a given reference value of power spectral density, usually the maximum specified value.

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联系方式：xuyj@beice-sh.com 13917165676