ASTM D 3580-95产品振动实验的试验方法(垂直正弦曲线运动)

ASTM D 3580-95 Standard Test Methods for Vibration (Vertical Linear Motion)

Test of Products

产品振动试验的标准测试方法

1. Scope

1.1 These test methods cover the determination of resonances of unpackaged products and components of unpackaged products by means of vertical linear motion at the surface on which the product is mounted for test. Two alternate test methods are presented:

Test Method A-Resonance Search Using Sinusoidal Vibration, and

Test Method B-Resonance Search Using Random Vibration.

1.2 This information may be used to examine the response of products to vibration for product design purposes, or for the design of a container or interior package that will minimize transportation vibration inputs at these critical frequencies, when these products resonances are within the expected transportation environment frequency range. Since vibration damage is most likely to occur at product resonant frequencies, these resonances may be thought of as potential product fragility points.

1.3 Information obtained from the optional dwell test methods may be used to assess the fatigue characteristics of the resonating components and for product

modification. This may become necessary if the response of a product would require design of an impractical or excessively costly shipping container.

1.4 These test methods do not necessarily simulate the vibration effects that the product will encounter in its operational or in-use environment. Other, more suitable test procedures should be used for this purpose.

1.5 Test levels given in these test methods represent the correlation of the best information currently available from research investigation and from experience in the use of these test methods. If more applicable or accurate data are available, they should be substituted.

2. Referenced Documents

2.1 ASTM Standards:

D 996 Terminology of Packaging and Distribution Environments

D 4332 Practice for Conditioning Containers, Packages, or Package Components for Testing

D4728 Test Method for Random Vibration Testing of Shipping Containers

E 122 Practice for Choice of Sample Size to Estimate the Average Quality of a Lot or Process

2.2 Military Standard:

MIL-STD 810, Method 514 Vibration

3. Terminology

3.1 Definitions- For definitions of terms used in these test methods, see Terminology D 996.

3.2 Descriptions of Terms Specific to This Standard:

3.2.1 decade- the interval of two frequencies having a basic frequency ratio of 10 (1 decade = 3.322 octaves).

3.2.2 decibel (dB)- a logarithmic expression of the relative values of two quantities. For relative power measurements, the dB value equals 10 times the base-l0 logarithm of the ratio of the two quantities, that is, dB = 10

{Pl/P2}.

3.2.3 mean-square- the time average of the square of the function.

3.2.4 octave-the interval of two frequencies having a basic frequency ratio of 2 (1 octave = 0.301 decade).

3.2.5 overall g rms-the square root of the integral of power spectral density over the total frequency range.

3.2.6 power spectral density (PSD)-a term used to quantify the intensity of random vibration in terms of mean-square acceleration per unit of frequency. The units are g 2 /Hz (g 2 /cycles/s). Power spectral density is the limiting mean square value in a given rectangular bandwidth divided by the bandwidth, as the bandwidth approaches zero.

3.2. 7 random vibration- oscillatory motion which contains no periodic or quasiperiodic constituent.

3.2.8 random vibration magnitude- the root-mean- square of the power spectral density value. The instantaneous magnitudes of random vibration are not prescribed for any given instant in time, but instead are prescribed by a probability distribution function, the integral of which over a given magnitude range will give the probable percentage of the time that the magnitude will fall within that range.

3.2.9 resonance- for a system undergoing forced vibration, the frequency at which any change of the exciting frequency in the vicinity of the exciting frequency, causes a decrease in the response of the system.

3.2.10 root-mean-square (rms)- the square root of the mean-square value. In the exclusive case of a sine wave, the rms value is 0.707 times the peak.

3.2.11 sinusoidal vibration- periodic motion whose acceleration versus time waveform has the general shape of a sine curve, that is, y = sine x

3.2.12 sinusoidal vibration amplitude- the maximum value of a sinusoidal quantity.

By convention, acceleration is typically specified in terms of zero-to-peak amplitude, while displacement is specified in terms of peak-to-peak amplitude.

3.2.13 transmissibility- the ratio of the measured acceleration amplitude at a point of interest in the product to the measured input acceleration amplitude of the test surface of the apparatus.

3.2.14 vertical linear motion- motion occurring essentially along a straight vertical line, with no significant horizontal or off-axis components.

4. Significance and Use

4.1 Products are exposed to complex dynamic stresses in the transportation environment. The determination of the resonant frequencies of the product may aid the packaging designer in determining the proper packaging system to provide adequate protection for the product, as well as providing an understanding of the complex interactions between the components of the product as they relate to expected transportation vibration inputs.

5. Apparatus

5.1 Vibration Test Machine- The machine shall consist of a flat horizontal test surface of sufficient strength and rigidity such that the applied vibrations are essentially uniform over the entire test surface when loaded with the test specimen. The test surface shall be driven to move only in vertical linear motion throughout the

desired range of amplitudes and frequencies.

5.1.1 Sinusoidal Control- The frequency and amplitude of the motion shall be variable, under control, to cover the range specified in 10.4.

5.1.2 Random Control- The frequency and amplitudes of motion shall be continuously variable, under control, to achieve the bandwidths, amplitudes, and overall g rms values specified in 10.5.

5.2 Specimen-Mounting Devices- Devices of sufficient strength and rigidity are required to attach the product securely to the test surface. The mounting devices shall not have significant resonances in the test frequency range. They shall rigidly mount the product in a manner similar to the way in which it will be supported in its shipping container. Relative motion between the test surface and the specimen mounting interface shall not be permitted.

5.3 Instrumentation:

5.3.1 Sensors, signal conditioners, filters, and a data acquisition apparatus are required to monitor or record, or both, the accelerations and frequencies at the test surface of the apparatus and at points of interest in the product. The instrumentation system shall have a response accurate within ±5 % over the test range.

5.3.1.1 For Test Method A, the frequencies and acceleration amplitudes or transmissibilities may be taken manually or by means of a recording instrument. A

stroboscope or video system may be beneficial for visual examination of the specimen under test.

5.3.1.2 For Test Method B, the data acquisition apparatus shall be capable of recording or indicating the transmissibilities between points of interest in the product to the test surface, over the frequency bandwidth specified in 10.5.

6. Hazards

6.1 Precaution -These test methods may produce severe mechanical response in the product being tested. Therefore, the means used to fasten the product to the test surface must be of sufficient strength to keep it adequately secured. Operating personnel shall remain alert to potential hazards and take necessary precautions for their safety. Stop the test method immediately if a dangerous condition should develop.

7. Sampling

7.1 Test specimens and number of samples shall be chosen to permit an adequate determination of representative performance. Whenever sufficient products are available, five or more replicate samples should be tested to improve the statistical reliability of the data obtained (see practice E 122).

8. Test Specimens

8.1 The product as intended for packaging shall constitute the test specimen. Sensor(s) may be applied as appropriate to measure data points of interest with the minimum possible alteration of the test specimen. In particular, sensors shall be lightweight and have flexible cables to prevent changing

either the effective weight or stiffness of the components to which they are mounted, thereby changing the resonant frequencies of the components. Parts and surfaces of the specimen may be marked for identification and reference. When necessary to observe interior components of the product during tests, holes may be cut in noncritical area or noncritical panels may be removed.

9. Conditioning

9.1 Condition test specimens prior to test, and maintain in accordance with any requirements. In the absence of other requirements, conditioning in accordance with Practice D 4332 is recommended with a standard conditioning atmosphere of 23±2°C (73.4±3.6°F) and 50±2 % relative humidity.

10. Procedure

10.1 Perform the tests in the conditioned environment or immediately upon removal from that environment.

10.2 Attach the test specimen to the test surface, near the center of the apparatus in a manner that will prevent the pecimen from leaving or moving across the test

surface during vibration. Caution is necessary to avoid excessive pressure or mounting methods that could influence the characteristics of the product.

10.3 Test intensities shall be sufficient to vibrate the product at acceleration and frequency levels that determine if product resonances exist in the expected

transportation environment. Experience has shown that most individual transportation environments contain frequencies ranging from 3 Hz to 100Hz. Acceleration levels sufficient to excite resonance normally range from 0.25 to 0.5 g.

10.4 Sinusoidal Vibration-Test Method A:

10.4.1 Sweep the frequency range from 3 to100 Hz and return using automatic or manual sweep, while maintaining a nearly constant acceleration level.

10.4.2 Select an acceleration level between 0.25 and 0.5 g (zero to peak). Starting at 3 Hz, vary the frequency of vibration at a continuous logarithmic rate of 0.5 to 1 octave/min to 100Hz and back to 3 Hz. Record any resonant responses of the product, repeat the cycle if necessary.

10.5 Random Vibration-Test Method B:

10.5.1 Start the vibration system such that the PSD levels do not overshoot the desired spectrum during startup. It is recommended that tests be initiated at least 6 dB below full level and incremented in one or more subsequent steps to full test level. Operate at full test level for a time duration long enough for the control system to

stabilize and for the data to be averaged sufficiently to represent stable spectrum shapes and levels, usually 3 min or more. This time is dependent upon the

characteristics of the vibration test machine and control system, the setup, and the weight and characteristics of the test specimen.

10.5.2 Use one of the spectra from Test Method D 4728, a spectrum representative of the expected transportation environment, a flat broadband spectrum, or a spectrum known to be appropriate. It is recommended that the minimum frequency range be from 3 to 100Hz, the overall amplitude s of the spectrum be not less than 0.25 g rms, and that the maximum variation in power spectral density over the total frequency range be 30 db or less. Record any resonant responses of the product.

10.6 Monitor the amplitude and frequency data sensed on t he test surface to ensure that the desired test conditions are produced. Mount the accelerometer to either the top or bottom of the test surface, as close to the test item as possible, or in a location which produces data representative of table motion.

10.7 Monitor the test specimen and its components for any resonant vibrations. Use a stroboscope; sensors and readouts; and visual, auditory, or other means as applicable to determine these resonances. Any resonances with transmissibilities of 2 or greater may be considered significant. For sine testing, the frequency sweep may be interrupted or reversed if necessary for short time periods in order to properly identify a resonating component.

10.8 Record the frequencies of any resonances and identify the product

components that are resonating. For sine testing, if different frequencies are recorded for each resonating component on the upsweep as compared to the downsweep (a typical situation), record both frequencies and the corresponding sweep direction.

10.9 Test the product in each of the potential shipping orientations of concern.

10.10 Optional Sinusoidal Dwell Test- Perform a sinusoidal dwell test at each resonant frequency found in 10.8, if it is determined to be within the expected transportation environment, to examine the fatigue characteristics of the resonating components. Dwell time, acceleration level, and damage criteria are to be specified by the user. Adjust the frequency of the vibration as necessary to maintain resonance.

10.11 Optional Random Vibration Test- Perform a random vibration test to examine the fatigue characteristics of the resonating components and the interactions between them. Test duration, random spectrum, and damage criteria are to be specified by the user. For spectrum examples, see 10.5.2.