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32:, or any other transient acceleration input, in terms of how a Single Degree Of Freedom (SDOF) system (like a mass on a spring) would respond to that input. The horizontal axis shows the natural frequency of a hypothetical SDOF, and the vertical axis shows the peak acceleration which this SDOF would undergo as a consequence of the shock input.
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Different damping ratios produce different SRSs for the same shock waveform. Zero damping will produce a maximum response. Very high damping produces a very boring SRS: A horizontal line. The level of damping is demonstrated by the "quality factor", Q which can also be thought of transmissibility in
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Any transient waveform can be presented as an SRS, but the relationship is not unique; many different transient waveforms can produce the same SRS (something one can take advantage of through a process called "Shock
Synthesis"). Due to only tracking the peak instantaneous acceleration the SRS does
117:. Lab tests have previously confirmed that this system survives a certain shock waveform—say, the shock from dropping the chassis from 2 feet above a hard floor. Now, the customer wants to know whether the system will survive a
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Calculate (by direct time-domain simulation) the maximum instantaneous absolute acceleration experienced by the mass element of your SDOF at any time during (or after) exposure to the shock in question. This acceleration is
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shock waveform—say, from dropping the chassis from 4 feet above a carpeted floor. If the SRS of the new shock is lower than the SRS of the old shock at each of the three frequencies
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The resulting plot of peak acceleration vs test system frequency is called a Shock
Response Spectrum. It is often plotted with frequency in Hz, and with acceleration in
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An SRS is of little use for fatigue-type damage scenarios, as the transform removes information of how many times a peak acceleration (and inferred stress) is reached.
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sinusoidal vibration case. Relative damping of 5% results in a Q of 10. An SRS plot is incomplete if it doesn't specify the assumed Q value.
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the damage by fatigue following the application of a large number of cycles, thus taking into account the duration of the vibration (
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the exceeding of characteristic instantaneous stress limits (yield stress, ultimate stress etc.). We then define the
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The most direct and intuitive way to generate an SRS from a shock waveform is the following procedure:
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The SDOF system model also can be used to characterize the severity of vibrations, with two criteria:
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Like many other useful tools, the SRS is not applicable to significantly non-linear systems.
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Consider a computer chassis containing three cards with fundamental natural frequencies of
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not contain all the information in the transient waveform from which it was created.
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G, Environmental Test
Methods and Engineering Guidelines, 2000, sect 516.6
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Mechanical
Vibration and Shock Analysis. Volume 2: Mechanical Shock
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SRS representation of the transient input shown above in SRS form.
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298:, is a toolbox in the public domain to calculate SRS.
262:Harris Shock and Vibration Handbook, Fifth Edition
171:(ERS), similar to the shock response spectrum;
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77:Repeat steps 2–4 for many other values of
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296:http://freesrs.sourceforge.net/
48:Q) for your SRS to be based on;
279:, Second Edition, Wiley, 2009.
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260:Harris, C., Piersol, A.,
168:extreme response spectrum
264:, McGraw-Hill, (2002),
177:Fatigue damage spectrum
146:Details and limitations
26:Shock Response Spectrum
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311:Mechanical vibrations
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92:Example application
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194:Shock data logger
51:Pick a frequency
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233:Explanation
36:Calculation
205:References
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294:FreeSRS,
252:-Research
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119:different
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250:Research
188:See also
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180:(FDS)).
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