Prerequisite Reference Papers
David O. Smallwood, An Improved Recursive Formula for Calculating Shock Response Spectra, Shock and Vibration Bulletin, No. 51, May 1981. DS_SRS1.pdf
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Consider a component mounted on a structure where the base input is measured by an adjacent accelerometer on the structure. An envelope power spectral density (PSD) is needed so that component design and test levels can be derived, with the appropriate added statistical uncertainty margin.
Assume that the base input has been measured over a series of accelerometer time histories. This could be the case for an automobile driven at different speeds over different road conditions, for example.
The envelope PSD can be derived using fatigue damage spectra as shown in: FDS_PSD_multiple.pdf
The C++ programs are:
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Here is an alternate program that allows for repetition for a given time history file. This is useful, for example, if a short time duration was measured to represent a longer service duration.
Now assume that there are three measured acceleration time histories where the repetition number is 10, 50 and 100, respectively.
The input file format would be:
Substitute your own file names and multipliers accordingly.
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– Tom Irvine