There is a need in certain structural dynamics finite element analysis problems to perform a response analysis in the time domain. This would be the case, for example, if the stiffness was non-linear. Loss-of-clearance or contact between two adjacent vibrating parts is another analysis example.… Read more
Gnuplot is a portable command-line driven graphing utility for Linux, OS/2, MS Windows, OSX, VMS, and many other platforms. The source code is copyrighted but freely distributed (i.e., you don’t have to pay for it). It was originally created to allow scientists and students to… Read more
Some power spectral density test specifications are too high in amplitude for a given shaker system. Bandsplitting can be cautiously used in these cases. Here is a brief guideline paper: bandsplit.pdf Here is a Matlab script that implements bandsplitting per the guidelines: bandsplit.zip The main script… Read more
These Matlab scripts determine an optimum envelope for an acceleration power spectral density: envelope_plateau.zip The optimum envelope is the that which yields the lowest GRMS and Velocity RMS values. The acceleration is assumed to be the base excitation for an array of independent, parallel single-degree-of-freedom… Read more
The scripts in: cross_psd.zip calculate the cross power spectral density of two signals. These scripts have an option to sub-divide the data into segments and then take an ensemble average. This tends to smooth the resulting magnitude and phase curves, but the spectral frequency resolution… Read more
Single-degree-of-freedom System ______________________________________________________________________ Please see the following post for an important revision: Peak Response to Random Vibration with Probability of Exceedance ______________________________________________________________________ Consider a single-degree-of-freedom system subjected to a broadband random vibration base input, where the input is stationary and has a normal distribution. (The… Read more
The Matlab scripts in PSD.zip calculate the power spectral density function for a time history. The main script is: PSD.m The remaining scripts are supporting functions. * * * A Fortran power spectral density program is given at: PSD.F * * * See also: Matlab Random Vibration… Read more
The overall RMS level of a power spectral density function is equal to the square root of the area under the curve. Power spectral density specifications are typically given in log-log format. Thus special integration rules apply. The Matlab scripts in psd_integ.zip calculate the overall… Read more
This set of Matlab scripts calculates the response of a single-degree-of-freedom system to an acceleration power spectral density base input: sdof_ran.zip The power spectral density may vary arbitrarily with frequency. The main script is: sdof_ran.m The user must specify the natural frequency and damping ratio. The… Read more
