Humility
“Being humble means recognizing that we are not on earth to see how important we can become, but to see how much difference we can make in the lives of others” ― Gordon B. Hinckley
Tire Imbalance Frequency
Image courtesy of Discount Tire Static Imbalance (left image) Occurs when there is a heavy or light spot in the tire that prevents the tire from rolling evenly and causing the tire and wheel to undergo an up-and-down motion. Dynamic Imbalance (right image) Occurs when… Read more
Transmissibility of a Three-Parameter Isolation System
I recently came across a vendor that offers an isolator design using the concept in the figure above. The system is also referred to as the standard-linear solid model (SLS) by Zener, and is used as a simplified model for structural damping. It is a… Read more
Cylindrical Shell Enclosed by Shear Diaphragms
The following Matlab script calculates the natural frequencies of a cylindrical shell which is enclosed at each end by a “shear diaphragm.” SD_SD_cylinder.m * * * Reference: Leissa, Vibration of Shells, NASA SP-288 See also: Vibrationdata Rings, Cylinders, Shells & Cones Page – Tom Irvine
Fortran tips
I am relearning Fortran, including the features which have been added since I last used it some twenty years ago.Here is a method for compling a sample Fortran program NAME.F. This method checks for memory leaks.gfortran -fbounds-check -o NAME NAME.F ./NAMETom’s Fortran programs & related… Read more
Cepstrum Analysis
The cepstrum function was originally developed for characterizing the seismic echoes resulting from earthquake and bomb explosions. It has also been used to determine the fundamental frequency of human speech, to analyze radar signal returns, and to evaluate machinery vibration. A cepstrum of time history… Read more
Autocorrelation & Cross-correlation
Cross-correlation is a measure of similarity of two waveforms as a function of a time-lag applied to one of them. Autocorrelation is the cross-correlation of a signal with itself. It is a time domain analysis useful for determining the periodicity or repeating patterns of a… Read more
2012 Spacecraft & Launch Vehicle Dynamic Environments Workshop
I had the opportunity to give the keynote speech at the workshop. Here is my presentation, which is rather non-technical. Enjoy… Dynamics Engineering: A Call to Serve – Tom
Cross Power Spectral Density
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
von Karman Continuous Gust PSD
FAA Federal Aviation Regulations FAR-25 Appendix G, Continuous Gust Design Criteria, requires a continuous turbulent gust analysis for transport aircraft. The gust PSD function is given in: The von Karman Vertical Gust Spectrum A Matlab script for generating a continuous gust velocity PSD is given… Read more