Structural damping depends on materials, joints, boundary conditions, friction, acoustic radiation, etc. Damping may be nonlinear, increasing as the excitation and response levels rise. The damping for a given structure or component must be measured! But here is some empirical background data… Papers Damping Properties of… Read more
For the past eight years, I have written a required monthly status report to another organization for my NASA contractor work. I have written my accomplishments and planned work in short, concise sentences, usually in numbered list format. I was then notified by this organization… Read more
There is a widely-taught principle in my church that “Obedience is the first law of heaven.” This may have been an extrapolation from Alexander Pope’s quote that “Order is heaven’s first law.” But discernment must precede obedience. The Lord placed Adam and Eve in the… Read more
Shock and vibration analysis can be performed either in the frequency or time domain The time domain method requires more computation time but is much better suited for transient and nonstationary excitation Time domain methods are also better for rainflow fatigue cycle counting Students should… Read more
We are not human beings having a spiritual experience; we are spiritual beings having a human experience. – Pierre Teilhard de Chardin (1881-1955) Quoted by: President Thomas S. Monson, BYU Devotional Be a Light to the World, November 1, 2011 * * * * *… Read more
The punch file method may be used to extract the mass & stiffness matrices from Nastran models. The format is awkward since zero terms are not stored. Also the matrices are assumed to be symmetric, and the upper triangular portion above the diagonal is not… Read more
A sound file from the attack on the U.S. Embassy in Cuba has now been made available on the Internet. I did a spectral analysis of this file using my Matlab GUI scripts. The sound source is still unknown. The attacks have caused hearing, cognitive,… Read more
This is a work-in-progress… The fatigue units are available to students who enroll in the Shock & Vibration course series. __________________________________________________________________ M.H.A. Bonte, A. de Boer, R. Liebregts, Prediction of mechanical fatigue caused by multiple random excitations: stress_psd_1.pdf Dr.-Ing. Marinus Luegmair, Dr.-Ing. Alexander Ziehl, Von Mises… Read more
The top figure is the time history from the El Centro earthquake, North-South horizontal component. The middle is the corresponding Waterfall SRS with 4 second segments and with 50% overlap. The bottom is the spectrogram. The Waterfall SRS is calculated by first taking the complete… Read more