admin Structural system & component damping can measured via modal testing with applied force excitation. One excitation method is an impulse hammer test. Another method is a small shaker attached to structure via a stinger rod. Damping can also be measured by mounting the test unit… Read more
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
Honeycomb sandwich structures are designed to have a high stiffness-to-mass ratio. The stiff, strong face sheets carry the bending loads, while the core resists shear loads. The face sheets are typically made from aluminum or carbon fiber with epoxy resin. The honeycomb core material is… Read more
Aerospace pyrotechnic shock response spectrum (SRS) specifications are almost always given with an amplification factor Q=10 Corresponding time history waveforms for the base input acceleration are almost never given with the specifications Users are allowed to synthesize their own waveforms to satisfy the SRS for… 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
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
NASA SP-8072 Acoustics Loads Generate by the Propulsion System (Alternate SP-8072 link) The liftoff analysis has been added to the GUI package at: Vibrationdata Matlab GUI The function can be accessed via: >> vibrationdata > Miscellaneous Functions I > Acoustics Vibroacoustics & SEA > acoustics >… Read more
This post is a work-in-progress… Combined Ascent Loads for Launch Vehicle Analysis Equivalent Axial & Line Loads for Launch Vehicles Launch Vehicle and Spacecraft Primary Structure Response to High Frequency Shock and Vibration – Tom Irvine