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
Figure 1. Boeing 787 Aircraft Carbon fiber/epoxy laminates are widely used in aeronautic and aerospace structural components mainly because of their excellent specific mechanical properties. These laminates show mechanical properties similar or higher than the conventional metallic materials in terms of strength-to-weight and stiffness-to-weight ratios. The… Read more
Rolls Royce Engine Blade-off Test Video Link 1 Video Link 2 The engine blade-off test is performed to make sure that the engine can survive a fan. compressor or turbine blade breaking off within the engine, without fragments being ejected through the outside… Read more
The Lomb-Scargle Periodogram is a least-square method which is useful for calculating the Fourier transform of a time history with gaps or an uneven sampling rate. Reference Paper This function has been added to the vibrationdata GUI package Python script & Utility: lomb_scargle.py tompy.py -… Read more
Aircraft and launch vehicles behave as unconstrained systems in flight, with six rigid-body modes. These vehicles may be “trimmed” using aerodynamic control surfaces and thrust vector control to prevent rotation about the vehicle center-of-gravity (CG). There is a need to calculate the vehicle’s displacement response… 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