NASA/JPL Component Shock Testing Machine Qualification Shock Test Philosophy for Reusable Launch Vehicle Components by Tom Irvine MPE = Maximum Predicted Environment Proposed Rule: Initial Qualification (one flight): 3 shocks per axis at MPE + 6 dB For each additional flight: 1 shock per axis… Read more
Effective Modal Mass and Modal Participation Factors
ModalMass_revK.pdf Effective modal mass and modal participation factors provide a quantitative basis for identifying dynamically significant vibration modes and for guiding modal truncation in structural dynamic analyses. This paper presents a unified formulation for both base-excited systems and grounded systems subjected to externally applied forces.… Read more
Fatigue Cracks in Anodized Coatings
Image reference: https://onlinelibrary.wiley.com/doi/full/10.1002/adem.202300394 What Is Anodizing? Anodizing is widely used to improve corrosion resistance and surface durability in aluminum and other light metals. However, under cyclic loading, anodized coatings can play a surprising, and sometimes detrimental, role in fatigue performance. Thanks for reading Tom’s Substack!… Read more
Dithering Vibration
Figure 1. Space Shuttle Orbiter Ku-band Antenna Introduction Mechanical vibration is usually undesirable in a structure because it can lead to fatigue and other types of failures. Vibration does have its beneficial uses, however. For example, dither vibration was used to ensure that the Space… Read more
Elephant Communication via Infrasound
🐘 The Secret Language of Giants: How Elephants Communicate Through Infrasound When we think of animal communication, we might picture birdsong or whale calls. But elephants, some of the most intelligent and socially complex mammals on Earth, have evolved a secret communication channel that humans… Read more
Tom & Friends’ ebooks
An Introduction to Shock & Vibration Response Spectra Revision H eBook Shock & Vibration Stress & Strain as a Function of Velocity, Revision Q, eBook link Launch Vehicle POGO, Combustion Instability & Thrust Oscillation: Dynamics, Instabilities, and Mitigation Techniques link Airport, Traffic & Community Noise… Read more
Equipment Racks & Earthquakes
Seismic-restrained Isolators The following is an edited response from ChatGPT. Resonant response of the equipment rack circuit boards should not be an issue, because circuit board fundamental frequencies are typically above 200 Hz, whereas seismic energy is mostly below 20 Hz. But electronic components may… Read more
MDOF Frequency Response Function Natural Frequency & Damping Extraction including Modal Frequency Overlap
Here is a revision of what has become an ongoing epic project. I am learning a great deal about modal curve-fitting and using AI. Slides More later... - Tom
Shock, Vibration, Fatigue & Acoustics Classes Beginning January 2026
Each class and each part is one-hour long. The format is similar to a college semester system. Students will receive IACET CEUs. Class Registration Link Basic Shock & Vibration IntroductionVibration TestingExcitation FunctionsSine VibrationSine Sweep VibrationRandom Vibration StatisticsSDOF Response to RandomNon-Gaussian RandomFourier TransformFFTWaterfall FFTSample RateLeakage &… Read more
Tapir Stock Trading Program
Update August, 2, 2025 Last Friday was a downer. But Tapir has these tickers doing well: AZO, URI, MSFT Update ticker list which can be used with the Tapir program: stocks_etf_tickers.txt ________________ Update July 27, 2025 Tapir's recommendations: SPY, IVV, PH, VOO, GS Matlab code… Read more