Uncategorized - Vibrationdata Blog

Effective Modal Mass and Modal Participation Factors

March 7, 2026February 7, 2026 by Tom Irvine

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

January 16, 2026 by Tom Irvine

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

Elephant Communication via Infrasound

January 10, 2026 by Tom Irvine

🐘 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

Qualification Shock Testing for Launch Vehicle Components, Multiple Flights

November 28, 2025 by admin

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

Tom & Friends’ ebooks

March 2, 2026November 27, 2025 by admin

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

October 22, 2025 by admin

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

January 5, 2026August 31, 2025 by admin

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

January 5, 2026August 29, 2025 by admin

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

July 13, 2025 by admin

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

Shock, Vibration, Fatigue & Acoustics Classes Beginning June 2025

March 9, 2025 by admin