# shaker (blogs) — RSS Amplifier Recent posts from the 1 feeds in the RSS Amplifier directory that cover shaker. Page: Feed: --- ## [Aircraft Landing Gear Dynamic Analysis](https://blog.vibrationdata.com/2026/08/21/aircraft-landing-gear-dynamic-analysis/) _2026-08-21 · Tom Irvine · Vibrationdata Engineering Blog_ A landing gear is the only structure on the airplane that is designed to be hit. Everything else is sized to carry loads that arrive smoothly. The gear is sized to absorb a defined amount of kinetic energy in a fraction of a second, several times a day, for tens of thousands of cycles, while ... Read more ## [NASTRAN FRF & Modal Transient Analysis](https://blog.vibrationdata.com/2026/08/21/nastran-frf-modal-transient-analysis/) _2026-08-21 · Tom Irvine · Vibrationdata Engineering Blog_ SOL 111 or SOL 112? Why a Synthesized Time History Earns Its Keep A base input power spectral density arrives on a specification sheet, and the reflex is automatic. Build the model, run SOL 111, read the RMS stress, apply a three-sigma factor, and compare against allowable. The whole exercise takes an afternoon on a ... Read more ## [Spring Surge](https://blog.vibrationdata.com/2026/08/18/spring-surge/) _2026-08-18 · Tom Irvine · Vibrationdata Engineering Blog_ Every introductory vibration course begins by drawing a mass on a spring and declaring that the spring has stiffness but no mass. That assumption is the reason the single-degree-of-freedom system has exactly one natural frequency instead of infinitely many. It is an excellent assumption almost all of the time. It fails in a specific and ... Read more ## [The Round House on Highway 101](https://blog.vibrationdata.com/2026/08/14/the-round-house-on-highway-101/) _2026-08-14 · Tom Irvine · Vibrationdata Engineering Blog_ The Wall Street Journal ran a piece this week on a circular house in Novato, California, listed for sale for the first time since it was built. Sam Harkleroad put it up in 1963: 1,560 square feet of floor area, roughly 50 feet in diameter, cantilevered off a single cylindrical core, and designed to rotate ... Read more ## [The Barrett Vibroacoustics Scaling Method](https://blog.vibrationdata.com/2026/08/07/the-barrett-vibroacoustics-scaling-method/) _2026-08-07 · Tom Irvine · Vibrationdata Engineering Blog_ The Barrett scaling law is one of the oldest tools in the launch vehicle random vibration toolbox, and it is still one of the most used. It answers a question that comes up on every new program before a single accelerometer has been mounted: I have flight data from a previous vehicle, and I have ... Read more ## [Rossiter Tones in Aircraft Cavities](https://blog.vibrationdata.com/2026/08/04/rossiter-tones-in-aircraft-cavities/) _2026-08-04 · Tom Irvine · Vibrationdata Engineering Blog_ Cut a rectangular hole in an aerodynamic surface and fly it at high subsonic or supersonic speed, and the hole will sing. Not quietly. Overall sound pressure levels inside a fighter weapon bay routinely exceed 160 dB, and the energy is not spread evenly across the spectrum. It is concentrated into a set of sharp ... Read more ## [Aircraft External Store Buffet Random Vibration Modeling](https://blog.vibrationdata.com/2026/08/03/aircraft-external-store-buffet-random-vibration-modeling/) _2026-08-03 · Tom Irvine · Vibrationdata Engineering Blog_ A large external store is to be carried under an aircraft wing on a pylon. The airframe manufacturer runs its buffet analysis and hands the store vendor an acceleration power spectral density at the pylon/wing interface. The vendor applies that PSD as base excitation to a finite element model of the pylon and store, usually ... Read more ## [Random Vibration Response Peak Distribution](https://blog.vibrationdata.com/2026/08/02/random-vibration-response-peak-distribution/) _2026-08-02 · Tom Irvine · Vibrationdata Engineering Blog_ Nearly every random vibration fatigue course teaches that the response of a single-degree-of-freedom system to broadband base excitation has Rayleigh-distributed peaks. The claim is repeated so often that it has hardened into doctrine. It is a good approximation for the largest peaks, which is why it has survived. But it is quantitatively wrong for the ... Read more ## [Quadratic Failure Metrics in Random Vibration](https://blog.vibrationdata.com/2026/08/02/quadratic-failure-metrics-in-random-vibration/) _2026-08-02 · Tom Irvine · Vibrationdata Engineering Blog_ A random vibration analysis in a finite element code will happily report an RMS von Mises stress, or an RMS resultant shear force in a bolt, and the analyst will happily multiply it by three and compare it against an allowable. Both quantities are useful. Both are also quietly non-Gaussian, and their spectral content is ... Read more ## [Seismic Mass under Large Shaker](https://blog.vibrationdata.com/2026/07/31/seismic-mass-under-large-shaker/) _2026-07-31 · Tom Irvine · Vibrationdata Engineering Blog_ A question that comes up whenever a laboratory is planning its first large electrodynamic shaker installation: the specification and the quotations keep referring to a seismic mass, or a reaction mass, or an inertia block. Is that a real, physically heavy object that has to be purchased and installed? Or is it a tuned-mass arrangement ... Read more ## [Snapshot Showdown on Google Play (Sponsored)](https://crawlproof.com/a/eEUWyVdn2pjl) _2026-07-31 · **Sponsored**_ Available on Google Play for Android devices. ## [Large Shaker Seismic Mass](https://blog.vibrationdata.com/2026/07/31/150879/) _2026-07-31 · Tom Irvine · Vibrationdata Engineering Blog_ A question that comes up whenever a laboratory is planning its first large electrodynamic shaker installation: the specification and the quotations keep referring to a seismic mass, or a reaction mass, or an inertia block. Is that a real, physically heavy object that has to be purchased and installed? Or is it a tuned-mass arrangement ... Read more ## [Random Vibration Above 2000 Hz: Deriving and Verifying an MPE for Engine-Proximate Components](https://blog.vibrationdata.com/2026/07/30/random-vibration-above-2000-hz-deriving-and-verifying-an-mpe-for-engine-proximate-components/) _2026-07-30 · Tom Irvine · Vibrationdata Engineering Blog_ The Problem Here is a problem that comes up more often than the standards would suggest. An engineer is deriving a random vibration maximum predicted environment (MPE) for launch vehicle components mounted very close to the engines. Accelerometer data from engine test stand and stack tests show significant broadband energy above 2000 Hz, with peaks ... Read more ## [Does Compression Grow Cracks?](https://blog.vibrationdata.com/2026/07/23/does-compression-grow-cracks/) _2026-07-23 · Tom Irvine · Vibrationdata Engineering Blog_ Does Compression Grow Cracks? — Vibrationdata Vibrationdata Fracture Fatigue Stress intensity conventions At a stress ratio of R = −1, the choice between full-range and clipped ΔK is worth a factor of 2n in life. It is usually the largest single lever in a spectrum fatigue deck, and the conservatism runs the opposite direction ... Read more