Modal test data processing methods perform curve-fitting on measured frequency response functions. These are indirect methods for extracting natural frequencies and damping ratios. The FRF methods also yield mode shapes which may be complex if the system has non-proportional damping. Each complex mode shape can… Read more
Internal friction and heat generation cause a deviation from perfect elasticity, resulting in the hysteresis loop in the stress-strain curve. The damping capacity ψ is: ψ = ΔW/W where W is the initial strain energy and ΔW is the energy lost during one cycle of oscillation. Some damping capacities… Read more
Introduction The best vibration fixtures are simple, rigid, lightweight with the minimum number of features. Shaker and power amplifier systems are limited in terms of voltage, current and force pounds. Lighter fixtures are needed to achieve higher acceleration levels. Materials Aluminum alloy is a good… Read more
Tapiola Lutheran Church in Espoo, Finland, Opened in 1965 Helmholtz-type resonators are built into the walls of the church. The slots between brick pairs and cavities behind them act as both absorbers and diffusors of sound. The absorption reduces the reverberation time as desired for… Read more
The plot shows the applied strain on the horizontal axis and the resisting stress on the vertical axis. The area inside the triangle represents the maximum energy that can be absorbed elastically, if the member is strained up to its proportional limit stress. The member… Read more
Some San Francisco Bay Area residents from Marin County to the Presidio have noticed a sustained, series of high-pitched tones. The sound reached a new peak volume, and recordings of the eerie noise spread across social media in early June,. The sound is due to… Read more
PV = pseudo velocity The following method is intended for components which are to be tested to power spectral density (PSD) specifications on shaker tables. The method can be applied to sine-on-random specifications as well. The purpose of this document is to recommend velocity severity… Read more
Liquid fuel rocket engines undergo hot fire testing before flight in order to verify their performance, design integrity, etc. The engines are mounted to heavy-duty, immovable stands for this purpose. These tests are also referred to as static fire tests. Furthermore, the tests are almost… Read more
New Shepard Launch I have been working at Blue Origin in Kent, WA since February 2019. This is an excellent work environment with engaging technical opportunities. Blue Origin is hiring engineers including some for vibroacoustics. Please see: https://www.blueorigin.com/careers Applicants must be a U.S. citizen or permanent… Read more
This is a work-in-progress. Here are some slide presentation with an emphasis on launch vehicles. Equivalent Static Loads for Random Vibration & Alternate Link Damping & Isolation & Alternate Link Liftoff Vibroacoustics & Alternate Link Ascent Vibroacoustics & Alternate Link Launch Vehicle Pogo, Combustion Instability… Read more