A reader sent in a question that every test engineer runs into sooner or later: For mission synthesis we get three-axis data from the real machine. What is the best way to simulate the same thing on a single-axis shaker table to create the same… Read more
This post is a reply to a recent LinkedIn questionon whether a low-energy impact really costs a bonded joint any fatigue life. It is a good question, and the answer has a number attached to it. The question was posed about aluminum-to-composite adhesively bonded joints:… Read more
The pair below sits on South Bayshore Drive in Coconut Grove, Miami, on the site of the old Grand Bay Hotel. Bjarke Ingels Group designed them, DeSimone Consulting Engineers made them stand up, and they were completed in 2016. Each tower rotates a total of… Read more
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… Read more
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… Read more
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,… Read more
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… Read more
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… Read more
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… Read more