Tom Irvine View larger image Figure 1. Olive View Hospital, 1994 Northridge earthquake: 0.9 g on the ground, 2.3 g on the roof. Source: USGS Fact Sheet 068-03. A component bolted to a roof or an upper floor does not feel the earthquake. It feels the floor.… Read more
A large welded machine base comes out of the fabrication shop looking straight and square. It goes to the machine shop, where the mounting pads are milled flat to a few hundredths of a millimetre. The next morning the pads are out of flat again.… Read more
This February 2027 course series provides practical training in shock, vibration, fatigue, structural dynamics, FEA, machinery vibration, acoustics, and rotor dynamics for engineers working with test data, qualification requirements, failure analysis, and mechanical system reliability. Each one-hour class is organized in a semester-style format, with… Read more
A reader has a measured time history, he wants a low-frequency sine test level from it, and the FFT does not seem to give him the real amplitude at each frequency. His governing handbook sends him to something called ESI, which produces a swept sine… Read more
Tom Irvine A phone that slips out of your hand is a shock problem, and a surprisingly rich one. The drop height fixes only one thing, the velocity at impact. Everything that matters after that, the pulse duration, the peak acceleration, and where the stress… Read more
A colleague who has started building a simulator wrote in with a short question. He has welded rods in S355 or S420 steel, the welding process is not yet fixed, and he expects that a fatigue assessment will be needed. He has not worked with… Read more
Two days ago a wind storm came through our neighborhood in Madison, Alabama. Limbs came down, the power flickered, and by evening everything seemed to be over. This morning, in calm air, one of the wooden distribution poles on our street broke through at about… Read more
View larger image Figure 1. A circular laminated elastomeric bearing on a pier cap, instrumented with displacement transducers straddling the bearing and additional sensors on the pier face. The rubber cover bulges between the internal steel shim planes. Whether a lead core is buried inside… Read more
The Constraint Factor You Inherited — Vibrationdata Vibrationdata Fracture & Fatigue Crack closure modeling The Constraint Factor You Inherited Newman’s crack opening equation contains a single user input, α, that most analysts take from a material file default without ever deciding on it. At the… Read more
A slender store hanging under a fighter wing sits in an acoustic field near 164 dB overall. A wind chime tube hanging from a porch beam sits in an acoustic field near 40 dB. The store is asked to survive; the chime is asked to… Read more