Highly Accelerated Life Testing (HALT) is a process for ruggedization of preproduction products. It is also referred to as AST (Accelerated Stress Testing). Highly Accelerated Stress Screening (HASS) is the production screen for products once they have been characterized in HALT. HALT and HASS each use… Read more
A typical SRS specification has a ramp and plateau. The best way to meet this specification type is with a complex oscillating pulse. In some cases, a classical shock pulse may be used, but this will cause an over-test at certain frequencies. Also, classical pulses… Read more
1. Band-Splitting 2. Time-Level Equivalence 3. PSD Synthesis using Sine Series PowerPoint Slides: webinar_41_psd_topics.pptx Audio/Visual File: NESC Academy PSD Special Topics – Recommend viewing in Firefox with Sliverlight Plugin * * * Matlab script: Vibrationdata Signal Analysis Package * * * Here is a brief guideline… Read more
Shock and vibration environments produce dynamic stresses which can cause material failure in structures. The potential failure modes include fatigue, yielding, and ultimate stress limit. F.V. Hunt wrote a seminal paper on this subject, titled “Stress and Stress Limits on the Attainable Velocity in Mechanical… Read more
Wayne Tustin is a pioneer in the field of shock and vibration training. I have had the opportunity to learn from him at several IEST meetings and other conferences. He taught me the meaning of SRS (G) and PSD (G^2/Hz) units, when I was… Read more
There is a need in certain structural dynamics finite element analysis problems to perform a response analysis in the time domain. This would be the case, for example, if the stiffness was non-linear. Loss-of-clearance or contact between two adjacent vibrating parts is another analysis example.… Read more
Engineers prepare the MESSENGER spacecraft for a vibration test at The Johns Hopkins University Applied Physics Laboratory, Laurel, Md., where the Mercury-bound NASA spacecraft was designed and built. * * * Introduction Flight configured spacecraft are subjected to base input vibration tests for certain programs.… Read more
N571UP, the aircraft involved, seen taking off from Dubai in November 2008 * * * A UPS Boeing 747-400 flying between Dubai International Airport and Cologne Bonn Airport crashed close to Dubai airport, killing the two crew members, on September 3, 2010. The aircraft had… Read more
Some power spectral density test specifications are too high in amplitude for a given shaker system. Bandsplitting can be cautiously used in these cases. Here is a brief guideline paper: bandsplit.pdf Here is a Matlab script that implements bandsplitting per the guidelines: bandsplit.zip The main script… Read more
MIL-STD-180G, Table 514.6C-X, Vibration induced by the main rotor and blade passing frequencies… Here is a script for calculating the sinusoidal frequencies and amplitudes: helicopter.m – Tom Irvine