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
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… Read more
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… Read more
Certain equipment must be designed and tested to withstand vibration. This is common in the automotive, aerospace, military and other industries. The equipment is typically mounted to a shaker table and then subjected to a base input random or sine sweep vibration test. The random… Read more
Certain equipment must be designed and tested to withstand external vibration excitation. This is common in the military, naval, aerospace and other industries. The equipment is typically mounted on a shaker table and subjected to base excitation. The input may be random vibration if the… Read more
An important parameter in random vibration analysis is the peak response, which can be the maximum relative displacement, velocity, acceleration, stress or strain. The peak response can then be compared with the threshold for yielding, ultimate failure, etc. The peak is also important for fatigue… Read more
There is a need to derive a power spectral density (PSD) envelope for nonstationary acceleration time histories, including launch vehicle data, so that components can be designed and tested accordingly. Three methods are considered in the following paper using an actual flight accelerometer record. The… Read more
Prerequisite Reference Papers David O. Smallwood, An Improved Recursive Formula for Calculating Shock Response Spectra, Shock and Vibration Bulletin, No. 51, May 1981. DS_SRS1.pdf Rainflow Counting Tutorial Fatigue Damage Spectrum, Time Domain Fatigue Damage Spectrum Dirlik Method for PSDs Optimized PSD FDS Nonstationary * *… 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
Aerospace and military components must be designed and tested to withstand shock and vibration environments. Some of this testing occurs as qualification, whereby a sample component is tested to levels much higher than those which it would otherwise encounter in the field. This is done… Read more