My colleagues at Sandia National Laboratories have presented some conference papers recently on energy response spectrum. Here is a paper that I wrote on this topic: energy_response_spectrum.pdf Also, I have added the energy response spectrum as an option for acceleration time histories to the Vibrationdata… Read more
Here is a job opening in Huntsville, Alabama for helicopter air frame finite element analysis: http://www.avnikdefense.com/index.php/careers/current-openings/9-available-positions/37-mid-level-mechanical-engineer-structural-analyst I spoke with the CEO, Michele Kochoff Platt. This is an excellent opportunity. So please forward this link to any of your colleagues who are seeking employment. Note that… 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
Assume that input and response acceleration PSDs have been measured. The corresponding displacement PSDs can be readily calculated. But the relative displacement cannot be calculated accurately because the phase angles are discarded in the PSD calculation. The best method is to perform the relative displacement… Read more
Here are some questions from students that I recently received for shaker table testing of equipment. How are vibration standards developed and how do they relate to the operational environment? Standards may have different purposes. Some of the common ones are: Envelope the actual field… Read more
Here are some papers… Notes on Mechanical Shock & Bending Waves Waves in Structures * * * Functions for calculating wave speeds are given in: Matlab script: Vibrationdata Signal Analysis Package The functions can be accessed via >> vibrationdata > Miscellaneous > Acoustics & Vibroacoustics… Read more
A function for calculating the natural frequencies and mode shapes for an elastic beam undergoing rotation is given in: Matlab script: Vibrationdata Signal Analysis Package The function can be accessed via: >> vibrationdata > Miscellaneous > Structural Dynamics > Beam Bending FEA > Rotating Beam,… Read more
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 function for calculating the natural frequencies and mode shapes for an elastic beam supported by end springs is included in: Matlab script: Vibrationdata Signal Analysis Package The function can be accessed via: >> vibrationdata > Miscellaneous > Structural Dynamics > Beam Bending > Beam… Read more
Maximum predicted environment (MPE) levels can be derived for acoustic, shock, and vibration levels where flight data is available. The enveloping for multiple sets of data can be performed using tolerance factors as described in the following papers. Normal Tolerance Factors for Upper Tolerance Limits:… Read more