Like Robert Frost, I have miles to go before I sleep, and all because I took the road less traveled… This is a long-term work-in-progress… I am including SEA in my Matlab GUI package. The functions can be accessed via: vibrationdata > Miscellaneous Functions I… Read more
A spacecraft at launch is subjected to a harsh acoustic and vibration environment resulting from the passage of acoustic energy, created during the liftoff of a launch vehicle, through the vehicle’s payload fairing. In order to ensure the mission success of the spacecraft it is… Read more
One of my colleagues asked whether uncertainty margin should be added to the input or the response, particularly for a nonlinear system. I recommend adding to the response. He asked that I write a paper using an acceleration base input which he supplied. The results… 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
From a colleague… I just wanted to let you know that we would have a GS-13 posting out next week seeking for an experienced strength/fracture engineer to fill a vacant position in my branch here at LSP. I would appreciate very much if you can… Read more
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