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
I recently flew as a passenger on a Boeing 717-200 aircraft similar to the one shown in the image. This aircraft has two Rolls-Royce BR700 engines, with the following specifications: Maximum Engine Rotational Speeds (Both Engines) N1 Low Pressure Turbine = 6,195 RPM (103 Hz) N2… Read more
Here is a paper showing how fatigue damage can be calculated from a stress response PSD for a plate excited by an acoustic pressure field: acoustic_fatigue_plate.pdf The calculation method is given at: Fatigue Damage for a Stress Response PSD * * * The Matlab scripts… Read more
This Webinar unit shows how to perform spectral analyses on sound files using the Matlab & Python Vibrationdata packages. PowerPoint File: Webinar_sound_files.ppt – Matlab & Python Audio/Visual File: NESC Academy Sound File Processing – Recommend viewing in Firefox with Sliverlight Plugin * * * The sample… Read more
I recently flew as a passenger in a CRJ-200 (aka CL-65) jet similar to the one shown in Figure 1. This aircraft has two General Electric CF34-3B1 turbofan engines, as shown in Figure 2. Here are the rotational speeds for each rotor. N1 Fan Speed… Read more
Formulas for calculating the speed of sound in gases, liquids, and solids is given in: speed.pdf A Matlab function for these calculations is included in the package given at: Vibrationdata Matlab Signal Analysis Package The speed of sound calculator can be accessed within this package… Read more
Here is a chart showing the natural frequencies of piano keys: piano.pdf Here is a paper on some basic music theory: music.pdf * * * See also: Fun with Sound Files Wind Chime Acoustics Tuning Fork Sound and Vibration: tuning.pdf * * * – Tom… Read more
This set of scripts calculates the response of an SDOF system to an applied force PSD. A transfer function is derived. Then its square is applied to the force PSD to calculate the response, using point-by-point multiplication and integration. sdof_ran_force.zip Important note: The following scripts… Read more
There is a need to derive a PSD envelope for nonstationary acceleration time histories, including launch vehicle data, which may be similar to that shown in the above figure. A PSD can be derived using rainflow fatigue cycle counting along with a Miners-type relative fatigue… Read more
A colleague recently wrote to me regarding the merits of using statistical energy analysis to predict the vibration levels in a NASA launch vehicle. Here is my reply: I use “old-school” empirical scaling techniques. These work reasonably well for deriving component-level maximum predicted environments. I… Read more