PowerPoint File:

* * *

Data: elcentro_NS.dat – time (sec) & accel (G)

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also:

Seismic Peak Ground Acceleration

* * *

- Tom Irvine

PowerPoint File:

* * *

Data: elcentro_NS.dat – time (sec) & accel (G)

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also:

Seismic Peak Ground Acceleration

* * *

- Tom Irvine

Posted in Shock, webinars | Leave a Comment »

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 for calculating the plate responses are included in the vibroacoustics section of the Vibrationdata GUI package, available at: Vibrationdata Signal Analysis Package

* * *

See also:

Steady-State Response of a Rectangular Plate Simply-Supported on All Sides to a Uniform Pressure: ss_plate_uniform_pressure.pdf

Steady-State Vibration Response of a Plate Fixed on All Sides Subjected to a Uniform Pressure: fixed_plate_uniform_pressure.pdf

- Tom Irvine

Posted in Acoustics, Fatigue | Leave a Comment »

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:

* * *

The sample data file for the CRJ900 aircraft is available at:

* * *

The Matlab & Pythons packages are available at:

Matlab script: Vibrationdata Signal Analysis Package

Python Signal Analysis Package GUI

* * *

See also:

* * *

- Tom Irvine

Posted in Acoustics, webinars | Leave a Comment »

PowerPoint File:

Webinar_23_Classical_Shock_Pulses.pptx

Audio/Visual File:

Response_to_Classical_Pulse_Excitation.wmv

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also:

Laplace Transforms in Shock & Vibration Analysis

* * *

- Tom Irvine

Posted in Shock, webinars | Leave a Comment »

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 7300 RPM (122 Hz)

N2 Core Speed 17710 RPM (295 Hz)

I made an audio recording from within the aircraft cabin nearing the end of climb-out, after hearing some distinct sine tones against the background random noise. The audio file is: CRJ200.wav

A Fourier transform of the sound file is shown in Figure 3.

A spectral peak occurs at 113 Hz, which is 93% of the N1 Fan speed.

A pair of spectral peaks occur at 277 and 278 Hz. These are about 93% of the N2 Core speed. The 1 Hz difference could be due to the N2 rotors of each engine being slightly out-of-sync with one another.

The other peaks remain unidentified.

Again, this recording was made from inside the cabin. So the fuselage walls would have attenuated some of the engine-generated acoustic energy, particularly at higher frequencies.

* * *

See also: Bombardier

- Tom Irvine

Posted in Acoustics, Aircraft | 1 Comment »

PowerPoint File:

Unit_22_integration_part_2.ppt

Audio/Visual File:

Integeration_Differentiation_part_2.wmv

* * *

Data Files:

two_wheeled_trailer_vertical.txt

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also:

* * *

- Tom Irvine

Posted in Matlab, webinars | Leave a Comment »

The Pierson–Moskowitz (PM) spectra is an empirical relationship that defines the distribution of energy with frequency within the ocean. The result is given as a wave height power spectra density.

Developed in 1964, the PM spectrum is one of the simplest descriptions for the energy distribution. It assumes that if the wind blows steadily for a long time over a large area, then the waves will eventually reach a point of equilibrium with the wind.

This is known as a fully developed sea. Pierson and Moskowitz developed their spectrum from measurements in the North Atlantic during 1964.

* * *

Here is a paper: wave_height.pdf

Here is a Matlab script: ocean_wave_PSD.m

- Tom Irvine

Posted in Matlab | 1 Comment »

%d bloggers like this: