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PowerPoint File:

Webinar_13_PSD_sdof_response.pptx

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Matlab script: Vibrationdata Signal Analysis Package

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See also: Vibrationdata Webinars

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- Tom Irvine

PowerPoint File:

Webinar_12_PSD_data.pptx

Audio/Visual File:

PSD data.wmv

Data:

Taurus_auto.dat – Time(sec) & Accel(G)

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Matlab script: Vibrationdata Signal Analysis Package

* * *

See also: Vibrationdata Webinars

* * *

- Tom Irvine

Here is a signal analysis package GUI written using Tkinter: vibrationdata_gui_python.zip

It is compatible with Python versions 2.7 to 3.3, and hopefully future 3.x versions.

vibrationdata.py is the main script.

The remaining scripts are supporting functions.

These scripts demonstrate the use of multiple windows.

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The following signal analysis functions are currently available:

Statistics
Trend Removal & Scaling
Butterworth Filter
Bessel Filter
Fourier Transform
Fast Fourier Transform (FFT)
Waterfall FFT
Power Spectral Density (PSD)
SDOF Response to Base Input
Shock Response Spectrum (SRS)
Rainflow Cycle Counting
Differentiate Time History
Integrate Time History
Autocorrelation
Cross-correlation
Cepstrum & Auto Cepstrum
Sound Pressure Level (SPL)

The following PSD functions are also available:

Overall GRMS
SDOF Response to Base Input PSD
Vibration Response Spectrum (VRS)

The following miscellaneous functions are also available:

Sine Amplitude Conversion
SDOF Response: Peak Sigma for Random Base Input
SDOF Response to Classical Pulse Base Input

More will be added in future revisions…

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See also: Python Wiki

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- Tom Irvine

PowerPoint File:

Webinar_11_PSD.ppt

The sample PSD specification is taken from:  NAVMAT-P9492

Audio/Visual File:

PSD.wmv

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Reference Papers:

Integration of the Power Spectral Density Function

Statistical Degrees-of-Freedom

Power Spectral Density Units [ G^2 / Hz ]

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Matlab script: Vibrationdata Signal Analysis Package

* * *

See also: Vibrationdata Webinars

* * *

- Tom Irvine

PowerPoint Files:

Webinar_9_white_noise_FFT.pptx

Webinar_10_Sample_Rate.pptx

Audio/Visual Files:

Sample Rate, Nyquist Frequency & Aliasing.wmv

White Noise FFT.wmv

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Matlab script: Vibrationdata Signal Analysis Package

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See also:

IEST-RD-DTE012: Handbook for Dynamic Data Acquisition and Analysis

Aliasing References

Vibrationdata Webinars

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- Tom Irvine

SaturnV

A rocket vehicle behaves as a free-free beam during flight. The vehicle’s body bending modes can be excited by wind gusts, aerodynamic buffeting, thrust offset, maneuvers, etc. The bending motion can interfere with the vehicle’s control system. The guidance, navigation and control algorithms must be designed with sufficient stability to withstand these perturbations and the resulting elastic body response.

Reference

Description and Performance of the Saturn Launch Vehicle’s Navigation, Guidance, and Control System (NASA TN D-5869)

See also

Beam Bending Natural Frequencies & Mode Shapes

- Tom Irvine

V1 is the critical takeoff speed for an aircraft at which the pilot must make a decision.

The aircraft can still safely stop if the takeoff is aborted prior to V1. The abort could be due to an engine failure, bird strike, blown tire, etc.

After the aircraft reaches V1, it must takeoff to avoid crashing at the end of the runway. But the pilot can then fly the aircraft around for a landing.

V1 depends on the runway length, wind, and on the aircraft’s weight, thrust, lift, braking capability, etc.

Vr is the rotate speed. It is not always the same as V1. At this speed rotation is begun as the pilot pitches the plane upward.

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Nevertheless, aborts do occur after the aircraft reaches V1.

Here is a report by the The NLR Air Transport Safety Institute which states that tire/wheel vibration is a cause or factor in some of the cases.

REJECTING A TAKEOFF AFTER V1…WHY DOES IT (STILL) HAPPEN?

The NLR Air Transport Safety Institute (NLR-ATSI) is a research and consultancy organization embedded in the National Aerospace Laboratory of the Netherlands (NLR).

- Tom Irvine

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