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I have added a function for generating random time histories with user-specified skewness & kurtosis to the Vibrationdata Matlab Signal Package posted at:

Vibrationdata Matlab Signal Analysis Package

The function includes an option for band-limiting the signal via lowpass filtering.

Tom Irvine

PowerPoint Slides:

webinar_35_fatigue_sine_random.pptx

Audio/Visual File:

Using_Fatigue_to_Compare_Sine_and_Random_Environments.wmv

YouTube version

* * *

References:

Steinberg’s Vibration Analysis for Electronic Equipment

Rainflow Fatigue Posts

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also: Vibrationdata Webinars

Thank you,

Tom Irvine

PowerPoint Slides:

webinar_34_rainflow_fatigue_beam.pptx

Audio/Visual File:

Rainflow_Cycle_Counting_for_Continuous_Beams.wmv

YouTube version

* * *

References:

Steinberg’s Vibration Analysis for Electronic Equipment

Rainflow Fatigue Posts

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also: Vibrationdata Webinars

Thank you,

Tom Irvine

NASA-STD-5019, Fracture Control Requirement for Spaceflight Hardware (excerpt)

4.1.1.12 Low-Risk Part

This section addresses parts that can be classified non-fracture critical because of large structural margins and other considerations that make failure from a pre-existing flaw extremely unlikely.

a. For a part to be classified low risk, it shall be constructed from a commercially available material procured to an aerospace standard or equivalent.

b. Aluminum parts shall not be loaded in the short transverse direction if this dimension is greater than 7.62 cm (3 in).

c. A part whose failure directly results in a catastrophic hazard shall be excluded from being classified low risk, except when the total (unconcentrated) stresses in the part at limit load are less than 30 percent of the ultimate strength for the material used and requirements (1) through (3) and either (4) or (5) are met.

* * *

Thus fatigue and fracture analyses are not required for parts with peak stress less than 0.3*ultimate.

* * *

- Tom Irvine

Here is a Matlab script for the ground PPV: blast_ground_velox.zip

References:

http://www.dot.ca.gov/newtech/researchreports/reports/2001/vibrations.pdf

ftp://ftp.odot.state.or.us/techserv/geo-environmental/Material%20Sources/Resources/Blasting_and_Community.pdf

- Tom Irvine

Here is a Matlab GUI script

burst_overpressure.zip

* * *

WHAT HAPPENS WHEN A TIRE EXPLODES?

Air Safety Week had an interesting article on the energy released by exploding tires in their August 7, 2000 issue. It was addressing the tire failure on the Concord. If you go to page 3 you will find a chart-Energy Released by Catastrophic Tire Deflations.

If you “used the same numbers” for a P-3 (Navy aircraft) main landing gear tire at 200 pounds per square inch (psi) tire pressure to approximate the energy released by a 747 main landing gear tire failure (194 psi)-it would be 301,071 foot pounds. . . . equal to 0.60 sticks of dynamite.

If the tire burst at the maximum pressure of 1,170 psi it would release 1,215,789 foot pounds of energy-an amount equal to 4.4 sticks of dynamite.

* * *

References:

http://www.pnl.gov/main/publications/external/technical_reports/PNNL-18696.pdf

https://www.metabunk.org/attachments/blast-effect-calculation-1-pdf.2578/

- Tom Irvine

PowerPoint Slides:

Webinar_33_Rainflow_Fatigue.pptx

Audio/Visual File:

Rainflow_Cycle_Counting.wmv

YouTube version

* * *

References:

Steinberg’s Vibration Analysis for Electronic Equipment

Rainflow Fatigue Posts

* * *

Matlab script: Vibrationdata Signal Analysis Package

* * *

See also: Vibrationdata Webinars

Thank you,

Tom Irvine

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