There are many variables which affect the touchdown shock level of an aircraft. These include: Descent or sink rate Forward and side velocities Roll, pitch, and yaw angles and corresponding rates Weight and center of gravity Cross wind, wind shear, gusts, etc. Runway contact loads… Read more
There is a occasional need in shock & vibration analysis for a user to generate his or her own time history. The resulting time history could be used to test a modal transient script, for example. The scripts in generate.zip can be used to output the… Read more
The following was written by Rabbi Shmuley Boteach. The most confusing story of the Bible involves G-d’s commandment to Abraham to sacrifice his son Isaac. What was this G-d, who would later declare that all human, and especially child, sacrifice to be an abomination, thinking?… Read more
These Matlab scripts apply a two-pole Bessel lowpass filter to a time history signal: Bessel_lowpass_filter.zip The main script is: Bessel_lowpass_filter.m The remaining scripts are supporting functions. The filter coefficients were derived using a bilinear transformation, as shown in Bessel_filter_two_pole.pdf * * * The U.S. Navy… Read more
The united tribes of Israel had grown steadily in wealth, power and glory or 120 years, under the reigns of Saul, David and Solomon. Solomon’s son Rehoboam became the next king. Rehoboam raised the taxes, which caused the northern tribes to rebel against him. Jeroboam… Read more
Consider a component which is to be subjected to a shock test using a shaker table. The test specification for this example is a Shock Response Spectrum (SRS). The control computer must synthesize a time history for the test. The typical method is via a… Read more
Time Waveform Replication (TWR) for shock testing on shaker systems has been receiving some attention in MIL-STD-810G and elsewhere. The goal is to test components to measured field time histories for realism. I did some related work with NASA’s Robin Ferebee a few years ago,… Read more
Single-degree-of-freedom System ______________________________________________________________________ Please see the following post for an important revision: Peak Response to Random Vibration with Probability of Exceedance ______________________________________________________________________ Consider a single-degree-of-freedom system subjected to a broadband random vibration base input, where the input is stationary and has a normal distribution. (The… Read more
Matlab scripts for a Butterworth Sixth order filter are given in: Butterworth.zip The main script is: Butterworth_filter.m The scripts have options for lowpass, highpass and bandpass filtering. There is also an option for refiltering for phase correction. The scripts also demonstrate the calculation of the… Read more
“Shock Diamonds” in the afterburner of a NASA SR-71B Jet * * * Sound pressure levels are limited by the physical characteristics of the surrounding medium. The ambient air pressure at sea level is “one atmosphere,” or approximately 14.7 psi on the absolute scale. The… Read more