I have added an exponential decay option to the wavelet synthesis function. This arranges the wavelets so that they will “resemble” a pyrotechnic-like time history. The function is included in the GUI package at: Matlab Link Note that the conservative ramp-plateau enveloping in the SRS… Read more
Shock
Launch Vehicle Separation Source Shock Scaling Hypothesis
Consider the case where flight or test pyrotechnic source shock data has been measured on a launch vehicle with a 1-meter diameter aluminum cylindrical shell. Assume that the source device is frangible joint with a certain number of grains per length. Now the same device… Read more
Damping Identification from Shock Data via Wavelet Responses
Structural system & component damping can measured via modal testing with applied force excitation. One excitation method is an impulse hammer test. Another method is a small shaker attached to structure via a stinger rod. Damping can also be measured by mounting the test unit… Read more
An Indirect Method for Converting a Shock Response Spectrum Specification to a New Q Value
Aerospace pyrotechnic shock response spectrum (SRS) specifications are almost always given with an amplification factor Q=10 Corresponding time history waveforms for the base input acceleration are almost never given with the specifications Users are allowed to synthesize their own waveforms to satisfy the SRS for… Read more
Waterfall SRS, 1940 El Centro Quake
The top figure is the time history from the El Centro earthquake, North-South horizontal component. The middle is the corresponding Waterfall SRS with 4 second segments and with 50% overlap. The bottom is the spectrogram. The Waterfall SRS is calculated by first taking the complete… Read more
JPL Tunable Shock Beam
The NASA/JPL Environmental Test Laboratory (ETL) developed and built a tunable beam shock test bench based on a design from Sandia National Laboratory many years ago. ETL has been using this test system successfully since October 2008. The excitation is provided by a projectile driven… Read more
Embraer E190 Landing Shock
I recently flew as a passenger on a E190 similar to the one in the top image. The landing shock is shown in the bottom image. The data was recorded on a Slam Stick X, sampled at 400 samples/sec. The initial set of peaks have… Read more
A330-200 Landing Shock
Image Courtesy of Justin Kane I recently flew as a passenger on a A330-200 similar to the one in the image. I used a Slam Stick X Vibration Data Logger to measure the landing shock, with the sensor mounted on the cabin floor. The acceleration… Read more
A320 Landing Shock
I recently flew as a passenger on a A320 similar to the one in the image. I used a Slam Stick X Vibration Data Logger to measure the landing shock, with the sensor mounted on the cabin floor. The resulting acceleration time history is shown… Read more
SRS Synthesis – New Option
(Click here for better image of Matlab GUI screenshot) I have added an “Exponential Decay” option to the wavelet synthesis function in the Matlab GUI package. The goal is to synthesize a wavelet series that has a gradual overall exponential decay, somewhat similar to an… Read more