Shock - Vibrationdata Engineering Blog

Surface Ship Shock, SRS, DDAM, MIL-DTL-901, UNDEX

July 23, 2026July 7, 2026 by Tom Irvine

The image shows a MIL-S-901D Barge Test. A reader recently wrote in with two requests: (1) blog posts on surface ship shock and shock response spectra derived from acceleration data, and (2) coverage of underwater explosion (UNDEX) shock effects on submerged components such as batteries.… Read more

Strain Rate Effects: Why Metals Get Stronger but Less Ductile Under Dynamic Loading

July 22, 2026June 30, 2026 by Tom Irvine

Strain Rate Effects: Why Metals Get Stronger but Less Ductile Under Dynamic Loading Introduction A common observation in shock, impact, and ballistic engineering is that metals behave differently under dynamic loading than they do under slow, quasi-static loading. A structural steel or aluminum alloy that… Read more

Another Method for Pyrotechnic-like Time History Synthesis for an SRS Specification

December 13, 2020 by admin

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 & Vibration Test Fixture Design

July 24, 2026August 11, 2020 by admin

Introduction Vibration test fixtures are the mechanical interface between the shaker system and the unit under test (UUT). Their purpose appears simple: hold the test item securely and transmit the specified vibration input. In practice, fixture design is one of the most important and often… Read more

Material Shock Loading

July 19, 2026July 20, 2020 by admin

The plot shows the applied strain on the horizontal axis and the resisting stress on the vertical axis. The area inside the triangle represents the maximum energy that can be absorbed elastically, if the member is strained up to its proportional limit stress. The member… Read more

Launch Vehicle Separation Source Shock Scaling Hypothesis

July 22, 2026June 28, 2019 by admin

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

July 22, 2026May 18, 2018 by admin

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

July 22, 2026January 23, 2018 by admin

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

July 23, 2026April 2, 2017 by admin

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

July 20, 2026October 29, 2016 by admin

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