Figure 1. Boeing 787 Aircraft Carbon fiber/epoxy laminates are widely used in aeronautic and aerospace structural components mainly because of their excellent specific mechanical properties. These laminates show mechanical properties similar or higher than the conventional metallic materials in terms of strength-to-weight and stiffness-to-weight ratios. The… Read more
Certain equipment must be designed and tested to withstand vibration. This is common in the automotive, aerospace, military and other industries. The equipment is typically mounted to a shaker table and then subjected to a base input random or sine sweep vibration test. The random… Read more
Equipment must be designed and tested to withstand shock and vibration. Ideally, all equipment would be tested on a shaker table with six-degree-of-freedom control (three translations and three rotations). Such tables and control systems exist but are very expensive. Furthermore, any multi-axis testing requires careful… Read more
This is a work-in-progress… I am creating a series of webinars with Matlab exercises for seismic testing. Here are the slides. Telcordia Technologies Generic Requirements GR-63-CORE: Bellcore_GR_63_Core.ppt This unit contains an alternative waveform for VERTEQII. CEI.IEC 980, Recommended practices for seismic qualification of electrical equipment… Read more
Stentor Satellite Equipment mounted in satellites must withstand acoustic-driven random vibration at liftoff and during the transonic and maximum dynamic pressure phases of flight. The equipment must be designed and test accordingly. The equipment is mounted on shaker tables for the random vibration testing,… Read more
Certain equipment must be designed and tested to withstand external vibration excitation. This is common in the military, naval, aerospace and other industries. The equipment is typically mounted on a shaker table and subjected to base excitation. The input may be random vibration if the… Read more
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
There is a need to derive a power spectral density (PSD) envelope for nonstationary acceleration time histories, including launch vehicle data, so that components can be designed and tested accordingly. Three methods are considered in the following paper using an actual flight accelerometer record. The… Read more
Prerequisite Reference Papers David O. Smallwood, An Improved Recursive Formula for Calculating Shock Response Spectra, Shock and Vibration Bulletin, No. 51, May 1981. DS_SRS1.pdf Rainflow Counting Tutorial Fatigue Damage Spectrum, Time Domain Fatigue Damage Spectrum Dirlik Method for PSDs Optimized PSD FDS Nonstationary * *… Read more
Assume that input and response acceleration PSDs have been measured. The corresponding displacement PSDs can be readily calculated. But the relative displacement cannot be calculated accurately because the phase angles are discarded in the PSD calculation. The best method is to perform the relative displacement… Read more