PowerPoint Slides: Webinar_29_stress_velocity.pptx Audio Visual Files: Recommend viewing in Firefox with Sliverlight Plugin NESC Academy Stress-Velocity Relationship Part I NESC Academy Stress-Velocity Relationship Part II * * * Acceleration Time History: Time (sec) & Accel (G) srs1000G_accel.txt * * * References: Stress-Velocity Relationship: sv_velocity.pdf Bending Frequencies of… Read more
PowerPoint Slides: Webinar_28_mdof_SRS.pptx Audio/Visual Files: Recommend viewing in Firefox with Sliverlight Plugin NESC Academy Multi-degree-of-freedom SRS Part I NESC Academy Multi-degree-of-freedom SRS Part II Three-dof System Example: three_dof_srs_revC.pptx * * * Acceleration Time History: Time (sec) & Accel (G) srs2000G_accel.txt * * * References:… Read more
The original Tacoma Narrows Bridge was opened to traffic on July 1, 1940. It was located in Washington State, near Puget Sound. Strong winds caused the bridge to collapse on November 7, 1940. Initially, 35 mile per hour winds excited the bridge’s transverse vibration mode,… Read more
Method 1 Secondary & Component loads can be specified in the form of a Mass-Acceleration curve as described in: NASA-STD-5002, Paragraphs 4.2.1.2, 5.3.2, 5.4. The Mass-Acceleration curve can be derived from measured flight or test data, or analytical loads. Care must be taken to avoid… Read more
NASA-STD-5002, Load Analyses of Spacecraft and Payloads, 1996 5.3.2 Transient load analysis (excerpt) Statistical variation of parameters governing the forcing functions is accommodated by generating multiple cases of forcing functions for a single flight event. After all cases are analyzed, the maximum transient load is… Read more
PowerPoint File: webinar_17_SDOF_force.pptx Audio/Visual File: NESC Academy SDOF – Response to Applied Force – Recommend viewing in Firefox with Sliverlight plugin * * * Reference Papers: T. Irvine, Machine Mounting for Vibration Attenuation, Rev B, Vibrationdata, 2000 link Bruel & Kjaer Booklets: Mobility Measurement link Modal… Read more
Here is a paper which gives a derivation of the equations of motion: semidefinite_force.pdf It also covers the transfer functions which can be calculated if the rigid-body mode is omitted. Here is a Matlab script: semidefinite_force.zip The main script is: semidefinite_force.m The remaining scripts are… Read more
A rocket vehicle behaves as a free-free beam during flight. The vehicle’s body bending modes can be excited by wind gusts, aerodynamic buffeting, thrust offset, maneuvers, etc. The bending motion can interfere with the vehicle’s control system. The guidance, navigation and control algorithms must be… Read more
This post is a work-in-progress… Frequency Response Function based substructuring (FBS) predicts the dynamic behavior of a coupled system on the basis of free interface FRFs of the uncoupled components. Here is a tutorial paper: Frequency Response Function Substructuring Modal damping requires special consideration: Notes on… Read more
The Newmark-beta method can be used to solve structural dynamics problems in the time domain, of the form: M (d^2x/dt^2) + C dx/dt + K x = F This method performs direct integration on the mass, damping and stiffness matrices which may be fully-coupled. Here… Read more