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Vibration Response Spectrum Page

INTRODUCTION

Mechanical shock pulses are often analyzed in terms of shock response spectra. The shock response spectrum assumes that the shock pulse is applied as a common base input to an array of independent single-degree-of-freedom systems. The shock response spectrum gives the peak response of each system with respect to the natural frequency. Damping is typically fixed at a constant value, such as 5%, which is equivalent to an amplification factor of Q=10.
A similar tool is available for vibration. This tool is the vibration response spectrum. This function gives the root-mean-square response of each system to an acceleration base input. The base input is an acceleration power spectral density.
The vibration response spectrum is particularly suited for random vibration inputs.
The vibration response spectrum has many uses, such as deriving and evaluating test specifications.

This page offers tutorials which explain the vibration response spectrum, as well as software tools for implementing this function.

 

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 Vibraton Response Spectrum Tutorials

 Introduction to the Vibration Response Spectrum
 vrs.pdf 

Use of the Vibration Response Spectrum to Evaluate Flight Data Compliance with Test Specification Levels

 VRS_case_history.pdf
 Derivation of Miles Equation for Base Excitation
 Miles.pdf
Robert L. Towner, NASA
Practical Approach for Random Load Factors
PowerPoint Presentation, FEA model, and Hand-calculation notes.
RLF.pdf
RandomLoadFactors.pdf
Derivation of Miles Equation for Relative Displacement Response to Base Excitation
 Miles_rel_disp.pdf
 Derivation of Miles Equation for Applied Force
Miles_force.pdf
 Simmons, Miles Equation
 Simmons_MilesEquation.pdf
Application of Miles Equation to Multi-degrees-of-freedom Systems
(Refer to Section 3.2.1.2 of this Document)
 mdof_miles.pdf
Robin Ferebee & Jess Jones, Comparison of Miles' Relationship to the True Mean Square Value of Response for a Single-degree-of-freedom System  Ferebee_Miles.pdf
 Enveloping Data via the Vibration Response Spectrum
 envelope.pdf

Deriving a Random Vibration Maximum Expected Level with Consideration for Kurtosis
envelope_kurtosis.pdf
Optimizing a Circuit Board Natural Frequency with Respect to Random Vibration.

The optimization is achieved using the vibration response spectrum.
 cb_opt_fn.pdf
Equivalent Shock and Vibration Tests for Quasi-static Acceleration
 quasi_static_accel.pdf
Methods for Converting a Power Spectral Density to a Shock Response Spectrum
psd_srs.pdf
Equivalent Static Load for Random Vibration. The static load is taken from the three-sigma vibration response.
eqstatic.pdf
Partial Fractions in Shock and Vibration Analysis
partial.pdf
 

 VRS Software

 Description
  Executable
  Source Code
Vibration response spectrum of a single-degree-of-freedom system subjected to base excitation.
  vrs.exe
  vrs.cpp
VRS for a fixed frequency domain.  This program is useful if the lower and upper natural frequency bounds of the component are known.
 vrs_range.exe
  vrs_range.cpp
Conversion of a shock response spectrum to a power spectral density
New method envelope_srs_psd.exe
Old method
srs_to_psd.exe
New method
envelope_srs_psd.cpp
Old method
srs_to_psd.cpp
Conversion of a vibration response spectrum to a power spectral density.
 vrs_to_psd.exe
vrs_to_psd.cpp 
Vibration response spectrum of an acceleration time history.
th_vrs.exe
th_vrs.cpp
Response of an individual single-degree-of-freedom system to base excitation PSD.
sdof_ran.exe
 sdof_ran.cpp
Response of an individual single-degree-of-freedom system to an applied force PSD.
sdof_ran_force.exe
 sdof_ran_force.cpp
Vibration response spectrum of a single-degree-of-freedom system subjected to an applied force.
vrs_force.exe
vrs_force.cpp
Response of an individual single-degree-of-freedom system to base excitation via Miles equation.
 miles.exe
 miles.cpp
Peak SDOF response from the Rayleigh distribution
peak_response.exe
peak_response.cpp

 

 Matlab Scripts

 Miles Equation for Base Excitation
 Miles.m
 Miles Equation for Applied force
 Miles_force.m
 Vibration Response Spectra Matlab Code
VRS.zip
 
Determine the response of a particular SDOF system to a power spectral density base input 
sdof_ran.zip
 Enveloping Data via the Vibration Response Spectrum

envelope.m

Functions:

env_vrs_best.m
env_interp_best.m
env_generate_sample_psd.m
env_generate_sample_psd2.m
env_compare.m
env_grms_sam.m
env_make_input_vrs.m
env_vrs_sample.m
env_interp_sam.m
env_vrms_sam.m
env_drms_sam.m
env_checklow.m

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