I recently flew from Spokane to Seattle, Washington on an Alaska/Horizon Air Bombardier Q400 aircraft, similar to the one in the above image. This model aircraft has two Pratt & Whitney Canada PW150A turboprop engines. I captured the following video during cruise using a Motorola/Android… Read more
Here is a paper for… Extending Steinberg’s Fatigue Analysis of Electronics Equipment Methodology to a Full Relative Displacement vs. Cycles Curve electronic_rd_n.pdf extending_Steinberg.pptx This paper also shows in a very roundabout way that “fatigue damage equivalence” between sine and random vibration occurs when the sine… Read more
This Matlab script calculates the one-sided, full amplitude FFT of an acceleration time history: FFT_VD.zip It gives the output FFTs in acceleration, velocity and displacement formats. It is useful for evaluating machine and pump vibration where there are distinct sine tones and harmonics. The main… Read more
Please see the following update: MDOF Frequency Response Function Natural Frequency & Damping Extraction including Modal Overlap. Post Link The half-power bandwidth method can be used to estimate the damping ratio and corresponding Q value from the frequency response function of a structure which has… Read more
Here is a good website for curve-fitting: zunzun From the website… Here you can curve fit and surface fit your 2D and 3D data online with a rich set of error histograms, error plots, curve plots, surface plots, contour plots, VRML, auto-generated source code, and… Read more
This blog entry is a work-in-progress. Fatigue analysis can be performed in the time domain using rainflow cycle counting. This is an elegant, brute-force approach. One advantage of the time domain approach is that it tends to highlight the occurrences of peaks above 3-sigma for… Read more
These Matlab scripts calculate the response of a single-degree-of-freedom system to base excitation: sdof_base.zip sdof_base.m is the main script. The remaining scripts are supporting functions. The base excitation may be a half-sine pulse, terminal sawtooth pulse, arbitrary pulse, or a PSD. * * * See… Read more
Functions for calculating the response of a two-degree-of-freedom system to base excitation are given in the Vibrationdata analysis package posted at: Matlab script: Vibrationdata Signal Analysis Package * * * See also: Two-degree-of-freedom Systems * * * – Tom Irvine
Here is a set of scripts that calculate the natural frequencies and mode shapes for a two-degree-of-freedom system. The scripts are posted at: two_dof_system.zip The main script is: two_dof_system.m The remaining scripts are supporting functions. * * * See also: Two-degree-of-freedom Systems – Tom Irvine
The Dunkerely method is used to estimate the lower natural frequency limit for a system of connected subsystems. It complements the Rayleigh method which gives an upper limit estimate. A Matlab script for performing this estimate is given in Dunkerley.zip More later…. – Tom Irvine