Options for including mean stress have been added to the Vibrationdata GUI package’s Fatigue Toolbox, for both stress time histories and PSDs. Four methods are available: Gerber Goodman Morrow Soderberg Matlab script: Vibrationdata Signal Analysis Package Here are some charts from Iowa State University: Fatigue… Read more
A typical SRS specification has a ramp and plateau. The best way to meet this specification type is with a complex oscillating pulse. In some cases, a classical shock pulse may be used, but this will cause an over-test at certain frequencies. Also, classical pulses… Read more
In some cases, the sampling rate of measured data needs to be increased, particularly for time domain analysis. One method is do a cubic spline curve-fit. This is an “engineering judgment” process with some limitations. The “Input Data” in the figure above is a 12… Read more
GTCP85-98D APU The APU is a small gas turbine engine which is normally located in the tail cone of the aircraft but, in some cases, is located in an engine nacelle or in the wheel well. The APU can be started utilizing only the aircraft… Read more
Here is series of course units that I have developed for circuit board analysis: Circuit_Board_Slides (The zip file can be downloaded using the icon with the downward pointing arrow.) The corresponding Matlab software allows for the creation of finite element models for rectangular boards. The… Read more
Here is letter that I recently send to some of my colleagues… We have been discussing establishing a database of shock data both for characterizing source shock levels and attenuation through material distance and joints. We have also discussed sharing attenuation curves if the… Read more
I have added a feature for rectangular plate bending modes to the Matlab GUI package. Matlab script: Vibrationdata Signal Analysis Package The script allows for the addition of point masses and point constraints. This is a work-in-progress. The next step will be to add base… Read more
I have added a feature for a two-degree-of-freedom system subjected to an applied force to the Matlab GUI package. The applied force options are steady-state sine, arbitrary time history and PSD. Matlab script: Vibrationdata Signal Analysis Package The new feature can be accessed via: Vibrationdata… Read more
There is a need in certain analysis problems to correct an acceleration signal so that its integrated velocity and double integrated displacement each oscillates about its respective zero baseline. This may require using high pass filtering, trend removal and tapering throughout the integration process. Trial-and-error… Read more
I recently flew as a passenger on a Boeing 717-200 aircraft similar to the one shown in the image. This aircraft has two Rolls-Royce BR700 engines, with the following specifications: Maximum Engine Rotational Speeds (Both Engines) N1 Low Pressure Turbine = 6,195 RPM (103 Hz) N2… Read more