admin Maximum predicted environment (MPE) levels can be derived for acoustic, shock, and vibration levels where flight data is available. The enveloping for multiple sets of data can be performed using tolerance factors as described in the following papers. Normal Tolerance Factors for Upper Tolerance Limits:… Read more
Here are some papers: Electronic Circuit Board Design Reliability Lessons Learned: electronics_design_reliability.pdf Effect of Conformal Coating on Circuit Board Vibration Response: conformal_coat.pdf * * * Steinberg’s Vibration Analysis for Electronic Equipment describes the methods for designing electronic equipment that must work with a high degree of… Read more
I have added a function for calculating the free vibration response of an SDOF system to initial conditions to the Vibrationdata GUI package. Matlab script: Vibrationdata Signal Analysis Package >> vibrationdata > Miscellaneous > Structural Dynamics > Spring-Mass Systems > SDOF Free Vibration Response to… Read more
I am currently researching IEEE Std 693… One of its recommended shaker test methods for power equipment is to use a “sine beat” acceleration time history. The main frequency is selected as the equipment’s natural frequency. The minimum number of beats is 5 with a… Read more
A function for calculating cylindrical shell natural frequencies via the wave method is now included in the Vibrationdata GUI package. Matlab script: Vibrationdata Signal Analysis Package This function may be accessed via: vibrationdata > Structural Dynamics > Rings & Cylinders > Cylinder, Wave Model Reference… Read more
The following is mostly an academic problem. The Response of an Undamped Two-degree-of-freedom System Subjected to Base Displacement via Modal Analysis: twodof_base_disp_modal.pdf The Response of an Undamped Two-degree-of-freedom System Subjected to Base Displacement via Laplace Transforms: twodof_base_disp_Laplace.pdf * * * See also: Two-degree-of-freedom Systems – Tom… Read more
Sloshing can occur in swimming pools, trucks carrying liquids, rocket vehicle propellant tanks and in other situations. Sloshing of propellants may adversely affect the stability of a space vehicle and the integrity of the tank structure. Sloshing describes the free-surface oscillations of fluid in a… Read more
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