A Program in Basic to Calculate Electronic Box Moment of Inertia
For a preliminary dynamic analysis of a complex electronic chassis it is often assumed as a beam with relatively constant cross-section. With this approach, many weak points can be revealed in the initial design. Design changes can then be incorporated early in the program. The moment of inertia of the cross-section along the X and Y axis will be needed for determining the resonant frequency for vibration along the Y-axis and the X-axis. Also dynamic loads, deflections stresses can be determined. The chassis cross-section is broken into elements. The neutral axis of the whole section is first found. Each element has a moment of inertia about its own centroid or center of gravity. In addition, there is a much greater moment of inertia for each element because of the distance of its center of gravity to the neutral axis of the whole section. This moment of inertia is equal to the area of the element multiplied by the distance of its C.G. to the neutral axis squared.
Thus, the moment of inertia of the entire section about its neutral axis equals the summation of the two moments of inertia of the individual elements. This along the Y-axis and the Xaxis. If there are many elements in the chassis cross-section, this process becomes very tedious. A program written in Basic, using Apple lie simplifies this process. This is an interactive program, which asks the user questions for input data about the chassis cross-section, then it tabulates the input data followed by the results.
KeywordsEpoxy Beach Flange Fiberglass
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- 1.Steinberg, Dave S., “Vibration analysis for electronic equipment”, John Wiley and sons, Inc. 1973, P. 323–325.Google Scholar