Harmonic - CAESAR II - Help

CAESAR II Users Guide

Language
Русский
Product
CAESAR II
Search by Category
Help
CAESAR II Version
12

For each forcing frequency listed in the dynamic input, CAESAR II performs a separate analysis. These analyses are similar to static analyses and take the same amount of time to complete. At the completion of each solution, the forcing frequency, its largest calculated deflection, and the phase angle associated with it are listed. The root results for each frequency, and the system deflections, are saved for further processing. Only twenty frequencies may be carried beyond this point and into the output processor. When all frequencies are analyzed, the software presents the frequencies. You can then select the frequencies and phase angles needed for further analysis. This choice can be made after checking deflections at pertinent nodes for those frequencies.

Selecting Phase Angles

Phased solutions are generated when damping is considered or when you enter phase angles in the dynamic input.

For all phased harmonic analyses, you can select separate phase angle solutions, including the cycle maxima and minima, for each excitation frequency. Each separate phase angle solution represents a point in time during one complete cycle of the system response. For a solution without phase angles, you know when the maximum stresses, forces, and displacements occur. When phase angles are entered, you do not know when the maximum stresses, forces, and displacements are going to occur during the cycle. For this reason, the displacements and stresses are often checked for a number of points during the cycle for each excitation frequency. You must select these points interactively when the harmonic solution ends.

There is a complete displacement, force, moment, and stress solution for each frequency/phase selected for output. You have the option of letting the software select the frequency/phase pairs offering the largest displacements on a system basis. The largest displacement solution usually represents the largest stress solution, but this is not always guaranteed. The displaced shapes for the remaining frequencies are processed like static cases, with local force, moment, and stress calculations. Control then shifts to the Dynamic Output Processor, which provides an animated display of the harmonic results.

All harmonic results are amplitudes. For example, if a harmonic stress is reported as 15,200 psi, then the stress due to the dynamic load, which is superimposed onto any steady state component of the stress, can be expected to vary between +15,200 psi and -15,200 psi. The total stress range due to this particular dynamic loading is 30,400 psi.