Question

3. What is Modal Analysis? What are the most widely used methods for performing modal testing? (3 points) gven fundamental frequencies and the associated mode shapes (2 points) TO 20 30 40 50 Frequency (Hz)

Answer 1

A modal or natural frequency analysis forms the basis of several other dynamic analyses, including the modal approach formulations and response spectrum analysis. In addition, the results of a modal analysis will tell you much about the dynamic characteristics of the model, including whether or not you really have a dynamic system at all. For this reason, analysts often run a normal modes analysis first to examine the basic model dynamics and to check for modeling problems.The results of this analysis produces a mode shape and frequency. Note that the output mode shape is an eigenvector with the maximum value set to 1.0. Thus, the resulting deformations are scaled such that the largest deformation within the structure is 1.0 and is not representative of the scale of the deformations expected during actual vibrations.Modal analysis can include constraints or not. Models run without constraints should have their first 6 vibration frequencies of essentially 0 since it's a "free" mode. Partially constrained models will have less than 6 "free" modes.A harmonic of such a wave is a wave with a frequency that is a positive integer multiple of the frequency of the original wave, known as the fundamental frequency.