Search results
Results From The WOW.Com Content Network
The blades are excited using three mechanical shakers and the response is measured using 12 accelerometers mounted to Blade 3; in the next stage of the test, the accelerometers can be moved to Blade 2 and 3 to measure response at those locations. [1] Modal analysis is the study of the dynamic properties of systems in the frequency domain.
The goal of modal analysis in structural mechanics is to determine the natural mode shapes and frequencies of an object or structure during free vibration.It is common to use the finite element method (FEM) to perform this analysis because, like other calculations using the FEM, the object being analyzed can have arbitrary shape and the results of the calculations are acceptable.
Modal impact hammer with interchangeable tips and accompanying temporal and frequency responses An ideal impact to a structure is a perfect impulse, which has an infinitely small duration, causing a constant amplitude in the frequency domain; this would result in all modes of vibration being excited with equal energy.
The formula for the variation around the mode (ModVR) is derived as follows: = = where f m is the modal frequency, K is the number of categories and f i is the frequency of the i th group. This can be simplified to = where N is the total size of the sample.
A modal analysis calculates the frequency modes or natural frequencies of a given system, but not necessarily its full-time history response to a given input. The natural frequency of a system is dependent only on the stiffness of the structure and the mass which participates with the structure (including self-weight). It is not dependent on ...
The normal or dominant mode of a system with multiple modes will be the mode storing the minimum amount of energy for a given amplitude of the modal variable, or, equivalently, for a given stored amount of energy, the dominant mode will be the mode imposing the maximum amplitude of the modal variable.
A molecular vibration is a periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. The typical vibrational frequencies range from less than 10 13 Hz to approximately 10 14 Hz, corresponding to wavenumbers of approximately 300 to 3000 cm −1 and wavelengths of approximately 30 to 3 μm.
In fiber optics, mode volume is the number of bound modes that an optical fiber is capable of supporting. [11]The mode volume M is approximately given by and (+), respectively for step-index and power-law index profile fibers, where g is the profile parameter, and V is the normalized frequency, which must be greater than 5 for this approximation to be valid.