Modal analysis using FEM: Difference between revisions

Revision as of 11:54, 6 July 2016

Revision as of 00:13, 7 August 2018

Line 6:

It is also possible to test a physical object to determine its natural frequencies and mode shapes. This is called an [[modal analysis|Experimental Modal Analysis]]. The results of the physical test can be used to calibrate a finite element model to determine if the underlying assumptions made were correct (for example, correct material properties and boundary conditions were used).

== FEA eigensystems ==

For the most basic problem involving a linear elastic material which obeys [[Hooke's Law]],

Line 46:

which is expected when all terms having a time derivative are set to zero.

=== Comparison to linear algebra ===

In [[linear algebra]], it is more common to see the standard form of an eigensystem which is

Line 56:

multiplied through by the inverse of the mass,

<math> [M]^{-1} </math>,

it will take the form of the latter.<ref>Thomson, William T., '' Theory of Vibration with Applications'', 3rd Ed., Prentice-Hall Inc., Englewood Cliffs, 1988, page 165</ref>

Applications'', 3rd Ed., Prentice-Hall Inc., Englewood Cliffs, 1988, page 165</ref>

Because the lower modes are desired, solving the system

more likely involves the equivalent of multiplying through by the inverse of the stiffness,

Line 85 ⟶ 84:

{{Reflist}}

== External links ==

*[http://frame3dd.sourceforge.net/ Frame3DD open source 3D structural modal analysis program]