DC:21.1 FINITE ELEMENT ANALYSIS (FEA)

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Why?: When we have to find an effect (stress, strain, flux, etc) which is distributed throughout a volume, and is too difficult to calculate by hand.

How: Break a part into discrete chunks (elements), Apply driving functions, constraints, etc., then solve for physical effects.

Elements

- different types of elements may be used in a FEM mesh

- elements that are too deformed will yield poorer results

- if a field variable will be subject to a large change over an area, then smaller elements should be used to improve the approximation.

CAD systems will often allow a user to manually, and automatically mesh a part.

Generative meshing algorithms will

- mesh a part roughly,

- solve the problem using the rough mesh,

- identify elements with large errors,

- reduce the element sizes in the critical areas,

- resolve the problem to obtain a more accurate result.

Errors of 10% or more are easy to get using FEA systems. Care must be taken when examining results.

Boundary conditions used in FEA systems include,

- x, y, and/or z positions fixed

- x, y, and/or z axis rotations fixed.

- applied force

- applied moment

Automeshing

- Still a research topic, and many various methods are available

- Generally the computer breaks geometry into subsections

********* Include Automeshing figure

********* Include Ideas FEM notes

********** Include my FEM notes