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Element Quality Check Criteria in FEA meshing - FEA applications and Tutorials

Quality of the element is very important criteria , in FEA pre-processing. Higher the qulaity of the mesh, we can get reliable results given that you have given perfect boundary conditions.

At the same time, we should also consider the memory limitation of the computers available with us. So , we should optimize the FE model equally considering the cost of the solving and accuracy that is needed.



Understanding Element Quality Checks


Quality checks measure different aspects of an element's deviation from an ideal size and shape. That ideal shape depends upon the element type.You can choose one or more checks and set threshold values, or limits for deviation, for each. You can perform these checks on shell and solid elements.
There are several ways to check your mesh. You can use:
  • Auto Mesh Checking to have the software automatically evaluate aspects of element quality while it generates a mesh
  • Element Quality Checks to set quality threshold values and evaluate element quality once you've generated a mesh
  • The various element quality icons and menu commands, such as Coincident Nodes or Coincident Elements, to run individual quality checks
Once you've identified element quality problems, you can use tools such as Plump or Straighten Edge to fix distorted tetrahedral elements. You can also use the Node or Element menu commands to adjust other elements.
After you've checked the mesh, you can generate statistical data on element quality or create a result set and display the elements in Post Processing. You can also filter the selection of elements from the results of these mesh checks.

Understanding Quality Threshold Values

This table lists the possible threshold values for each type of element and shows how they're calculated. In this table:
  • X = supported by Quality Checks
  • LX = calculations use linearized edges
  • SX = calculations use shape functions
  • LMX = calculations use linearized midside to corner edges
Quality
Check
Threshold1
Threshold2
Quad Shell
Tri Shell
Solid
Linear
Parabolic
Cubic
Skew
(>) 0-360
-
X
X
-
X
SX
SX
Warp
(>) 0-180
-
X
-
-
X
LMX
LMX
Taper
(>) 0-1
-
X
-
-
X
LMX
LMX
Aspect
Ratio
(>) 0-100
-
X
X
X
X
LX
LX
Distortion
(<) 0-1
-
X
X
X
SX
SX
-
Stretch
(<) 0-1
-
X
X
X
X
SX
LX
Jacobian
(<) 0-inf
-
X
X
X
SX
SX

Element
Size
(<) 0-inf
(>) 0-inf
X
X
X
X
LX
LX
Quad Included Angles
(<) 0-90
(>) 90-180
X
X
X
X
SX
SX
Tri Included Angles
(<) 0-60
(>) 60-180
X
X
X
X
SX
SX


Using Automatic Mesh Checking

Nowadays, every pre-processing software comes with automatic mesh checking feature. We can use Auto Mesh Checking to have the software automatically evaluate element quality while it generates a mesh. The Automatic Mesh Checking form lets you specify values for checks such as Distortion and Stretch.

This form also lets you control whether mesh smoothing is turned on for meshes that contain linear or parabolic tetrahedrons. Mesh smoothing improves stretch and distortion.