Brick Elements: Bubble Modes

Description

Incompatible displacement modes (so-called bubble modes) are introduced into the 8-node hexahedral brick element to improve its performance. They are also introduced into the 4-node plane stress and plane strain elements for the same reason.

A special integration scheme is used to ensure that the resulting element passes the patch test. The patch test states that when a displacement field that gives a state of arbitrary constant strain is applied to the patch, all the elements within the patch should produce that same state of constant strain.

The bubble modes are not used in analysis with the following materials:

• Nonlinear elasto-plastic material.
• Nonlinear material with creep.
• Nonlinear soil materials. Note that bubble modes are included for Linear Elastic Soil material.

See Also

• Entities: Brick Elements
• Global: Plate Properties
• Global: Brick Properties