Home / Examples / Stress Analysis [Galileo] / Example 22: Blocks Set with Discontinuous Boundary

Example 22: Blocks Set with Discontinuous Boundary

General

The [discontinuous] boundary condition is studied in this example. The model consists of two blocks in contact with each other.
The bodies in contact are usually considered to be fixed.
The bodies will never separate through the pulling force caused by mechanical loads. By setting the discontinuous boundary condition on the contacting face, the bodies in contact can separate.
The deformation, the displacement distribution, and the stress distribution are solved.
Unless specified in the list below, the default conditions will be applied.

Results will vary depending on Femtet version and the PC environment.

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

Analysis Conditions

Item	Settings
Solver	Stress Analysis [Galileo]
Analysis Type	Static Analysis
Options	N/A

Model

The two bodies are made of polyethylene.

The bottom faces of the bodies are fixed and one body is pulled outward. The pulling force is applied on an edge of the body.

The discontinuous boundary condition is set on the contacting face of the two bodies.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	BLOCK	000_Polyethylene(PE) *
1/Solid	BLOCK	000_Polyethylene(PE) *

* Available from the material DB

Boundary Conditions

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
FIX/Face	Mechanical	Displacement	UX=0, UY=0, UZ=0
NONCONT/Face	Symmetry/Continuity	Discontinuous	Select [Discontinuous]
PULL/Edge	Mechanical	Distributed Edge Load	X=1,Y=Z=0 [N/m]

Results

The contour diagram shows the magnitude of displacement.

The face on which the discontinuous boundary condition is set is treated as two independent faces. Therefore the two bodies are separated by a gap.

For comparison, the model with the continuous boundary condition is analyzed.

If the continuous boundary condition is set on it, the two bodies remain in contact and deform simultaneously as shown below.

NOTE

In this example, one of the bodies is pulled outward and it bends away from the other.

If the force is applied inward, one of the bodies will bend towards the other, and get into it as if it does not exist, which causes the wrong result. In such a case, simple contact should be used.

The simple contact boundary condition with off-contact can be used the same as the discontinuous boundary condition. Please note, however, that the calculation time of the simple contact boundary condition is longer than that of the discontinuous boundary condition.