Specifying Leaflet Constraints and Loads

In addition to the two constraints already present within the starting simulation, a further rigid contact constraint and pressure load must be defined.

The rigid contact constraint is set up to prevent the leaflet material from deforming past the second symmetry plane defined on the Y-Z plane of the ContactPlane coordinate system. To do this the rigid contact constraint is applied along the surface normal of the contact plane.

The load segment defines the pressure load experienced by the inner surface of the leaflet material using interpolated values that come from a .csv file that you import into the simulation.

To create the contact constraint:

Right-click the Regions > Leaflet > Segments node and select Create Segment > Surface Segment.
Rename the Surface Segment 1 node to Contact.

Select the Contact node and set the following properties:


Properties	Value
Surfaces	Parts > Leaflet > Surfaces > Inner
Type	Constraint

Select the Contact > Physics Conditions > Solid Stress Constraints node and set Method to Rigid Contact.

Edit the Physics Values node and set the following properties:


Node	Properties	Value
Penalty Contact Enforcement	Penalty Parameter	1.0E12 Pa/m
Rigid contact plane	Normal	[0.0, 0.0, 1.0]
Rigid contact plane	Coordinate System	Laboratory > ContactPlane

To define the pressure load over time:

In the simulation tree, right-click the Tools > Tables node and select New Table > File Table.
In the Open window, navigate to the solidStress folder of the downloaded tutorial files, select PressureOverTime.csv and click Open.
Right-click the Reports node and select New > User > Expression.
Rename the Expression 1 node to PressureBC.

Select the PressureBC node and set the following properties:


Properties	Value
Definition	interpolateTable(@Table("PressureOverTime"), "Time [s]", SPLINE, "Pressure [Pa]", ${CycleTimeReport})
Dimensions	Pressure

The interpolateTable definition used for the PressureBC report takes the value defined in the CycleTime report and interpolates the PressureOverTime table, using a spline interpolation method. This enable you to find the corresponding pressure value for that specific point in time.

To define the pressure load on the outer surface of the leaflet:

Within the Regions > Leaflet node, right-click the Segments node and select Create Segment > Surface Segment.
Rename the Surface Segment 1 node to Pressure.
Select the Pressure node and set Surfaces to Parts > Leaflet > Surfaces > Outer.

Select the Pressure > Physics Conditions > Solid Stress Loads node and set the following properties:


Node	Property	Setting
Solid Stress Loads	Method	Pressure
Surface Load Linearization	Linearize Load	Activated

Expand the Physics Values > Pressure node and set Value to ${PressureBCReport}.

To define the motion of the solid region:
1. Right-click the Tools > Motions node and select New > Solid Displacement.
2. Select the Regions > Leaflet > Physics Values > Motion Specification node and set Motion to Solid Displacement.
The solid displacement motion allows for the mesh to deform as the displacement is computed in response to the applied pressure load.