cylindrical coordinate system

[VCaiwei]

I'm sorry to bother everyone. I have searched on the Internet and in the sofa documentation, but I couldn't find it. Is there a way to set up a cylindrical coordinate system? I want to apply a displacement boundary condition along the radial direction in the cylindrical coordinate system using .

[bakpaul]

Hello !

You didn't finish your sentence, so I don't know what you want to use, is it springs, projective contraints or Lagrangian constraints ?

Anyway, what you want to do look alot like a rotationnal boundary condition. You can do such thing with either of the mechanism mentionned above.

[VCaiwei]

Oh, I'm very sorry!
In fact, I want to run a finite element simulation related to transcatheter aortic valve stents. Figure 1 shows my stent, which is a super-elastic Nitinol memory alloy.

Fig.1

Specifically, first compress the stent as shown in Figure 2, and then release it in the aortic model. This way, the situation of stent release in a real clinical patient can be simulated, as shown in Figure 3.

Fig.2

Fig.3

However, when attempting in SOFA, I found that I encountered difficulties when compressing the stent into the catheter (or simply compressing it into a long strip) : I first take the surface pressure < SurfacePressureForceField >, impose method to the inward force on it, but I want to support doesn't compress to form, as shown in figure 4, the code I listed last.

Fig.4

I referred to the simulation we ran in ABAQUS before and adopted the method of applying displacement boundary conditions in a certain direction to the model to compress it. So I went and found the constraint
< PartialFixedProjectiveConstraint >
and
< LinearMovementProjectiveConstraint indices>

However, they can only set displacements in the x, y, and z directions, the compression I want in the cylindrical coordinate system along the radial direction inward.
I'm very confused about this. Are there any other ideas?

My code:

<?xml version="1.0" ?>
<Node name="root" dt="0.01" gravity="0 -9.81 0">

    <!-- 加载插件 -->
    <!--<RequiredPlugin name="Shell"/>-->
    <RequiredPlugin name="Sofa.Component.Collision.Detection.Algorithm"/> <!-- Needed to use components [BVHNarrowPhase BruteForceBroadPhase CollisionPipeline] -->
    <RequiredPlugin name="Sofa.Component.Collision.Detection.Intersection"/> <!-- Needed to use components [MinProximityIntersection] -->
    <RequiredPlugin name="Sofa.Component.Collision.Geometry"/> <!-- Needed to use components [TriangleCollisionModel] -->
    <RequiredPlugin name="Sofa.Component.Collision.Response.Contact"/> <!-- Needed to use components [CollisionResponse] -->
    <RequiredPlugin name="Sofa.Component.IO.Mesh"/>
    <RequiredPlugin name="Sofa.Component.StateContainer"/>
    <RequiredPlugin name="Sofa.Component.Topology.Container.Dynamic"/>
    <RequiredPlugin name="Sofa.GL.Component.Rendering3D"/>
    <RequiredPlugin name="Sofa.Component.SceneUtility"/>
    <RequiredPlugin name="Sofa.Component.Topology.Mapping"/>
    <RequiredPlugin name="Sofa.Component.Visual"/>
    <RequiredPlugin name="Sofa.Component.LinearSolver.Iterative"/>
    <RequiredPlugin name="Sofa.Component.ODESolver.Backward"/>
    <RequiredPlugin name="Sofa.Component.SolidMechanics.FEM.Elastic"/>
    <RequiredPlugin name="Sofa.Component.Mass"/> 
    <RequiredPlugin name="Sofa.Component.MechanicalLoad"/> <!-- Needed to use components [TrianglePressureForceField] --> 
    <RequiredPlugin name="Sofa.Component.Constraint.Projective"/> <!-- Needed to use components [FixedProjectiveConstraint] --> 
    <RequiredPlugin name="Sofa.Component.Engine.Select"/>


    <VisualStyle displayFlags="showBehavior " />
    <CollisionPipeline verbose="0" />
    <BruteForceBroadPhase/>
    <BVHNarrowPhase/>
    <CollisionResponse response="PenalityContactForceField" />
    <MinProximityIntersection name="Proximity" alarmDistance="0.5" contactDistance="0.1" />

    <DefaultAnimationLoop/>


    <MeshGmshLoader name="stent_loader" filename="stent29.msh"/>
    <MeshOBJLoader name="CRI_loader" filename="mesh/cyl1.obj"/>

    <Node name="stent">
        <EulerImplicitSolver name="cg_odesolver" rayleighStiffness="1" rayleighMass="1" />
        <!--<MatrixLinearSystem template="CompressedRowSparseMatrixMat3x3" name="linearSystem"/>
        <CGLinearSolver name="linear_solver" iterations="20" tolerance="1e-8" threshold="1e-12" template="CompressedRowSparseMatrixMat3x3" linearSystem="@linearSystem"/>-->
        <CGLinearSolver name="linear_solver" iterations="25" tolerance="1.0e-9" threshold="1.0e-9"/>
        <TetrahedronSetTopologyContainer name="topo" src="@../stent_loader" printLog="0"/>
        <TetrahedronSetTopologyModifier name="Modifier"/>
        <MechanicalObject name="StentDofs" template="Vec3d" position="@stent_loader.position"/>
        <UniformMass totalMass="1.0"/>
        <TetrahedronFEMForceField name="femForce" template="Vec3d"
        method="large" 
        poissonRatio="0.3" youngModulus="5e4" 
        computeVonMisesStress="1" 
        showVonMisesStressPerNodeColorMap="true"/>   

        <PartialFixedProjectiveConstraint name="partialFixedProjectiveConstraint" indices="2083 2150 2217" fixedDirections="0 1 0" />  <!--1是固定-->
        <!--<DirectionProjectiveConstraint direction="0.5 0.5 0" indices="@StentDofs.indices" drawSize="0.03" />-->

        <Node name="Visu">
            <MeshSTLLoader name="visu_loader" filename="mesh/stent29.stl" handleSeams="1"/>
            <OglModel  name="Visual" src="@visu_loader" color="1.0 1.0 0.5 1.0"/>
            <BarycentricMapping input="@.." output="@Visual" />
        </Node>
<!--超弹性
        <TetrahedronHyperelasticityFEMForceField name="FEM" materialName="ArrudaBoyce" ParameterSet="3448.2759 31034.483"/>
-->

        <Node name="SurfANDCollis">
            <MeshSTLLoader name="loader" filename="mesh/stent29.stl"/>
            <MeshTopology src="@loader"/>
            <MechanicalObject src="@loader" name="CollisModel"/>

            <TriangleCollisionModel group="1" />
            <LineCollisionModel group="1" />
            <PointCollisionModel group="1" />
        <!--            
            <TriangleCollisionModel  selfCollision="1" />
            <LineCollisionModel    selfCollision="1" />
            <PointCollisionModel  selfCollision="1" />
        -->
<!--OR
        <LinearMovementProjectiveConstraint indices="@p1.position" template="Vec3d" keyTimes="0 0.5 1 1.5" movements="
                0 0 0 0 0 0
                -10 0 -10 0 0 0 
                -10 0 -10 0 0 0 
                -10 0 -10 0 0 0 " />-->
                
            <SurfacePressureForceField triangleIndices="1-2834 10109-13157" 
            pressure="-500.0" pulseMode="0" pressureSpeed="20000.0" />
<!--Here I have listed all the nodes, but it is too long, so I have only abbreviated it here-->

            <BarycentricMapping input="@.." output="@." />
        </Node>


        <!--数据导出
        <VTKExporter name="VTKExporter" listening="true" 
            position="StentDofs.position" pointsDataFields="StentDofs.force" 
            filename="D:/SOFA/share/sofa/examples/Demos/output/cube_"  
            edges="1" triangles="1" quads="1" tetras="1" 
            exportEveryNumberOfSteps="10" />-->

    </Node>


</Node>

[hugtalbot]

Hi @VCaiwei

In SOFA you can impose boundary conditions in several ways:

• weak form using springs : RestShapeSpringForceField (the rest shape being any MechanicalObject you want)
• projective using ProjectiveConstraints, AttachProjectiveConstraint between the dofs of your object and the targeted shape
• Lagrangian multipliers when you could define BilateralInteractionConstraint between the dofs of your object and the targeted shape

I hope this helps

[github-actions[bot]]

⚠️ ⚠️ ⚠️
@VCaiwei
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding

[github-actions[bot]]

⚠️ ⚠️ ⚠️
@VCaiwei
In accordance with our forum management policy, the last reply is more than 4 months old and is therefore closed. Our objective is to keep the forum up to date and offer the best support experience.

Please feel free to reopen it if the topic is still active by providing us with an update. Please feel free to open a new thread at any time - we'll be happy to help where and when we can.