Contact couldn't be detected between 2 beams

[Hoangn06]

Hello everyone,

I'm testing a contact between beams. So 2 beams was created like this photo:

The two ends of the lower beam were fixed, and I applied a linear force to the two ends of the upper beam to pull it downward and cause it to collide with the lower beam with this script:

</Node>

<DefaultAnimationLoop computeBoundingBox="false"/>
<VisualStyle displayFlags="showForceFields" />
<MeshGmshLoader name="meshLoaderWeb" filename="maillage_2_fils.msh" />

<CollisionPipeline />
<BruteForceBroadPhase/>
<BVHNarrowPhase/>
<MinProximityIntersection name="Proximity" alarmDistance="0.5" contactDistance="0"/>
<CollisionResponse name="Response" response="PenalityContactForceField"/>

<Node name="2 fils">
    <EulerImplicitSolver />
    <CGLinearSolver iterations="200" tolerance="1e-09" threshold="1e-09"/>
    <EdgeSetTopologyContainer name="topo" src="@../meshLoaderWeb" />
    <EdgeSetGeometryAlgorithms template="Rigid3d" name="GeoWeb" drawEdges="true"/>

    <MechanicalObject template="Rigid3d" name="WebModel" showObject="1" showObjectScale="3" />
    <UniformMass name="mass" totalMass="1" />

    <BeamFEMForceField name="beamFF" radius="0.0001" radiusInner="0" template="Rigid3d" youngModulus="5000" poissonRatio="0.3" />
    <FixedProjectiveConstraint indices="0 63" />
    <LinearForceField points="64 127 " forces="0 0 0 0 0 0       0 -0.2 0 0 0 0  " times="0 5" />   
            
            <Node name="Collision">
              <MechanicalObject />
              <IdentityMapping  />
              <LineCollisionModel  />
            </Node>

</Node> 

But the contact couldn't be detected and the upper beam just go through the lower beam. Can anyone please help to solve this problem?

Thank you in advance.

[Hoangn06]

Hello,

Does someone know how to solve this problem..?

Thank you

[hugtalbot]

Hi @Hoangn06

Here you simulate the two beams within the same node, as a single MechanicalObject therefore as a single object.
You need to split your beams into two objects.

You can watch the online tutorials where we explain these principles.

[Hoangn06]

Hi @hugtalbot,

I understand. I'm testing this because the purpose of my study to simulate about 30-60 beams that collide with each other.

Is there a way to accelerate the import and setup for that many beams, or do I have to do it manually for each beam which will cost a lot of times to set up..?

Thank you

[bakpaul]

You could script that using Python scene description instead of xml. Then generating multiple beam shouldn't be an issue.

[Hoangn06]

Hello @bakpaul,

I have gmsh files for all the beams. Can I put all the files into a folder and than create a python function that import/declare MechanicalObject/declare ForceField/declare Collision for each beam in the folder?
Thank you!

[Hoangn06]

Hello @hugtalbot, @bakpaul,

I've create now 2 objects:

<Node name="plugins">
    <RequiredPlugin name="Sofa.Component.IO.Mesh"/> <!-- Needed to use components [MeshGmshLoader] -->  
    <RequiredPlugin name="Sofa.Component.LinearSolver.Iterative"/> <!-- Needed to use components [CGLinearSolver] -->  
    <RequiredPlugin name="Sofa.Component.Mass"/> <!-- Needed to use components [MeshMatrixMass] -->  
    <RequiredPlugin name="Sofa.Component.MechanicalLoad"/> <!-- Needed to use components [ConstantForceField] -->
    <RequiredPlugin name="Sofa.Component.StateContainer"/> <!-- Needed to use components [MechanicalObject] -->  
    <RequiredPlugin name="Sofa.Component.ODESolver.Backward"/> <!-- Needed to use components [EulerImplicitSolver] -->  
    <RequiredPlugin name="Sofa.Component.SolidMechanics.FEM.Elastic"/> <!-- Needed to use components [TetrahedronFEMForceField] -->  
    <RequiredPlugin name="Sofa.Component.Topology.Container.Dynamic"/> <!-- Needed to use components [TetrahedronSetGeometryAlgorithms, TetrahedronSetTopologyContainer] -->  
    <RequiredPlugin name="Sofa.Component.Visual"/> <!-- Needed to use components [VisualStyle] -->  
    <RequiredPlugin name="Sofa.GL.Component.Rendering3D"/> <!-- Needed to use components [OglModel] -->  
    <RequiredPlugin name="Sofa.Component.Constraint.Projective"/> <!-- Needed to use components [FixedProjectiveConstraint] -->  
    <RequiredPlugin name="Sofa.Component.Topology.Container.Constant"/> <!-- Needed to use components [MeshTopology] -->  
    <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 [LineCollisionModel] -->  
    <RequiredPlugin name="Sofa.Component.Collision.Response.Contact"/> <!-- Needed to use components [CollisionResponse] -->  
    <RequiredPlugin name="Sofa.Component.Mapping.Linear"/> <!-- Needed to use components [IdentityMapping] -->  

</Node>

<DefaultAnimationLoop computeBoundingBox="false"/>
<VisualStyle displayFlags="showForceFields" />
<MeshGmshLoader name="meshLoaderFil1" filename="fil_1.msh" />
<MeshGmshLoader name="meshLoaderFil2" filename="fil_2.msh" />

<CollisionPipeline />
<BruteForceBroadPhase/>
<BVHNarrowPhase/>
<MinProximityIntersection name="Proximity" alarmDistance="0.5" contactDistance="0"/>
<CollisionResponse name="Response" response="PenalityContactForceField"/>

<Node name="fil_1">
    <EulerImplicitSolver />
    <CGLinearSolver iterations="200" tolerance="1e-09" threshold="1e-09"/>
    <EdgeSetTopologyContainer name="topo" src="@../meshLoaderFil1" />
    <EdgeSetGeometryAlgorithms template="Rigid3d" name="GeoWeb" drawEdges="true"/>

    <MechanicalObject template="Rigid3d" name="WebModel" showObject="1" showObjectScale="3" />
    <UniformMass name="mass" totalMass="1" />

    <BeamFEMForceField name="beamFF" radius="0.00001" radiusInner="0" template="Rigid3d" youngModulus="5000" poissonRatio="0.3" />
    <FixedProjectiveConstraint indices="0 63" />                
            <Node name="Collision">
              <MechanicalObject />
              <IdentityMapping  />
              <LineCollisionModel  />
            </Node>


</Node> 


<Node name="fil_2">
    <EulerImplicitSolver />
    <CGLinearSolver iterations="200" tolerance="1e-09" threshold="1e-09"/>
    <EdgeSetTopologyContainer name="topo" src="@../meshLoaderFil2" />
    <EdgeSetGeometryAlgorithms template="Rigid3d" name="GeoWeb" drawEdges="true"/>

    <MechanicalObject template="Rigid3d" name="WebModel" showObject="1" showObjectScale="3" />
    <UniformMass name="mass" totalMass="1" />

    <BeamFEMForceField name="beamFF" radius="0.00001" radiusInner="0" template="Rigid3d" youngModulus="5000" poissonRatio="0.3" />
    <LinearForceField points="0 63 " forces="0 0 0 0 0 0       0 -0.2 0 0 0 0  " times="0 5" />   
    
            <Node name="Collision">
              <MechanicalObject />
              <IdentityMapping  />
              <LineCollisionModel  />
            </Node>


</Node> 

The problem right now when I launch the simulation: I received non-stop the error:

[MinProximityIntersection(Proximity)] Null distance between contact detected

My 2 beams disappeared totally and everything on my computer turned so slow. Can you please help me on this problem?

For information I created each beam with the length of 2e-3 with Python.
And if you want to test out the simulation. You can find the 2 mesh files and the simulation scn in the Drive in here: https://drive.google.com/drive/folders/10mTxqnopmDWp9XwhVaeLkIpDqUQoVMET?usp=sharing

[hugtalbot]

Hi @Hoangn06

You should make sure that the two beams are not in contact at start.

[Hoangn06]

Hi @hugtalbot

The 2 beams are not in contact at the configuration:

Am I doing something wrong here?

[hugtalbot]

Your meshes seem to have an issue too @Hoangn06

[Hoangn06]

Here in closed view of the mesh:

Right now, there are 200 elements per beam... what is the issue are you talking about? @hugtalbot

[Hoangn06]

Hello,

I discover why the beams disappeared. I let the Young modulus and the mass super small ( a little confusion about the unit of simulation ).

Right now, the simulation works ok but the problem is the simulation couldn't detect the contact between 2 beams. Actually it shows in the interface that there is LineCollision but the upper beam just go right through the lower beam:

The new script xml:

version="1.0" ?>

<Node name="plugins">
    <RequiredPlugin name="Sofa.Component.IO.Mesh"/> <!-- Needed to use components [MeshGmshLoader] -->  
    <RequiredPlugin name="Sofa.Component.LinearSolver.Iterative"/> <!-- Needed to use components [CGLinearSolver] -->  
    <RequiredPlugin name="Sofa.Component.Mass"/> <!-- Needed to use components [MeshMatrixMass] -->  
    <RequiredPlugin name="Sofa.Component.MechanicalLoad"/> <!-- Needed to use components [ConstantForceField] -->
    <RequiredPlugin name="Sofa.Component.StateContainer"/> <!-- Needed to use components [MechanicalObject] -->  
    <RequiredPlugin name="Sofa.Component.ODESolver.Backward"/> <!-- Needed to use components [EulerImplicitSolver] -->  
    <RequiredPlugin name="Sofa.Component.SolidMechanics.FEM.Elastic"/> <!-- Needed to use components [TetrahedronFEMForceField] -->  
    <RequiredPlugin name="Sofa.Component.Topology.Container.Dynamic"/> <!-- Needed to use components [TetrahedronSetGeometryAlgorithms, TetrahedronSetTopologyContainer] -->  
    <RequiredPlugin name="Sofa.Component.Visual"/> <!-- Needed to use components [VisualStyle] -->  
    <RequiredPlugin name="Sofa.GL.Component.Rendering3D"/> <!-- Needed to use components [OglModel] -->  
    <RequiredPlugin name="Sofa.Component.Constraint.Projective"/> <!-- Needed to use components [FixedProjectiveConstraint] -->  
    <RequiredPlugin name="Sofa.Component.Topology.Container.Constant"/> <!-- Needed to use components [MeshTopology] -->  
    <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 [LineCollisionModel] -->  
    <RequiredPlugin name="Sofa.Component.Collision.Response.Contact"/> <!-- Needed to use components [CollisionResponse] -->  
    <RequiredPlugin name="Sofa.Component.Mapping.Linear"/> <!-- Needed to use components [IdentityMapping] -->  

</Node>

<DefaultAnimationLoop computeBoundingBox="false"/>
<VisualStyle displayFlags="showForceFields" />
<MeshGmshLoader name="meshLoaderFil1" filename="Beams/beam_0.msh" />
<MeshGmshLoader name="meshLoaderFil2" filename="Beams/beam_1.msh" />

<CollisionPipeline />
<BruteForceBroadPhase/>
<BVHNarrowPhase/>
<MinProximityIntersection name="Proximity" alarmDistance="0.5" contactDistance="0"/>
<CollisionResponse name="Response" response="PenalityContactForceField"/>

<Node name="fil_1">
    <EulerImplicitSolver />
    <CGLinearSolver iterations="200" tolerance="1e-09" threshold="1e-09"/>
    <EdgeSetTopologyContainer name="topo" src="@../meshLoaderFil1" />
    <EdgeSetGeometryAlgorithms template="Rigid3d" name="GeoWeb" drawEdges="true"/>

    <MechanicalObject template="Rigid3d" name="WebModel" showObject="1" showObjectScale="3" />
     <UniformMass name="mass" totalMass="6.45e+3" />

    <BeamFEMForceField name="beamFF" radius="2e-5" radiusInner="0" template="Rigid3d" youngModulus="5e+10" poissonRatio="0.3" />
    <FixedProjectiveConstraint indices="0 63" />                
            <Node name="Collision">
              <MechanicalObject />
              <IdentityMapping  />
              <LineCollisionModel  />
            </Node>

</Node> 

<Node name="fil_2">
    <EulerImplicitSolver />
    <CGLinearSolver iterations="200" tolerance="1e-09" threshold="1e-09"/>
    <EdgeSetTopologyContainer name="topo" src="@../meshLoaderFil2" />
    <EdgeSetGeometryAlgorithms template="Rigid3d" name="GeoWeb" drawEdges="true"/>

    <MechanicalObject template="Rigid3d" name="WebModel" showObject="1" showObjectScale="3" />
    <UniformMass name="mass" totalMass="6.45e+3" />

    <BeamFEMForceField name="beamFF" radius="2e-5" radiusInner="0" template="Rigid3d" youngModulus="5e+10" poissonRatio="0.3" />
    <LinearForceField points="0 63 " forces="0 0 0 0 0 0       0 -0.2 0 0 0 0  " times="0 5" />   

            <Node name="Collision">
              <MechanicalObject />
              <IdentityMapping  />
              <LineCollisionModel  />
            </Node>


</Node> 

Can someone help me with this?
Thank you!