Hi everyone,
I'm pleased to share an interesting Visual Scripting MODSIM study on an Isogrid thrust chamber. The study has also been published on LinkedIn, where you can read more about it here:

https://www.linkedin.com/posts/catia_optimizing-thrust-chamber-design-with-catia-activity-7475789883731681280-ppFr?utm_source=share&utm_medium=member_desktop&rcm=ACoAAC_tjHUBBll-hMuX8fbodSWL5syn7dHj-5M

Context and Objectives 

Propulse NTNU is a student rocketry team at the Norwegian Institute of Science and Technology which gives students hands-on experience with engineering projects. In the context of Project Heimdal, Propulse NTNU developed a thrust chamber which allows to propel the vehicle into the sky. For their architecture they chose to use an isogrid structure which allow to have a stiff and light structure.

Our study will aim to realize the geometry of the thrust chamber made by NTNU using CATIA Visual Scripting and to explore several designs in order to choose the best one according to predefined objectives and constraints. The main goal is to build a robust MSR scenario based a geometry built with CATIA Visual Scripting. 

Video

Design in CATIA Visual Scripting

All the design was done with CATIA Visual Scripting and the design parameters are the following : 

• The number of sections (which drives the density of the isogrid) 
• Holes diameter 
• Isogrid thickness

                                                                                 Number of sections : 16   

                                                                                      Number of sections : 7 

FEM Construction 

For the FEM construction, 2 approaches are possible. The first one is to study the whole model with 3D elements which will have augmented computing times and is less suited for thin structures as the one we are studying. The second approach is to use shell and beam elements which is more relevant for those type of structures. We will study both of these approaches as they are both possible using Visual Scripting. 

3D Mesh :

As the geometry and the loads are symmetric, we will study 1/4 of the model. 

This mesh is a terahedron mesh using TET10 elements with a mesh size of 2.1mm. With those meshing parameters we obtain approximately 100 000 elements (depending on the design). 

 Hybrid mesh (Shell and beams)

The first step is to retrieve the midsurface and the neutral axis for the beams which can be done easily in Visual Scripting.

The shell and beam sections are directly linked to parameters defined in the Visual Scripting Design Sequence. This way, each time the design is updated, the mesh is also updated. 

Material 

In both meshes, the material used is Aluminium-2219-T1 which has the following properties :

For the remainder of the study, we will focus on the 3D mesh. 

Scenario

In this structural analysis, we will clamp the thrust chamber on one side and apply a uniform pressure of 5 MPa on the inside surface. This way, the following boundary conditions and loads are applied : 

•   Symmetry boundary condition (as we are studying 1/4 of the model)

   

• Clamped surface boundary condition 

   

• Uniform pressure of 5 MPa on the internal surface

To ensure a robust MSR Scenario, the following method is applied : 

• Publish surfaces of interest/functional surfaces from Visual Scripting Design Sequence 
• Create publication on those functional surfaces in the abstract shape (important to do it at the abstract shape level, otherwise it will be impossible to select the publication during the group definition phase)

• Create proximity groups (nodes, elements, element faces...) using the publications defined just before 

  
• Apply boundary conditions/loads on the groups defined 

Using this method, even if the geometry is rebooted each time, the groups and the publications allow to renew the link each time and ensure a robust MSR Scenario. 

Parametric optimization

Using CATIA Visual Scripting, it is easy to make the parameters vary and therefore it can be very interesting to combine it with a DOE/Parametric Optimization.

For this study, we will only vary the isogrid density. 

• Design variables : Number of sections (7 to 16 - step of 1), which drives the intensity of the isogrid 
• Response Variables : Magnitude Displacement, Von Mises Stress 
• Constraints : Max Von Mises Stress < 390 MPa (limit elastic of Aluminium-2219-T1)
• Objectives : Minimize mass

The following results are obtained : 

                                                                    Stress Max (MPa) for the different designs 

                                                                     Mass (g) for the different designs 

Given the results, the best design is the one with 12 sections as it is the lightest design that has a maximum stress below the elastic limit of the material. 

3DXML

Release : 26XFD02

Other videos describing the workflow