Coupling Shell Elements With Solid Elements

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MAE 656 - AdvancedComputer Aided Design

05. Shells and Membranes Doc 03

Coupling Shell Elements withSolid Elements


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Introduction

In this session we will learn how to create shell structuresfrom solid elements.

We will also see how we can couple solid structures withshell structures.

This last option can be used when some structuralcomponent, attached to a shell structure, wants to bestudied in detail. i.e. ply drop-off

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cba Dr.XavierMartinez,2012 05.ShellsandMembranes Doc03


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Introduction

Specifically, we will learn:

1. How to create shells structures from the mid-plane ofsolid elements

2. How to create shell structures from the outer surfaces of

solid elements

3. How solid elements can be coupled with shell elements

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Base Model

As base model we willuse the following

beam support. We willfirst solve it as a solidstructure.

The support is madeof Structural Steel

The support dimensions and loadshave been obtained from Huei-Huang Lee. Finite ElementSimulations with ANSYS Workbench13. Theory Applications CaseStudies. SDC Publications (2011)

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Base Model - Geometry

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To create the solid geometry, we will first define thesupport seat plate, in plane xz.

We will create it as three different sketches that will beextruded 16mm as frozen.


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The web plate isdefined extruding

5mm in directionBoth - Symmetric asketch drawn in xy

plane.The web plate isdefined asAdd

Material


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The last step consists in blending the external corners witha radius of 16mm and the connection of the seat plate with

the web with a radius of 10mm


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Base Model - Mesh

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The solid will bemeshed with the

automatic meshsuggested by Ansys,using a relevance value

of 100


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Base Model Boundary Conditions

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The boundary conditions applied are a pressure of 1.0MPain the seat plate.

The edge of theweb plate is fixedsupported.


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Base Model Results

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The main two results that will be studied are the totaldisplacement and the Von-Mises stresses

Total Deformation Von-Mises Stress


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Shell Create Mid-plane Surfaces

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In Design Modeler > Tools, there is an option that createssurface elements at the mid-surface of solids. This process

can be done manually or automatic


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Shell Create Mid-plane Surfaces

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The result is the shell model sought.

We will apply the sameboundary conditions tothis model and we willcompare the results with

those obtained from thesolid simulation


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Shell Create Surfaces from Solids

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The solid contour can beused to create 3D surfaces.

This is done with thecommand Thin/Surfacethat can be found inDesign Modeler> Create.

This command asks us todefine the surfaces of the

solid geometry that wewant to use as surfaces.


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If a thickness is specified,the result is a thin walled

solid. If thickness isdefined as zero, the resultis a surface element.


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As we have done with the other shell model, we will applythe same boundary conditions defined for the 3D case and

we will analyze the results obtained.

In this case, the results are substantially different, as thestructural element studied is also different.


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Shell-Solid model

If the center solid is nottransformed into shell

elements, we will end upwith three different parts:a solid body and twosurface bodies

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Shell-Solid model

We will not group these three bodies in a single part;because Ansys Workbench does not recognize a single part

with surfaces and solids (only the solid will be displayed).

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The union of these threeparts is done in the Design

Modeler, using the body tobody connection.


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Shell-Solid model

Once all bodies are connected, the mesh is defined, and theboundary conditions are applied, it is possible to calculate

the solution.

The solution obtained with this model will be compared

with the solution obtained with all previous models.

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Documents

Coupling Shell Elements With Solid Elements