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Tutorial Number 16: CEL,moulding of a polymeric bottle
Stefano MorlacchiMay 2014
Strategic Simulation & Analysis LtdSouthill Barn, Southill Business Park, Cornbury Park, Charlbury, Oxfordshire, OX7 3EW
T. 01608 811777 F. 01608811770 E.info@ssanalysis.co.uk W. www.ssanalysis.co.uk
1. Introduction
In this tutorial, you will setup a Coupled-Eulerian-Lagrangian (CEL) model of the
moulding process of a polymeric bottle. Plastic bottles might be created by
moulding melt polymer within rigid frames. You will build the model using
Abaqus/CAE and then visualize the results of the simulation with Abaqus/Viewer.
Preliminaries
- Units. Before starting to define any model, you need to decide which system ofunits you will use. ABAQUS has no built-in system of units but all inputs must be
specified in consistent units. Some common systems of consistent units are
shown in Figure 1. In this tutorial, the unit system based on inches is used.
However, the international systems based on m or mm are kindly suggested for
all your future models!!!!!
Figure 1: Consistent sets of units available in Abaqus.
- Main assumptions and limitations. In order to keep the tutorial simple and fastto solve, the external and internal frames will be considered as rigid bodies while
the melt polymer will be modelled as a simple elastic material with very low
stiffness. Also, no 2D modelling is allowed with CEL so a thin layer of 3D elements is here considered.
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2. Setting up the model
Import the file Tutorial 16.sat (File Import Part) containing the geometry of the different components of the system: the Eulerian region (green), the internal
(blue) and external (white) moulds and the initial region where the polymer is
defined at the beginning of the analysis (red). Import the file and then rename the
parts as Eulerian, External, Internal and Initial. In the model tree, click with the
right button on Eulerian, select edit and choose Eulerian as type of the part.Figure 2 shows the initial assembly of the model and its relevant dimensions in
inches.
Figure 2: Assembly of the model comprehending the internal (blue) and external (white)
moulds, the Eulerian region (green) and the initial state of the polymer (red). Measures
are in inches.
3. Material and section properties
Define two material models called polymer for the bottle and steel for theinternal and external moulds. Due to the rigid body definitions, the steel
mechanical properties in terms of Young modulus and Poisson ratio will not have
any influence on the actual solution while the density chosen will drive the
computational cost of the analysis due to the explicit solver used.
Consistently to the geometric dimensions, stresses are defined in lbf/in2 while
density is defined in lbf*s2/in4 where:
1 Pascal (Pa) = 1.4504e-4 lbf/in2
1 kg/m3 = 9.3572e-8 lbf s2/in4
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1. Go into the Property Module and click the Create Material icon
a. In the Edit Material dialog box, name the material Polymer.b. From the material editors menu bar, select Mechanical Elasticity
Elasticc. Enter a Young modulus equal to 30.5 lbf/in2 (0.21 MPa) and a Poisson ration
equal to 0.35.
d. From the material editors menu bar, select General Density
e. Enter a density value equal to 0.0001345 lbf s2/in4 corresponding to 1455
kg/m3.
f. Click OK to exit the material editor
Repeat the same as above for a material called Steel using the following data:Young modulus = 30,450,000 lbf/in2 (~ 210 GPa)
Poisson Ration = 0.35
Density = 0.00072 lbf s2/in4 (7800 kg/m3)
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2. Go into the Property Module and click the Create Section icon
Create a solid homogeneous section called Section-Steel using the Steel material
previously defined. Create another solid section called Section-Eulerian selecting
Eulerian as type and polymer as base material.
3. Go into the Property Module and click the Assign Section icon Assign Section-Steel to the internal and external moulds and the Eulerian section
to the Eulerian part. The initial part does not need any section assignment since it
will not be part of the actual simulation but only used to define the initial
conditions.
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4. Assembly and Step definitions
1. Go into the Assemby module and select the Create Instance button on top ofthe toolbox. Create an instance for each of the four parts.
N.B. It is important that in every CEL analysis, all the parts in contact with the
Eulerian material overlap the Eulerian region at the contact surface.
2. Go into the Step module and select the Create Step button.Create a Dynamic Explicit step choosing 2 seconds as Time step and making
sure that the Nlgeom parameter is on.
3. In the model tree, explode the Field Output requests container and doubleclick on F-Output-1. Set the number of interval as 50, add EVF (Eulerian Volume
Fraction) as new element output in the Volume/thickness/coordinates container
and click OK.
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5. Mesh
Go into the Mesh module to discretize the moulds and the Eulerian part. Selecthexahedral swept elements for all the parts.
1. Mesh of the moulds. For each mould select 0.075 as global element size and 0.04 as local element
size for the edges shown in the following picture. Lastly, set 2 as the number of
elements in the thickness of the moulds and 0.02 as local element size at the top
of the internal mould. Select Hexahedral elements, Sweep technique and Medial
axis algorithm in the mesh controls, then mesh the parts.
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2. Mesh of the Eulerian Body. Set the Global element size of the Eulerian body as 0.03 and mesh it with
hexahedral elements.
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6. Interactions
Go into the Interaction modules. Three main tasks have to be performed here.
1. Create a new General Contact Interaction. Click on the first button of the toolbox to create a new interaction. Select Initial as
step and General contact as contact type.
In the General Contact window, select All* with self as contact domain andclick on the Create Interaction property button close to the Global property
Assignment. Select Contact in the new window that appears and create a contact
property with a Hard Contact normal behaviour and a frictionless tangentialbehaviour. Click OK to go back to the edit Interaction window, select the new
interaction property in the global property assignment menu and click OK to exit.
2. Create two new rigid bodies constraints. First, click on Tool Reference Point from the menu toolbar to create a new
reference point for each mould.
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Click on the third button of the toolboxs left column to create two new rigid bodyconstraints for the internal and external moulds. Select Rigid Body as ContraintType, Body(Elements) as region Type and the new Reference Points as the
control points.
3. This step is fundamental for any CEL analysis where the Eulerian mesh does
not conform to the initial material boundaries and aims at identifying which part of
the Eulerian region initially contains the material. To achieve this goal, you have
to first click on Tools Discrete Field Volume Fraction Tool . Follow theinstruction and select the Eulerian part first and then the Initial part as the
reference instance. This operation will create a discrete field that will then be
associated to the Eulerian part in terms of predefined field in the initial step. At
this point you have to remove the instance of the Initial part from the assembly.It might be useful to only suppress it since every change in the mesh of the
Eulerian body will require a new calculation of the initial discrete field.
7. Load module
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Go into the Load module.
1. Create the boundary conditions for the external and internal moulds. Because of the rigid boy constraints previously defined, the boundary conditions
have to be applied to the Reference points.
a. Click on the Create Boundary condition Icon, and create an encastre at thereference point of the external mould to fix all its degrees of freedom.
b. Create a displacement boundary condition at the reference point of the internal
mould. Click on the Create Boundary condition Icon, select Step-1 as the stepand displacement/rotation as type. Select the Reference point of the internal
mould, enter 1.45 in the U1 degree of freedom and 0 in all the others. Then, click
on the Create Amplitude Icon on the right and create a tabular amplitudereplicating a standard ramp and apply it to the displacement condition.
2. Create the boundary conditions for the Eulerian Region. a. Click on the Create Boundary condition Icon, select Velocity/Angular velocityas Type, select the two faces of the Eulerian region with face normal to the Z axisand select the v3 degree of freedom to fix the normal velocity on this faces.
b. repeat the same operation by constraining the normal velocity (V2) at thesurfaces normal to the Y axis.
3. Click on the Create Predefined Field Icon, select the Initial step, Other ascategory and Material Assignment as Type than click continue. Select the
Eulerian part in the viewport and the option Discrete Fields in the Volume fraction
definition. At this point Select the whole Eulerian part and the Discrete Field
previously created from the menu option.
8. Job module
1. Create and Run the job.
a. Go into the Job Module. Click the Job Manager icon.
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b. In the Job Manager dialog box, click Create to create the job namedCEL_BOTTLE.
c. In the Edit Job window, go to Parallelization and select at least 2 processors(4 if available) and domain as parallelization method. Then, click OK.
d. In the Job Manager dialog box, select the job created, click Submit andmonitor the solution.
9. Results visualization
At the end of the simulation, enter the Visualization module by clicking results inthe Job manager.
a. Colour the parts by part instances by selecting the colouring strategy in the
horizontal toolbar and click on the View cut Manager in the vertical toolbar.
Here, click on EVF_VOID to only show the elements of the Eulerian partcontaining material. Then, animate the solution to view the results.
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b. In the vertical Toolbar, select the Plot contours on deformed shape icon and
view the SVAVG Mises contour map, then Animate the solution. From theResult options menu select the option Compute scalars before averaging
and then put 100% the averaging threshold.
c. As you will notice, parts of the polymer overlap the rigid moulds in the contact
surfaces. This error is due to the rough discretization used. In the following
picture, you can see the results with a more refined mesh. If time and
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computational resources are available, please refine the mesh of youEulerian body and rerun the simulation. Rememeber to recalculate a new
Discrete Field with the volume fraction tool!!!!
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