Workshop 3

    Importing and Editing an Orphan Mesh—

    Pump Model

    Goals

    ； Import an orphan mesh from an input file.

    ； Edit nodal coordinates.

    ； Delete elements.

    Introduction

    In this workshop you will import a pump housing mesh. Some modifications of its

    geometric features follow.

    Orphan mesh import

    Follow the steps below to import the mesh of the pump housing model.

    1. Start a new session of Abaqus/CAE from the ../CAE/Workshops/pump

    directory.

    2. From the main menu bar, select File?Import?Model. From the list of available

    models, select pump_ribs.inp.

    3. Abaqus/CAE takes a few seconds to import the model. A new model is created

    (named pump_ribs). In the Model Tree, expand PUMP–1 underneath the Parts

    container (as shown in Figure W3–1) and double-click Mesh to make this part

    current and switch to the Mesh module.

     Figure W3–1. Pump model

    Copyright 2006 Abaqus, Inc Introduction to Abaqus/CAE

    W3.2

    The part mesh appears as shown in Figure W3–2.

    Figure W3–2. Orphan mesh of pump housing

    Editing nodal coordinates

    Your first task will be to change the inner diameter of the hole that goes through the top of the pump. The coordinates of the nodes along the inner diameter need to be changed. Since these nodes lie on a circular surface, it will be advantageous to define a cylindrical coordinate system and simply change the radial coordinate of the nodes. Follow the steps below to achieve this task.

    1. Open the Views toolbar, and select the X–Y view. Turn off the perspective view

    by clicking the Turn Perspective Off tool (), and zoom into the component so

    that the hole is clearly visible (see Figure W3–3).

    Tip: If the Views toolbar is not visible, select View?Toolbars?Views from the

    main menu bar.

    Figure W3–3. Top view of pump housing

    2. From the main menu bar, select Tools?Datum. The Create Datum dialog box

    appears (see Figure W3–4). Select CSYS as the datum type. Select the 3 points

    method. When prompted for the type of coordinate system, choose Cylindrical.

    Place the coordinate system at the origin (0.0, 0.0, 0.0) and click Create Datum.

    A cylindrical datum coordinate system is created. The origin of the coordinate

    system coincides with the position of the center of the hole.

    ? Dassault Systèmes, 2008 Introduction to Abaqus/CAE

    W3.3

    Figure W3–4. Create Datum dialog box

3. You will now modify the inner diameter of the hole. From the main menu bar of

    the Mesh module, select Mesh?Edit. In the Edit Mesh dialog box, select Node

    as the category and Edit as the method, as shown in Figure W3–5.

    Figure W3–5. Edit Mesh dialog box

? Dassault Systèmes, 2008 Introduction to Abaqus/CAE

    W3.4

     Toggle off the selection of entities closest to the screen Select entities inside the

    drag shape Circular drag shape

    Figure W3–6. Selection filters

    4. The nodes can be selected in one of two ways:

    a. Try selecting the nodes individually (the default selection technique) using

    the selection filter settings indicated in Figure W3–6. The center of the drag

    shape should be the center of the cylindrical coordinate system defined earlier

    (see step 2). Select a perimeter point for the drag shape such that you include

    all the nodes on the inside surface of the hole. The selected nodes will be

    highlighted in red after the selection, as shown in Figure W3–7. You may

    wish to rotate your model to check whether all the nodes have been selected

    properly.

    b. You may also select the nodes using the face angle method (i.e., by specifying

    the maximum deviation in the angle between adjacent element faces). This

    technique is generally more efficient than selecting the nodes individually: all

    nodes that pertain to the element faces that satisfy the face angle criterion are

    automatically selected. In the prompt area, choose by face angle as the

    method by which the nodes will be selected. Then, click on any element face

    located on the inner surface of the hole. The nodes on the inner surface are

    highlighted in red after the selection. As before, rotate your model to make

    sure all the nodes have been selected properly.

    c. Once you are satisfied with the selection (using either method), click Done in

    the prompt area.

    Figure W3–7. Modified nodes

    5. The Edit Nodes dialog box appears, as shown in Figure W3–8. This dialog box

    will be used to change the diameter of the hole. Click Select in the upper right

    corner of the dialog box, and choose the cylindrical coordinate system defined in

    ? Dassault Systèmes, 2008 Introduction to Abaqus/CAE

    W3.5 step 2 by clicking on it in the viewport when prompted to choose a local

    coordinate system.

    6. Using the Coordinates specification method, change the 1–coordinate (i.e., the

    radial coordinate) by selecting Specify from the pull down list and entering 0.6.

    Click OK to close the dialog box and then Done in the prompt area to complete

    the operation.

    Figure W3–8. Edit Nodes dialog box

Deleting elements

    You will now remove the ribs on the pump housing. Begin by removing some of the

    elements in the rib located near the front of the housing, as shown in Figure W3–9. Use

    the X–Z view from the Views toolbar and rotate the pump to view one of the front ribs, as shown in Figure W3–9.

    Ribs

    Figure W3–9. Rib elements

    1. From the main menu bar, select Mesh?Edit. In the Edit Mesh dialog box, select

    Element as the category and Delete as the method.

    2. When prompted to select the elements to be deleted, use the Selection toolbar to

    change the drag shape to a Polygon. Select some of the elements located near the

    90; bend of the rib, as shown in Figure W3–9.

    3. In the prompt area, toggle on Delete associated unreferenced nodes.

    ? Dassault Systèmes, 2008 Introduction to Abaqus/CAE

    W3.6 4. Zoom out and rotate the view to confirm that only elements pertaining to the ribs

    have been selected. If any other elements are highlighted, deselect them using

    [Control]+Click. When you are satisfied with the selection click Done to delete

    the elements and their associated nodes.

    The remaining ribs on the pump housing can be removed by carefully selecting

    them in a similar fashion. This can be a tedious and time-consuming process for

    large, complicated models. To facilitate such tasks, elements may also be deleted

    using sets.

    5. In the prompt area, click Sets to open the Region Selection dialog box. In this

    dialog box, select the set RIBS and toggle on Highlight selections in viewport

    to highlight the elements belonging to this set.

    6. Click Continue to delete the remaining rib elements.

    7. Click Cancel to close the Region Selection dialog box.

    The pump housing without the ribs is shown in Figure W3–10.

    8. Save the model database. Name the model database file PumpAssembly.cae.

    Figure W3–10. Pump housing without ribs

    ? Dassault Systèmes, 2008 Introduction to Abaqus/CAE