Linear%20Structural%20Analysis

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Linear Structural Analysis

• Workshop 4.1

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Workshop 4.1 - Goals

• Workshop 4 consists of a 5 part assembly
  representing an impeller type pump. Our primary
  goals are to analyze the assembly with a preload
  on the belt of 100N to test
• That the impeller will not deflect more than
  0.075mm with the applied load.
• That the use of a plastic pump housing will not
  exceed the materials elastic limits around the
  shaft bore.

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Workshop 4.1 - Assumptions

• Well assume the pump housing is rigidly mounted
  to the rest of the pump assembly. To simulate
  this, a frictionless support is applied to the
  mounting face.
• Similarly, frictionless surfaces on the mounting
  hole counter bores will be used to simulate the
  mounting bolt contacts. (Note if accurate
  stresses were desired at the mounting holes, a
  compression only support would be a better
  choice).
• Finally, a bolt load (X 100 N) is used on the
  pulley to simulate the load from the drive belt.
  The bolt load will distribute the force over the
  face of the pulley only where the belt contact
  occurs (compression only).

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Workshop 4.1 Contact Assumptions

• For the workshop we will use the 2 forms of
  linear contact available in DS, bonded and no
  separation. Its important to review and
  understand all assumptions related to contact
  behavior when including it in an analysis.

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Workshop 4.1 - Start Page

• From the launcher start Simulation.
• Choose Geometry gt From File . . . and browse
  to the file Pump_assy3.x_t.
• When DS starts, close the Template menu by
  clicking the X in the corner of the window.

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Workshop 4.1 Preprocessing

• Set the working unit system to the metric mm
  system.
• Units gt Metric (mm, Kg, N, C, s).
• Highlight the pump housing (part 1) in the tree.
• Model gt Geometry gt Part 1.
• From details import the material polyethylene.

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. . . Workshop 4.1 Preprocessing

• Change the first 4 contact regions (shown below)
  to No Separation.
• Hold the shift key and highlight the first 4
  contact branches.
• From the detail window change the contact type to
  no separation.
• The remainder of the contacts will be left as
  bonded.

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Workshop 4.1 - Environment

• Apply the bolt load
• Highlight the Environment branch.
• Highlight the pulley surface shown.
• Insert a bolt load.
• RMB gt Insert gt Bearing Load
• From the detail window change to Components and
  X 100 N.

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. . . Workshop 4.1 - Environment

• Highlight the mating face on the pump housing
  (part 1).
• Insert a frictionless support.
• RMB gt Insert gt Frictionless Support.

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. . . Workshop 4.1 - Environment

• Now we will add the frictionless supports to the
  8 countersink portions of the mounting holes
  (shown here).
• Each of the required surfaces could be selected
  individually while holding the CTRL key however
  we will use a macro (select by size) provided
  with the DS installation. After selecting the
  initial surface, running the macro finds and
  selects all surfaces of the same size (area).
  Note, this macro also works with edges or bodies.

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. . . Workshop 4.1 - Environment

• Highlight 1 of the countersink surfaces
  (arbitrary).
• Run the select by size macro
• Choose Tools gt Run Macro . . .
• In the browser choose selectBySize.js
• Note typical path shown below.
• Open

C\Program Files\ANSYS Inc\v100\AISOL\DesignSpace\
DSPages\macros
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. . . Workshop 4.1 - Environment

• With all surfaces selected apply a frictionless
  surface support.
• RMB gt Insert gt Frictionless Support

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Workshop 4.1 Macro Notes

• The result of running the selectBySize macro is
  that all similarly sized surfaces are
  automatically added to the selection set as shown
  on the previous page.
• While the selections here (8 surfaces) would be
  trivial to select individually, this technique
  can be a valuable time saver when a large
  selection set is needed.
• Care should be taken when using select by size.
  All entities of the same size will be selected.
  Make sure extra selections do not occur.
• Other macros are also available in the same
  directory. Macros are written in Jscript and can
  be opened and viewed using typical text editors
  such as Notepad.

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Workshop 4.1 - Solution

• Add results to solution
• Highlight the solution branch
• RMB gt Insert gt Stress gt Equivalent (von-Mises)
• Repeat to add Total Deformation

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. . . Workshop 4.1 - Solution

• Because of the presence of frictionless supports
  non bonded contact, DS will trigger the use of
  weak springs during the solution. If we know the
  model is fully constrained we can turn off this
  function. Before turning off weak springs make
  SURE that rigid body motion is prevented.
  Failing to do so can result in an unconverged
  solution.
• Highlight the Solution branch and from the
  details window change Weak Springs from
  Program Chosen to Off.

1. Solve

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Workshop 4.1 Postprocessing

• When the solution is complete highlight the
  results to plot each.
• While the overall plots can be used as a reality
  check to verify our loads, the plots are less
  than ideal since much of the model is only
  slightly effected by them.
• To improve the quality of results available we
  will scope results to individual parts.

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. . . Workshop 4.1 Postprocessing

• Highlight the Solution branch and switch the
  selection filter to Body select mode.
• Select the impeller (part 2).
• Insert equivalent stress.
• RMB gt Insert gt Stress gt equivalent (von Mises)
• Notice the detail for the new result indicates a
  scope of 1 Body.

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. . . Workshop 4.1 Postprocessing

• Repeat the procedure on the previous page to
  insert Total Deformation results for the
  impeller part.
• Repeat the procedure to add individually scoped
  stress and total deformation results to the pump
  housing (part 1).
• Rename the new results as shown here to simplify
  postprocessing.
• Solve again.
• Note adding new results and resolving the model
  will not cause a complete solution to take place.
  Results are stored in the database and new
  quantities requires only an update.

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. . . Workshop 4.1 Postprocessing

• By checking the impeller deformation we can
  verify that one of our goals is met. The maximum
  deformation is approximately 0.024mm (goal lt
  0.075mm).

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. . . Workshop 4.1 Postprocessing

• Inspection of the housing stress shows that,
  overall, the stress levels are below the
  materials elastic limit (tensile yield 25
  MPa). We can again using the scoping technique to
  isolate the result in the area of interest.

Maximum stresses
Area of interest
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. . . Workshop 4.1 Postprocessing

• To simplify scoping first hide the pulley and
  impeller parts.
• Select the pulley then RMB gt Hide Body (note
  although we are hiding the entire body this also
  works while in face or edge select mode).
• Repeat for the impeller part.

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. . . Workshop 4.1 Postprocessing

1. Highlight the Solution branch and switch the
   selection filter to Face select mode.
2. Select the 5 surfaces shown on the pump housing
   (part 2).

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. . . Workshop 4.1 Postprocessing

• Insert equivalent stress.
• RMB gt Insert gt Stress gt equivalent (von Mises)
• Notice the detail for the new result indicates a
  scope of 1 Body.
• Select the back face (shown here) and repeat the
  process.

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. . . Workshop 4.1 Postprocessing

• Inspect the new results to determine if our goal
  has been met.
• Finish the workshop by inserting any figures that
  you feel are required and generating a Report.