Spring 2008, MET 415 - FEA Applications I

Prof. Dave Johnson, dhj1@psu.edu

Penn State - Erie, The Behrend College

Homework Assignment 4B

Concepts:

• 2D Plane Stress (with thickness) Element Types
  • 2D 8-Node Structural Solid
  • Behavior Option: Plane Stress w/Thickness
  • Real Constant for thickness value
  • Multiple parts / different materials & real constants (assignment of element Attributes)
• Model construction with actual, physical interference
• Contact pairs with ramped, initial interference
• NON-Linear Solution:
  • small or large deformations ?
  • gradual load application (substeps)
  • automatic time stepping
  • iterative solution, (equilibrium) convergence
  • results controls
• Postprocessing:
  • Selecting (scoping) to examine results in each part
  • Contact Manager: display contact pair results
    

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A STEEL cantilever beam (left) is 0.5" x 0.5" x 5" and overlaps (1") at the tip with a TITANIUM cantilever beam (right) which is 0.25" x 0.25" x 4".  There is an interference of 0.005" between these parts.

Use the ANSYS material library for properties of both bodies (1020 Steel & Titanium)

Model two rectangles for a 2D simulation.  These rectangles must physically overlap by the amount of interference defined for this problem.  Assign material and real constant attributes to the areas and mesh.

Use the Contact Manager/Contact Wizard to create a contact pair at the interface between these parts.  Specify default contact options except under the "Initial Adjustment" Tab, select "Include Everything With Ramped Effect."  Ignore friction between these parts.

Turn in:

• A plot showing the elements using color to distinguish different MATERIAL assignment AND showing different thickness in a 3D view with element shape based on real constant data
  [under PlotCtrls > Style > Size and Shape ... > turn ON the "Display of Element Shape Based on Real Constants" and specify a "Real Constant Multiplier" of 1.  Also, PowerGraphics must be ON]
• A plot showing ALL constraints and loads.
• A plot showing the normal stress (SX) for each beam, separately.
• A plot showing the contact pressure distribution between the parts
• A hand calculation of the force (Fy) created by the interference COMPARED to the Reaction Solution for EITHER part (not both).
• A hand calculation of the normal bending stress in the outermost fiber of each beam COMPARED to the normal stress (SX) for each beam.  [Beware of the "excessive constraint singularity" at the fixed end of each beam]
• The modeling session log file (with comments added).
  After successfully solving the model, Utility Menu: File > Write DB log file... > use a file name like "HW-4Blog.txt" and "Write Essential Commands ONLY"