FEA Presentation

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PRASAD PETKAR FEA Engineer, QA PTC - Simulation
Products Division
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Education
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Computer Aided Design Experience

• Three years experience with Pro/Engineer
  (Versions 2001, Wildfire,
• Wildfire 2.0)
• Part and assembly modeling experience in Pro/E
  using standard and
• advanced feature creation techniques,
  simplified reps, family tables,
• skeletons, shrink wraps etc.
• Worked on Pro/Sheetmetal, Pro/E (Behavioral
  modeler extension)
• Worked on Product Data Management (PDM)
  software,
• Pro/Intralink, to verify seamless management
  of Pro/E and
• Mechanica files
• Familiar with other CAD software packages Solid
  Edge, SolidWorks

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Finite Element Analysis Experience

• Pro/Mechanica (Structure/Thermal) Three years
  extensive experience with
• Pro/Mechanica, CAE software integrated in
  Pro/Engineer. Various Structural/Thermal
• Analyses performed were
• Static Analysis to compute stresses and
  displacements
• Contact analysis to compute contact forces,
  stresses and load transfer through contact area
• Buckling analysis to calculate critical buckling
  loads for the structure
• Large deformation static analysis
• Pre-stress static analysis
• Modal analysis to calculate free and constrained
  natural frequencies
• Vibration analysis including dynamic frequency,
  time, random and shock
• Steady state and Transient thermal analysis

Contd
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Finite Element Analysis Experience

• Pro/Mechanica FEM mode (Pre and post processor
  for 3rd party solvers viz.
• Nastran and Ansys)
• Generated H meshes for Pro/E models and
  applied boundary conditions.
• Verified accuracy of exported mesh elements
  and properties associated to
• it in pre-processor output decks. Verified
  accuracy of post processed
• solution by displaying fringe plots and
  result graphs.
• HyperMesh
• Used HyperMesh to mesh solid models of seat
  and head restraint
• created in Solid Edge as part of graduate
  research.
• LS- DYNA
• Used LS- DYNA to to perform non-linear crash
  analysis to analyze
• effectiveness of seat and restraint systems
  for occupant protection for rear
• impact crash situation. LS- DYNA was combined
  with rigid body dynamics
• software to generate human dummy model to
  provide complete crash
• environment.

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Structural Analysis Responsibilities

• As an FEA Engineer in Quality Assurance
  Department of PTCs simulation
• products division, functions performed were
• Designed and modeled various parts and assemblies
  using standard and advanced feature creation
  techniques, simplified reps and family tables
• Assigned materials to components. Modeled various
  idealizations viz. beams, shells, masses,
  springs, midsurface compressed shells etc. to set
  up finite element model
• Defined various connections viz. edge/perimeter
  welds, spot welds, bolt/screw fasteners to
  connect components in an assembly
• Set various structural boundary conditions viz.
  surface loads, pressure loads, bearing loads,
  surface constraints etc.
• Defined various displacement/stress measures at
  datum points in the model to obtain specific
  numerical results
• Post processed fringe results for stress/
  displacements to visualize
• structure behavior.
• contd

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Structural Analysis Responsibilities

• Identified structure failure for applied load
  based on different material failure
• criterion by plotting failure index fringe
  plots.
• Plotted graphs of measures to obtain critical
  stress/displacement values
• Performed hand-calculations to verify accuracy
  of numerical results for
• simple models with closed form solutions
• Verified stress/displacement behavior for more
  complex models by making
• logical sense of results in absence of closed
  form solution
• Performed local/global sensitivity studies by
  varying design sensitivity
• parameters over a range and viewing graphs of
  desired outputs viz.
• stress/displacement measures as function of
  the parameters
• Performed design optimizations for design goal
  in terms cost, mass, displacement,
• stress etc by specifying multiple design
  parameters and constraints
• Filed performance issue reports in case of
  result inaccuracy or analysis
• failure. Followed up on the issues to get it
  fixed
• Following slides show sample of various models
  created and analyzed.

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Fastener Connections

• In Pro/Mechanica Wildfire 2.0 release, Fastener
  connection is being introduced. Designed various
  assembly models connected by bolt Fasteners.

Shaft flanges bolted together to carry
tensional loads
Brackets bolted together by plates
Contd
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Fastener Connections
Pressurized vessel capped by pressure plate
bolted at the end
Load carrying bracket bolted to the wall
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Fastener Connections Meshing

• Meshed assemblies using AutoGEM. Verified that
  correct regions corresponding to contact area of
  bolt head and nut are getting meshed around bolt
  holes.

In Mechanica Wildfire version, elements in the
model can be viewed in Pro/Mechanica Integrated
mode. Have extensively worked to implement this
functionality by verifying successful meshing for
various 3D and 2D complex solid, shell and mixed
models.
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Fastener Connections Result verification

• Plotted stress fringe plots for the models and
  verified that load is not transferred through
  mated geometry and is transferred only through
  fasteners.

Contd
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Fastener Connections Result verification
New Mechanica measures were introduced to
calculate various quantities for each bolt
connection. Plotted various measure graphs for
shear stress/force, tensile stress/force carried
by each bolt and performed hand calculations to
verify numerical values. Verified that
shear/tensile stresses in the bolts do not exceed
allowable values. Performed sensitivity studies
to visualize effect of various design parameters
viz. bolt diameter, hole location etc. on various
bolt measures and whole model. Performed
optimization to obtain minimum bolt diameter for
given allowable stress by varying model
dimensions.
Fastener Shear Stress Vs. P-loop pass
Fastener Shear Force Vs. P loop pass
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Assembly Links

• In Mechanica 2001, automatic assembly links were
  introduced to connect midsurface compressed shell
  parts mated together. Extensively tested this
  functionality to verify element linkage at mated
  interface.

Presence of assembly links is validated by
structural analysis as both the parts are
displaced together when load is applied to only
bottom part.
Two shell compressed parts are mated leading to
generation of automatic assembly link at mated
interface.
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Free connections

• Free connection were introduced in Wildfire
  release to selectively delete automatic assembly
  links between mated midsurface shell parts.
  Verified that assembly links do not get created
  at free interface definition.

Presence of free connections is validated by
structural analysis as only bottom part which is
loaded is displaced keeping top part undeformed.
Free connections defined at mated interfaces of
previous parts using surface regions.
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Buckling Analysis

• Buckling analysis is used in design of axially
  loaded compression members which are relatively
  slender. Performed buckling analysis to calculate
  critical load using BLF and verified accuracy of
  calculations.

Buckling of axially loaded support structure.
Fringe plots show first 2 buckling
modes. Calculated buckling load factors (BLF)
were 1.41, 5.25, 8.57.. leading to conclusion
that critical load at which structure will fail
by buckling is 1.41 times applied load.
To vary/reduce
critical load, performed sensitivity analysis
with structure height and c/s area as parameters
to visualize effect of slenderness ratio on BLF,
i.e. critical load.
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Contact Analysis Seat belt
Structural contact analysis is used to solve
design problems when parts come in contact but
exact contact region is unknown. Performed
contact analysis for seat buckle and clip
assembly to find contact stresses and pressures.
Seat-buckle and clip assembly with contact
regions and boundary conditions defined.
Fringe plot of contact pressure distribution for
belt and clip parts.
Evaluated contact stresses to check if they
exceed material yield stress, which signifies
failure of material in contact by crack/flaking
in area of contact. Also checked if stresses
do not exceed allowable value in any other part
of the model.
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AutoGEM Mesh Controls

• In Wildfire 2.0, AutoGEM mesh control
  functionality is added to give user more control
  over element/node distribution and element count.
  Verified effectiveness of this functionality by
  meshing various 2D and 3D complex models for
  various control settings.

Minimum element edge control to ignore small
edges/curves below specified element edge length.
Primary use is to ignore small cosmetic features
while meshing thus significantly reducing element
count.
Edge distribution control to specify number of
element edges along selected curve. Primary use
is to easily refine mesh density in area of
interest (contact, high stress etc.) to increase
result accuracy.
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Stress Analysis of Engine Block
Meshed and performed stress analysis on complex
customer Engine block model.
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Graduate Research Project
Design and analysis of seat and head restraint
system for occupant protection In rear impact
crash simulation.
Meshed 3D seat model with seatbelt.
Contd
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Graduate Research Project
Simulation run in LS-DYNA and ATB ( Articulated
Total Body) coupled software. Non linear seat
material (low-density foam) and vehicle motion
defined in LS-DYNA. Human dummy generated in
ATB. Analyzed effect of various seat design
factors on head motion leading to neck injury.
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Conclusion Relevance

• 4 years experience with various CAD/FEA
  software tools.
• Experience in effectively performing
  structural/thermal finite
• element analysis by specifying boundary
  conditions to validating
• results using hand calculations and result
  plots.
• Excellent written and oral communication skills
  gained through
• interaction with customer Engineers,
  technical-marketing, product
• development team and through creating reports
  to document test
• results and software issues.
• Good project management and multitasking skills
  obtained by
• working simultaneously on diverse
  time-sensitive projects.

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Thank You