An Introduction to Finite Element
Analysis with Pro/MECHANICA
Stephen Seymour, P.E.
Seymour Engineering & Consulting Group, LLC
www.seymourecg.com
Presentation Outline
• Introduction to Pro/Mechanica
• Capabilities and differences
• Cantilever beam demo
• Materials, loads, and constraints
• Element types and meshing
• Idealizations, connections, and
contact
• Analysis definition and convergence
• Reviewing results
What is Pro/Mechanica?
• Pro/Mechanica is general finite
element analysis (FEA) software
tool that is directly integrated into
Pro/Engineer
• Pro/Mechanica (also referred to
as Simulation) is generally
classified as a structural and
thermal Computer Aided
Engineering (CAE) tool.
Pro/Mechanica Capabilities
• Static structural stress/strain/disp
• Modal, prestressed modal, and mechanical vibration
• Buckling
• Non-linear contact / large deformation
• Fatigue
• Hyperelastic materials
• Steady state thermal analysis
• Transient thermal analysis
How Does Pro/Mechanica Differ?
• Pro/Mechanica is a linear P-element
finite element solver
• Most other commercial FEA packages
are H-element codes
• The difference:
convergence method
– P: varies element
shape functions
– H: mesh refinement
How Does Pro/Mechanica Differ?
• Pro/Mechanica by default is a
linear finite element solver with
some non-linear capabilities
• Automated convergence via
element shape function
adaptation
– Multi-pass adaptive (MPA)
– Single pass adaptive (SPA)
Analysis Methodology
Cantilever Beam Demonstration
• Goal: determine
the maximum
bending stresses
Solution Comparison
Analytical Solution
• Analytical model
based on classic
beam theory for
slender uniform
cross section beams
Solution Comparison
Pro/Mechanica FEA Solution
• Pro/Mechanica FEA
results indicate
maximum bending
stress is approximately
6000 psi
• Stress varies linearly
along length of beam
as expected
Applying Material Properties
Parts
• Pro/Mechanica provides a default library of materials
• Ability to create custom materials with descriptions
• Be careful of units!
Applying Material Properties
Assemblies
• Ability to assign different materials
to different components
• Material assignment can be
performed at either assembly or
individual part level
• Material properties must be
assigned before meshing
Degrees of Freedom (DOF)
• The primary 6 independent motions of any solid
body. 3 translation and 3 rotation
• All static structural FEA problems required no rigid
motion, therefore after constraints (and idealizations)
there must be no motion
Displacement Constraints
• Constraints can be defined on surfaces,
edges, or points
• Constraints can be free, fixed, or prescribed
relative to the coordinate system selection
• Constraint coordinate systems can be
Cartesian, cylindrical, or spherical.
Symmetry Constraints
• The symmetry constraint will
simulate a symmetry type
boundary condition by
constraining motion normal
(perpendicular) to the selected
surface
• Should not be used with
asymmetrical loading conditions
• Should not be used with modal
analyses
Loads
Forces and Moments
• Most common of all load types
• Can be applied on surfaces, edges,
and points
• Can reference user defined coordinate
systems
• Moments must be specified with the
advanced option Total Load at Point
Loads
Other
• Bearing loads
• Centrifugal loads
• Gravity loads
• Pressure loads
• Temperature loads
• Thermal simulation result loads
• Remember: gravity in the IPS unit
system is 386.4 in/sec2
Element Types
Solid Elements
• Tetrahedral shape
• 3 translational DOFs at nodes
• Rotational constraints not required
• Shown in blue
• Ideal for solid bodies with large
cross-sectional areas
• Not well suited for thin bodies
Element Types
Shell Elements
• 2D or 3D triangles and quadrilaterals
• 6 translational DOFs at nodes
• Shown in green
• Ideally suited for parts with thin
cross-sections (i.e. tank walls, sheet
metal components, etc.)
• Non-linear contact not possible for
this element type
Element Types
Beam Elements
• 2D or 3D point-to-point or thru
curve
• 6 translational DOFs at nodes
• Shown in light blue with crosssection (Shown here in red for
clarity)
• Well suited to represent beams
with a 10:1 slenderness ratio
Mesh
• Meshing can be done either before
or during analysis
• The greater the # of elements…the
longer the solution time
• Mixed element meshes are
possible
• Convergence problems can
typically be resolved by refinement
in high gradient locations
Mesh Controls
• Control the density of
elements within specific
regions of the model
• Can be applied on volumes,
surfaces, and edges
• Ability to specify regions of
exclusion where
singularities may exist
Idealizations
Masses
• Mass idealizations (also known as mass
elements) are attached to a single point
(either datum or vertex) within your model
• Mass idealizations by default are mass
only with no inertia. However, an
advanced mass element may also
included mass moments of inertia (MMOI)
to increase the accuracy of the solution
• Be careful of mass unit!
Idealizations
Springs
• Spring idealizations can simulate the
behavior of real world springs in the model
without having to solid model a spring
• Spring idealizations can range from very
simple extension only springs that are
defined point-to-point….to complex springs
that can have varying linear and torsional
spring constants in all 6 degrees of
freedom
Connections
• There are four main connection types:
–
–
–
–
Interface
Weld
Rigid link
Weighted link
Connections
Interface
• Bonded
–
Merges coincident faces together
for the analysis
• Free interface
– Allows coincident faces to act
independently of one another
• Contact
–
Interpenetration not allowed.
Can be frictionless or infinite friction
Connections
Welds
• Three main types of welds:
–
–
–
End weld
Perimeter weld
Spot weld
• End and perimeter welding extend the base shell
geometry
• Spot welds are created using beams. May specify
alternate material.
Connections
Rigid Link
• Can be created to points, edges,
curves, and surfaces
• Couples the DOF
• Features with rigid links cannot have
localized displacements or rotations
• Improper use of rigid links can
adversely affect results
Connections
Weighted Link
• Developed primarily for distributing
mass or loads
• Allow the attachment of mass
idealizations without stiffening structure
• Source point must be a
datum point, target entities
can be points, edges,
or
surfaces
Analysis Definition
• Once loads, constraints, and
materials have been defined it
is time to define the type of
analysis to be performed
• Choose from the drop down list
the analysis type or study you
wish to perform
• Some analysis types may
require additional licensing
Analysis Definition
• Analysis name entered will be
subfolder name where files reside
• Multiple load sets can be analyzed
independently or summed.
• Select the convergence method
• Choose output options
• Enable/Disable the exclusions of
elements from the analysis
Convergence Options
• Multi-Pass Adaptive (MPA)
–
Polynomial order is repeatedly increased until
specified convergence is obtained (default 10%)
• Single Pass Adaptive (SPA)
– First pass using order of 3. Second pass order is
increased to a max of 9 in high stress gradient areas.
• Quick check
–
Mechanica performs a single pass at a uniform
polynomial order of 3.
Convergence Options
Multi-Pass Adaptive (MPA)
• Percentage represents max
allowable change from pass
to pass
• A poorly converged model is
equal to pretty picture
• Converged model doesn’t
imply accurate solution
– GIGO principle
– Poor boundary conditions
Reviewing Results
Launch The Results Viewer
• There are three options for viewing
the completed results:
– Select the analysis and choose
the results icon
– Start the results viewer from
Pro/Mechanica or Pro/Engineer
Reviewing Results
Results Selection
• Select from the drop down
the result you wish to plot
• Fringe is the default display
type, but vector and graph
plots are possible
• P-level is a plot of the
highest polynomial order
used for each element
throughout the domain
Reviewing Results
Results Display Location
• Gives the option to plot results
on specific geometric entities
• For assemblies results may be
plotted on certain components
only or in exploded view
Reviewing Results
Results Display Options
• Control color display and
animation effects
• Continuous tone creates smooth
result plots, but requires more
computing time and memory
• To see the true deformation set
the scaling to a value of 1 and
uncheck the % box
Results
• Dynamical query results
• Animate deformed shape
• Create section planes
• Customizable legend
Conclusion
• This completes the
introduction to Finite
Element Analysis (FEA)
with Pro/Mechanica
• Many more features
available
• Remember: always make
sure your results make
sense
• GIGO principle