using mid-stage validation to increase confidence … › public › ...using mid-stage validation...
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expert material testing | CAE material parameters | CAE Validation | software & infrastructure for materials | materials knowledge | electronic lab notebooks
Using Mid-stage Validation to Increase
Confidence in Simulation of TPOs
Megan Lobdell, Brian Croop, Hubert Lobo
DatapointLabs
Technical Center for Materials
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Material Testing Expertise
• Product development / R&D support • CAE-centric
• Commitment to simulation accuracy
• All kinds of materials • Over 1,800 materials tested each year
• All kinds of material behavior • Over 200 physical properties:
• Mechanical properties
• Thermal properties
• Flow properties
• Globally available at www.datapointlabs.com visit | browse | buy | download
Plastic
Rubber
Film
Metal
Foam
Composite
Cement
Ceramic
Paper
Wire
Fiber
Tensile
Compressive
Flexural
Stress-strain
Poisson’s ratio
High strain rate
Bulk modulus
Fatigue
Viscoelasticity
Stress relaxation
Creep
Friction
Hyperelasticity
Thermal expansion
Thermal
conductivity
Specific heat
PVT
Rheology
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strengthening the materials core of manufacturing enterprises
Objective
• Create a process to validate solver+ simulation inputs before real-
life application
• Benefits
• increase confidence
• reduce risk
• save time
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strengthening the materials core of manufacturing enterprises
CAETestBench Validation Mechanism
• Use a standardized geometry
• May not be real-life part
• Test must be ‘perfect’
• Boundary conditions can be correctly simulated
• Load case can be correctly simulated
• Comparison
• Obtain test output that is also available in simulation
• For example, DIC strain pattern, force v. time…
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strengthening the materials core of manufacturing enterprises
Overview of this Validation
• Measure properties
• Obtain material model parameters
• Perform open loop validation
• not a test used to create the material model
• Simulate and compare to experiment with DIC
• Quantify simulation accuracy
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strengthening the materials core of manufacturing enterprises
Case 1: Ribbed Plaque 3 Point Bend
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strengthening the materials core of manufacturing enterprises
Test Setup
• Instron 8872 universal
testing machine (UTM)
• 1 mm/min displacement
of nose
• Apply speckle patter to
part to allow use of DIC
strain capture
• Two camera DIC to
capture 3D strain
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strengthening the materials core of manufacturing enterprises
Simulation Setup
• Nose pin: • Constrained in all DOF with 2.5mm displaced in Z
(Quasi-Static)
• Fixed Support pins
• Part geometry constrained to prevent rigid body movement in the x y direction
• Contact applied in initial step
• Element Formulation: C3D8R (Hex)
• Mesh: 2.25 mm2
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strengthening the materials core of manufacturing enterprises
Material Model
• Tensile and Density Tests
• Elastic
• E = 1572 [MPa]
• υ = 0.29
• Plastic curve (Right)
• Density
• ρ = 7.9 E-06 [tonne/mm3]
• Measured at QS speeds
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strengthening the materials core of manufacturing enterprises
Comparison Simulation to Experiment
•Strain vs. Displacement •Diverges after 2 mm
•Force vs. Displacement •Similar response throughout
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strengthening the materials core of manufacturing enterprises
Side by Side Comparison of Strains
• Matched the strains in the legend for the DIC image for
easy comparison
• The lower strains match closely but the shape of the
higher strains on the experiment end up more triangular
than the simulation
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strengthening the materials core of manufacturing enterprises
Results
• Abaqus/Explicit models the elasto-plastic behavior of
a ductile plastic up to moderate strains when complex
modes of deformation are present (complex material
model)
• At larger deformations the model deteriorates due to
limitations of the elastic-plastic model (Lobo 2006)
• Limits of simulation validity can be applied.
Deformations beyond 2 mm may produce inaccurate
strain prediction.
• Although strains showed inaccuracy, force values
were accurate to higher deformations.
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strengthening the materials core of manufacturing enterprises
Case 2: Dart Impact
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strengthening the materials core of manufacturing enterprises
Test Setup
• Dynatup 8250 Impact Tower
• Plate thickness: 3.175 mm
• Clamp Diameter: 76 mm
• Dart diameter:12.7 mm
• Dart weight: 23 kg
• Impact velocity: 3.35m/s
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strengthening the materials core of manufacturing enterprises
Simulation Setup
• Plate diameter: 76 mm
• B.C.s: fixed sides
• Impact velocity: 3.35m/s
• Initial velocity rigid body of dart
• Eroding Surface-to-Surface Contact
• Element formulation: -1 (fully integrates S/R solid)
• Mesh: 3.21mm2
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strengthening the materials core of manufacturing enterprises
Material Model
• Tensile and Density Tests
• Elastic
• E = 2117 [MPa]
• E = 1664 [MPa] (mat89)
• υ = 0.45
• Density
• ρ = 9.09 E-10 [tonne/mm3]
• Strain Rate (0.01/s-100/s)
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strengthening the materials core of manufacturing enterprises
Comparison Simulation to Experiment
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strengthening the materials core of manufacturing enterprises
Additional Testing for MAT187: ABS
• SAMP-1 allows user to include many different options
• Post yield Poissons
• Yield surface
• Failure based on Triaxiality
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strengthening the materials core of manufacturing enterprises
Comparison Simulation to Experiment
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strengthening the materials core of manufacturing enterprises
Results
• MAT_089 performs well in cases where the modulus
is not rate-dependent
• MAT_187 modeled the softening behavior prior to
failure best
• Measured tensile failure strain cannot be used for
FAIL
• Extrapolation needed to simulate failure
• Measurements showed that biaxial strain at failure was close to
simulation failure strains
• Without testing the strains for a failure mode, the somewhat arbitrary
choice of failure strain seems to be unavoidable with our approach.
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strengthening the materials core of manufacturing enterprises
Conclusions
• Validation of simulation quantifies the difference between virtual
world and reality
• Should be performed each time a material is being tested for use
in simulation
• Data, model, and simulation can be checked using test cases
that contain real-life behaviors, giving confidence to the analyst