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June 2-3 . Detroit ,
USA
Testing of Elastomers and Plastics in Support of Analysis
Kurt Miller, Axel Products, Inc.
June 2-3 . Detroit ,
USA
axelproducts.com
June 2-3 . Detroit ,
USA We Measure Structural Properties
Elastic-plastic Models Hyperelastic Models
Stress – Strain–Time-Temperature
June 2-3 . Detroit ,
USA
What’s New? Combinations & Failure
• Rubber + Softening • Rubber + Viscoelasticity
• Plastic + Rate • Rubber Set • Plastic + Creep • Rupture of Rubber • Fatigue • All things Hot and Cold • Directional Properties
• Plastic-Rubber Stuff • Plastic + Rate + Failure • Plastic + Unload • High Strain + Failure
June 2-3 . Detroit ,
USA
Strategy: Isolate Behaviors • Separate Elastic & Plastic
• Go to the Application Temperature
• Observe Failure
• Grow the Defect
• Go Very Slow
• Go Very Fast
You Can’t Model Everything!
June 2-3 . Detroit ,
USA Rubber
June 2-3 . Detroit ,
USA What Does Incompressible Mean?
June 2-3 . Detroit ,
USA
Volumetric Compression
K/G Relationship to Poisson's Ratio
0
20
40
60
80
100
0.3 0.32 0.34 0.36 0.38 0.4 0.42 0.44 0.46 0.48 0.5
Poisson's Ratio
K/G
K/G
21
1
3
2
G
K
Poisson’s ratio approaching 0.5 means infinite bulk modulus, K
For elastomer materials, Poisson’s ratio is difficult or impossible to measure
accurately. For plastic materials, it is hard to measure VC accurately.
June 2-3 . Detroit ,
USA
Incompressibility
Not a spring and dashpot
June 2-3 . Detroit ,
USA Hyperelastic Models
Available Hyperelastic models:
• Arruda-Boyce Hyperelastic Material • Blatz-Ko Foam Hyperelastic Material • Extended Tube Material • Gent Hyperelastic Material • Mooney-Rivlin Hyperelastic Material • Neo-Hookean Hyperelastic Material • Ogden Compressible Foam Hyperelastic Material • Ogden Hyperelastic Material • Polynomial Form Hyperelastic Material • Response Function Hyperelastic Material • Yeoh Hyperelastic Material
Specialized Hyperelastic models:
• Anisotropic Hyperelastic Material • Bergstrom-Boyce Material • Mullins effect • User-Defined Hyperelastic Material
• Material response is isotropic, isothermal, and elastic and is assumed fully or nearly incompressible.
• There are many hyperelastic models available in ANSYS which can cover wide varieties of elastomers used in Industries.
June 2-3 . Detroit ,
USA
Hyperelastic Surface
June 2-3 . Detroit ,
USA
June 2-3 . Detroit ,
USA Hyperelastic Models
Curve Fitting feature
• Material curve fitting allows you to derive coefficients from experimental data that you provide for your material.
• With this capability, you compare experimental data versus program-calculated data for different nonlinear models and determine the best material model to use.
• ANSYS provides curve-fitting, based on experimental data, for all of the available hyperelastic models. Any of the hyperelasticity models in ANSYS can be used.
June 2-3 . Detroit ,
USA
Loading Conditions
• Some common Elastomers exhibit dramatic strain amplitude and cycling effects at moderate strain levels
Conclusions:
1. Test to realistic strain
levels
2. Use application specific
loadings to generate
material data
3. Need to load and unload
to separate elastic from
plastic
June 2-3 . Detroit ,
USA
Loading Conditions
• Some common Elastomers exhibit dramatic strain amplitude and cycling effects at moderate strain levels
Conclusions:
1. Test to realistic strain
levels
2. Use application specific
loadings to generate
material data
3. Need to load and unload
to separate elastic from
plastic
June 2-3 . Detroit ,
USA Loading Conditions
• Some common Elastomers exhibit dramatic strain amplitude and cycling effects at moderate strain levels
Conclusions:
1. Test to realistic strain
levels
2. Use application specific
loadings to generate
material data
3. Need to load and unload
to separate elastic from
plastic
June 2-3 . Detroit ,
USA Loading Conditions
• Single Loading
• Softening
• Load vs Unload
• Amplitude Effect
• Set
June 2-3 . Detroit ,
USA
Structural Properties
June 2-3 . Detroit ,
USA Structural Properties
June 2-3 . Detroit ,
USA
Structural Properties (small deformation plasticity)
June 2-3 . Detroit ,
USA Plastic
June 2-3 . Detroit ,
USA Plastic
• Modulus is Unclear
• Yield is Unclear
• Load = Unload?
• Set
June 2-3 . Detroit ,
USA
Thermoplastic Elastomers
June 2-3 . Detroit ,
USA Teflon
June 2-3 . Detroit ,
USA Simple Shear
1. Additional Strain State
2. Using DIC Strain Measuring
June 2-3 . Detroit ,
USA
Long Term Creep
June 2-3 . Detroit ,
USA Plastic
Long Term Creep Experiments
Often Required for Metal Replacement Applications
Structural Applications May Require a Range of
Stress Levels and Temperatures
June 2-3 . Detroit ,
USA
Time
June 2-3 . Detroit ,
USA Plastic Rates
June 2-3 . Detroit ,
USA
Structural Properties
June 2-3 . Detroit ,
USA
Structural Properties
June 2-3 . Detroit ,
USA
Structural Properties
June 2-3 . Detroit ,
USA
Fracture in Plastic
June 2-3 . Detroit ,
USA
Fracture in Rubber
June 2-3 . Detroit ,
USA
Minimum Requirement for Crack Growth
Intrinsic Strength Option (>106 cycles)
Quantify endurance limit
TcT0
cyc
mm
dN
dc
2m
JT
Cra
ck g
row
th r
ate
Energy Release Rate
Ultimate Strength
Endurance Limit
cyc
mm810
June 2-3 . Detroit ,
USA
•ANSYS teams with Axel Product, Inc. (www.axelproducts.com) to offer this course that covers material testing, material modeling and finite element analysis of structural plastics such as Polyethylene (PE), Polypropylene (PP), Polyvinyl chloride (PVC) etc.
ANSYS Experimental Structural Plastic Training at Axel Products
June 2-3 . Detroit ,
USA
•ANSYS teams with Axel Product, Inc. (www.axelproducts.com) to offer this course that covers material testing, material modeling and finite element analysis of elastomers.
ANSYS Experimental Elastomers Training at Axel Products
June 2-3 . Detroit ,
USA
Thank You for Listening.
• Kurt
Tuesday, May 26, 2015 2015 Automotive Simulation World Congress 38
