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8/8/2019 Understanding and Coping with Material Modeling
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Understanding and Coping with
Material Modeling Limitations in FEA
Hubert Lobo
DatapointLabs, NY
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DatapointLabs
Researc q ality aterial testi
ISO 17025 r cti envir nment
Results in 5 ays (48 urRUS service)
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omainexpertise in material calibration
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Limitations in FEA
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expert material testing
TestPaks
= Materials testing +CAE material parameter onversion
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over 20 CAE software codes
testing
Your CAE
data conversionmaterials +
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Modeling Limitations
Understandingmaterial model requirements
Gapsbet eenmaterial dataandmodel
Obtainingpertinent properties
Difficulties inparameter conversion (fitting)
Preparationof input files
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Unclearmodel requirements
Modeling terminology not
compatible it testing terminology
Conf sion ca ses inter retation errorCommonmistakes
Engineering/tr e/plastic stress-strain
Engineering instea of tr e yiel stress
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Gaps between model and data
Non-linear elasti it
Elasti limit well below
lassi al ield point
ignifi ant plasti
strains prior to ield
Post-yield with ne king
behavior
3
3
. . . . .
Engineering train %)
Engineering
tress
Pa)
data
Plasti Point
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Handling complex phenomena
0
10
20
30
40
50
60
70
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Strain mm/mm
Stress
Pa
UT 1-39.62-1
UT 1-39.62-2
yield point
necking starts
neck propagation
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Getting pertinent properties
Importanceofmeasuring t e right property
rtifact freedata
Properly esigne experi ents
eg.not sing crosshea isplace ent
to calc late strain
Traceabledata (ISO 17025)
NIST tracea le instr ents
Certifie traine technicians
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Getting theright samples
Spatial variation
Properties ary ith location
For ing, stretching, ol ing
Environmental variation
Ageing andconditioning
ProcessvariationDegradation fromprocessing
Recycledmaterials
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Model Fitting
Complexnon-
linear regression
Importanceof
good fits
Evaluating quality
of fitteddata
Vis al meas res
Q antitati e
meas res
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ComplexModeling
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Model limitation
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Validation
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Comparison to experiment
0
10
20
30
40
50
60
0 0.05 0.1 0.15 0.2 0.25 0.3
Str i (mm/mm)
Str
ss(
)
LS- Y Sim l ti
T sil x rim t
T 24 l
limitation
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Input file creation
Time-consumingexotic formats
Errorpronedataentry
eed todefine theundefinable Some terms not nown
Some terms ass med
Impact on simulation = unknown
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Solutions
Try tounderstand themodel completely
Measure the correct data ithprecision
andminimumnoiseMeasure the right material
Select thebest model for thedata
Ensure thebest fit ofmodel todata
Validateagainst asimpleexperiment
Createerror-free input file
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Improvements
Simple improvements an add power
Validated models represent baseline
Models an be tuned for multi-a ial loadings
Measure Calibrate Validate Tune
