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A Digital Twin for solid mechanics : How can we use images to build more predictive models ?
Florent Mathieu - IBFEM 18 - 05/09/18
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Motivations
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• S. Bouissou, Airbus : “We have to develop the next generations of planes in 30% less time, which means we have to perform 30% less testing.
But the certification agencies need the same amount of data.”
• D. Mellé, Safran Landing Systems : “In a landing gear, every kg counts and can help keeping our seller’s performance promises.
But our designs already seem to be at the top of what we can do, at least with the safety margins we’re currently using.”
Goal: more data points, less development time
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Experiences : what is currently done
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Digitalisation of the design process (PLM, SDM)
An Integrated Simulation Tool Framework for Process Data Management, Cognizant, 2015
© MSC Software
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Current performance levels
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Causes : • Increasing complexity of the products • Lack of foresight of product performances
(leading to design iterations)
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Client problem : Simplify model validation
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Design process in « model-based engineering »
DESIGN SIMULATION TESTS
PAIN POINTS : • Time of study • Budget overrun • Risks of delaying production
Digital thread
• Additional time: 10 to 100% of the project
• 1 test = 5k€ - 200k€
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Solution : 2 patents, 2 tools
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Design process in « model-based engineering »
DESIGN SIMULATION TESTS
Digital thread
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IMAGE PROCESSING Digital Image Correlation, multi-camera
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DIGITAL TWIN Model
comparison & correction
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Digital Image Correlation : images to the rescue
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DIC = Following visible strains and displacements
Various applications, from the sample to the structure
Main limitations : - standardization - “two-screen syndrome” :
comparing to the simulation is even more complex
-> qualitative measurement tool
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Subset-base vs FE-Based DIC (in theory)
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DIC = minimizing a correlation residual (reference image-deformed image)
Subset-based DIC
Repeated minimizations of Φc over the subsets
FE-based DIC
Global minimization of Φc over the region of interest (“gray level equilibrium”)
Reference image
Deformed image
Displacement field
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Subset-based DIC
FE-based DIC
Subset-base vs FE-Based DIC (in practice)
Reference system transfer (Tools ? Errors ?)
Mesh mapping (Tools? Errors ?)
CLOUD POINT MEASUREMENT (camera reference system)
CLOUD POINT MEASUREMENT (part reference system)
MESH-PROJECTED MEASUREMENT
MESH-BASED MEASUREMENT
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Software solution – DIC on the FE simulation Mesh
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FEATURES Image processing Displacements/strain
measurements Test/Simulation direct
comparison External data importation
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3D Simulation Testing Digital Twin
Our next proposition : a digital twin for 3D solid mechanics
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Load sensors
Strain gauges
LVDT
Cameras
Computed forces
Computed displacements
Computed strains
Boundary conditions, updated simulation parameters
Challenges : • Format compatibility (simulation & test) • “Heavy client” software development
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Use case – Composite bumper beam
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Unification of test and simulation data
MODEL
TEST SIMULATION
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sub-title
Experimental
Simulation initiale
0 5 10 15 20 25 30 U (mm)
25000
20000
15000
F (N) 10000
5000
MEASUREMENT Not an image-based geometry, but an image-based loading !
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@ SAFRAN Aircraft Engines
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Sol
utio
n
• FAN composite blade (LEAP engine) • Complex internal structure • Local behavior impossible to identify • Equivalent modeling was not satisfying
• Development of a custom SAMCEF connection module to DIC (then LS-DYNA, Abaqus, Zebulon)
• Automated parameter identification • Integration to the R&D team toolbox
• “These methods are undeniably faster than what we were able to do before, and give us results we didn’t have”
• “We think that will allow us to reduce the number of tests by capitalizing more on them, to reduce testing costs and processing time”
• Automated data processing
J. Schneider, composites expert
Con
text
R
esul
ts
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@ SAFRAN Landing Systems
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Con
text
S
olut
ion
Res
ults
• “Demo” part : short fiber composite • Compression test • Goal : validation of the simulation
• Multi-camera DIC systems (6) • Strain & displacement surface measurement • Global test/simulation comparison
• Global quality evaluation • Direct boundary conditions correction from measured data • Creation of an “augmented” simulation • “The comparison is way simpler and more complete than
what we usually have”
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@ CETIM
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Sol
utio
n
• New material – long fiber composite • Defects in structural parts • Goal : measure sensitivity to defects • Tests: traction and compression
• Displacement measurement on the FE mesh of the part • Use of measurement as input for boundary conditions • Global test/simulation comparison
• Evaluation of the model quality • Correction directly from the measurement data • “Augmented” and calibrated FE model
Con
text
R
esul
ts
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@ ALSTOM
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Sol
utio
n
• Fatigue testing of a train bogey • Problems with simulation results validation • Questions about a possible loading evolution in time
• Displacement measurement on the FE mesh • Integration of other sensors results (gauges, LVDT) • Automatic matching of simulation on the test results data
set (forces, displacements, strains)
• Evaluation of the model quality • Correction directly from the measurement data • Physical explanation for the lack of performance
(boundary conditions identification) • Reduction of simulation gauge error by 30%
Con
text
R
esul
ts
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What to do in the future ?
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• Current state of our work : proving that a better validation is possible (mostly on our side) through adapted tools
• Next step : proving that a better validation needs adapted processes
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Current validation process
Testing
Test specification : loading case, measurement devices, boundary conditions
Comparison with Excel
Test set-up, installation of measurement devices
Specification document
Measurement results (.csv, hbm)
DESIGN OFFICE TEST LAB
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In the future
DIGITAL TWIN
Testing
Test/simulation one-click comparison, simulation « augmenting »
FROM DESIGN TO TESTING
FROM TESTING TO A BETTER SIMULATION
Test set-up, installation of measurement devices
Validation as a cross-team activity
- 3D model of the part - Sensor positioning - Load case
Virtual sensors (force, strain, fields) positioned on the 3D model
Measurement results (.csv or live)
Test specification : loading case, measurement devices, boundary conditions
DESIGN OFFICE TEST LAB
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Key messages
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• Simulation will not be (for a long time) the only way to develop high-risk products : testing has to be integrated to the validation digital thread, for performance and for risk management
• Test-simulation comparison has to be addressed with adapted tools, and imaging can play a central role (field measurements, FEA model “augmenting”)
• Challenges : implementing new tools and new processes for an unknown (ie not measured yet) gain
• How do you deal with validation ? Are there technical limitations ?
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COMBLEZ L’ECART ENTRE ESSAIS ET SIMULATIONS
Intégration des essais dans la chaîne numérique
Réduction des coûts de développement et de conception