Identification of scatter sources and significant         reduction of scatter occurrence with                      DIFFCR...
Agenda Introduction                     Reasons for scatter Analysis methods                     Basic analysis method...
Introduction: Reasons for scatter     Potential scatter of simulation results is still a challenging issue     For the d...
Introduction: Reasons for scatter due tophysics         Reasons                    Contact / no contact   90° contact   bu...
Analysis methods: Stability analysis withDIFFCRASH Postprocessing tool: Identification and separation of multiple sources...
Analysis methods: Basic analysismethods Functionals (per Node):                     PD3MX (max. scatter in 3D)          ...
Analysis methods: Scatter visualization© Fraunhofer SCAI
Analysis methods: Correlation based methods Correlation analysis                     Find strong correlation in data -> ...
Analysis methods: PCA based methods Data Reduction for simulation results: 20 – 200 runs                     Parameter c...
Analysis methods: PCA based methods Global PCA                     Computation of scatter modes for the whole model     ...
Analysis methods:Principle Component Analysis (PCA) Covariance Matrix:                        A       Xi     X0, X j     ...
Example of the two most important modesfor the Ford Taurus© Fraunhofer SCAI
Example case: Chrysler NeonFrontal Impact on Rigid wallModel Unit: mm, s, TonInitial Velocity: 12.3 m/sTotal Mass : 1.219...
T = 00.00 ms        T = 80.00 ms© Fraunhofer SCAI
Target area                    T = 00.00 ms                      T = 80.00 ms                         Overall intrusion in...
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
Scatter propagation© Fraunhofer SCAI
What is the Source (in time and space) of this results Dispersion ?                    MDSplot                    Points r...
What is the Source (in time and space) of this result dispersion ?© Fraunhofer SCAI
What is the Source (in time and space) ofthis result Dispersion ?                                     Sub frame does NOT h...
What is the Source (in time and space) ofthis result Dispersion ?© Fraunhofer SCAI
What is the Source (in time and space) of  this result Dispersion ?                                                  Blue:...
Summary DIFFCRASH allows us to identify and quantify major sources of scatter The methods allow to devise design and mod...
Thank you very much for your attention...!                    Innovation Intelligence®© Fraunhofer SCAI
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Identification of Scatter Sources and Significant Reduction of Scatter Occurrence with DIFFCRASH

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The investigations described here are related to the unstable behavior of crash-results due to minor changes in the model. As an outcome the received crash-results become in some way unpredictable and the causes can be various, e.g. modeling failure, contact issues, numerical instabilities, physical instabilities, etc.

To identify and separate these scatter sources the results are analyzed by means of visualizing the standard deviation of scatter itself and computing scatter modes for selected parts of interest. These computations are based on the principle component analysis (PCA), a dimension reduction technique. Afterwards, new virtual crash results representing the most extreme values of these modes are computed and help identifying the original reasons which cause the scatter. Then correction can be applied resulting in substantial reduction of the original scatter.

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Identification of Scatter Sources and Significant Reduction of Scatter Occurrence with DIFFCRASH

  1. 1. Identification of scatter sources and significant reduction of scatter occurrence with DIFFCRASH Innovation Intelligence® Marian Bulla (Altair Germany) Dominik Borsotto (Fraunhofer SCAI) Clemens A. Thole (Fraunhofer SCAI)© Fraunhofer SCAI
  2. 2. Agenda Introduction  Reasons for scatter Analysis methods  Basic analysis methods  Correlation based methods  PCA based methods Example Case  Analysis of a Chrysler NEON model (RADIOSS)© Fraunhofer SCAI
  3. 3. Introduction: Reasons for scatter  Potential scatter of simulation results is still a challenging issue  For the design and optimization of car models it is very helpful to deal with a simulation model, which generates similar results even if slight changes of the model are performed.  Keyword: Predictability  Reasons for scatter are various.© Fraunhofer SCAI
  4. 4. Introduction: Reasons for scatter due tophysics Reasons Contact / no contact 90° contact buckling Element failures friction© Fraunhofer SCAI
  5. 5. Analysis methods: Stability analysis withDIFFCRASH Postprocessing tool: Identification and separation of multiple sources of scatter: location and time Statistical Analysis of full simulation models  Basic analysis methods  Correlation based methods  PCA based methods © by SCAI-FHG© Fraunhofer SCAI 5
  6. 6. Analysis methods: Basic analysismethods Functionals (per Node):  PD3MX (max. scatter in 3D)  PD3AV (avg. scatter in 3D)  PDXMX (max. scatter in X-direction)  PDYMX (max. scatter in Y-direction)  PDZMX (max. scatter in Z-direction)  PD3IJ (Simulation runs with max. distance) Relies on different positions of the same node in multiple simulations© Fraunhofer SCAI
  7. 7. Analysis methods: Scatter visualization© Fraunhofer SCAI
  8. 8. Analysis methods: Correlation based methods Correlation analysis  Find strong correlation in data -> causal chains (backtracking of instabilities)  Elimination of a detected source from the set of results (Orthogonal projection)© Fraunhofer SCAI
  9. 9. Analysis methods: PCA based methods Data Reduction for simulation results: 20 – 200 runs  Parameter changes (Material properties, thicknesses, barrier loc.)  2.000.000 nodes/elements  150 states (time steps in the results)  Dimension: 1 Billion 200 Billion values PCA Analysis  Small number of modes representing the results  Find the dominating components in the result data, which have the strongest impact on the simulation results  Subspace comparison to identify buckling  Modes consist of a linear combination of all simulation runs© Fraunhofer SCAI
  10. 10. Analysis methods: PCA based methods Global PCA  Computation of scatter modes for the whole model  Visualization as an virtual computed simulation result Local PCA  Computation of scatter modes for single parts or groups of parts out of the model Difference PCA  Different origins of scatter can be identified and physically meaningful components can be determined© Fraunhofer SCAI
  11. 11. Analysis methods:Principle Component Analysis (PCA) Covariance Matrix: A Xi X0, X j X0 i, j 2 Eigenvalues/Eigenvectors of the Covariance matrix: , i i i Vectors in the space of coefficients i L2 Norm of X0 X( i) Number of i determines the upper bound of the essential size of the solution space λi (Importance measures) 50 0.25 40 0.2 30 0.15 20 0.1 10 0.05 0 0 1 11 21 31 41 51 61 71 81 91 0 20 40 60 80 100© Fraunhofer SCAI
  12. 12. Example of the two most important modesfor the Ford Taurus© Fraunhofer SCAI
  13. 13. Example case: Chrysler NeonFrontal Impact on Rigid wallModel Unit: mm, s, TonInitial Velocity: 12.3 m/sTotal Mass : 1.219 TonRandom Noise: 1.0 E-6 mmSeed variation (0.00 to 0.9)© Fraunhofer SCAI
  14. 14. T = 00.00 ms T = 80.00 ms© Fraunhofer SCAI
  15. 15. Target area T = 00.00 ms T = 80.00 ms Overall intrusion in dashboard© Fraunhofer SCAI
  16. 16. Scatter propagation© Fraunhofer SCAI
  17. 17. Scatter propagation© Fraunhofer SCAI
  18. 18. Scatter propagation© Fraunhofer SCAI
  19. 19. Scatter propagation© Fraunhofer SCAI
  20. 20. Scatter propagation© Fraunhofer SCAI
  21. 21. Scatter propagation© Fraunhofer SCAI
  22. 22. Scatter propagation© Fraunhofer SCAI
  23. 23. Scatter propagation© Fraunhofer SCAI
  24. 24. Scatter propagation© Fraunhofer SCAI
  25. 25. Scatter propagation© Fraunhofer SCAI
  26. 26. Scatter propagation© Fraunhofer SCAI
  27. 27. Scatter propagation© Fraunhofer SCAI
  28. 28. Scatter propagation© Fraunhofer SCAI
  29. 29. Scatter propagation© Fraunhofer SCAI
  30. 30. Scatter propagation© Fraunhofer SCAI
  31. 31. Scatter propagation© Fraunhofer SCAI
  32. 32. Scatter propagation© Fraunhofer SCAI
  33. 33. Scatter propagation© Fraunhofer SCAI
  34. 34. Scatter propagation© Fraunhofer SCAI
  35. 35. Scatter propagation© Fraunhofer SCAI
  36. 36. Scatter propagation© Fraunhofer SCAI
  37. 37. What is the Source (in time and space) of this results Dispersion ? MDSplot Points represent simulation results X-Axis: Contribution of most important mode Y-Axis: Contribution of 2nd important mode. virtual derived simulationresultsd to visualize the dominating effect.© Fraunhofer SCAI
  38. 38. What is the Source (in time and space) of this result dispersion ?© Fraunhofer SCAI
  39. 39. What is the Source (in time and space) ofthis result Dispersion ? Sub frame does NOT hit Sub frame hits Engine at ~ 40 ms Engine at ~ 40 ms© Fraunhofer SCAI
  40. 40. What is the Source (in time and space) ofthis result Dispersion ?© Fraunhofer SCAI
  41. 41. What is the Source (in time and space) of this result Dispersion ? Blue: Original scatter modes Green: Without scatter of engine/Subframe“Switching OFF” this scatter source (analytically in DiffCrash) indicatesa significant reduction of displacement scatter in Dashboard area.  Issue area has to be analyzed further, by local © Fraunhofer SCAI investigation e.g. with the help of MultiDomain .
  42. 42. Summary DIFFCRASH allows us to identify and quantify major sources of scatter The methods allow to devise design and modeling suggestions to reduce scatter of simulation results Next steps e.g.:  Applying the multidomain - technique to get a modeling of the critical region in more detail.  Geometrical changes can force a deterministic behavior in a next step.  First results of an adapted Chrysler NEON model look very promising regarding the reduction of scatter at the front wall OUTLOOK:  Postprocessor interface for GNS Animator (1st prototype ) and others.© Fraunhofer SCAI
  43. 43. Thank you very much for your attention...! Innovation Intelligence®© Fraunhofer SCAI

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