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Lightweight design and vehicle safety are just a few challenges during the vehicle development process. They can only be achieved by using innovative CAE approaches. In order to be able to accurately represent crash events the complexity of Finite Element models is continuously increasing. This is true for the discretisation of component geometries as well as for the description of material properties with models including advanced failure criteria (material failure and failure of any kind of joining). Such detailed full vehicle crash models for explicit solvers may become computationally very expensive. For this reason the innovative Multi-Domain simulation process was developed by Altair for the FE code RADIOSS. It allows the simulation of complex full vehicle crash models with highly detailed components. By splitting the model in multiple domains with own explicit time steps the computational performance can be maintained compared to conventional approaches (mono-domain with a single time step). The RADIOSS Multi-Domain approach has been implemented on the Ford Motor Company high performance computer cluster. First benchmarks at Ford R&A Europe have shown promising results, revealing a further potential within the industrial environment of crash analyses.
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7th European Altair Technology ConferenceMunich / June 24-26, 2014
Radioss Multi-Domain – Innovative Simulation Technique for CPU Time efficient Prediction of Material Failure in Full Vehicle Crash Simulations
Aleksandar Bach (Ford Research and Advanced Engineering Europe)Hüseyin Cakir
Vincent Dampure (Altair Engineering GmbH)
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Contents
� Motivation
� Radioss Multi-Domain Approach
� Validation + Examples
� Summary
2
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Motivation: Standard vs. refined Mesh 3
���� Accurate prediction with refined mesh only
Discplacement [mm]
Imp
ac
tor
Fo
rce
CAE_STANDARD
CAE_REFINED
TEST
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Motivation 4
� Accurate prediction of crash events requires increased model complexity
o Local mesh refinement (shell / solid elements)
o Advanced material models incl. failure criteria
� Increase of model size + reduction of explicit time step
���� Increase of total CPU time beyond acceptable range of industrial applications
Objectives of RADIOSS Multi-Domain approach
Improve CPU time efficiency by maintaining the accuracy (compared to standard Mono-Domain approach)
test
CAE
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Contents
� Motivation
� Radioss Multi-Domain Approach
� Validation + Examples
� Summary
5
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
What is Multi-Domain 6
� Split global model into physically equivalent “sub-domains”
� Each domain using its own time step (tF » tS)
� Force and momentum transfers between domains will be calculated by a separate program (RAD2RAD)
RAD2RAD
full domain (tF) sub-domain (tS)
full fullexplicit time step t
tF: full domain
tS: sub-domain
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Pre-Processing / Model Set-up 7
� User-friendly environment � single input file format (since Radioss V11.0.201)
- Define parts to be treated as sub-domain
- Define additional engine file per sub-domain
- Define cross contact between full domain and sub-domain
� Possible links between domains
- Common nodes
- Kinematic condition (/INTER/TYPE2: non-conforming meshes, beam2shell or solid2shell connections)
- General contact (/INTER/TYPE7, 11, 18, 24, …)
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Multi-Domain will be efficient if … 8
Minimize communication between domains
� Size of sub-domain is less than 30% of full domain (nodes/elements)
� Time step ratio between full domain and sub-domain ≥ 3
� Keep cross contact between full and sub-domain as small as possible
Minimize size of cross contact
� Use only segments of full domain which are potentially impacting parts of sub-domain (manual work)
� Development of automated contact optimization urgently needed (development ongoing)
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Parallelization of Multi-Domain Architecture 9
� No benefit of previous Multi-Domain release with more CPUs
� Due to parallelization of RAD2RAD process the performance of current Multi-Domain release was significantly improved
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Contents
� Motivation
� Radioss Multi-Domain Approach
� Validation + Examples
� Summary
10
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Method Development / Validation Procedure 11
COUPON
LEVELCOMPONENT
LEVEL
FULL VEHICLE
LEVEL
SYSTEMATIC VALIDATION PROCEDURE
� New CAE methodologies have to be checked by systematic
validation procedure in order to guarantee accuracy and robustness
of application for further industrial use
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Coupon Level 12
source: Research project FOSTA/AVIF Nr. P 806/06/2009 / A262 / S24 / 10162/08
Frauenhofer (IWM)
material properties
tensile test / 22MnB5 sample
� Metallurgical notch is significantly impacting
the crash performance
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Coupon Level / Multi-Domain vs. Mono-Domain 13
test data by Frauenhofer (IWM)
CAE Model
CAE vs. Test
� CAE correlates well with
test data
� No differences between
Multi-Domain and Mono-
Domain simulation
sub-domainfull domain
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Component Level 14
3PB of 22MnB5 beam
� Geometrical notch is significantly impacting the crash performance
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Component Level 15
CAE vs. Test
� Coarse mesh is not able to predict material failure correctly
� Fine mesh correlates perfectly with test data
� No differences between Multi-Domain and Mono-Domain simulation
coarse mesh (7mm)
fine mesh (1mm)
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Full Vehicle Level 16
full domain sub-domain with detailed SW
model (incl. HAZ)
side impact / run with 48 CPUs full vehicle crash model
number of elements ~ 2 millions
element ratio: sub-domain / full domain ~ 4%
time step ratio: full domain / sub-domain 2
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Full Vehicle Level / Multi-Domain vs. Mono-Domain
time time
en
erg
ies
intr
usio
n
17
global energies intrusion (@ B-pillar lower)
� The results are comparable for the Multi-Domain and
Mono-Domain simulation
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Full Vehicle Level / Run Time 18
„Multi-Domain #1sub-domain in global contact
side impact Mono-Domain Multi-Domain #1global contact
Multi-Domain #2cross contact
run time [h] ~ 27 ~ 100 ~ 15
Multi-Domain #2sub-domain in cross contact
slow-down 3.7 speed-up
1.8� For efficiency reasons it is
essential to optimize the contact between the sub-domain and full domain
� Automated routine urgently required (development ongoing)
major
improvement
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Example: Full Vehicle Level / Further CPU Benchmarks 19
case number of
elements
element ratiosub- / full domain
time step ratiofull / sub-domain
Speed-upMulti-/Mono
0.5 m 4% 4 3
1.2 m 2% 3 4
2.3 m 5% 4.4 / 10 3 / 4
0.35 m 20% 5 2
1.5 m 5% 7 6
� CPU speed-up highly depending on modeling conditions
(ratio of elements and time step, size of cross contact)
7th European ATC / Munich / June 24-26, 2014A. Bach, H. Cakir (Ford), V. Dampure (Altair)
Summary 20
� The Multi-Domain simulation approach is very important for Ford
� Multi-Domain is available and in use on Ford high performance computing cluster, improvements regardinguser friendliness and performance were achieved
� Benchmarks on full vehicle level are showing promising potential of CPU time reduction at increased computing accuracy
Next Steps
� Optimization of cross contact
� Automated mesh refinement of critical parts and part replacement in full vehicle model