Virtual Crash Test Dummies: A Data Management TestVirtual Crash Test Dummies: A Data Management Test
July 7, 2010
Physical crash dummies may have dozens of sensors and othersophisticated mechanical parts, but their digital brethren can be just ascomplicated. With more than 100,000 elements and dozens of validation tests tomanage, companies delivering the complex FEA simulation models that lie at theheart of the virtual crash test dummies are starting to leverage a new type ofsoftware platform to facilitate the process.
One such company is SIMULIA,a division of Dassault Systemes thatspecializes in simulation software, including the Abaqus FEA program. Abaqus isused by many in the automotive industry to create virtual crash test dummymodels, but SIMULIA also separately develops and qualifies its own virtualcrash test dummy models, including versionsof the BioRID (Biofidelic Rear Impact Dummy) and WorldSID (Worldwide SideImpact Dummy). To streamline the time and effort involved in creating,validating and updating the virtual models, a SIMULIA team now employs thecompany's own Simulation Lifecycle Management (SLM) platform to automate theprocess and ease the data management burden. As a result, SIMULIA has been ableto cut back the time it takes to validate the virtual crash dummies from fourweeks to as little as four days.
"We're using SLM in both the development of the virtualcrash test dummies as well as with the maintenance of the virtual crash dummiesand the synchronization with the new versions of the Abaqus FEA software," saysPaul Lalor, SIMULIA's product manager for the SLM suite of products. "Thevirtual crash test dummies need to be managed and we need to assure the OEMsthat the dummies they're using in their car programs, together with theversions of the analysis software, are indeed fully validated."
Data Management Challenge
Deploying SLM to promote simulation reuse, aid in theonerous data-management burden and, ultimately, shorten the development andvalidation cycle couldn't come at a better time. Virtual crash test dummies arein high demand as leading automotive OEMs increasingly transform their vehicledevelopment programs to embrace the digital world, using 3-D CAD and simulationtools to model and test vehicle designs virtually as opposed to building costlyphysical prototypes. The cost of building and crashing a prototype vehicle ishigh enough, but the physical crash test dummies, which come in a variety oftrue-to-life human dimensions and are made of myriad materials, includingcustom-molded urethane and vinyl, are expensive in their own right, oftencommanding a price tag of more than $200,000 per dummy. The reason? Thephysical dummies are highly complex, loaded up with sensors, and equipped withribs, spines, necks, heads and limbs so they can respond to impact in ways thatare realistic to how a human body might respond.
To ensure the validity of any kind of safety testing, thevirtual dummies have to consistently mimic the behavior of the physical crashtest dummies and produce data that correlates well to the physical crash testresults. To do so in any highly consistent and repeatable manner requiresstandardization of FEA models, ensuring that each virtual dummy exhibitspredictable responses to crash impact loads and accelerations. A typical FEAdummy model will have about 100,000 elements, 150,000 nodes and 500,000 degreesof freedom. To ensure there are comparable results between this extensivevirtual dummy and its physical counterpart, the SIMULIA engineers have to runcomponent, sub-assembly and full-model tests of each dummy model, whichgenerates a huge amount of data and outputs for comparison. For instance, theteam might run a sub-assembly test to assess the stresses on a full rib cagemodel hit from the side by a pendulum, while also doing a full-body test of anentire dummy model to see what happens when it's hit from the side by a virtual"solid" barrier.
On top of this, there's another layer that complicates thedata-management challenge. Each time a new version of the physical crash testdummy is introduced or a new version of the crash simulation software isreleased, vendors have to go through a lengthy qualification process to ensurethat same level of consistency is retained. Traditionally, this has been alabor-intensive process for a SIMULIA team, which had to manually runsimulations for the 30 to 60 tests in both the current and previous versions ofthe Abaqus software. Teams also had to run post-processing steps to generatethe curve plots describing the analysis results, as well as generate statisticalcomparisons to ensure the same variables were in agreement between thedifferent versions of Abaqus. "It used to be a horrible, labor-intensive, poorlymanaged process, (and with SLM), it's now a highly automated, highly managedprocess with a lot of collaboration," Lalor says.
SLM, which serves as both a central repository for thesimulation data and as a process controller, allows the SIMULIA engineers tosave and manage their simulation data, reuse simulations, retain performancemetrics and protect their intellectual property. The Isightsoftware within SIMULIA also allows them to automate much of the simulationprocesses - another key factor in reducing the overall validation cycle times,Lalor explains. Specifically, Isight enabled the team to create a workflow thatlet them launch all of the Abaqus analysis tasks on a compute cluster as wellas another workflow that helped determine the correlation between results fromthe different Abaqus versions on identical dummy tests. "We can literally pressa button and launch all of the validation tests on a high-performance computingcluster and then generate a report to tell me which of the 350 tests matchedand which didn't," Lalor says. "That gives us an 80 percent reduction inmaintenance cycles."
Since building and validating virtual crash test dummies isa team, not an individual sport, the use of SLM and Isight has also aided incollaboration. "This allows multiple team members to collaborate on the samedata in a controlled way," Lalor says. "Before SLM, the data was on individualpeople's hard drives or shared drives and you had to call `Joe' to ask aboutchanges in a file."
First Technology SafetySystems, which uses Abaqus as well as other simulation tools to create itsphysical and FEA crash test models, sees process automation as the wave of thefuture for simplifying what is now, admittedly, a labor-intensive, datamanagement process. "We definitely see a need for this," says Roel Van DeVelde, CAE sales and customer relations manager for FTSS Americas. "Today, it'svery labor-intensive to make sure we use the correct data, and we plan to havethe resources available in the next six to 18 months to have our models readyto integrate into this kind of process automation environment."
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