Miniaturization playing larger role in crash testing27 April 2010
Miniaturization helps OEMs get more value from crash testing.
OEMs expect more bang for their buck when vehicles undergo crash testing, according to Phil Glyn-Davies, Crashworthiness and Component Test Laboratory Manager at the U.K.’s Millbrook Proving Ground. “There has been a move in the sector for our customers to require larger amounts of data acquisition from each crash test, as opposed to using multiple vehicles.”
He said that until recently all the data acquisition systems (DAS) for a frontal crash test could be placed in the trunk of a vehicle. “But now, the same vehicle is being used for a rear crash test, too, so small DAS have to be located and restrained without causing damage to the vehicle.”
During a crash test, Millbrook’s equipment in the vehicle—dataloggers and cameras—may be subjected to acceleration of up to 100 g. Therefore, the lighter in weight they are, the more effective they will be and the less likely they are to interfere with results.
Weight savings is equally important with regard to new generations of hybrid- and pure-electric vehicles. “We have programs going forward that involve both,” says Glyn-Davies. “They bring some particular challenges but mainly associated with post-crash safety. Some of these systems run up to 600 V, and you have to ensure that vehicle integrated cutoff technology operates correctly in a crash environment. The battery must disconnect properly, but more importantly we have to be certain that there is no risk of either direct or indirect electric shock.”
Proposed testing requirements of hybrid- and pure-electric vehicles require some measurements to be taken from the vehicle conducted about 5 s after impact.
The weight of the battery of an electric vehicle need not play a significant role in crashworthiness, said Glyn-Davies, but the stiffness of equipment packaged in the vehicle does: “For example, hydrogen fuel cell storage tanks are very stiff, particularly when pressurized. So there is a real challenge to package these but leave space for occupants and for a controlled deformation of the vehicle’s structure.”
Miniaturization of DAS and the development and adoption of wireless technology have been crucial in reducing operating costs. Glyn-Davies said that before the advent of robust wireless technology, some 200 m (660 ft) of cable run would need to be towed behind a test vehicle, adding cost and weight. “Now, wireless technology makes crash testing quicker to perform and there is less risk of losing data that was a potential risk through damage to cables.”
And miniaturization of systems now facilitates increasingly sophisticated monitoring. Compact cameras can be placed beneath seats, in engine compartments, and close to the feet of a crash test dummy, without the need for heavy and awkward-to-position support brackets.
Millbrook is starting to install very small DAS directly into dummies. “New dummies will have the capability to produce in excess of 200 channels of data for more advanced crash test results,” says Glyn-Davies.
An extreme example of how the evolution of DAS is supporting a wider element of usage concerns testing blast effects on military vehicles. Until recently, data-logging equipment could not be positioned inside a vehicle, but miniaturization of DAS now allows this.
Adds Glyn-Davies: “As we move forward into a low-carbon future, space and weight issues have become more acute and the trend towards tiny, light, highly sophisticated wireless onboard data collection is set to grow.”
Other significant aspects of Millbrook’s test work include component testing. Its Component Test Laboratory’s core capability is laboratory-based. Vehicle interiors are a particular focus, with components including instrument panels and center consoles. OEMs particularly want to know how well equipment will perform and exceed the warranty period and also whether equipment meets customer expectations.
But much of the work is for “key-life” vehicle testing. This includes operation and longevity of air vents and internal buttons; thermal fluctuations of components that may induce warping; discoloration; sagging; squeaks and rattles.
Individual tests may last for any period from 48 h to a month. For all series vehicles, testing is required at several development stages and during production. This includes conformity of new model tests, midcycle upgrades, and production testing. Although simulation testing is reducing costs and development time, real-life testing will probably always be necessary to confirm computer-generated results.
Certainly, pure-electric and hybrid-electric vehicles do bring new challenges to this area of testing. Says Glyn-Davies: “An electric vehicle is, of course, extremely quiet, and the interior is void of the usual harmonics associated with IC engines. Any unwanted noises from rattles and squeaks will be only too evident to the driver—who will be quick to complain!
“And when hybrid vehicles are driven in electric-motor mode, their stopped IC engine can easily suffer bearing damage. However, the same multi-axis vibration equipment used to test warranty issues can be used to test these conditions.”
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