Passive safety: Top marks for safety

Mar 7, 2011
  • Comprehensive protection: seven airbags and NECK-PRO head restraints
  • Anticipatory safety: with PRE-SAFE® system as an option
  • Best purchasing decision: top marks in US safety test
  • Crash performance under the microscope: sophisticated simulations
The C-Class safety concept has been optimised based on the analysis of real-life accidents. As part of the standard specification, seven airbags, belt tensioners, belt force limiters and NECK-PRO crash-responsive head restraints offer the occupants an extremely high level of protection should an accident occur. The body structure has been designed to ensure that, in the event of a frontal collision, the impact forces are distributed over a wide area and on four independently acting impact levels, meaning that the passenger compartment remains largely intact. Around 70 percent of all the bodyshell panels are made from state-of-the-art, high-strength steel alloys that minimise weight and maximise safety.
The C-Class also features the anticipatory occupant protection system PRE‑SAFE® as an option. This Mercedes-Benz innovation uses the time between detection of a potential accident situation and a possible collision to initiate preventive protective measures, thus reducing the loads exerted on the occupants in the event of a crash by up to 40 percent.
Crash-test rating: top marks in Europe and the USA
The safety concept also does brilliantly in standardised rating crash tests. The renowned American Insurance Institute for Highway Safety (IIHS), for instance, declared the Mercedes-Benz C-Class Top Safety Pick three times in a row (in 2009, 2010 and 2011) – deeming it to be the best purchasing decision with regard to safety. The
C-Class achieved good ratings in all the safety criteria which were examined.
Each year, the experts at the IIHS rate car models based on stringent safety criteria, thereby providing an important tool to help buyers make a decision. In the assessments the vehicles are subjected to front and side crash tests. The safety specialists in the US also evaluate protection against neck injuries in rear impacts. For all three criteria, the C-Class was awarded top marks.
By rating the C-Class a Top Safety Pick, the IIHS has confirmed the vehicle’s extremely good performance in crash tests conforming to Euro NCAP (the European New Car Assessment Programme), in which the C-Class was awarded five stars, making it one of the safest cars on the market.
Crash-test simulation: two million finite elements
Extensive crash-test simulations formed the basis for safety development work on the C-Class. This is a field which has made great leaps forward: at the beginning of the 1990s, Mercedes-Benz was performing around 200 computerised crash tests per annum. By the year 2000 this number had already increased to 1500 simulations, and in 2010 more than 50,000 were carried out. And this is by no means the only impressive set of statistics: for the tests on the W 201, the C-Class’s predecessor from the 1980s, the computer model consisted of 25,000 finite elements. Nowadays the level of detail is much greater – the digital replica of the current C-Class (W 204), for example, comprises around two million elements. And the planar grid of the virtual vehicle structure is now composed of tiny rectangles and triangles with an edge length of three millimetres. This facilitates a far more precise and detailed deformation analysis than previously, when, at 25 millimetres the elements were so much larger.
But it is not just the software that has clocked up huge advances, for the hardware has undergone an impressive process of development, too: the C‑Class that was unveiled in 2007 was the first series-production car in the world to be developed using the trend-setting digital prototype (DPT) method. The digital prototype made it possible for all the simulation methods to be pooled for the first time, and thus to create a completely virtual car.
As well as the high development speed, the decisive advantage that computer simulation has over real crash tests lies not only in the fact that the vehicles are not destroyed; even more important than that is the ability which today’ s engineers have to detect and follow what actually happens in an impact in great detail. As if with x-ray eyes the engineers can track the course of deformation in extreme slow motion and from any perspective they wish, thus delving further and further into the details every year.
By way of example, in order to be able to reconstruct a vehicle’s spot welds and its tensile shear and compressive strength precisely in the computer model, the simulation experts have performed over 9000 component tests. But there are still limits to simulation, such as fuel density and the performance of the door lock during the crash. This is why real-life and simulated crash texts will continue to complement one another at the company’s Technology Centre in Sindelfingen, where they work in close cooperation.