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The Safety Concept of the New Volkswagen Polo Matthias Rabe, Head of Passenger Car Safety, Volkswagen AG The safety concept for the new Volkswagen Polo introduces new standards in this class. The starting point for the development of this concept was Volkswagen’s policy to maintain an exceptionally high level of safety standards – standards which are more demanding even than those prescribed by existing laws and foreseeable developments.
Development work in this area covers all aspects of crash safety, including front-end, offset, side, rear-end, rollover and car-to-car impact. The use of state-of-the-art, coordinated development tools such as DMU (Digital Mock-Up) enabled us to incorporate the myriad of wide-ranging demands into this vehicle’s constructional design. Computer-aided crash simulators provided information on crash properties at a very early stage in development, with the results of those findings later scrutinised when the developed specimens were put through the paces of rigorous crash testing. Numerical simulations enabled us to use a variety of methods to reenact real crash scenarios. Multibody simulations (using the MADYMO program) allowed us to simulate vehicle occupants and optimise restraint systems. Structurally relevant computations on aspects such as frontend, side and rear-end impact or head-on-dashboard impact were carried out using the PAMCRASH finite-element program. Thus, during the course of several hundred computer run-throughs, we were able to optimise the parameters that were not definable in crash testing.
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The safety concept for the new Volkswagen Polo introduces new standards in this class.
Safety Characteristics of the Body Shell The safety structure for the new Polo was designed based on findings by the Volkswagen Group’s own accident research unit coupled with the world’s most rigorous consumer and legally stipulated crash testing of front-end, rear-end and side impact. Our safety concept is founded on a thoroughly new, independent platform construction which first proved its inherent potential to provide occupant safety when the Skoda Fabia, on which it was used, achieved a 4-star Euro NCAP rating. To optimise the Polo’s crashrelevant behaviour, we used a
simulation model comprising some 300,000 elements. The analysis of structural measures based not only on body-shell deformation and intrusion speeds but also on the impact it caused to occupants was an integral part of crash-design calculations even in the early stages of the project. The central aim of our safety principle is to ensure a sufficient occupant survival cell in all relevant accident situations. Structural members made of highest-tensile steels distribute impact pressure over a broad surface, directing its flow to specific vehicle structures where it is absorbed according to predefined specifications. Thus, the structure can withstand as high as possible AutoTechnology 1/ 2002
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a level of force, even in cases of local body-shell strain, for example in an offset or pole crash situation, thereby keeping deformation to a minimum.
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Simulation of an offset crash with a deformable barrier at 64 km/h.
Front-End Impact To make sure that the deformation which occurs in the Polo IV is in optimum response to any given front-end impact situation, this vehicle is equipped with a sophisticated system of structural elements which convert and distribute the energy. In addition to a cross-member of highest-tensile steel and platinum-weld longitudinal members designed to
pled from the longitudinal members, so that, even if more powerful engines are in play, the impact on the footwall area is kept to an absolute minimum. A crash-optimised foot pedal cluster (COF) further reduces the potential for foot injuries. A minimum amount of potential shift in the steering wheel, in conjunction with a telescopic safety steering column, reduces the risk of injury to the head and chest area and ensures that the driver’s airbag has sufficient room for proper inflation.
Side Impact include sections of high-tensile material quality (ZstE260), this system also features a bulkhead cross-member of optimised panel thickness and material quality in the footwall area. As such, the design offers optimum potential protection from intruding front wheels in the event of real-life car-to-car accident situations in which the proportion of vehicle overlap is often very low. In the event of front-end impact, the subframe is decou-
AutoTechnology 1/ 2002
The safety structure of the new Polo
Offset crash.
A low level of overall intrusion, the harmonious deformation of the B-pillar and the time benefits in terms of intrusion speeds are all indicators of the high level of safety potential that the new Polo will provide in the event of a side impact. Surrounding reinforcements in the side structure and the door keep the structure from collapsing and ensure that the distance between the A- and Bpillars is changed as little as possible upon collision. Thus, even in
the event of an offset front-end impact with only partial vehicle overlap, occupants can still be rescued from the vehicle via the door, since the vehicle door will still open with ease. In order to optimise the performance of the new Polo in the event of a side impact, we used a simulation model consisting of approximately 300,000 finite elements. This model defines both the body shell as well as all panelling and fitting components relevant in the event of a side impact, and it offers a finite-element dummy which enables the injury criteria for the occupant to be assessed. The end deformation of the vehicle as predicted by the computer simulation for a side impact was verified by the crash tests, providing high-level confirmation of the exceptional stability of this vehicle’s structure. Rear-End Impact((Sub)) Like all VW passenger cars, the new VW Polo is designed to fulfil the most rigorous of rearend-impact crash tests – the USstandard FMVSS 301 test, which involves impact with a 1,800-kg
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System of structural members in the vehicle front-end. barrier at an impact speed of 30 mph (48 km/h). Ensuring that there is no leakage of fuel is one of the aspects that this test focuses on.
Rollover Impact
Extract from the FEM computation for front-end impact with specification of the occupant-relevant analysis points for deformation.
In order to ensure a sufficiently large survival cell for vehicle occupants in the event of a rollover crash, one of the elements of safety-relevant development at Volkswagen was dynamic rollover testing. The A-, B- and C-pillars and the roof framework were designed to achieve the stability needed for the roof construction. The use of instrumented dummies helped to determine the impact on occupants.
Occupant Restraint Systems The vehicle’s front seats and the outer seats at the rear are all fitted with automatic 3-point seat belts. Seat belt height adjusters
for the front seats mean that occupants can adjust the settings for optimum safety fit and comfort. The driver and front-passenger seats are also fitted with electrically triggered seat belt tensioners which feature seat belt pressure limiters. Even before the vehicle occupant is pushed forward in the event of a frontal crash, the tensioners pull in the seat belt slack, so that occupants are ideally fixed to the occupant cell. The job of the seat belt pressure limiters is to reduce the force of the restraint and thus the risk of excessive belt pressure being applied to the occupant’s chest. The Polo features a newly developed airbag system – with a volume of 64 litres and 95 litres for the driver and the front-passenger airbags, respectively. The front-passenger airbag and the driver’s side airbag can be deactivated via a key switch. This new airbag system has shown itself to provide optimum protection in real-life accident situations. The gas generators run on a nonaside, i.e. environmentally friendly, propellant. The development of a seamless airbag cover means that the airbag can be invisibly integrated into the shift console. The side airbags integrated into the front-seat backrests offer additional protection in the event of a side impact. These airbags have a volume of 12 litres and are designed to effectively reduce chest, stomach and pelvic injuries in a crash. Because they are fitted into the seats themselves, occupants can be sure that they will provide optimal protection in any seating position. An inflatable curtain system will be available for the Polo as of 2002. This
A dynamic rollover test.
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airbag will extend across the entire region from the A- to the C-pillar, providing comprehensive head protection for both front and back-seat passengers. The rear seats in the Polo feature fittings for ISOFIX child seats. Rather than using the seat belts integrated into the seats of the car to fix the child seat into place, this system attaches the seat directly to the vehicle body shell using a quick-clasp fastener. Compared with conventional systems, the installation of this child seat is considerably easier, so that the risk of error is virtually nonexistent. As the seat will normally remain in the car, only the child itself now needs to be belted up before each car trip, which makes the system exceptionally user-friendly.
The Polo features a newly developed airbag system – with a volume of 64 litres and 95 litres for the driver and the front-passenger airbags.
The Polo’s robust body shell and the use of optimised occupant restraint systems put this vehicle ahead of its class when it comes to providing a supreme level of safety potential.
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Crash-relevant reinforcement measures in the side structure and door.
Repairs The costs of insuring a car are an important factor as far as vehicle economy is concerned. And vehicle insurance categories are determined according to the incidence of claim for each type of vehicle and the extent of necessary repairs in the event of such claims. Continued systematic development of the bumper systems has enabled us to achieve a defined reduction in energy at low speeds and thus lower the incidence of damage to the body shell or other components.
Summary The interaction of the safety features of this vehicle – i.e. its solid body-shell structure and the newly developed occupant restraint systems with which it is equipped – provide the new Volkswagen Polo with superior safety potential that sets a new benchmark in its class. This is
true both in terms of self-protection in an offset crash with a deformable barrier or total headon impact, and in terms of all possible side-impact scenarios – even in the event of a pole crash for vehicles fitted with the optional inflatable curtain system (available as of 2002). The high level of integrity reflected in the new Polo’s occupant cell as well as the excellent design coordination of its body-shell structure and occupant restrain systems means that this vehicle offers a high degree of safety potential in the event of accidents involving other vehicles.
Polo FEM imulation for side impact.
Side impact
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