10/04/2011

www.gupta-verlag.de/rubber

BASF: World's first production-ready thermoplastic wheel rim

[image_0]The smart all-plastic wheel rim is over 30 % lighter than a standard production aluminium wheel. The plastic rim weighs only 6 kg and is made of the new polyamide Ultramid Structure from BASF. This contributes to a noticeable reduction in the vehicle's weight by a total of 12 kg and translates into lower fuel consumption when the vehicle is equipped with a conventional engine. In the case of a battery-powered auto such as the smart forvision, the result is greater range. The complete rim (to be technically correct: the wheel) - consists of two parts: the actual supporting component and a wheel cover that is also manufactured from BASF Ultramid. Both parts have a supporting function and withstand high loads under driving conditions. The wheel cover can be painted in any colour used for the vehicle. In Frankfurt, it was shown - like the complete smart forvision - in white and copper. "Thermoset rims are already being used in racing and for short production runs”, explained Heiko Hess, who is responsible for wheel development at BASF. "However, compared to thermoplastic rims, which can be injection moulded, they are considerably more complex, more expensive to manufacture and thus unsuitable for high-volume production”. Speciality plastic for high loads
The new Ultramid Structure from BASF's polyamide line is a composite plastic that can withstand high loads, because it is reinforced with long fibres and was introduced at the K 2010 plastics trade fair in Düsseldorf. The long-fibre reinforcement makes it especially strong - it can replace metal wherever energy absorption is a major requirement, e. g. in crash absorbers, seat structures, battery holders, engine mounts, and other structural components. The Ultramid Structure grade used here is particularly rigid, impact-resistant, and dimensionally stable. Designed on the computer
As was the case with numerous Ultramid parts in recent years, the universally applicable simulation tool Ultrasim from BASF, was used when designing this high-strength Ultramid rim. With the aid of a topology optimisation the shape and position of the ribs in the plastic rim can be predicted and optimised on the computer without compromising the design. The form of the wheel was already defined in an early design phase and had to be modified only slightly on the actual part. As a result, it was possible to develop this highly safety-relevant part, which previously existed only in metal, in close cooperation with the Daimler wheel rim experts in a very short period of time. The extensive load tests that the wheel had to pass at smart and BASF included the tolerance test on the wheel measuring machine, the fatigue test on the biaxial wheel test stand (ZWARP test), the biaxial wheel test, the impact/radial impact test when dropped from a tower and the burst test. Coupling to the axle, and thus load transfer, is accomplished by means of metal inserts and bolts.

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