Model for testing noise in cars developed by LTU
Swedish and international automotive industry will benefit from a new simulation model to locate annoying noises in cars. The model has been developed within the competence center CASTT at Luleå University of Technology, in close collaboration with the automotive testing industry in Norrbotten.
- It allows car manufacturers at the design stage to estimate if and where unwanted noise between sealing plan may be in their new upcoming car models. Through this knowledge, for example, the test phase of the vehicles can be refined and focused in the right areas so that future problems can be avoided, says Matti Rantatalo, a researcher at Luleå University of Technology who developed the model within CASTT (Center for Automotive System Technologies and Testing).
The model is based on research that Matti Rantatalo has developed within the framework of his doctoral studies with a focus on squeaks and other types of noise in cars in cold climates.
The starting point is the requirements on the ability to seal and insulate both the internal and external environments from heat, cold, noise, dirt, etc. The rubber seals should, in other words, be able to isolate and at the same time creating a soft contact between door and frame. But in the case of complex designs and shapes of cars, the effect may be that the gasket is not stuck to the car, but starts to slide in a disadvantage way against e.g a door.
- When the seal slides along a metal surface under the wrong conditions you get different kinds of sounds with squeaks and creaks, says Matti Rantatalo.
He has both studied how sounds can be identified and how they can be simulated. To cope with the identification they had to, as an aside in his research in CASTT, build a test track. It was built up by the test industry in northern Sweden in order to artificially make the cars rattle at different frequencies during a single test round. Car manufacturers were interested in such a solution to figure out if it starts to squeak or creak before starting to produce the car.
- It is of course a possibility for them to bring down costs significantly if you can foresee problems at an early stage, says Matti Rantatalo.
Matti Rantatalo's work was mostly about building computer-based models of rubber seals and simulations to analyze how the creaking sounds can be created when a car door is allowed to slide along a seal. "Stick Slip" is the namen of the phenomenon that makes noise if e.g a door is moving too much compared to the seal.
- It's pretty much like putting a bow-and-drop. When the seal is released from the door it flungs back quickly, creating a sound pulse and it is the one that sounds, he says.
There are plans to apply the research results of future research for testing of tires where the traction is assessed and classified.
