What are some chassis and tire simulations

Depict tires realistically


Fraunhofer researchers have developed a tool that can simulate tires: "CDTire / 3D" represents the wheels realistically and takes into account the heat that is generated when driving and changes the properties of the tires.

The engineers and designers have a good grip on the simulation of the vehicle itself. However, the tires are a challenge, because they behave in a complex and non-linear manner, explain the experts from the Fraunhofer-Gesellschaft. The calculation is either tedious, computationally intensive and cannot be integrated into the overall model, or it provides imprecise results. Researchers at the Fraunhofer Institute for Industrial Mathematics ITWM in Kaiserslautern have developed "CDTire / 3D", a simulation tool that can master this. "With this technology, we have found a good balance between computing time and accuracy," reveals Dr. Manfred Bäcker, head of tire and vehicle simulation at the ITWM. The simulation depicts reality well and is fast at the same time. From April 13th to 17th, the scientists will present the software at the Hanover Fair at the joint Fraunhofer booth "Simulation".

Illustration via structural mechanics shell model

The scientists map the properties of the tire using a structural-mechanical shell model. "Instead of depicting it as a volume model, we represent the tire as a shell - that saves a lot of simulation time and still takes all properties into account," explains Bäcker. According to the Fraunhofer-Gesellschaft, the scientists proceed as follows: First, the researchers calculate individual shells for each functional position of the real tire. That means one for each steel belt ply, one for the bandage and so on. They then combine these into a single shell. The special thing about this is that the model also takes the side wall into account.

In the simulations that have been common up to now, the car manufacturers have to completely readjust the parameters as soon as the tire width changes in the simulation or the tire pressure varies, the scientists explain. "We have completely separated the geometry and material properties from each other, so you can change the geometry of the tire without having to adapt the model," emphasizes Bäcker.

Include temperature

In addition to this simulation, the scientists now also include the temperature: the tire is deformed or warped while driving, and the brakes also give off heat. As a result, it heats up and thus also changes its properties. The researchers feed the results from "CDTire / 3D" into the temperature model, use these calculations to simulate how the heat spreads in the tire and link the results back to the structural model, explains the institute. The Swiss Formula 1 team Sauber, for example, is planning to use the temperature model in the future to make their racing cars faster, reveals the Fraunhofer-Gesellschaft.

"Since the system has a modular structure, we can link the temperature model to any simulation tool," emphasizes Bäcker. It can also be linked to the "CDTire / Realtime" tool. This software can be used, for example, to design an electronic control system such as the Electronic Stability Program, or ESP for short: If the car breaks away, the ESP brakes individual wheels in a targeted manner. Like the temperature calculation, this tool runs in real time, but so far only on large computers in the laboratory. In the future, it could be used on microcontrollers installed in the car while driving in order to increase the accuracy of the ESP. Bäcker estimates that it will take another year or two until then.