Style and finesse, quality and safety in development
With FEM calculation, every shot is a hit
At Breyton, the driving experience is at the heart of rim development. For company founder Edmund Breyton, both the convincing design and the high quality standards are the key to success. In order to secure this in the future, Breyton is always working on expanding the physical and technical limits, among other things through FEM calculations with Ansys.
For high-quality light alloy wheels, minimal weight is crucial for excellent driving characteristics and especially high driving dynamics. That’s why Breyton wheels are among the lightest in the world. Optimum strength, based on FEM (Finite Element Method) calculations, ensures safety and comfort, while the right balance of elasticity and stiffness supports performance without compromising comfort. This, combined with an attractive and clean design, makes it clear why Breyton rims are so desirable.
Predicting future properties
Every rim is developed according to TÜV specifications and standards, and finally tested by TÜV according to the complete guidelines. That's why Breyton started replicating TÜV test stands with Ansys software more than 20 years ago, so that all necessary rim tests can be performed digitally as FEM simulations as early as possible. As a result, the rim specialists are now able to predict future characteristics and properties of their products very accurately, as well as clearly identify and rectify potential difficulties before they occur.
Initially, it was not common for other companies in the industry to rely on FEM calculations for rim development. But over the past decade, the use of FEM software has gradually become more widespread. Edmund Breyton, however, believes his company is still ahead of the curve in this respect. Other wheel suppliers, such as ABT and HOFELE, also see it that way, and therefore have entrusted Breyton with the development and calculation of new light alloy wheels, which they then launch on the market under their own names. Breyton development was strengthened a few years ago by mathematician Jan Weber, who expanded the basis and methods of the simulation to bring the calculations even closer to reality.
“Since then, we can say that every move is a success, because every design tested with the help of simulations passes the TÜV tests without a hitch,” emphasizes Edmund Breyton with pride. Mathematician Jan Weber adds: “However, you have to know what you are doing. This starts with the construction of the simulation model, continues with the determination of the correct boundary conditions, and of course also concerns the interpretation of the calculation results and the conclusions drawn from them.” In order to reliably meet these requirements, a lot of simulation experience and industry knowledge is needed. Jan Weber and Edmund Breyton therefore complement each other ideally.
The TÜV bending circulation test is decisive
Among other things, TÜV performs a rolling test to check the forces acting on the tire and wheel on a straight stretch of road. Another impact test simulates a lateral impact on the rim, such as occurs when the vehicle hits a curb at too high a speed. By far the most important TÜV test for the product safety of light alloy wheels is the bending test. It simulates the forces or load changes that occur on the rim during cornering and the resulting long-term stresses. To do this, the inner rim flange is fixed firmly to a test table with a clamping ring and the rim is subjected to a rotating moment on the wheel contact surface very often and over a long period of time.
"When simulating the bending rotation test, we have to think very carefully about how we apply the forces and the moment," explains Jan Weber. "For example, we can choose any orientation of the load angle to individual rim spokes. Should it be directly at a junction of a spoke into the rim bed or rather between two spokes, that would lead to fundamentally different results." Previous experience has shown the best way to relieve highly stressed areas. Since the energy supplied has to be dissipated through the rim, it should be distributed as best as possible over the entire geometry. For example, by making certain non-problematic areas softer.
In order to be able to localize the higher-loaded areas with sufficient precision, the mesh must be generated in a sufficiently fine manner. Since it is not possible to predict where the stress peaks will occur, the mesh must be as fine as possible everywhere so that the stress peaks become visible. “We first calculate with a somewhat coarser mesh, usually with more than 200,000 nodes, to get an initial overview,” reports Jan Weber. “After that, we sometimes refine the mesh to five million nodes so that we are also be able to assess the important details accurately. Of course, we then consider the calculated results for different angles of attack and a number of load cases in each case, which leads to longer calculation times.”
Manufacturing conditions must always remain in view
Critical areas often occur where the spoke merges into the rim bed. However, depending on the design, stress peaks also occur at completely different locations, which is not always predictable but can of course be influenced. When designing the rims, manufacturing conditions must always be kept in mind, because even relatively thin spokes must be able to be manufactured safely during the molding process. In addition, the strength depends on the solidification time during molding. If this is not taken into account, vents that are not visible from the outside can form. These reduce the strength and can negatively influence the TÜV tests.
Edmund Breyton also faces similar challenges when it comes to the material data of the rims from the various suppliers. These vary depending on the molding processes and manufacturing techniques used. This fact must be taken into account in the Wöhler curve, which represents the number of load cycles until a material breaks. In order to maintain a certain margin, calculations are therefore more conservative than with ideal material data.
Simulations lead us safely to the goal
In the development phase of a new rim design, many calculations are necessary because the rim should not be produced in only one size and width. Often, more than a dozen versions of the product are planned, all of which must be calculated, as the behavior changes with each modification. For a basic development, which is then produced in the specified parametric dimensions, small manual adjustments are often still required, which are due to the design characteristics.
In conclusion, company founder Edmund Breyton notes: "We are a niche manufacturer with relatively small quantities. Consequently, tool production and MOT costs together can be up to 30 percent of the manufacturing costs. That’s why we can’t spend a lot of time trying things out. Instead, we have to strictly follow the path we have chosen, which leads us safely to our goal with simulations. This is because the FEM software allows us to recognize and reuse not only fundamental, but also unexpected possibilities for improvement. These boundary conditions underline the importance of simulation for our business model, which would not be profitable without simulation. FEM software is also simply a tool for us to successfully drive our pursuit of quality in material, design and functionality."
bd breyton design GmbH
Author: Gerhard Friederici, CADFEM
Images: bd breyton design GmbH