PSI - Issue 75

Said Allouch et al. / Procedia Structural Integrity 75 (2025) 299–310 S. Allouch / Structural Integrity Procedia (2025)

302

4

The same wheel is subsequently measured on a BiAx machine using a basic load program. The resulting time histories are analyzed to calculate additional RFS values. A comparison of the RFS values from both measurements allows the necessary adjustments to the load file, while incorporating a safety factor to account for the number of samples required for test evaluation and the scatter in the manufacturing quality. After several iterations, the deviation between the two RFS values should be less than 5% at each strain gauge (SG). Fig. 2 illustrates the development of the BiAx/ZWARP load file. For each wheel application, a load program must be created, which is highly time intensive. As a result, standardized load programs have been developed to simplify the development process. This was possible due to the narrow range of tire and wheel sizes which were used at that time. Examples of standardized load programs include LBF Standard (Eurocycle), OEM ’ s Standard (AKR), and SAE (SAE International, 2021). The adjustment of these programs typically follows linear correlations, such as the global correction factors C v , C h for the LBF Standard. Where C v accounts for vertical loading conditions and C h addresses horizontal loading conditions. Recent developments in vehicle technology (e.g., e-vehicles, bigger wheel sizes, new tires, ...) indicate that certain influences must be represented in greater detail, and from past experiences, the standard load programs should be adjusted accordingly. 4. Factors Influencing Load Files The load files and thus the lifetime assessment under different load conditions is influenced by several critical factors that contribute to the overall load conditions experienced by the wheel. Fig. 3 highlights the key influencing factors. Understanding these are essential for accurately replicating real-world conditions and predicting the service life of vehicle components.

Fig. 3. Impact factors on BiAx load file passenger car wheels.

4.1. Static Load

The static wheel load is the load exerted on the wheel when the vehicle is stationary. It is primarily determined by the vehicle's weight and how that weight is distributed across its wheels. This static load serves as a baseline for understanding the forces acting on the wheel before dynamic factors come into play. Typically, a car has four identical wheels, and they will be designed for the higher loaded front axle. If front and rear axles differ in load and wheel size, an additional load file might be necessary. One crucial aspect is that the stresses in a wheel do not correlate linearly across different static loads. Within a narrow range of static loads, a deviation of ±5% can be linearly compensated, meaning the existing load program remains valid. However, if the deviation exceeds ±5%, the load file is no longer applicable, requiring the development of a