PSI - Issue 75

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

305

7

5.1.1. Details of the investigation

One executable load program for passenger car application, equivalent to LBF design spectra, was developed for a wheel with the tire size 275/45R20, and the validity of this load file was evaluated for other tires: 275/50R20, 275/40R20, 275/35R20, and 275/30R20. Table 1 displays all the parameters for the case study.

Table 1: Details of the used measurement wheel.

Vehicle type Passenger car

Wheel size

Wheel load [kg]

Tire pressure (flat track | ZWARP) [bar]

Torque [Nm]

8.5x19

725

3 | 4

140

The wheel forces for determining the load spectrum for a fatigue-life calculation were defined according to LBF experience. For the flat track roll rig a wheel was equipped with strain gauges placed at critical locations to measure internal strain and compare it to the stresses:

• Strain gauge 01: Outer rim flange • Strain gauge 02: Inner rim flange • Strain gauge 03: Inner spoke transition to the bolting area • Strain gauge 04: Inner mid of spoke • Strain gauge 05: Inner spoke transition to the rim

The damage calculation was carried out with a S-N curve with a knee-point at 5·10 7 load cycles, a slope of k = 4.5, and k’ = 7 . The stress value of the S-N curve at the knee point is selected in such a way that the defined damage sum of 0.5 is achieved. 5.1.2. Results and Analysis First, the wheel forces (peak loads) were used in the experimental stress analysis for all tire sizes. Fig. 5. The results of the stress analysis were then transformed into the LBF standard design spectrum, and the target damage was calculated. The load file was developed for the wheel with the tire 275/45R20. As shown in Fig. 6.

Fig. 5. RFS values of all tires.