PSI - Issue 82

Kübra Polat et al. / Procedia Structural Integrity 82 (2026) 267–273 K. Polat, M. M. Topaç/ Structural Integrity Procedia 00 (2026) 000–000

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cause repeated loads that may lead to fatigue and high stress. Thus, due to its complex loading conditions, the axle beam is a key structural component affecting vehicle dynamics, safety, and comfort (Wimmer, 1998; Wimmer and Alsdorf, 2006). Fig. 1 shows the front axle geometry of a heavy-duty commercial vehicle. Under normal driving conditions, the wheel is exposed to vertical, driving, braking, and lateral forces (Jazar, 2008). Wheel loads are expressed as accelerations, forces, or moments, and since accelerations are independent of axle load, they can be reused for different vehicle weights. The forces and coefficients for driving cases are shown in Fig. 1b.

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

! !

!"

a

z

M

x

Idler Arm

z

Front Axle Spring Seat

x G R U F

Vehicle Body

z

M

x

Tyre

M P

U

Tie Rod

!

F

Road

!

M P

Fig. 1. Front axle assembly used in heavy commercial vehicles [Courtesy of BMC Automotive Industry and Trade Inc.]; (b) Free body diagram for the wheel (Mitschke, 1972) .

The axle beam accounts for about 10% of a vehicle’s unsprung mass (Mathur and Kurna, 2015; Güler et al., 2012). Reducing this mass is critical for improving ride comfort and road holding. Thus, axle design has long been considered a subject of weight reduction studies (Loosle et al., 1980; Neugebauer et al., 1989; Wimmer, 1998). However, holes may cause failure by reducing structural integrity which is particularly critical for heavy-duty rigid front axles operating under high loads (Hilgers and Achenbach, 2023; Reimpell et al., 2001). Therefore, hole optimization is essential for both mass reduction and fatigue life. In this study, different hole forms obtained from the literature (Yan et al., 2022) were applied to the axle beam shown in Fig.1. Then, the effects of these hole forms on the mass, stress, and failure behavior under the critical driving case were investigated, and the most suitable hole form for the axle beam was identified. To the authors' knowledge, there is no study in the open literature on the use of different hole forms for axle beam lightweighting.

Nomenclature F

vertical wheel load wheel contact point wheel diameter

E,F

d

w

tyre width aspect ratio

h

H

distance between point E and the wheel rotation axis

2. Load Model The loads acting on the front axle vary significantly depending on different driving scenarios (Gillespie, 1992). Therefore, it is crucial to consider different load cases in terms of both stability and fatigue life for axle design (Hilgers and Achenbach, 2023). Since wheel loads are often unavailable in early design stages, standard load cases based on typical driving conditions are commonly used (Heißing and Ersoy, 2010). These cases are summarized in Table 1.