Experimental Modal Analysis of Mass Sensitivity in Automotive Wheel Rims

Closely spaced or repeated modes in symmetric ring like structures, such as automotive wheel rims, complicate the accurate interpretation of modal parameters. Intentional or unavoidable local mass additions can strongly alter the dynamic response, depending on their placement. This work presents an experimental sensitivity study focused on quantifying natural frequency variations when localized masses are applied to pre identified nodal and anti nodal regions. First, Experimental Modal Analysis (EMA) was performed on a standard wheel rim under free free boundary conditions to establish a reliable reference state. Based on this baseline, a step by step mass modification strategy was implemented through three distinct approaches: (I) peripheral attachment of masses at nodal points, (II) attachment of a concentrated mass at the central hub, and (III) selective mass loading at the anti node positions of the fundamental mode. The experimental results indicate that attaching a ۲۰۰ g mass at nodal locations for Modes ۱, ۲ and ۶ results in a negligible frequency variation (<۰.۳ %), confirming their stationary nature. Mass loading at the central hub primarily affected the axial “Umbrella” mode, clearly differentiating it from radial modes. Conversely, anti nodal mass loading for the fundamental mode produced a maximum frequency shift of ۱.۹۶ %, demonstrating the high sensitivity of these locations. Overall, the results substantiate that the magnitude of frequency variation can reliably distinguish between nodal and anti nodal regions, as well as between axial and radial behaviors in complex wheel like structures.

کلیدواژه ها:

Modal Sensitivity ، Mass Loading ، Nodal and Anti-Nodal Effects ، Experimental Modal Analysis