Project Scope
Characterize Formula SAE chassis dynamics across the frequency range excited by rotating components.
Experimental Setup
- Free-free boundary condition: car suspended on low-stiffness bungies and a highpass filter to remove translational modes
Design Solution
- Roving-hammer modal test with 43 tri-axial accelerometers, steel hammer tip for maximum excitation energy
- 256 Hz bandwidth, 512 spectral lines for 1 Hz resolution, 5 averages per point
- Tube chassis simplified to nodes at welded joints, modeled in Inspire and Hypermesh
- Strike points at the roll cage top and front bumper corners, with drive-point checks for validation
Results Processing
- Full chassis instrumented and struck at all 43 nodes; higher-amplitude strikes cut low-frequency noise while holding high-frequency response
- Data curve-fit incrementally through the bandwidth in PolyMax Plus
- 12 mode shapes identified, from 40.7 Hz up to 188.5 Hz
- Reciprocity checks, modal synthesis, and MAC matrix comparison used to validate the results
Project Summary
This was an ME4701 project I completed in Spring 2026. The goal of the project was to identify potential chassis resonances that could be excited by rotating components like the wheels and engine. First the chassis was modeled in Hyperworks to easily import the node locations into TestLab. The chassis was instrumented with 43 tri-axial accelerometers wired to a SCADAS III. Preliminary strikes showed noise at low frequencies, so we switched to firmer hammer hits, which cut that noise while still exciting the higher modes cleanly. We curve-fit the response data through the bandwidth in stages and identified 12 distinct mode shapes between 40.7 Hz and 188.5 Hz. Reciprocity testing came back strong in the Y and Z directions, with only slight variance in X. The MAC matrix confirmed the mode shapes were independent. This process highlighted the importance of organizing experimental data, especially with so many channels and strike points.
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