I tested a scaled wing model on a shake table to find its bending frequencies, then checked the measurements against a Rayleigh estimate and a SolidWorks modal study.
My work included the test setup, sine-sweep and random-noise runs, SolidWorks model, Rayleigh calculations, and data analysis.
Scaled wing model during the lab · photo from our Lab 7 presentation
31.75 Hzfirst mode, sine sweep
31.5 Hzfirst mode, random noise
32.1 HzSolidWorks first-mode prediction
Test question
Where does the wing resonate?
The tapered wing and attached engine masses change how it bends. I wanted to identify its first two bending frequencies, compare two test methods, and see how closely analytical and CAD predictions matched the hardware.
Physical testShake table, base and tip accelerometers, and a dynamic signal analyzer.
Two inputsA sine sweep excited one frequency at a time; random noise excited a range of frequencies together.
ComparisonThe frequency response peaks were compared with Rayleigh's method and a SolidWorks frequency study.
What I did
From model to measured response
01 · Predict
Estimate the first mode
Applied Rayleigh's energy method to the distributed wing and attached masses.
02 · Simulate
Study the mode shapes
Built a SolidWorks model and compared its bending modes with the physical response.
03 · Measure
Run a sine sweep
Used accelerometers at the base and tip to measure the wing's frequency response.
04 · Cross-check
Apply random noise
Used averaged FFT response data to check whether the same natural frequencies appeared.
Experimental evidence
Two inputs, nearly the same first frequency.
The analyzer's frequency-response peaks identify resonance. The sine-sweep and random-noise results agreed within 0.25 Hz for the first bending mode.
Sine sweep
The first peak was read at 31.75 Hz. Original analyzer photo from slide 5.
Random noise
The averaged response showed a first peak at 31.5 Hz. Original analyzer photo from slide 10.
Frequencies reported in the Lab 7 results table. The Rayleigh calculation estimated only the first mode.
Bending mode
Sine sweep
Random noise
Rayleigh
SolidWorks
First
31.75 Hz
31.5 Hz
36.2 Hz
32.1 Hz
Second
251.5 Hz
251.5 Hz
—
246.9 Hz
SolidWorks tracked the test
The reported first-mode error was 1.1% versus sine sweep and 1.9% versus random noise. Its second-mode result was also within 1.9% of the measured value.
Rayleigh ran high
The 36.2 Hz estimate exceeded the first-mode measurements by about 14–15%. The assumed deflection shape and simplified support conditions may explain part of the difference.
Model versus hardware
The first bending shape matched what we saw.
The first SolidWorks mode showed the wing bending about its central support, consistent with the visible up-and-down response during resonance testing. The CAD model predicted about 32.1 Hz for that mode.
Limit of the comparison: this was a scaled lab model. Clamp flexibility, mesh choices, and measured dimensions could shift the frequency, so agreement with one setup does not cover every mounting condition.
SolidWorks first bending mode · screenshot from our Lab 7 presentation
Two-person lab with Angelique Thioux. Photos, analyzer screens, and CAD image are from our ME 3317 Lab 7 presentation.
