Rotordynamic screening arithmetic
Constant-Frequency Order-Crossing Calculator
Intersect user-supplied constant modal frequencies with excitation-order lines over a speed range. Results are candidates for further analysis, not confirmed critical speeds.
Arithmetic crossing candidates
Order-line intersection
The calculation is exact for the entered constant fmode and order k. Fractional orders are allowed because asynchronous/subharmonic excitations can exist, but the page does not assert that any entered order is physically present.
Why this is not a full Campbell solution
The Ansys Rotordynamic Analysis Guide describes Campbell curves from modal analyses at multiple rotational-speed load steps, including speed-dependent frequencies, forward/backward whirl, stability and sufficient resolution. It notes that crossing accuracy depends on Campbell-diagram quality. A 2025 NASA technical memorandum likewise plots varying modal frequencies against engine-order lines and calls their intersections potential resonant conditions.
No operating-speed verdict: this page omits gyroscopic/Coriolis effects, bearing/seal/support speed dependence, mode tracking and shape, damping/logarithmic decrement, stability, forcing amplitude/phase, excitation coupling, nonlinearities, thermal/load states, uncertainty and response analysis. It does not prescribe a 20% margin or tell an operator to traverse a resonance quickly.
