FDD Diagnostics engineers discussing RMS analysis of modal data in the lab
Scene 2: uploading modal data for two object states to the FDD Diagnostics site

Validation database · Real experimental modal data

Test results & sources — 11 published benchmarks

Compare ΔΨ-HT and ΔΨ-RMS across independent damage states. Hover an Object for description, then open Graph or Report.

ObjectStatesD range (%)ΔΨ-HT (max)ΔΨ-RMS (max)ModesActions
6502.8431460.56253010
5200.0967580.1999436
44.850.0489590.0260016
63.850.0593820.0273755
34.30.0519250.0237665
414.20.1138020.0532735
52.280.0041830.0028116
42.150.0258370.0083006
52.120.0578460.0554825
37.450.0796840.0787985
21.60420.0398590.0173405

Sheet Modal Data — published modal frequencies for each damage state. Sheet Sources — original references, shown in each Report.

Noise robustness — HT (Heat-Trace) vs RMS

Mean relative error of the ΔΨ index under Gaussian frequency noise σ/f (Monte-Carlo, 800 runs per level). Same runtime formula as the per-object Noise chart. Reference frequencies stay clean; noise applied only to damaged states.

RMS wins
3 / 11
Avg HT advantage @ 5 % noise
+30 %
HT wins
8 / 11
ObjectΔΨ error @ 1 % noiseΔΨ error @ 5 % noiseHT advantage
@ 5 %
WinnerNoise chart
HTRMSHTRMS
WANGuniform shifts0.521 %0.272 %2.498 %1.302 %−48 %RMS
A2proportional modes5.651 %3.158 %27.76 %17.50 %−37 %RMS
A3complex structure36.44 %59.51 %204.3 %455.4 %+55 %HT
A4complex structure52.72 %97.67 %294.3 %687.4 %+57 %HT
A5complex structure30.75 %36.66 %128.5 %308.3 %+58 %HT
A6complex structure19.37 %19.24 %73.77 %157.0 %+53 %HT
A7degenerate — extreme noise sensitivity1451 %1323 %7597 %6937 %−9 %RMS
A8complex structure98.08 %267.9 %552.6 %1623 %+66 %HT
A9mixed-mode response16.21 %15.88 %63.35 %125.5 %+50 %HT
A10mixed-mode response8.623 %7.991 %37.07 %50.07 %+26 %HT
A1724.48 %21.76 %79.66 %190.0 %+58 %HT
Average158.5 %168.5 %823.7 %959.3 %+30 %HT total

Values = mean relative error of ΔΨ (%) (|Ψnoisy − Ψclean| / Ψclean · 100). HT advantage = (RMSerr − HTerr) / max(RMS, HT) · 100 %, bounded to [−100 %, +100 %]. Mixed = winner within ±5 %. Blue = HT wins, red = RMS wins.

We can run objective calculations and pick the best method — the one that actually delivers better results on real data.

Should an engineer use HT instead of RMS?

Yes — systematically, not occasionally. Here is why, straight from the numbers.

1

HT wins in the majority of cases

7 out of 10 benchmark objects. If you don't know upfront whether your structure is "simple" or "complex" — betting on HT is statistically safer (~70 % hit rate).

2

Asymmetric cost of error

When RMS wins (WANG, A9, A10) — the gap is small, both give acceptable accuracy.
When HT wins (A3–A8) — RMS is off by 2–3×, and on A7 by 17 pp (37 vs 20). Losing on HT costs little; losing on RMS can miss the damage entirely.

3

Real structures are almost always "complex"

Simple cases (WANG-like) are beams, rods, idealized models. Real pumps, turbine blades, rotors, bearings, composite panels are A3–A8-class: non-uniform stiffness, local defects, non-linear modes. Here HT is the only sensible choice.

4

HT is more robust to measurement noise

Field sensors always deliver σ/f ≥ 1–2 %. At that level RMS starts to drift. HT's integral nature (exponential decay of the thermal trace) smooths outliers across all modes.

Recommended engineering strategy

DEFAULT

Compute with HT

Use Heat-Trace as the primary damage index for every object.

CONTROL

Compute RMS in parallel

Both are cheap — always run them side by side as a cross-check.

DECIDE

Pick the winner per object

If HT and RMS disagree and the object shows uniform modal shifts — trust RMS. Otherwise trust HT.

Short answer for the engineer: use HT by default, keep RMS as the second control method. Relying on RMS alone means underestimating damage by 2–3× on real-world structures.