Trevor Haines
Senior Stress Analysis Engineer
Wichita, Kansas
Works on structural integrity and fatigue analysis for commercial aircraft components, with most projects centered around vibration issues, load-path validation, and recurring field failures that don’t show up cleanly in initial simulation models. Has spent years bridging the gap between FEA teams, manufacturing engineers, and test technicians to resolve problems that only appear under real operating conditions. Frequently pulled into late-stage investigations where timelines are tight and root causes are unclear.
Aerospace
Aerospace
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16 years
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I have been testing ML on long strain gauge records to flag early fatigue issues and loose joints. The models are great at obvious anomalies, but the score is often not actionable. We saw bursts of false alarms at maneuver transitions, and one model sailed past an actual early crack because the signature was sequence driven and quiet, not a spike.What helped was not a bigger net, but better features and guardrails. Rainflow cycle pairs, R ratio and mean stress, dwell time statistics, modal band...
I spent the last month chasing a 2x spread in rib attach fastener life between two ostensibly identical test articles. FEM said margins were healthy and shaker PSDs matched, yet one article cracked at 35% of life. The only consistent difference: clamp-up. A slightly different primer stack and a torque tool calibration shift gave about 20% lower preload and a big jump in joint slip.Once we measured loss of preload across thermal cycling, the vibration damping fell and strain hotspots moved to the...
I trialed a regression model to estimate fatigue damage on a bracket from rainflow histograms and mean stress, trained on shaker coupon data. Cross-validation looked great.Flight test broke it. Temperature drift shifted strain by +/- 50 microstrain; the model turned that bias into big damage deltas. The spectra also had long dwells and a few high spikes not in training. Shot peen residual stress and clamp-up changed local mean stress and crack closure, which the model could not see.What worked:...
Random vibe specs still lean on Gaussian assumptions. We qualify to a PSD, GRMS, and notches look fine on the shaker. Then a fleet bracket cracks in months. Pull the flight recorder: same RMS, very different story. Spiky content, high crest factor, kurtosis around 7-9.We repeated the test with kurtosis control and strain gages at the hot spot. Same PSD, same GRMS, but damage doubled. The strain rainflow histogram shifted right, and Miner's sum went from 0.4 to 0.9 for the same hours. The fi...
Most fatigue surprises I see trace back to bad loads, not bad models. We burn weeks on mesh refinement, then feed the solver a generic sine-on-random or legacy spectrum that ignores how the hardware actually vibrates.Recent example: a gearbox mount bracket that our CAE said had plenty of life. Flight test found cracks around 120 hours. Post-test data showed narrowband peaks from gear mesh sidebands and a control-loop tone riding on the random. Our shaker spec smeared that content, and we modeled...
We signed off a bracket after updating the FE model to match test frequencies within 3 - 4%. Flight test later found a crack at a fillet. Root cause: the test fixture was much stiffer than the installed structure. Mode shapes looked fine by eye, but strain energy parked itself in a different spot. Our accelerometers missed the local rotation, MAC looked great overall, and only after teardown did strain gauges show roughly 2x strain at the fillet in flight.Lesson learned: frequency correlation al...
Last quarter we tried ML to flag outliers in shaker and flight strain data before fatigue analysis. Unsupervised models spotted "interesting" runs, but most were just sensor drift, bad zeroing, or fixture chatter. Helpful to catch housekeeping issues, but it didn’t replace time in the plots.Where it did help: automated rainflow and PSD feature extraction tied to test logs, and a simple classifier to detect grip slip and thermal drift. Where it struggled: extrapolating to new configs or...
Recently chased a high-cycle fatigue crack in a simple bracket. FEM predicted 30% margin, shaker replication said otherwise. Root cause: test article had realistic stack-up, paint, sealant, aged isolators, and torque scatter, which changed joint stiffness and damping. Our model used ideal bolts and uniform contact. Strain gauges lit up at a lug we barely meshed.Updating joint modeling (surface contact with micro slip, preload scatter, frequency-dependent damping) closed the gap. The life went fr...