How a Rail Defect Grows Between Inspections
A rail defect does not appear; it grows. One small surface crack propagates under repeated axle loads, and the interval between harmless and dangerous can be shorter than the interval between inspections. Manual walking inspection covers a fixed length on a fixed schedule regardless of where the loading is heaviest.
Understanding propagation is what makes condition-based maintenance make sense to an engineering audience. Without it, automated inspection reads as a way to do the same walk faster rather than as a way to inspect the right sections more often. What does not belong on screen is safety-critical thresholds: defect classification limits, action codes, and the intervention rules that follow them are set by the infrastructure manager and must not appear as a supplier's numbers.
The template traces one defect through seven scenes: one on how a crack initiates, two on propagation under load and why the growth curve is not linear, one on what fixed-interval inspection misses, two on how repeated automated passes build a rate of change rather than a snapshot, and one on how a maintenance team prioritises from that.
