Takeoff, turbulence, maneuvering, and landing all generate fluctuating stresses
in structural components such as wings, fuselage skins, and turbine blades.
Over time, these repeated loads may lead to fatigue damage and eventually structural failure
if not properly analyzed during the design and maintenance phases.
Engineering Question
If an aircraft wing experiences repeated stress cycles during thousands of flights,
how much fatigue damage will accumulate and will the structure remain safe
throughout its service life?
Typical Loading Scenario
During flight, wings experience cyclic stresses due to aerodynamic lift forces.
These stresses vary depending on flight conditions such as turbulence,
maneuver loads, and landing impact forces.
Simulation tools or structural monitoring systems may generate a stress time history
representing these loading conditions.
How Stress Values Are Calculated
In aircraft structures, stresses are often generated due to bending loads acting
on the wing during flight. Engineers calculate the stress using the bending stress formula:
σ = (M × c) / I
- σ = bending stress (MPa)
- M = bending moment caused by aerodynamic lift (N·m)
- c = distance from the neutral axis to the outer surface of the structure (m)
- I = second moment of area of the cross-section (m⁴)
During flight simulations or structural monitoring tests, the bending moment
changes continuously as aerodynamic loads vary. Using this formula,
the changing stress values are calculated and recorded over time.
These stress samples are then exported as a CSV file for fatigue analysis.
Example Stress History Data
A simplified example of stress values measured in the wing structure may look like this:
120 150 170 160 140 165 180 155 145
Each value represents a stress level in MPa recorded during changing flight loads.
This stress sequence can be exported as a CSV file from simulation software
or structural monitoring sensors.
Fatigue Analysis Workflow
Engineers can evaluate fatigue damage using the following steps:
- Export stress history data from structural simulations or sensors.
- Upload the stress sequence into the FatigueLab Fatigue Damage Calculator
- Apply rainflow cycle counting to identify stress cycles.
- Use the material S-N curve to estimate fatigue life for each cycle.
- Calculate cumulative fatigue damage using Miner’s Rule.
Why Fatigue Analysis Matters in Aerospace
Aircraft structures must withstand thousands of flight cycles over many years
of operation. Accurate fatigue analysis helps engineers:
- Predict structural lifespan
- Prevent catastrophic fatigue failures
- Schedule maintenance inspections
- Ensure passenger safety
Because aerospace components experience millions of stress cycles during their
service life, fatigue analysis is a critical part of aircraft structural design.