Case Study 4 – Combined Load Fatigue Test

Combined Load Fatigue Testing

A 2m long high strength alloy steel shaft was the subject of a fatigue loading investigation using theoretical analysis and FE analysis.

The engineering investigation highlighted potential improvements via material changes and reduction in stress concentrations.

Rework and replacement costs were very high so a full scale test was commissioned to confirm results before committing to an upgrade.

Test Equipment – Large complex rig required to confirm Engineering calculations for multiple load cases

  • Rotating bending – at customer specified RPM and curvature.
  • Rotating bending with addition of controlled torque (300kW power required).
  • Fluctuating (fully reversed) torque combined with axial load.


Data acquisition

  • Strain gauges required at multiple locations to confirm boundary conditions and component loading match analysis.
  • Real-time data was a combination of:
    • Hard wired gauges for slow rotation and fully reversed torque load.
    • Pressure transducers and load cells to confirm torsional loading.
    • Wireless telemetry for data during rotating tests.
  • Additional data acquisition utilised to monitor rotary speed, hydraulic system operating condition, coolant temperatures, coolant fan load, dynamometer load and temperature.