PRObability distribution of FAtigue strength of Rotor blades: PROFAR

Coupon testing

Static and fatigue tests have been performed on coupons to derive material properties and strength distribution as a basis for further analysis. Within the Profar project 27 fatigue tests and 8 static tests have been performed. From the FACT database 39 useful tests have been selected for comparison with Profar data.


Static and fatigue tests on rotor blades:

  • Flapwise prismatic tip section
  • Flapwise root section
  • Edgewise root section

Static and fatigue tests on coupons:

  • Fatigue R= 0.1
  • Fatigue R= -1
  • Static tensile
  • Static compression


  • Fatigue formulation with Goodman modification.
  • Comparison coupon data with existing data from literature.
  • Non-linear regression analysis of coupon results based on maximum stress for the whole population R=0.1 and R=-1; slope and UTS value are the results.

Typical creep and stiffness development during coupon fatigue test Results of R=-1 tests fitted with a fatigue formulation using a Goodman modification using multiple non linear regression


  • Fatigue formulation with Goodman modification describes influence of stress ratio very well.
  • PROFAR test results are in good agreement with FACT results when divided by the UTS-value of the relevant material.
  • Slopes of regression lines are close to 10 for blade and coupon tests as well.


For inquiries please contact:

Knowledge Centre WMC
Kluisgat 5
1771 MV Wieringerwerf
the Netherlands
phone +31(0)227-50 49 49