Wind turbines -Full scale structural testing of rotor blade
1 Scope
This standard defines the requirements for full-scale structural testing of wind turbine blades and for the interpretation and evaluation of achieved test results.
The standard focuses on aspects of testing related to an evaluation of the integrity of the blade, for use by manufacturers and third party investigators.
The following tests are considered in this standard:
•static load tests;
•fatigue tests;
•static load tests after fatigue tests;
•tests determining other blade properties.
The purpose of the tests is to confirm to an acceptable level of probability that the whole population of a blade type fulfils the design assumptions.
It is assumed that the data required to define the parameters of the tests are available and based on the standard for design requirements for wind turbines such as GB/T 18451.1 or equivalent. Design loads and blade material data are considered starting points for establishing and evaluating the test loads. The evaluation of the design loads with respect to the actual loads on the wind turbines is outside the scope of this standard.
At the time this standard was written, full-scale tests were carried out on blades of horizontal axis wind turbines. The blades were mostly made of fibre reinforced plastics and wood/epoxy. However, most principles would be applicable to any wind turbine configuration, size and material.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2900.53-2001 Electrotechnical terminology - Wind turbine generator systems (IEC 60050-415:1999, IDT)
GB/T 18451.1-2012 Wind turbine generator systems - Design requirements (IEC 61400-1:2005, IDT)
GB/T 27025-2008 General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:2005, IDT)
ISO 2394:1998 General principles on reliability for structures
3 Terms and definitions
For the purposes of this document, the terms and definitions related to wind turbines or wind energy given in GB/T 2900.53-2001 and the following apply.
3.1
actuator
device that can be controlled to apply a constant or varying force and displacement
3.2
blade root
that part of the rotor blade that is connected to the hub of the rotor
3.3
blade subsystem
integrated set of items that accomplishes a defined objective or function within the blade (e.g., lightning protection subsystem, aerodynamic braking subsystem, monitoring subsystem, aerodynamic control subsystem, etc.)
3.4
buckling
instability characterized by a non-linear increase in out of plane deflection with a change in local compressive load
3.5
chord
length of a reference straight line that joins the leading and trailing edges of a blade aerofoil cross-section at a given spanwise location
3.6
constant amplitude loading
during a fatigue test, the application of load cycles with a constant amplitude and mean value
3.7
creep
time-dependant increase in strain under a sustained load
3.8
design loads
loads the blade is designed to withstand, including appropriate partial safety factors
3.9
edgewise
direction that is parallel to the local chord
See 4.4.
3.10
elastic axis
the line, lengthwise of the blade, along which transverse loads are applied in order to produce bending only, with no torsion at any section
Note: Strictly speaking, no such line exists except for a few conditions of loading. Usually the elastic axis is assumed to be the line that passes through the elastic center of every section. This definition is not applicable for blades with bend-twist coupling.
3.11
fatigue formulation
methodology by which the fatigue life is estimated
3.12
fatigue test
test in which a cyclic load of constant or varying amplitude is applied to the test specimen
3.13
fixture
component or device to introduce loads or to support the test specimen
3.14
flapwise
direction that is perpendicular to the surface swept by the undeformed rotor blade axis
See 4.4.
3.15
flatwise
direction that is perpendicular to the local chord, and spanwise blade axis
3.16
full-scale test
test carried out on the actual blade or part thereof
Foreword I
Introduction III
1 Scope
2 Normative references
3 Terms and definitions
4 Notation
4.1 Symbols
4.2 Greek symbols
4.3 Subscripts
4.4 Coordinate systems
5 General principles
5.1 Purpose of tests
5.2 Limit states
5.3 Practical constraints
5.4 Results of test
6 Documentation and procedures for test blade
7 Blade test program and test plans
7.1 Areas to be tested
7.2 Test program
7.3 Test plans
7.3.1 General
7.3.2 Blade description
7.3.3 Loads and conditions
7.3.4 Instrumentation
7.3.5 Expected test results
8 Load factors for testing
8.1 General
8.2 Partial safety factors used in the design
8.2.1 General
8.2.2 Partial factors on materials
8.2.3 Partial factors for consequences of failure
8.2.4 Partial factors on loads
8.3 Test load factors
8.3.1 Blade to blade variation
8.3.2 Possible errors in the fatigue formulation
8.3.3 Environmental conditions
8.4 Application of load factors to obtain the target load
9 Test loading and test load evaluation
9.1 General
9.2 Influence of load introduction
9.3 Static load testing
9.4 Fatigue load testing
10 Test requirements
10.1 General
10.1.1 Test records
10.1.2 Instrumentation calibration
10.1.3 Measurement uncertainties
10.1.4 Root fixture and test stand requirements
10.1.5 Environmental conditions monitoring
10.1.6 Deterministic corrections
10.2 Static test
10.2.1 General
10.2.2 Static load test
10.2.3 Strain measurement
10.2.4 Deflection measurement
10.3 Fatigue test
10.4 Other blade property tests
10.4.1 Blade mass and center of gravity
10.4.2 Natural frequencies
10.4.3 Optional blade property tests
11 Test results evaluation
11.1 General
11.2 Catastrophic failure
11.3 Permanent deformation, loss of stiffness or change in other blade properties
11.4 Superficial damage
11.5 Failure evaluation
12 Reporting
12.1 General
12.2 Test report content
12.3 Evaluation of test in relation to design requirements
Annex A (Informative) Guidelines for the necessity of renewed static and fatigue testing
Annex B (Informative) Areas to be tested
Annex C (Informative) Effects of large deflections and load direction
Annex D (Informative) Formulation of test load
D.1 Static target load
D.2 Fatigue target load
D.3 Sequential single-axial, single location
D.4 Multi axial single location
Annex E (Informative) Differences between design and test load conditions
E.1 General
E.2 Load introduction
E.3 Bending moments and shear
E.4 Flapwise and lead-lag combinations
E.5 Radial loads
E.6 Torsion loads
E.7 Environmental conditions
E.8 Fatigue load spectrum and sequence
Appendix F (Informative) Determination of number of load cycles for fatigue tests
F.1 General
F.2 Background
F.3 The approach used
Wind turbines -Full scale structural testing of rotor blade
1 Scope
This standard defines the requirements for full-scale structural testing of wind turbine blades and for the interpretation and evaluation of achieved test results.
The standard focuses on aspects of testing related to an evaluation of the integrity of the blade, for use by manufacturers and third party investigators.
The following tests are considered in this standard:
•static load tests;
•fatigue tests;
•static load tests after fatigue tests;
•tests determining other blade properties.
The purpose of the tests is to confirm to an acceptable level of probability that the whole population of a blade type fulfils the design assumptions.
It is assumed that the data required to define the parameters of the tests are available and based on the standard for design requirements for wind turbines such as GB/T 18451.1 or equivalent. Design loads and blade material data are considered starting points for establishing and evaluating the test loads. The evaluation of the design loads with respect to the actual loads on the wind turbines is outside the scope of this standard.
At the time this standard was written, full-scale tests were carried out on blades of horizontal axis wind turbines. The blades were mostly made of fibre reinforced plastics and wood/epoxy. However, most principles would be applicable to any wind turbine configuration, size and material.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2900.53-2001 Electrotechnical terminology - Wind turbine generator systems (IEC 60050-415:1999, IDT)
GB/T 18451.1-2012 Wind turbine generator systems - Design requirements (IEC 61400-1:2005, IDT)
GB/T 27025-2008 General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:2005, IDT)
ISO 2394:1998 General principles on reliability for structures
3 Terms and definitions
For the purposes of this document, the terms and definitions related to wind turbines or wind energy given in GB/T 2900.53-2001 and the following apply.
3.1
actuator
device that can be controlled to apply a constant or varying force and displacement
3.2
blade root
that part of the rotor blade that is connected to the hub of the rotor
3.3
blade subsystem
integrated set of items that accomplishes a defined objective or function within the blade (e.g., lightning protection subsystem, aerodynamic braking subsystem, monitoring subsystem, aerodynamic control subsystem, etc.)
3.4
buckling
instability characterized by a non-linear increase in out of plane deflection with a change in local compressive load
3.5
chord
length of a reference straight line that joins the leading and trailing edges of a blade aerofoil cross-section at a given spanwise location
3.6
constant amplitude loading
during a fatigue test, the application of load cycles with a constant amplitude and mean value
3.7
creep
time-dependant increase in strain under a sustained load
3.8
design loads
loads the blade is designed to withstand, including appropriate partial safety factors
3.9
edgewise
direction that is parallel to the local chord
See 4.4.
3.10
elastic axis
the line, lengthwise of the blade, along which transverse loads are applied in order to produce bending only, with no torsion at any section
Note: Strictly speaking, no such line exists except for a few conditions of loading. Usually the elastic axis is assumed to be the line that passes through the elastic center of every section. This definition is not applicable for blades with bend-twist coupling.
3.11
fatigue formulation
methodology by which the fatigue life is estimated
3.12
fatigue test
test in which a cyclic load of constant or varying amplitude is applied to the test specimen
3.13
fixture
component or device to introduce loads or to support the test specimen
3.14
flapwise
direction that is perpendicular to the surface swept by the undeformed rotor blade axis
See 4.4.
3.15
flatwise
direction that is perpendicular to the local chord, and spanwise blade axis
3.16
full-scale test
test carried out on the actual blade or part thereof
Contents of GB/T 25384-2018
Foreword I
Introduction III
1 Scope
2 Normative references
3 Terms and definitions
4 Notation
4.1 Symbols
4.2 Greek symbols
4.3 Subscripts
4.4 Coordinate systems
5 General principles
5.1 Purpose of tests
5.2 Limit states
5.3 Practical constraints
5.4 Results of test
6 Documentation and procedures for test blade
7 Blade test program and test plans
7.1 Areas to be tested
7.2 Test program
7.3 Test plans
7.3.1 General
7.3.2 Blade description
7.3.3 Loads and conditions
7.3.4 Instrumentation
7.3.5 Expected test results
8 Load factors for testing
8.1 General
8.2 Partial safety factors used in the design
8.2.1 General
8.2.2 Partial factors on materials
8.2.3 Partial factors for consequences of failure
8.2.4 Partial factors on loads
8.3 Test load factors
8.3.1 Blade to blade variation
8.3.2 Possible errors in the fatigue formulation
8.3.3 Environmental conditions
8.4 Application of load factors to obtain the target load
9 Test loading and test load evaluation
9.1 General
9.2 Influence of load introduction
9.3 Static load testing
9.4 Fatigue load testing
10 Test requirements
10.1 General
10.1.1 Test records
10.1.2 Instrumentation calibration
10.1.3 Measurement uncertainties
10.1.4 Root fixture and test stand requirements
10.1.5 Environmental conditions monitoring
10.1.6 Deterministic corrections
10.2 Static test
10.2.1 General
10.2.2 Static load test
10.2.3 Strain measurement
10.2.4 Deflection measurement
10.3 Fatigue test
10.4 Other blade property tests
10.4.1 Blade mass and center of gravity
10.4.2 Natural frequencies
10.4.3 Optional blade property tests
11 Test results evaluation
11.1 General
11.2 Catastrophic failure
11.3 Permanent deformation, loss of stiffness or change in other blade properties
11.4 Superficial damage
11.5 Failure evaluation
12 Reporting
12.1 General
12.2 Test report content
12.3 Evaluation of test in relation to design requirements
Annex A (Informative) Guidelines for the necessity of renewed static and fatigue testing
Annex B (Informative) Areas to be tested
Annex C (Informative) Effects of large deflections and load direction
Annex D (Informative) Formulation of test load
D.1 Static target load
D.2 Fatigue target load
D.3 Sequential single-axial, single location
D.4 Multi axial single location
Annex E (Informative) Differences between design and test load conditions
E.1 General
E.2 Load introduction
E.3 Bending moments and shear
E.4 Flapwise and lead-lag combinations
E.5 Radial loads
E.6 Torsion loads
E.7 Environmental conditions
E.8 Fatigue load spectrum and sequence
Appendix F (Informative) Determination of number of load cycles for fatigue tests
F.1 General
F.2 Background
F.3 The approach used
