Test Body Clamping Method for Wind Turbine Rotor Blade Testing
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Solution Overview
Problem
Testing subcomponents of wind turbines, such as rotor blade components, poses challenges due to their anisotropic and hybrid nature, requiring precise control of force application to simulate realistic loading conditions while minimizing damage to clamping devices and efficiently determining structural parameters like elastic properties and load capacity.
Innovation Solution
The method involves defining a reference axis and applying forces along the z-direction at specific clamping points, ensuring the line of action coincides with the connecting line between clamping points to avoid shear forces and torques, using flexible clamping devices that allow rotation, and modifying the elastic center of gravity by adding additional material or springs to control bending moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If forces are applied at clamping points to simulate realistic loading conditions, then measurement precision is improved, but clamping devices are subjected to damaging shear forces and torques
Solution Approach 1:
The force application is segmented into two independent components: a longitudinal force component applied along the line connecting clamping points, and a bending moment applied independently. This segmentation allows the longitudinal loading to be applied without generating damaging shear forces or torques in the clamping devices, while the bending moment is applied separately to achieve realistic loading conditions.
Solution Approach 2:
The patent introduces an intermediary reference axis (z-axis) that passes through both clamping points. By aligning the longitudinal force application with this reference axis, the force is transmitted purely in tension or compression without generating parasitic shear forces or torques. This intermediary reference serves as a mediator that decouples the force application from the clamping device load paths.
2Productivity
If subcomponents are tested instead of full rotor blades, then productivity is improved, but the complex structure and anisotropic nature of rotor blades make parameter determination more difficult
Solution Approach 1:
The patent changes the parameter of force application by introducing a specific geometric configuration where the line of action of the longitudinal force passes through both clamping points. This parameter change ensures that the test results from subcomponents can be reliably extrapolated to full rotor blades, despite the complex anisotropic structure, because the loading conditions accurately represent in-situ conditions.
3Reliability
If clamping devices are made rigid to maintain stability, then reliability is improved, but bending moments cause damaging effects on the rigid clamping devices
Solution Approach 1:
The loading is segmented into a longitudinal component (tension/compression) and a bending component. The longitudinal force is applied in a way that does not generate damaging effects in rigid clamping devices, while the bending moment is applied independently as a separate load case. This allows rigid clamping devices to maintain stability without suffering from the combined damaging effects of shear forces, torques, and bending moments.
Data Source
Figure 1~2
Figure 3~5
Figure 6~7b
AI summary
The invention relates to a method for determining elastic properties of a test body (1) by means of tensile or compressive loading in a test stand, wherein a center of gravity line (2) is defined for a longitudinal axis for the test body, said center of gravity line running through elastic centers of gravity of infinitesimally thick discs which lie orthogonally to the longitudinal axis and into which the test body can be divided. The test body is clamped at two clamping points by means of clamping devices (13, 13'), and a force is introduced at at least one of the two clamping points in the direction of the respective other clamping point such that a line of action of a force introduced at at least one of the clamping points is substantially parallel to a connection line between the two clamping points. Furthermore, by providing additional material (11) or springs (17) to the test body (1), the center of gravity line (2) of the test body (1) is converted into a modified center of gravity line (12) of the entire system consisting of the test body (1) and additional material (11) or springs (17).