Brief Introduction of Wind Turbine Blade Detection Method

SIUI NDT

1. Industry Background

Wind turbine blades are an important part of the wind power generation system. Their production costs account for about one-fifth of the total cost of the entire system. They play a key role in converting wind energy into electrical energy in the system: the wind drives the blades to rotate, converting wind energy into mechanical energy. The power of the blade rotation passes through the gearbox and other transmission systems to increase the speed and transfer the mechanical energy to the generator. The generator uses the principle of electromagnetic induction to convert mechanical energy into electrical energy.

Currently, most wind turbine blades in service and in production are made of glass fiber composite materials, which have the advantages of light weight, high strength and stiffness. Limited by the production process, some defects will inevitably occur. These defects will accumulate as the operation time is extended, resulting in blade instability and damage. Therefore, testing the blades after they are manufactured or before installation to confirm whether there are defects is an important guarantee for the safe operation of the entire wind turbine system.

2. Blade Structure and Common Defect Types

2.1 Blade Structure

Wind turbine blades are generally hollow thin-walled structures, mainly composed of two parts: the shell and shear web, supplemented by the shell skin and other foam and wood board filling materials to form a complete blade. The shell and shear web are made of fiberglass composite materials, accounting for more than 90% of the total mass of the entire wind turbine blade, so that they are the key inspection objects.

2.2 Defect Types

When manufacturing blades, components such as the shell and shear web are first separately formed through special molds, and then the components are bonded to form a complete blade. In these two processes, various defects may occur due to process limitations or personnel operation problems. Defects such as delamination, and porosity may occur during the mold forming process. Defects such as lack of adhesive and de-bonding between the shell and shear web/skin may occur during the component adhesion process.

3. Common Detection Methods and Their Limitations

Wind turbine blades are mainly made of glass fiber composite materials, so they can be tested according to relevant standards for composite material testing. Currently, the commonly used non-destructive testing technologies for composite wind turbine blades include the following:

3.1 Visual Inspection

Defects can be found with the naked eye or with the help of a magnifying glass, but only on the outer surface and inner cavity of the blade. It has limitations and is affected by the subjective factors of the inspector.

3.2 Tapping Method Detection

Distinguishing defects by the sound emitted by tapping the workpiece requires high testing environment and personnel experience, and may damage the blades.

3.3 X-ray Inspection

The detection results are intuitive with high sensitivity, but it is difficult to detect defects parallel to the surface. The equipment is bulky, and the rays are harmful to the human body.

3.4 Infrared Thermal Imaging Detection

The equipment is simple and easy to operate, but it requires high heat transfer performance of the material, and it cannot quantitatively analyze the defect size.

3.5 Conventional Ultrasonic Testing

Limited by the probe size and view display, it can only detect point by point, and can only present A-scan echoes. The detection results are easily affected by human operations, and the detection rate is low.

4. Phased Array Detection Method

More and more wind turbine blade manufacturers are looking for faster, efficient and reliable detection methods. To meet this demand, SIUI provides a phased array solution for wind turbine blades. The testing system includes a 64:128PR PAUT flaw detector SyncScan 3 (SIUI) and a customized high-penetration probe.

SIUI phased array solution has the following advantages:

1) Used to detect various types of defects in glass fiber composite materials, such as porosity, delamination, de-bonding, etc.

2) Equipped with a customized low-frequency and high-penetration probe, it can effectively detect glass fiber blade workpieces with high attenuation and large thickness.

3) PA probe with 64 elements and 1.5 pitch, 96mm sound beam coverage.

4) The focus position can be flexibly changed according to the characteristics of the blade, improving the detection ability of large depth and high attenuation defects.

5) High-resolution images can be generated at different angles and depths, clearly showing tiny defects in the complex structure of the blade, improving detection accuracy.

6) Equipped with multiple functions such as 3D simulation and wireless data collection, the process of wind turbine blade inspection is more efficient and faster, and the images are intuitive.

However, when facing wind turbine blades with a length of 30 to 100 meters, it is necessary to consider how to improve the scanning efficiency. SIUI will offer a new solution with scanner to solve this problem.