What is Eddy Current Tester (ECT)

Eddy Current Testing (ECT) is a non-destructive testing (NDT) technique used to detect surface and

 near-surface defects in conductive materials. By inducing eddy currents in the material being tested,

 technicians can use the changes in the eddy currents to identify and evaluate defects in the material. 

Such as cracks, corrosion, wear and material inhomogeneity. Due to the non-contact nature,

 high sensitivity and wide range of applications of eddy current testing, eddy current testing is widely 

used in aerospace, automotive manufacturing, energy and other fields.

Basic principles of eddy current testing

The working principle of eddy current testing is based on electromagnetic induction. When an

 alternating current passes through the detection coil, an alternating magnetic field is generated on 

the surface of the conductive material, which induces eddy currents on the surface of the material. 

These eddy currents generate a reverse magnetic field that interacts with the initial magnetic field. 

If there are defects in the material (such as cracks, holes or corrosion), the flow of these eddy currents 

will be disturbed, resulting in changes in the magnetic field. The detection equipment can sense these

 magnetic field changes to identify and locate defects.

Steps of eddy current testing

1. Preparation: Select appropriate probes and equipment, and adjust the frequency and sensitivity of 

the equipment according to the properties of the material being tested and the detection requirements. 

Generally, the higher the detection frequency, the higher the detection sensitivity, but the shallower 

the detection depth.

2. Calibration: Before the formal test, the equipment is calibrated with a standard test block to ensure 

the accuracy of the test results. This step can help the tester determine the response of the equipment 

and adjust the test parameters.

3. Detection: The probe is placed on the surface of the material to be tested, and the probe generates 

eddy currents in the material through electromagnetic induction. The detection equipment will display 

the changes in eddy currents in real time. By analyzing these changes, the tester can determine whether

 the material has defects and the location and nature of the defects.

4. Data analysis: After the test is completed, the signals recorded by the equipment are analyzed to

 identify potential defects. Experienced testers can further evaluate the size, shape and location of the

 defects based on the amplitude, phase and other characteristics of the signal.

5. Report and evaluation: Based on the test results, a test report is generated, and the state of the

 material is evaluated based on the nature and location of the defects, and repair or maintenance 

suggestions are provided.

Application areas of eddy current testing

Due to its high sensitivity and easy operation, eddy current testing is widely used in various industries,

 especially those that require high precision and reliability. Main applications include:

- Aerospace: used to detect cracks and corrosion in key components such as aircraft wings, engine

 blades, landing gear, etc.

- Energy industry: monitors corrosion and wear of boiler pipes, heat exchanger tubes and nuclear power

 plant components in power plants.

- Automotive manufacturing: detects the quality of key parts such as engine components, bearings,

 gears, etc.

- Metalworking: detects surface and near-surface defects of metal materials and products (such as pipes

 and bars).

Advantages and limitations of eddy current testing

**Advantages:**

- Non-contact detection: Eddy current testing can be performed without contacting the object being 

tested, which is suitable for detecting high-temperature, dangerous or difficult-to-access objects.

- High sensitivity: It is very sensitive to surface and near-surface defects and can detect tiny cracks and 

corrosion.

- Real-time detection: The detection process is fast and quality can be monitored in real time on the

 production line.

Limitations:

- Limited depth: Eddy current testing is mainly used for surface and near-surface defect detection,

 and the detection depth is usually no more than a few millimeters.

- Material restrictions: It can only be used for conductive materials, and cannot detect non-conductive

 materials such as plastics and ceramics.

- Complex shapes are more difficult to detect: Objects with complex geometric shapes may cause 

uneven eddy current distribution, increasing the complexity of signal analysis.

Conclusion

Eddy current testing is an efficient and accurate non-destructive testing technology, especially suitable 

for detecting surface and near-surface defects of conductive materials. Although its application has 

certain limitations, eddy current testing has been widely used in many industrial fields due to its

 non-contact, real-time and high sensitivity. In order to give full play to the advantages of eddy current

 testing, operators need to have rich professional knowledge and experience, and choose appropriate

 equipment and methods based on specific testing needs.