Non destructive testing

Non-destructive testing (NDT) is a type of testing that is used to evaluate the properties of a material, component or system without causing damage. There are various methods of NDT, including visual inspection, ultrasonic testing, radiographic testing, magnetic particle testing, and liquid penetrant testing. These methods allow engineers and technicians to detect and diagnose defects, such as cracks, corrosion, or other damage, in materials and structures that would be difficult or impossible to detect with destructive testing methods. NDT is commonly used in industries such as aerospace, manufacturing, oil and gas, and power generation.

Non destructive testing methods

Non-destructive testing (NDT) methods are techniques that are used to evaluate the properties of a material, component or system without causing damage. Some common NDT methods include:

• Visual inspection: This involves the examination of a material or structure using the naked eye or with the aid of magnifying devices.
• Ultrasonic testing: This method uses high-frequency sound waves to detect internal defects or measure the thickness of a material.
• Radiographic testing: This method uses X-rays or gamma rays to create an image of the internal structure of a material or component, which can reveal defects such as cracks or voids.
• Magnetic particle testing: This method uses a magnetic field to detect surface and subsurface defects in ferromagnetic materials.
• Liquid penetrant testing: This method uses a liquid that is applied to the surface of a material and then removed, leaving any surface-breaking defects visible.
• Eddy Current Testing: This method uses electromagnetic induction to detect surface and subsurface defects in non-ferromagnetic materials.
• Acoustic Emission Testing: This method uses the acoustic waves generated by the material under stress to detect and locate defects.
• Thermography: This method uses infrared cameras to detect temperature variations on a surface, which can indicate the presence of internal defects.

These are some of the most common NDT methods, and each has its own advantages and limitations. The choice of method depends on the material, component or system being tested, the type of defects being sought, and the level of accuracy required.

Non destructive testing limitations

Non-destructive testing (NDT) methods have certain limitations that should be considered when choosing a method and interpreting test results. Some of the limitations of NDT include:

• Sensitivity: NDT methods can vary in their sensitivity, which is the ability to detect small defects. Some methods may not be able to detect very small or shallow defects, while others may produce a high number of false positives.
• Accessibility: Some NDT methods require access to both sides of a material or component, while others can only be used on one side. This can limit the scope of testing and the types of defects that can be detected.
• Surface conditions: Some NDT methods can be affected by surface conditions such as paint, corrosion, or other coatings. This can make it difficult to get accurate test results and may require additional preparation steps before testing.
• Operator skill: NDT methods require skilled operators to properly perform the test and interpret the results. Operator skill and experience can play a major role in the accuracy and reliability of test results.
• Cost: NDT methods can vary widely in cost, from relatively inexpensive visual inspection to more expensive methods such as radiographic testing.
• Interpreting the results: Some NDT methods produce results that require a high level of interpretation and expertise. For instance, radiographic testing results can be complex and may require a radiographic interpreter to interpret them.
• Environment: Some NDT methods can be affected by environmental conditions such as temperature, humidity, and electromagnetic interference.
• Size and shape: Some NDT methods are not suitable for testing large or irregularly shaped objects.

It is important to consider these limitations when choosing an NDT method and interpreting test results to ensure that the method is appropriate for the material, component or system being tested and that the results are accurate and reliable.

Non destructive testing — recommended articles

Acceptance sampling — Visual inspection — Process layout — Automated valuation model — Reliability — Parametric modeling — Radio frequency identification (RFID) — Overfitting — Common cause variation

References

• Dwivedi, S. K., Vishwakarma, M., & Soni, A. (2018). Advances and researches on non destructive testing: A review. Materials Today: Proceedings, 5(2), 3690-3698.
• Gholizadeh, S. (2016). A review of non-destructive testing methods of composite materials. Procedia structural integrity, 1, 50-57.
• Schabowicz, K. (2019). Non-destructive testing of materials in civil engineering. Materials, 12(19), 3237.