Non-destructive testing is a method of obtaining information about defects or material conditions without damaging the component’s functionality. Different methods are suitable for different types of objects and have different boundaries for testing.

Starting from the problems that need to be detected

Before choosing a testing method, it’s important to determine whether you want to detect surface openings, internal discontinuities, or other abnormalities. Different methods like penetrant testing, ultrasonic testing, radiographic testing, and eddy current testing have different physical mechanisms and are suitable for different materials and geometries. The name of the method alone doesn’t indicate its ability to detect certain parts.

Geometric conditions affect actual coverage

Steps, corners, thin walls, and obstructions may limit the area that can be tested. When developing a plan, it’s important to compare the actual accessible areas with those that need to be evaluated. Areas that cannot be covered or have limitations should be indicated in the report. Local results shouldn’t be generalized to the entire component.

When choosing a method, it’s important to consider the material, geometry, accessibility, and the type of defects you want to detect. The results should be interpreted in relation to the capabilities of the chosen method.

Testing and acceptance are two separate steps

The person responsible for testing should collect and record the indications, and the acceptance criteria should be based on applicable standards. Detecting indications doesn’t necessarily mean that the product is defective; not detecting anything doesn’t mean that all defects have been eliminated. Understanding this difference helps avoid treating testing equipment as a simple tool for determining compliance.

How the report is easy to use

A reviewable report should provide readers with clear information about the object being tested, the method used, the scope of the test, and the results. With visual representations of the areas to be tested and instructions on how to locate them, manufacturers can easily carry out subsequent reviews. When dealing with specific products, approved procedures and requirements of the relevant personnel should be followed, rather than selecting parameters based on general descriptions.

Process example: Deriving testing plans from area conditions

Assume that a component has both accessible external surfaces and complex internal areas. In such cases, it’s not appropriate to choose just one testing method and apply it uniformly across all areas. Instead, it’s better to divide the area into different sections, specifying the issues that need to be evaluated in each section, as well as any accessibility limitations. Then, appropriate methods can be determined by the relevant personnel. The report should also include this division of areas, so readers can understand which conclusions correspond to specific parts. This shows the logical approach to planning, but it doesn’t constitute a detailed testing procedure for a particular component.

Common questions: Can multiple methods be simply substituted for each other?

Whether a method is suitable depends on the target defects, materials, geometry, and verification criteria. Different methods may yield different information, so it’s necessary to evaluate their suitability before making a decision. Efficiency shouldn’t be the only factor considered.

Key points for verification during implementation

• The object of testing is clearly defined
• The suitability of the method has been confirmed
• Coverage limitations have been specified
• Acceptance criteria are consistent

Implementing a project also requires clarifying personnel requirements, equipment status, operating documents, and acceptance criteria. It’s not possible to equate the absence of indications with the absence of defects.

Further reading：NASA: Non-destructive testing methods and capabilities