Which of the following is NOT listed as one of the most common NDT methods?

• A. Magnetic particle method
• B. Dye penetrant method
• C. Radiographic method
• D. Thermography

Answer: (D)

Thermography isn’t typically considered one of the core NDT methods used for routine component inspection. The methods most often emphasized are magnetic particle testing for surface and near-surface defects in ferromagnetic materials, dye penetrant testing for surface-breaking flaws, and radiographic testing for internal features. Each of these is versatile, relatively quick, and broadly applicable to a wide range of components.

Thermography, which uses infrared imaging to map heat patterns, is valuable for locating thermal anomalies, insulation problems, or cooling issues. However, it relies on thermal contrast and controlled heating or cooling, and it has limitations in sensitivity to many types of metallic defects and in directly revealing cracks or voids. It also requires specialized equipment and interpretation.

Because of these reasons, thermography is not typically listed among the most common NDT methods, making it the correct choice for this question.