Which of the following is an example of a non-destructive testing method?

X-ray testing is recognized as a non-destructive testing (NDT) method because it allows the examination of materials without causing any permanent alteration or damage. In this testing process, X-rays penetrate the material and generate images that reveal internal structures, including defects such as cracks or voids. This method is widely used in various industries, including construction and manufacturing, to ensure the integrity of welds and materials without compromising their usefulness.

Destructive tensile testing, metal fatigue testing, and shock testing are considered destructive methods because they inherently involve subjecting materials to conditions that will result in their failure or deformation. Destructive tensile testing measures the strength and behavior of a material until it breaks, while metal fatigue testing evaluates the material's performance under repeated stress until it ultimately fails. Shock testing simulates conditions that materials might experience during sudden impacts or high-stress environments, often leading to damage. As such, these methods do not allow for the material's subsequent use after testing.