What type of test can detect internal indications within the test piece?

The ability to detect internal indications within a test piece is best achieved through volumetric testing methods. Volumetric tests assess the volume of the material being examined, which allows for the identification of internal flaws such as voids, inclusions, and cracks that might not be visible externally. This is crucial in ensuring the integrity and safety of components, particularly in welded structures, pressure vessels, and pipelines.

Volumetric testing techniques encompass methods like ultrasonic testing, radiographic testing, and magnetic particle testing, all of which provide information about the internal structure of the test piece through various means. Each method utilized can give insights into the internal condition of a material, making volumetric testing a vital approach when internal indications must be assessed.

In contrast, visual tests are limited to surface examination, leak testing checks for the presence of leakage rather than internal defects, and while ultrasonic testing is a volumetric method, it is just one of the techniques that falls under the broader category of volumetric testing.