What is assessed by an ultrasonic test?

An ultrasonic test is primarily designed to detect internal flaws within materials. This non-destructive testing method utilizes high-frequency sound waves to penetrate the material being inspected. When these sound waves encounter any discontinuities, such as cracks or voids within the structure, they reflect back to the sensor. The time it takes for the echoes to return is measured and analyzed to determine the location and size of any internal flaws.

Surface defects, while they can sometimes be detected indirectly in certain scenarios, are not the main focus of ultrasonic testing. Surface defects are typically assessed using other methods such as visual inspection or magnetic particle testing. The elastic limit of a material, which defines the point at which it will undergo permanent deformation, is measured through tensile testing rather than ultrasonic testing. Similarly, fatigue resistance pertains to a material's ability to withstand repeated loading and is evaluated through tests that specifically simulate cyclic stress conditions. Therefore, internal flaws are the primary concern addressed by ultrasonic testing, making it the correct choice in this context.