What NDT method is used to detect flaws in axles?

Ultrasonic testing (UT) and magnetic particle testing (MPT) are the primary Non-Destructive Testing (NDT) methods used to detect flaws in axles. Ultrasonic testing uses high-frequency sound waves to detect internal flaws that may not be visible on the surface. A transducer emits sound waves into the axle, and the waves are reflected back by any discontinuities, such as cracks or inclusions. The time it takes for the waves to return and the amplitude of the reflected signal are used to determine the location and size of the flaw. Magnetic particle testing is used to detect surface and near-surface cracks. The axle is magnetized, and then fine magnetic particles are applied to the surface. If there are any cracks or discontinuities, the magnetic field will be disrupted, causing the particles to accumulate at the flaw location, making it visible. Ultrasonic testing is particularly effective for detecting internal flaws, while magnetic particle testing is best for detecting surface flaws. Both methods are used to ensure the integrity of axles and prevent failures that could lead to derailments. The specific method chosen depends on the type of flaw being sought and the accessibility of the axle surface.