ASNT NDT STUDY GUIDE TOP GRADED 2024

Acoustic Emission Testing.. Acoustic Emission (AE) refers to the generation of transient elastic waves produced by a sudden redistribution of stress in a material. When a structure is subjected to an external stimulus (change in pressure, load, or temperature), localized sources trigger the release of energy, in the form of stress waves, which propagate to the surface and are recorded by sensors. With the right equipment and setup, motions on the order of picometers (10 -12 m) can be identified. Sources of AE vary from natural events like earthquakes and rockbursts to the initiation and growth of cracks, slip and dislocation movements, melting, twinning, and phase transformations in metals. In composites, matrix cracking and fiber breakage and debonding contribute to acoustic emissions. AE's have also been measured and recorded in polymers, wood, and concrete, among other materials. Detection and analysis of AE sig - 100-300 kHz 2) Discontinuities that are not readily detectable by acoustic emission testing are: - rounded inclusions The kaiser effect refers to: - the behavior where emission from a source will not occur until the previous load is exceeded. Kaiser effect is an absence of acoustic emission at loads not exceeding the previous maximum load level when material undergoes repetitive loading patterns. Discontinuities created in material during previous steps do not move or expand until former stress is exceeded resulting in Kaiser effect. The felicity effect is useful in evaluating: - fiber-reinforced plastic components Felicity effect is an effect in acoustic emission that reduces Kaiser effect at high loads of material. Under Felicity effect the acoustic emission resumes before the previous maximum load was reached. The total energy loss of a propagating wave is called: - Attenuation The Kaiser Effect is useful in distinguishing: - mechanical noise from growing discontinuities The term "counts" refers to the : - number of times a signal crosses a preset threshold The acoustic emission signal amplitude is related to: - the band pass filters. Threshold settings are determined by the: - background noise level Background noise can be reduced by : - electronic filtering Electromagnetic Testing - Electromagnetic Testing (ET), as a form of nondestructive testing, is the process of inducing electric currents or magnetic fields or both inside a test object and observing the electromagnetic response. If the test is set up properly, a defect inside the test object creates a measurable response. The term "Electromagnetic Testing" is often intended to mean simply Eddy-Current Testing (ECT). However with an expanding number of electromagnetic and magnetic test methods, "Electromagnetic Testing" is more often used to mean the whole class of electromagnetic test methods, of which Eddy-Current Testing is just one. Eddy-Current Testing (ECT) is used to detect near-surface cracks and corrosion in metallic objects such as tubes and aircraft fuselage and structures. ECT is more commonly applied to nonferromagnetic materials, since in ferromagnetic materials the depth of penetration is relatively small. Remote field testing (RFT) is used for nondestructive testing (NDT) of steel tubes and pipes. Magnetic flux leakage testing (MFL) is also used for nondestructive testing (NDT) of steel tubes and pipes. At present RFT is more commonly used in small diameter tubes and MFL in larger diameter pipes over long travel distances. Wire rope testing is MFL applied to steel cables, to detect broken strands of wire. Magnetic particle inspection (MT or MPI) is a form of MFL where small magnetic particles in the form of a powder or liquid are sprayed on the magnetized steel test object and gather at surface-breaking cracks.