Magnaflux NDT Glossary

Acceptance Standard: A statement of the qualities that an object must possess to be deemed acceptable for its intended purpose.

Accuracy: The degree of agreement between a measurement result and the actual (true) value of the quantity being measured.

AE: Abbreviation for Acoustic Emission.

Algorithm: A step-by-step method for solving a problem or accomplishing a task.

Alternating Current (AC): Current that reverses direction in a repetitive cycle, typically following a sine wave pattern.

Amplitude: The maximum value of a wave or signal measured from its average value.

Amplitude Distribution Analysis: A method of analyzing acoustic emission data by measuring the amplitude distribution of signals.

Angle Beam: A sound beam traveling into a test piece at an angle other than 90° to the surface.

Anisotropy: The characteristic of a material where properties vary depending on the direction of measurement.

Artificial Defect: A deliberately introduced discontinuity in a reference standard, used for instrument calibration or system checks.

ASNT: Abbreviation for the American Society for Nondestructive Testing.

ASTM: Abbreviation for the American Society for Testing and Materials.

Attenuation: The gradual loss of wave energy as it propagates through a medium, caused by absorption and scattering.

Back Reflection: A reflection from the far boundary of the test object.

Backscattering: Redirection of energy toward the source by scattering from small discontinuities or grain boundaries within a material.

Background Noise: Unwanted electrical or acoustic signals that interfere with the interpretation of test results.

Beam: The path or bundle of ultrasonic energy transmitted into a test object.

Beam Spread: The divergence of an ultrasonic beam as it propagates through a medium.

Bond Testing: A nondestructive test used to evaluate the quality of adhesion between bonded surfaces.

Burst: A short train of waves or pulses.

Calibration: The process of adjusting an instrument to provide known and reliable responses under specified conditions.

Calibration Block: A reference block containing artificial reflectors used to adjust or verify instrument performance.

Capacitance: The ability of a system to store an electric charge, measured in farads.

Cathode: The negative electrode of a device such as a battery, X-ray tube, or cathode-ray tube.

Cavitation: The formation and collapse of bubbles in a liquid due to intense ultrasonic vibrations.

Characteristic Acoustic Impedance: The product of the density of a medium and the velocity of sound within it.

Chart Recorder: A device that creates a permanent visual record of data, such as ultrasonic signals, on paper or film.

Coherence: The degree to which waves maintain a fixed relationship in phase and frequency.

Compression Wave: A wave in which particle motion is parallel to the direction of wave propagation, also called longitudinal wave.

Couplant: A medium (gel, water, oil) used to transmit ultrasonic energy efficiently from the transducer to the test piece.

Creep Wave: A wave that propagates near the surface of a test piece at an angle close to 90°.

Critical Angle: The incident angle at which refracted waves travel along the surface of the medium.

DAC (Distance Amplitude Correction): A curve plotted to compensate for amplitude variations due to distance in ultrasonic testing.

Decibel (dB): A logarithmic unit used to express ratios, often for sound intensity or signal amplitude.

Defect: A discontinuity that exceeds acceptance standards and makes a material or structure unsuitable for service.

Diffraction: The bending or spreading of waves when they encounter edges, holes, or small obstacles.

Discontinuity: An interruption in the normal structure of a material, such as cracks, porosity, or inclusions.

Dispersion: The phenomenon where different frequencies of a wave travel at different velocities in a material.

Divergence: The angular spread of an ultrasonic beam as it travels away from the source.

Duty Cycle: The ratio of the pulse duration to the total cycle time in pulsed wave testing.

Eddy Currents: Circulating electrical currents induced in a conductor when exposed to a changing magnetic field, used in NDT.

Elastic Limit: The maximum stress a material can withstand without permanent deformation.

Electromagnetic Testing: A method of nondestructive testing using magnetic or electric fields (e.g., eddy current testing).

Electromagnetic Spectrum: The complete range of electromagnetic waves, from radio waves to gamma rays.

Electroplating: The process of depositing a layer of metal onto a surface using an electric current.

Evaluation: The process of assessing test indications to determine their cause, significance, and acceptability.

Fatigue: Failure of a material caused by repeated cyclic loading.

Field: A region in which a physical effect, such as magnetism or sound, can be detected.

Filter: An electronic circuit that selectively passes or rejects signals of certain frequencies.

Flaw: A discontinuity or imperfection in a material or component.

Frequency: The number of cycles of a wave that occur per second, measured in hertz (Hz).

Gain: The increase in amplitude of a signal produced by an amplifier, expressed in decibels.

Geometric Discontinuity: A design feature that interrupts continuity of a material, such as grooves, holes, or notches.

Grain Noise: Random ultrasonic reflections from the grain structure of a material, which can mask flaw signals.

Harmonic: A wave whose frequency is an integer multiple of a fundamental frequency.

Helium Leak Test: A test that detects leaks by using helium as a tracer gas.

Hertz (Hz): The unit of frequency equal to one cycle per second.

Indication: The response or signal observed during testing that may be caused by a discontinuity or geometry change.

Intergranular Corrosion: Corrosion that occurs along grain boundaries in a material.

Laminar Discontinuity: A planar defect such as a lamination or delamination within a material.

Longitudinal Wave: A wave where particle motion is parallel to wave propagation direction.

Magnetic Flux: The total magnetic field passing through a given area.

Magnetic Particle Testing (MT): A nondestructive method that detects surface and near-surface flaws in ferromagnetic materials.

Noise: Unwanted electrical or mechanical signals that interfere with test interpretation.

Nondestructive Testing (NDT): The practice of evaluating materials or components without causing damage.

Penetrant Testing (PT): A surface inspection method using dye or fluorescent liquids to reveal cracks and defects.

Radiographic Testing (RT): An NDT method using X-rays or gamma rays to produce images of internal structures.

Resonance: The condition in which a system vibrates with maximum amplitude at certain frequencies.

Shear Wave: A type of wave in which particle motion is perpendicular to the direction of propagation.

Surface Wave: A wave that travels along the surface of a material with particle motion decreasing with depth.

Ultrasonic Testing (UT): An NDT method that uses high-frequency sound waves to detect flaws and measure thickness.

Visual Testing (VT): The observation of a test object by eye, sometimes aided with magnifying devices.

X-Ray Testing: A radiographic technique using X-rays to examine the internal structure of materials.