NDT Glossary

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• Echo - A signal indicating reflected acoustic energy.
  
• Echoes - A sound wave that continues to bounce around a room or off other barriers, or reverberate, until it has lost all its energy.
• Eddy Currents - Circular induced currents that are generated by an alternating current in the nearby coil.
• Eddy Current Inspection - An electromagnetic technique used on conductive materials for crack detection or the rapid sorting of small components for either flaws, size variations, or material variation, as well as other applications.
  
• Eddy Current Method - An electromagnetic NDT Method based on the process of inducing electrical currents into a conductive material and observing the interaction between the currents and the material.
  
• Eddy Current Scope - A scope that uses little electrical currents call "eddy currents" to find defects in different materials.
  
• Eddy Current Testing (EC) - An electromagnetic technique used on conductive materials for crack detection or the rapid sorting of small components for either flaws, size variations, or material variation, as well as other applications.
  
• EDGE Effect - Signal obtained when a surface prove approaches the sample’s edge.
• Effective Depth of Penetration -Depth at which eddy current density drops off to 5% of the surface density.
  
• Elastic - Able to return immediately to the original size and shape after being stretched or squeezed; springy.
  
• Elastic Constants - The factors of proportionality that relate elastic displacement of a material to applied forces.
  
• Elastic Deformation - Change of dimensions accompanying stress in the elastic range, original dimensions being restored upon release of stress.
  
• Elastic Limit - The maximum stress to which a material may be subjected with no permanent deformation after release of the applied load.
  
• Elastic Modulus - The ratio of the stress applied to an elastic body to the change in its shape.
  
• Elastic-Plastic Fracture Mechanics - A design approach used for materials that fracture or behave in a “plastic” manner, such as lower strength, high-toughness steels.
  
• Elastic Properties of Solids - Properties of a solid material defining how it will react to stress and strain.
  
• Elasticity - A term that describes how quickly molecules return to their original positions.
  
• Elastomer - A material with rubber-like properties-that is, quite elastic, returning to its original size and shape after being deformed.
  
• Electric Motor - A motor that converts electric energy into mechanical energy that can be used to do work.
  
• Electrical Contact - Contact of two conductors allowing current to pass.
  
• Electrical Current - The movement of electrons between atoms.
  
• Electrical Impedance - The total opposition that a circuit presents to an alternating current.
  
• Electrical Noise - Extraneous signals caused by externally radiated signals or electrical interferences within an ultrasonic instrument. A component of background noise.
  
• Electricity - A naturally occurring force that exists all around us.
  
• Electrochemical - Pertaining to combined electrical and chemical action. Deterioration (corrosion) of a metal occurs when an electrical current flows between cathodic and anodic areas on metal surfaces.
  
• Electrochemical Corrosion - Corrosion which occurs when current flows between cathodic and anodic areas on metallic surfaces.
  
• Electrode - An electrical conductor, usually of metal or graphite, that leads current into or out of a solution (electrolyte).
  
• Electrolyte - A material, usually a liquid or paste, that will conduct an electric current.
  
• Electromagnetic Acoustic Transducer - A device using the magneto effect to generate and receive acoustic signals for ultrasonic nondestructive tests.
  
• Electromagnet - Wrapping a wire into a coil creates an electromagnet, which behaves just like a regular permanent bar magnet when the current is flowing.
  
• Electromagnetic Acoustic Transducers (EMATS) - A scanning device which transmits and receives ultrasonic waves.
  
• Electromagnetic Field - A field that is created when energy from a power source such as a battery is applied to a circuit, making the electrons flow through a conductor, a new type of field is developed around the wire.
  
• Electromagnetic Induction - A process by which electrical current is induced in an electrical conductor by a changing magnetic field that acts upon the conductor.
  
• Electromagnetic Radiation - Energy in a wave form that possesses both electrical and magnetic characteristics. EMR radiates in the form of a wave which can accelerate charged particles. Electromagnetic radiation can travel through a vacuum and its energy varies greatly; radio waves have the longest wavelengths and the lowest frequency and energy, while X-rays and gamma rays have the shortest wavelengths and highest frequencies and energies.
  
• Electromagnetic Spectrum - The entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves.
  
• Electromagnetic Testing - A nondestructive way to test materials by using electromagnetic energy.
  
• Electromagnetism - The production of a magnetic field by current flowing in a conductor.
  
• Electromagnets - An iron bar placed through the center of the coiled wire would become a temporary magnet, as long as the electric current is flowing through the wire.
  
• Electromotive Force - The work or energy which causes the flow of an electric current. Expressed as volts. It should be noted that the term "force" is a misnomer. However, the term is so well established that its use continues in spite of its being incorrect.
  
• Electromotor Force - A force that causes electrons to move in a particular direction.
  
• Electron Volt - An amount of energy equal to the energy gained by one electron when it is accelerated by one volt,
  
• Electron - A negatively charged particle that is in constant motion and generally orbits the nucleus of an atom. The electron is the lightest known particle that possesses a charge.
• Electroscope - A fairly simple device comprised of a metal rod with two thin leaves attached to one end. If the electroscope is given a negative charge, the metal leaves will separate from each other. The rate of discharge of the electroscope is a measure of ions in the air and can be used as a basis of measurement and detection.
  
• Electrostatic Field - Electrons are said to have a negative charge, which means that they seem to be surrounded by a kind of invisible force field. This is called an electrostatic field.
  
• Electrostatic Generator - This device accelerates electrons to produce high energy radiation.
• Elements - Any material composed of only one kind of atom.
  
• Elementary Particle - Originally a term applied to any particle that could not be further subdivided; now applied only to protons, electrons, neutrons, antiparticles and strange particles, but not to alpha particles and deuterons.
  
• Ellipse - When a parabola is closed off by another curved surface an ellipse is produced.
  
• Elliptical Void Formula - A formula used to calculate the amount of time it takes for a viscous fluid to fill an elliptical defect in a material.
  
• Elongation - In tensile testing, the increase in the gage length, measured after fracture of the specimen within the gage length, usually expressed as a percentage of the original gage length.
  
• EMATs - Electromagnetic Acoustic Transducers
  
• Embrittlement - Reduction in the normal ductility of a metal due to a physical or chemical change.
  
• Emissivity - The energy emission rate usually expressed as r/c/hr @ 1ft or mr/mc/hr @ 1 ft.
  
• Emulsification Time - The period of time during which the emulsifier is permitted to combine with the liquid penetrant. Emulsification action begins when the emulsifying agents come in contact with the penetrant and ends with the removal of this agent, by water rinsing.
  
• Emulsifier - An agent, usually in liquid form which, when combined with a liquid penetrant that is insoluble in water, renders such a penetrant "soluble" thereby facilitating its removal by a water wash.
  
• Emulsifier Bath - The bath used to soak a part in a penetrate fluid to test for defects.
  
• Emulsifier Concentration and Contact Time - The time the material needs to be soaked in and the concentration of penetrate in the bath depends on the type of penetrate used and the desired results.
  
• Emulsifiers - An additive that promotes the formation of a stable mixture between two liquids like oil and water.
  
• Emulsion Penetrant - A mixture of water and oil produced by the addition of a third material, the liquid penetrant emulsifier.
  
• Emulsion Radiographic - A gelatin and silver bromide crystal mixture coated onto a transparent film base.
  
• Encapsulation - The process of sealing radioactive materials to prevent contamination.
  
• END Effect - Signal obtained when an internal or encircling probe approaches the end of a tube or rod (Similar to edge effect).
  
• Equiaxed Grain Structure - A structure in which the grains have approximately the same dimensions in all directions.
  
• Earing - The amount of wasted, irregular material (usually snipped or cut off) as part of the stamping or deep drawing process.
  
• Erosion - Destruction of metals or other materials by the abrasive action of moving fluids, usually accelerated by the presence of solid particles of matter in suspension. When corrosion occurs simultaneously, the term erosion-corrosion is often used.
  
• Error Analysis - The process used to evaluate the total error throughout an experiment. This can be due to bias error, precision error as well as others.
  
• Erythema Dose - The amount of radiation needed, when applied to the skin, to make it turn temporarily red.
  
• Etchants - A chemical used to etch a metal to reveal the structural details.
  
• Etch cracks - Shallow cracks in hardened steel, containing high residual surface stresses, produced on etching in an embrittling acid.
  
• Etching - Subjecting the surface of a metal to preferential chemical or electrolytic attack in order to reveal structural details.
  
• Eutectic Alloy - The composition in a binary alloy system which melts at minimum temperature. More than one eutectic composition may occur in a given alloy system.
  
• Evaluation - The process of deciding the severity of a condition after an indication has been interpreted. Evaluation determines if the test object should be rejected, repaired or accepted. See indication and interpretation.
  
• Evanescent Wave - A disappearing wave.
  
• Exfoliation - A type of corrsion that progresses approximately parallel to the outer surface of the metal, causing layers of the metal to be elevated by the formation of corrosion product.
  
• Expanded Sweep - A short duration horizontal sweep positioned to provide close examination of a particular signal.
  
• Exposure - The time which radiation is being exposed to something
  
• Exposure Film - Radiation intensity multiplied by time.
  
• Exposure Vaults and Cabinets - Exposure vaults and cabinets are areas that allow personnel to work safely in the vicinity while exposures are taking place
  
• External Discontinuities - Surface irregularities which cause density variations on a radiograph. These are observable with the naked eye.

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