Materials Testing and Calibration Terminology

Stands for the American Association for Laboratory Accreditation, a non-profit accrediting agency specializing in the accreditation of calibration and testing laboratories.

Is a process used by a qualified independent agency to verify the quality system and technical capability of a calibration laboratory to a recognized standard such as ISO 17025.

Defines how close a measured value is to the true value of the dimension.

Is the set of operations that establish, under specified conditions, the relationship between values of quantities indicated by a measuring instrument or measuring system or values represented by a material measure or a reference material and the corresponding values realized by standards.

Is a document that presents calibration results and other information relevant to a calibration.

Is the time intervals at which instruments, gages, and masters require calibration. These intervals depend on usage conditions and ensure their performance or size remains within acceptable limits.

Is a tolerance applied to gages and instruments beyond which they are not considered suitable.

Is a standard recognized by an international agreement to serve internationally as the basis for fixing the value of all other standards of the quantity concerned.

Are the extreme values of an error permitted by specifications, regulations, etc., for a given measuring instrument.

Is the technique that may include, but is not limited to: 1) The use of sound experimental design principles so the entire measurement process, its components, and relevant influence factors can be well characterized, monitored, and controlled; 2) Complete experimental characterization of the measurement process uncertainty including statistical variations, contributions from all known or suspected influence factors, imported uncertainties, and the propagation of uncertainties throughout the measurement process; and 3) Continuously monitoring the performance and state of statistical control of the measurement process with proven statistical process control techniques including the measurement of well-characterized check standards along with the expected workload and the use of appropriate control charts.

Includes all of the measuring instruments, measurement standards, reference materials, and auxiliary apparatus that are necessary to perform a measurement. This term includes measuring equipment used during testing and inspection, as well as that used in calibration.

Are the organizational structure, responsibilities, procedures, processes, and resources for implementing quality management.

Represents the smallest reading unit provided by an instrument.

Is the path by which materials are traceable back to their source, such as NIST in the United States. Direct traceability implies that the laboratory has its primary masters calibrated directly by such an agency for reduced measurement uncertainty.

Is a parameter associated with the result of a measurement that characterizes the dispersion of the values that the measurement.

Are materials or substances with one or more sufficiently homogeneous and well-established property values to calibrate an analytical instrument, assess a measurement method, or assign values to test samples.

Has had its composition certified by a recognized standardizing agency, such as the National Institute of Standards and Technology.

Is a highly sensitive method capable of trace multi-element analysis, often at the parts-per-trillion level. It determines a range of metals and several non-metals. ICP-MS also allows routine chemical testing for trace elements in super alloys and provides ultra-trace elemental analysis for high-purity alloys like those used in the semiconductor industry. Samples are decomposed to neutral elements in a high-temperature argon plasma to produce ions and are analyzed based on their mass-to-charge ratios. Aqueous samples are\ introduced by way of a nebulizer, which aspirates the sample with high-velocity argon, forming a fine mist. The aerosol then passes into a spray chamber that allows for the removal of larger droplets. Droplets small enough to be vaporized in the plasma torch pass into the torch body, where the aerosol mixes with more argon gas. A coupling coil transmits a radio frequency to the heated argon gas, producing an argon plasma at the torch. The hot plasma removes any remaining solvent and causes sample atomization followed by ionization.

Is a technique that determines elemental concentrations of major, minor, and trace elements in the sample. In theory, the technique can detect all elements except argon and can simultaneously analyze more than one element in metal alloys. In practice, good results are possible for about 70 elements with detection limits at the parts per billion level. It is an argon plasma operated at atmospheric pressure and sustained by inductive coupling to a radio frequency electromagnetic field. The high temperature in the plasma causes the sample to dissolve, volatilize, dissociate, atomize, and ionize. The sample is a solution of the test material introduced into the ICP as a fine aerosol of droplets produced by a nebulizer. The free atoms and ions generated in the plasma are electronically excited. The resulting radiation produces a spectrum of the wavelengths related to the elements in the sample. The intensity of the radiation is proportional to the quantities of each of the elements that are present in the sample.

Formerly Optical Emission Spectrometry (OES), uses the principle that free, energized atoms emit light at a narrow band of wavelength intervals. The interval or emission lines form a pattern characteristic of the atom that produced it. The intensities of the lines are proportional to the number of atoms that produced them and, thus, to the elements present. The concentration of the element is discoverable by measuring the line intensities. OES is used to measure major and trace elemental constituents in metal alloys. Some elements are difficult or impossible to determine using OES. These include nitrogen, oxygen, hydrogen, halogens, and noble gases.

Involves the analysis of samples without the use of instrumented methods {i.e., Atomic Absorption Spectrometry (AAA), Optical Emission Spectrometry (OES) and Inductively-Coupled Plasma Atomic Emissions Spectroscopy (ICP)}. In quantitative elemental analysis, the methods include gravimetry (for weighing chemical species), titrimetry, which involves volume measurement of a liquid, and several separation techniques that require various laboratory procedures. Wet analytical methods determine quantitative elemental composition and serve as a check on quantitative instrumental methods to analyze samples too small for instrumental methods, determine coating weights, or determine oxidation states.

Is a tolerance applied to gages and instruments beyond which they are not considered suitable.

Is a standard recognized by an international agreement to serve internationally as the basis for fixing the value of all other standards of the quantity concerned.

Are the extreme values of an error permitted by specifications, regulations, etc., for a given measuring instrument.

Is the technique that may include, but is not limited to: 1) The use of sound experimental design principles so the entire measurement process, its components, and relevant influence factors can be well characterized, monitored, and controlled; 2) Complete experimental characterization of the measurement process uncertainty including statistical variations, contributions from all known or suspected influence factors, imported uncertainties, and the propagation of uncertainties throughout the measurement process; and 3) Continuously monitoring the performance and state of statistical control of the measurement process with proven statistical process control techniques including the measurement of well-characterized check standards along with the expected workload and the use of appropriate control charts.

Includes all of the measuring instruments, measurement standards, reference materials, and auxiliary apparatus that are necessary to perform a measurement. This term includes measuring equipment used during testing and inspection, as well as that used in calibration.

Are the organizational structure, responsibilities, procedures, processes, and resources for implementing quality management.

Represents the smallest reading unit provided by an instrument.

Is the path by which materials are traceable back to their source, such as NIST in the United States. Direct traceability implies that the laboratory has its primary masters calibrated directly by such an agency for reduced measurement uncertainty.

Is a parameter associated with the result of a measurement that characterizes the dispersion of the values that the measurement.

Is the change in the length of a crack per number of load cycles. This data enables estimates of the remaining fatigue life of a component before a dangerous crack size develops.

Is the ability of a metal to deform to a permanent position before it fractures.

Are the maximum stress a material can sustain without any permanent deformation remaining after the complete release of the stress.

Is the amount of permanent deformation determined after fracture by realigning and fitting together the broken ends of the specimen.

Is measured at the time of fracture and includes both permanent and elastic deformation of the tensile specimen. This measurement requires an extensometer on the specimen through the final fracture.

Is progressive and localized structural damage that occurs under cyclic loading.

Is the original length of that portion of the specimen used to determine the strain or length change.

Is the resistance of a material to deformation, particularly permanent deformation, indentation, or scratching.

Are the inherent values of a material associated with the elastic and plastic reaction after a force application.

Evaluates the properties of a metal or material related to its behavior when subjected to a force or load during testing. In mechanical testing, the behavior of the metal is either elastic or inelastic. Elastic behavior occurs with no permanent damage to the test sample. In contrast, inelastic or plastic behavior occurs when a material is permanently deformed by the applied force and, therefore, does not return to its original shape.

Determines properties without applying force to the test sample and is usually insensitive to the internal or atomic structure of the material. These properties include density, thermal and electrical conductivity, the coefficient of thermal expansion, magnetic permeability, melting temperature, and freezing temperature of materials.

Is the ratio of the true strain in the width direction to the true strain in the thickness direction of a sheet material loaded beyond yield.

Is the difference between the original cross-sectional area of the tension test sample and the area of its smallest cross-section after fracture. The area reduction is a percentage of the original cross-section.

Is a measure of the increase in hardness and strength caused by the permanent deformation of a tensile sample. “n” is the calculated exponent of the power curve obtained by mathematically approximating the shape of the stress-strain curve between yield and ultimate stress.

Is the maximum tensile stress that a material can sustain, calculated as the maximum load during a tension test carried to rupture, divided by the original cross-sectional area of the sample.

Is the engineering stress at which the permanent elongation of the sample has begun.

Is the engineering stress at which the permanent elongation of the sample has begun, as determined by constructing a line perpendicular to the strain axis of a stress-strain curve at a strain specified as a percentage of the gage length.

Is the stress ratio to the corresponding strain below the proportional limit and the greatest stress the sample can sustain without deviation from a linear relationship of stress to strain.

Is the grain size of a steel sample that exists in the austenite phase at a given temperature. ASTM Test Method E112 discusses methods to determine the grain size of steel samples.

Exhibit alternate bands parallel to the direction of rolling or forging that produce elongation of segregated areas. Usually, it appears as alternate layers of light and dark etching regions.

Causes surfaces normal to the axis of the microscope to appear bright during reflected light microscopy.

Are microstructures resulting from the permanent deformation of a metal or alloy. It exhibits elongated grains in the material.

Is the carbon loss from the surface of a steel part due to the reaction with one or more chemical substances during the heat treatment of the part. Partial decarburization is where the carbon content is less than the unaffected interior portion of the piece. Complete decarburization is where the carbon content is less than the solubility limit of carbon in ferrite so that only ferrite is present at the piece’s surface.

Is the presence of two distinct grain sizes in substantial amounts, with one size significantly larger than the other.

Is the controlled preferential attack on a metal surface to reveal structural details such as grain size or second phases such as carbides.

Is the grain size of the ferrite in predominantly ferritic steel.

Are the resulting fiber pattern observed in a hot- or cold-worked material, showing how the metal flowed during the forming process.

Are foreign materials in the structure of metals. They are called non-metallic particles, such as oxides, sulfides, silicates, and aluminates.

Is a diamond hardness measurement that can determine the depth of hardened areas and the hardness of small or thin samples. The resulting indentation elongates along one axis.

Is the controlled surface etching of a metallic sample to reveal a visible structure at low magnification, usually no greater than ten times. It can show flow lines and ingot patterns.

Is the austenitic grain size in steels from carburizing at 1700°F followed by slow cooling. The method is described in ASTM E 112 and is used to determine if the steel production used a fine-grain practice.

Is the branch of science related to the constitution and structure of metals and alloys and their relationship to the material’s properties.

Analysis requires examining a suitably etched metal sample with a microscope.

Are photographs taken at a relatively high magnification (50 times or greater) to show the microstructure of a suitably polished and etched sample.

Is a mechanical, chemical, or electrolytic process used to prepare a smooth reflective surface free from artifacts or damage introduced during sectioning or grinding and suitable for microscopic examination.

Is the formation of a new grain structure through nucleation and growth produced by subjecting a rolled or formed metal to elevated temperature for a time long enough to accomplish the change in the structure.

Is the concentration of alloying elements in specific regions in a metal, which causes variations in the etching characteristics of the sample.

Is a diamond hardness measurement similar to Knoop hardness, but with an indenter with equal length sides and looks diamond-shaped.

Are any discontinuity that does not meet the specified acceptance criteria.

Is the response or evidence from a non-destructive examination.

Are NDT indications caused by parts geometry (blind holes, keyways), magnetic writing, localized hardening, and scratches. They are considered non-relevant.

Determines whether indications are relevant, non-relevant, or false.

Are the magnetic field that leaves or enters the surface of a part due to a discontinuity or change of section.

Are NDT indications caused by a condition or type of discontinuity that is not rejectable.

re NDT indications caused by a condition or type of discontinuity that requires evaluation.