Glossary

ASTM E112 is the standard test method for determining average grain size in metallic materials, employing comparison charts, planimetric counting, or lineal intercept techniques.

A bend test evaluates ductility and soundness by bending a specimen to a specified angle or radius, revealing surface discontinuities or lack of fusion.

The Brinell hardness test measures hardness by pressing a carbide ball into the material under a specified load; the Brinell hardness number is the load divided by the indentation surface area.

Carburization is a heat treatment process that diffuses carbon into the surface of steel to increase hardness and wear resistance, creating a high-carbon case.

Case depth is the perpendicular distance from the surface of a case-hardened part to a defined hardness limit or microstructural feature, such as the effective or total case depth.

The Charpy V-notch test is an impact test in which a notched specimen is struck by a pendulum; the energy absorbed during fracture indicates notch toughness.

Coating thickness is the measured thickness of a protective or functional coating, typically determined by microscopic examination of a cross-section or by non-destructive methods.

Decarburization is the loss of carbon from the surface of steel due to heating in an oxidizing atmosphere, resulting in a soft surface layer with reduced strength.

The ductile-to-brittle transition temperature is the temperature at which a material's fracture mode changes from ductile tearing to brittle cleavage, often determined by Charpy testing.

Elongation is the increase in gauge length of a tensile specimen after fracture, expressed as a percentage of the original length; it measures ductility.

Engineering stress is the applied load divided by the original cross-sectional area of a tensile specimen; it does not account for the reduction in area during necking.

Grain size is a measure of the average size of grains in a polycrystalline metal, often expressed as an ASTM grain size number determined by comparison or measurement.

Hardness conversion is the process of converting a hardness value from one scale to another using empirical correlation charts, which are material-specific and approximate.

Hydrogen embrittlement is a loss of ductility in high-strength steels caused by absorbed hydrogen, often leading to delayed brittle fracture under sustained tensile stress.

Impact energy is the energy absorbed by a specimen during an impact test, measured in joules or foot-pounds; it quantifies a material's resistance to sudden fracture.

ISO/IEC 17025 is the international standard specifying general requirements for the competence, impartiality, and consistent operation of testing and calibration laboratories.

The Knoop hardness test uses an elongated diamond indenter under low load to measure microhardness; it is suited for brittle materials, thin coatings, and small regions.

Macro etching is a procedure using acid or other etchants to reveal macroscopic features such as weld penetration, segregation, flow lines, or cracks on a polished cross-section.

Micro etching is a chemical etching procedure used to reveal the microstructure of a metal for microscopic examination, highlighting grain boundaries, phases, and inclusions.

Microhardness testing measures hardness using very low loads, typically with Vickers or Knoop indenters, to assess small regions, thin layers, or microstructural constituents.

A mill test report is a certified document from a material producer listing the chemical composition and mechanical properties of a specific heat or lot of material.

The modulus of elasticity, or Young's modulus, is a material property measuring stiffness; it is the ratio of stress to strain within the elastic deformation range.

Necking is the localized reduction in cross-sectional area that occurs during tensile testing after the ultimate tensile strength is reached, preceding fracture.

Optical emission spectroscopy is an analytical technique that measures the light emitted from excited atoms in a spark or arc to determine the chemical composition of a metal.

The planimetric method is a grain size measurement technique per ASTM E112 that counts the number of grains within a known area to calculate the average grain size.

A procedure qualification record is a record of the welding variables and test results from a test weld used to qualify a welding procedure specification.

A proof load is a specified test load applied to a fastener to verify that it can sustain the load without permanent deformation or failure.

Reduction of area is the decrease in cross-sectional area at the fracture point of a tensile specimen, expressed as a percentage of the original area; it indicates ductility.

The Rockwell hardness test measures hardness by recording the depth of penetration of an indenter under a major load after a minor load; different scales use various indenters and loads.

The Rockwell superficial hardness test is a variant of the Rockwell test using lighter loads, suitable for thin materials, case-hardened surfaces, or small parts.

A stress-strain curve is a graph plotting stress versus strain during a tensile test, showing elastic deformation, yielding, strain hardening, necking, and fracture.

A tensile test is a mechanical test in which a specimen is pulled to failure to measure properties such as yield strength, ultimate tensile strength, and elongation.

A tensile test report is a document summarizing the results of a tensile test, including specimen dimensions, test conditions, and calculated mechanical properties.

True stress is the applied load divided by the instantaneous cross-sectional area of a tensile specimen; it accounts for the area reduction during necking, providing a more accurate flow curve.

Ultimate tensile strength is the maximum engineering stress reached during a tensile test; it represents the highest load sustained by the specimen divided by the original area.

The Vickers hardness test uses a diamond pyramid indenter under a specified load; the hardness number is proportional to the load divided by the indentation surface area.

The wedge tensile test is a fastener test using a wedge under the head to apply bending stress during tension, assessing ductility and head-shank integrity.

A weld procedure specification is a written document detailing the welding parameters, base materials, filler metals, and techniques required to produce a sound weld.

Welder performance qualification is a test verifying that a welder can produce a sound weld following a qualified welding procedure specification.

Yield strength is the stress at which a material begins to deform plastically; it is often determined using the 0.2% offset method on a stress-strain curve.