ISO 6892-1 Metallic Materials - Tensile Testing - Part 1: Test Method at Room Temperature

The ISO 6892-1 Metallic materials - Tensile testing - Part 1: Test method at room temperature standard, published by the International Organization for Standardization (ISO), describes a test method for tensile testing of metallic materials and defines the mechanical properties that can be determined at room temperature. The standard annex contains further recommendations for computer-controlled testing machines ( Annex A).

For the purposes of this standard, the following terms and definitions apply:

• The gauge length is the length of the parallel portion of the test piece whose elongation is measured at any instant during the test. The original gauge length is the length between the gauge length markings on the test piece as measured at room temperature before the test. The final gauge length after fracture is the length between the gauge length markings on the test piece as measured after fracture, with the test piece reassembled so that its axes lie in a straight line at room temperature.
• Parallel length is the length of the parallel reduced section of the test piece. For unmachined test pieces the concept of parallel length is replaced by the concept of the distance between grips.
• Elongation is the increase in the original gauge length at any time during the test.
• Percentage elongation is expressed as a percentage of the original gauge length. Percentage permanent elongation is the increase in the original gauge length of a test piece after removal of a specified stress and is expressed as a percentage of the original gauge length. Percentage elongation after fracture is the permanent elongation of the gauge length after fracture expressed as a percentage of the original gauge length.
• The extensometer gauge length is the initial gauge length used for the extensometer's elongation measurement. The use of an extensometer is mandatory for determining various properties that depend (partially or completely) on elongation.
• Extension is the increase in the extensometer gauge length at any time during the test. Percent extension (strain) is expressed as a percentage of the extensometer gauge length and is often called the engineering stress. Percent permanent elongation is the increase in the extensometer gauge length after a specified stress is removed from the test piece and is expressed as a percentage of the extensometer gauge length. Percent yield point elongation, (intermittent yield materials) the elongation between the onset of elongation and the onset of uniform work hardening, expressed as a percentage of the extensometer gauge length. Percent total elongation at maximum force (elastic elongation plus plastic elongation), expressed as a percentage of the extensometer gauge length. Percent plastic elongation at maximum force is the extensometer gauge length. Percent total elongation at fracture (elastic elongation plus plastic elongation), expressed as a percentage of the extensometer gauge length.
• The test rate is the rate used during the test. The strain rate is the increase in stress along the extensometer gauge length per time, as measured by the extensometer. The estimated strain rate along the parallel length is the value of the increase in stress along the parallel length of the test piece based on the crosshead separation rate and the parallel length of the test piece. The crosshead separation rate is the displacement of the crossheads per time. The strain rate is the increase in stress per time. The strain rate is used only in the elastic portion of the test (method B).
• Percentage reduction in area is the maximum change in cross-sectional area that occurs during testing and is expressed as a percentage of the original cross-sectional area.
• The maximum force is the highest force that the test piece withstands during testing for materials that do not exhibit intermittent yielding. For materials that exhibit intermittent yielding, the highest force that the test piece withstands during testing after the start of work hardening. For materials that exhibit continuous yielding but for which work hardening cannot be determined, the maximum force is not defined in this standard.
• The stress is obtained by dividing the force by the original cross-sectional area at any instant during the test. The tensile strength is the stress corresponding to the maximum force. The yield strength is the stress reached during the test at which plastic deformation occurs without any increase in force when the metallic material exhibits a yielding phenomenon. The upper yield strength is the maximum value of the stress before the first decrease in force. The lower yield strength is the lowest value of the stress during plastic yielding, ignoring any first-pass effects. The proof strength is the stress at which the plastic elongation is equal to a specified percentage of the extensometer gauge length. The proof strength is the stress at which the total elongation (elastic elongation plus plastic elongation) is equal to a specified percentage of the extensometer gauge length. The permanent permanent strength is the stress at which the specified permanent elongation or elongation, expressed as a percentage of the original gauge length or extensometer gauge length respectively, is not exceeded after the force is removed.
• Fracture is the phenomenon that is considered to occur when the test piece is completely separated.
• Computer controlled tensile testing machine is a machine in which the control and monitoring of the test, measurements and data processing are performed by the computer.
• The modulus of elasticity is the quotient of the stress change and the percent change in extension over the evaluation range, multiplied by 100 percent.

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