ISO 6892-2: Tensile Testing of Metallic Materials at Elevated Temperatures
ISO 6892-2 is one of the most commonly used testing standards for the tensile testing of metallic materials at elevated temperatures (above 35°C). ISO 6892-2:2018 is the current version of the metals testing standard. It was first published in 2011, when it canceled and replaced the previous standard governing elevated temperature testing - ISO 783:1999.
Elevated temperature testing is most commonly used in the aerospace industry, where metallic materials in aircraft engines and structures must exhibit high strength while running at high temperatures. This form of testing has become increasingly important in aerospace metals, as higher engine service temperatures are desired for improved efficiency. Similarly, ISO 6892-2 is relevant to important applications in power generation, automotive components, and petrochemical equipment. Wherever metal fasteners, hardware, or structural components are expected to carry loads in hot environments, ISO 6892-2 enables a standardized determination and qualification of their important tensile properties.
What Tips and Tricks Can Help Improve My Testing?
ISO 6892-2 describes two methods of elevated temperature testing, Method A and Method B. Since test speed typically has a much greater influence on mechanical properties at elevated temperatures compared to testing at room temperature, both methods strictly control the strain rates allowed while these properties are determined. This, along with narrow tolerances (±20%), minimizes measurement uncertainty of test results and lab-to-lab variability.
Method A is especially well suited for minimizing uncertainty and variability, hence its preferred use in the aerospace industry. It applies a narrow tolerance to a slower test speed that improves the repeatability of results, especially at higher temperatures. ISO 6892-2 also provides an alternative method for comparing room temperature test results directly to elevated temperature results at the same strain rates and tolerances. This is the purpose of Method B.
In the standard's Annex, ISO 6892-2 provides example comparisons of multiple specimens tested at varying strain rates in room temperature test conditions, and then multiple specimens of the same alloy tested at elevated temperatures (850°C). It's clear from these figures that strain-rate sensitivity increases significantly with higher temperatures.