Measurement Uncertainty of Mechanical Property in Tensile Tests: Strain Rate Embrittlement of HSLA Steels

International Standard ISO 6892–2 maintains that strain rate variations can induce the measurement uncertainty of mechanical properties in tensile testing, which will imperil the reliability of tension tests. In this paper, the measurement uncertainty of reduction in area relative to strain rate, called as strain rate embrittlement, is first described experimentally for some micro-alloy steels. Then the measurement uncertainty is clarified based on microscopic theory of elastic deformation in metals. It is shown that the elastic deformation of tension test induces the segregation of impurities to grain boundaries and the relevant embrittlement which produces the measurement uncertainty of reduction in area in tensile testing. This work gives a theoretical basis for correcting the present tension testing system to avoid the measurement uncertainty of mechanical property.