Determination of area reduction rate by spherical indentation test

摘要

Rate of area reduction is an important mechanical property to appraise the plasticity of metals, which is always obtained from the uniaxial tensile test. A methodology is proposed to determine the area reduction rate by continuous ball indentation test technique. The continuum damage accumulation theory has been adopted in this work to identify the failure point in the indentation. According to this theory, the damage is accumulated in the material during the test with voids nucleating and growing, which can be divided into two stages due to the variation in the degree of constraint. The turning point between two stages can be identified as the failure point where the material beneath the indenter collapses. The corresponding indentation depth of this point can be obtained and used to estimate the area reduction rate. The local strain limit criterion proposed in the ASME VIII-2 2007 alternative rules is also adopted in this research to convert the multiaxial strain of indentation test to uniaxial strain of tensile test. This method can be useful in engineering practice to evaluate the material degradation under severe working condition due to the non-destructive nature of ball indentation test. In order to validate the method, spherical indentation test is performed on ferritic steel 16MnR and B16, then the results are compared with that got from the traditional uniaxial tensile test. (C) 2016 Elsevier Ltd. All rights reserved.