ESTIMATION OF YIELD STRENGTH OF STRUCTURAL STEEL (API X60 GRADE) USING NON-CIRCULAR DIMINUTIVE SPECIMEN

摘要

Miniature specimen test technique provides a way of obtaining mechanical properties of components while consuming an amount of materials that is very small. In most situations, full-size specimen cannot be obtained without destroying the component, whereas extraction of miniature samples can be virtually nondestructive. It is possible to determine the mechanical properties of specific components at specific locations, using small punch (SP) specimen test technique. In this paper, for testing the diminutive non-circular specimen, a special die (specimen holder) and three different hemispherical headed punches are designed and developed. This paper also describes how small punch test experimental data (load vs. displacement curve) obtained from miniature square shape coupon specimen, can be used for the estimation of yield strength. For this purpose, an empirical correlation based on SP breakaway load is proposed for the estimation of yield strength. The proposed empirical correlation is validated by conventional uni-axial test data. The developed empirical correlation is employed for structural steel. The estimated yield strength value is also compared with the value obtained from existing empirical relations. It is noticed that yield strength obtained from SP test with the help of proposed empirical correlation is in good agreement with that obtained from standard uniaxial test.