Methodology to determine post yield material mechanical properties from spherical indentation

Abstract

Methodology to Determine Post Yield Material Mechanical Properties from Spherical Indentation Bharath Konda Conventional material testing methods, such as tensile tests require the preparation of specimens and is not applicable for small-size coupons or on-site, in-situ testing. In this research, a method of determining material stress-strain curve based on spherical indentation is studied. Spherical-indentation process is analyzed by finite element (FE) method and a systematic analysis of relationships between indentation parameters and true stress/plasticstrain (σ t-ε p) curve is performed for a range of material properties. A detailed methodology based on Tabor's empirical formula and Meyer's law is developed to determine the material strain hardening properties, Young's modulus and yield strength. It

Portable transparent indenter instrumentation for material surface characterization

“…The constraint factor as defined by Tabor [12] is constraint factor defined by Meyer's stress/stress and plays an important role in the yield strength determination by the Konda's approach [21]. A constant value of 2.8 produce an error of about 9%, while a constraint factor dependent on the strain hardening exponent [17], has an error of about 4 % or less in this research.…”

“…The contact radius and force are also used to obtain the strain-hardening factor using the Meyer's equation. With the strain hardness factor and the elastic modulus previously calculated, the yield strength could be found by the use of Konda's approach [21].…”

“…As a first step in Kondas's approach [21] require the calculation of the Meyer's exponent by Equation (4.18). The strain-hardening exponent is derived by Equation (2.29).…”

“…The mechanical parameters of the elastic modulus and the strain-hardening exponent have been experimentally derived for Aluminum Alloy 7075-T6 and Inconel Alloy 783. The Konda's approach [21] is used to calculate the yield strength and it has been implemented with satisfactory results. The mechanical parameter of failure stress cannot be experimentally found in order to define the complete true stress-true strain curve.…”

“…Figure 2.3 shows the application of Konda's approach[21]. The graph shows the calculation of the Meyer's coefficient by plotting the force versus the residual impression.…”