Methodology to determine post yield material mechanical properties from spherical indentation

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/plastic-strain (sigmat- epsilonp) 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 is noticed that Tabor's empirical formula is valid in the plastic region (deep indentation) with a small percentage error in the calculated values of yield strength. Based on the FE results, strain values have been predicted corresponding to which indentation gives satisfactory output. Steel and aluminum alloys, with same Young's modulus and yield strength but with different strain hardening coefficients, were selected for the simulation. FE simulation of 20 material models was performed. It is observed that the Tabor's constant is not equal to the value of 2.8 but takes different values for different materials. From the results it is concluded that the value of Tabor's constant decreases as the strain hardening value increases.

Name thesis:degree_name

MS

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical and Aerospace Engineering

Year dc:date.available

2005

Author dc:creator

• Konda, Bharath

Contributors dc:contributor

• Bruce S. Kang.

• Mechanical engineering

Identifier

https://researchrepository.wvu.edu/etd/1603

OAI identifier oai:identifier

oai:researchrepository.wvu.edu:etd-2606