A simple predictive model for spherical indentation

Abstract

A simple model is described with which the entire force versus penetration behavior of indentation with a sphere, during loading and unloading, may be simulated from knowledge of the four test material parameters, Young's modulus, Poisson's ratio, flow stress at the onset of full plastic flow and strain hardening index, and the elastic properties of the indenter. The underlying mechanisms are discussed and the predictions of the model are compared with data produced by an ultra low load, penetration measuring instrument.

Post-yield characterisation of metals with significant pile-up through spherical indentations

“…The characterisation method proposed by Field and Swain [2,14] is based on Tabor's work [1,9], supplemented by a model for extracting the indentation geometry from analysing the unloading portion of the P-h curve based on Hertz's contact solution. According to this solution, the contact depth h c is given by…”

Micropillar compression testing of powders

“…Equation 1 is derived by equating the load required to the yield the pillar (uniaxial compressive yield) with the load needed to yield the epoxy substrate (multiaxial contact yield), following [28,29]. Realistically, particles may be in contact within the green compacts, including below the surface.…”

Quantitative assessment and prediction of contact area development during spherical tip indentation of glassy polymers

“…In the general case, the projected contact area is defined as a function of the contact depth by a simple geometric relation: (3) where h c is the contact depth. Unfortunately, when in addition to elastic deformation, also plastic deformation occurs, no analytical solution exists that describes the relationship between the actual contact depth and the experimentally measured tip displacement.…”

“…Therefore the contact area cannot be determined directly from the load-displacement curves, which makes it impossible to determine the mechanical properties without assumptions or approximations about the contact area. Popular methods to determine mechanical properties from indentation were proposed by Oliver and Pharr for a Berkovich tip [2] and by Field and Swain for a spherical tip [3]. Essentially, the method is based on elastic contact theory of symmetric indenters.…”