An international workshop was held on April 22–23, 1995, at the Town and Country Hotel in San Diego, to discuss the scientific and standardization issues associated with instrumented indentation, also known as dynamic hardness testing or depth-sensing, ultra-low-load, or nano indentation. The workshop was sponsored jointly by the NIST Standard Reference Materials Program (SRMP) and the Institut...

We use instrumented indentation to characterize the mechanical and transport behavior of a pH-sensitive hydrogel in various aqueous buffer solutions. In the measurement, an indenter is pressed to a fixed depth into a hydrogel disk and the load on the indenter is recorded as a function of time. By analyzing the load–relaxation curve using the theory of poroelasticity, the elastic constants of th...

Porcine aortic valve leaflets are comprised of three layers, each of which has a different composition and consequently, different mechanical properties. Each layer exhibits non-linear stress-strain behaviour and is modelled using a hyperelastic material model. Our objective is to determine the mechanical properties of each layer from experimental force-indentation depth data, ensuring that the...

We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells are subject to a wrinkling instability. We study wrinkling in depth, presenting scaling laws for the critical indentation at which wrinkling occurs and the nu...

When people are asked to palpate a novel soft object to discern its physical properties such as texture, elasticity, and even non-homogeneity, they not only regulate probing behaviors, but also the co-contraction level of antagonistic muscles to control the mechanical impedance of fingers. It is suspected that such behavior tries to enhance haptic perception by regulating the function of mechan...

Recent experiments have shown that metallic materials display significant size effect at the micron and sub-micron scales. This has motivated the development of strain gradient plasticity theories, which usually involve extra boundary conditions and possibly higher-order governing equations. We propose a finite deformation theory of nonlocal plasticity based on the Taylor dislocation model. The...

This article establishes a new model for estimating the peak indentation force of the edge chipping of rocks when using a conical or a pyramidal point-attack pick. The investigation points out that the existing formulation in the literature is based on an inappropriate stress assumption and equilibrium, and hence leads to incorrect cutting force estimations. The new model developed in this stud...

This paper explores the evolution mechanisms of metastable phases during the nanoindentation on monocrystalline silicon. Both the molecular dynamics (MD) and the in situ scanning spreading resistance microscopy (SSRM) analyses were carried out on Si(100) orientation, and for the first time, experimental verification was achieved quantitatively at the same nanoscopic scale. It was found that und...

Carbide composites are materials based on the carbide phases of the refractory or high melting temperature metals. The hard carbide phase (WC, TiC) is usually embedded into soft matrix – pure metals (Fe, Co, Mo, Ni and others) or their combinations. The hard phase supports high hardness and strength of the carbide composites, while matrix is needed for toughness and plastic properties. The ordi...

This work uses a method based on indentation to characterize a polydimethylsiloxane (PDMS) elastomer submerged in an organic solvent (decane, heptane, pentane, or cyclohexane). An indenter is pressed into a disk of a swollen elastomer to a fixed depth, and the force on the indenter is recorded as a function of time. By examining how the relaxation time scales with the radius of contact, one can...