Theoretical analysis and finite element (FE) simulation have been carried out for a constant specific load rate (CSLR) indentation creep test. Analytical results indicate that both the representative stress and the indentation strain rate become constant after a transient period. Moreover, the FE simulation reveals that both the contours of equivalent stress and equivalent plastic strain rate u...

We present a detailed asymptotic analysis of the point indentation of an unpressurized, spherical elastic shell. Previous analyses of this classic problem have assumed that for sufficiently large indentation depths, such a shell deforms by 'mirror buckling'-a portion of the shell inverts to become a spherical cap with equal but opposite curvature to the undeformed shell. The energy of deformati...

We explore the collective mechanical behavior of monolayer assemblies composed of close-packed arrays of hollow silica nanoparticles using a spherical nanoindentor. Seven types of well-defined hollow nanoparticles are studied with their radii ranging from 100 to 300 nm and shell thickness ranging from 14 to 44 nm. Micromechanical models reveal the underlying deformation mechanisms during indent...

PURPOSE To measure the amount and duration of indentation depth achieved with biodegradable poly-L/D-lactide 96/4 (PLA96) and silicone sponge implants. METHODS Thirty rabbits underwent a scleral buckling procedure. A PLA96 buckling implant was used in 15 rabbits and a silicone sponge buckling implant was in 15 rabbits. A circumferential scleral buckling implant was sutured episclerally on the...

The present work shows the material flow analysis in indentation by the numerical two dimensional Finite Elements (FEM) method and the experimental two-dimensional Digital Image Correlation (DIC) method. To achieve deep indentation without cracking, a ductile material, 99% tin, is used. The results obtained from the DIC technique depend predominantly on the pattern conferred to the samples. Due...

Understanding the deformation mechanisms in ceramic materials is crucial for optimizing and implementing next-generation ceramic materials in body and vehicle armor systems. One particularly powerful tool for studying deformation mechanisms is transmission electron microscopy (TEM) of impacted materials. Indentation is useful for studying deformation mechanisms, since this method offers the abi...

The mechanical testing of thin layers of soft materials is an important but difficult task. Spherical indentation provides a convenient method to ascertain material properties whilst minimising damage to the material by allowing testing to take place in situ. However, measurement of the viscoelastic properties of these soft materials is hindered by the absence of a convenient yet accurate model...

The local mechanical properties of cells are frequently probed by force indentation experiments carried out with an atomic force microscope. Application of common contact models provides a single parameter, the Young's modulus, to describe the elastic properties of cells. The viscoelastic response of cells, however, is generally measured in separate microrheological experiments that provide com...

We monitored AEs during micro-indentation and pulse laser spallation test of CVD diamond film deposited on sintered SiC, and classified the fracture type by Lamb wave AE analysis. In the indentation test with a Rockwell sphere indenter, we observed Hertz ring cracks and simultaneously detected AEs from Mode-I fracture. Crack types were classified from polarity distribution of the first arrival ...

Abstract: Focusing on incremental bulk metal forming processes, the indentation process is gaining interest as a fundamental part of these kinds of processes. This paper presents the analysis of the pressure obtained in indentation under the influence of different punch geometries. To this end, an innovative Upper Bound Theorem (UBT) based solution is introduced. This new solution can be easily...