A review of the observations indentation‐induced fracture suggests that there is no simple generalization which may be made concerning crack initiation sequences. Here, we investigate material dependence sequence indentation cracks (cone, radial, median, half‐penny, and lateral) using an inverted tester allowing simultaneous viewing process measurement indeter load displacement during contact. Two normal glasses, two anomalous seven crystalline materials are examined. Key results include (i)...

We report the observation, by transmission electron microscopy, that single-crystal silicon and germanium are converted to an amorphous state at room temperature directly under both Vickers Knoop indentations. The effect is seen for crystal orientations of [001], [011], [111], with applied loads between 0.1 0.5 N. also observe materials become electrically conducting load process reversible on subsequent unloading reloading. Furthermore, transformed phase found make Ohmic contact...

The fracture behavior of Al 2 O 3 containing 5 vol% 0.15μm SiC particles was investigated using indentation techniques. A significant increase in strength achieved by the addition to base . Specifically, increased from 560 MPa for 760 composite samples (average values unindented hotpressed bars tested four‐point bending). After annealing h at 1300°C, average about 1000 MPa. Toughness estimated indentation‐strength data. While there a slight toughness, not sufficient account on particle...

We show how contact resonance atomic force microscopy (CR-AFM) can be used to accurately determine the radial elastic moduli of [0001] ZnO nanowires with diameters smaller than 150 nm. Using a realistic tip−nanowire geometry, we find indentation modulus from CR-AFM data and tangential shear friction-type measurements. Both pronounced increase when wire diameter is reduced below 80 The size dependence properties explained by core−shell model that accounts for bulk-like core an elastically...

A systematic study of the inert‐strength characteristics ceramics as a function crack size relative to grain has been made using controlled indentation flaws. The focus test program is on aluminas, with barium titanates and glass‐ceramics providing support data in confirmation general trends. On progressively diminishing load, strengths first show steady increase, but subsequently tend plateau, contact begins approach characteristic size. simple extension conventional fracture mechanics...

We report new results of microhardness and depth-sensing indentation (DSI) experiments for the fist nine minerals in Mohs scale: talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum. The scale is based on a relative measure scratch resistance, but because scratching involves both loading shearing, resistance not equivalent to hardness as measured by modern (indentation) methods; also related other material properties (fracture toughness, elastic modulus). To better...

Abstract Block copolymers with and without reactive functionalities can improve fracture resistance in brittle epoxies even when added relatively small amounts (<5 wt %). At certain compositions, amphiphilic block spontaneously self‐assemble into vesicles, spherical micelles, or wormlike micelles thermoset resins, these morphologies are retained the full curing of resins. The addition such leaves glass‐transition temperature blends unchanged, whereas increases up to a factor 3.5 for...

Abstract Amphiphilic block copolymers provide a unique means for toughening epoxy resins because they can self‐assemble into different inclusion shapes before curing. The two examples reported here are spherical micelles and vesicles, which form in blends containing symmetric or asymmetric poly(ethylene oxide)–poly(ethylene‐ alt ‐propylene) (PEO–PEP) copolymer with PEO volume fractions of 0.5 0.26, respectively. vesicles were characterized by transmission electron microscopy small‐angle...

A modified indentation technique for measuring toughness is described. The method retains the elastic/plastic basis of previous contact fracture descriptions but eliminates explicit reference to residual stress parameters in formulation. Accordingly, improved correlations between data and “conventional” K c values are obtained, even materials (e.g. anomalous glasses) with nonideal deformation responses .

Silicon devices are ubiquitous in many micro- and nano-scale technological applications, most notably microelectronics microelectromechanical systems (MEMS). Despite their widespread usage, however, issues related to uncertain mechanical reliability remain a major factor inhibiting the further advancement of device commercialization. In particular, fracture MEMS components have become increasingly important given continued reductions critical feature sizes coupled with recent escalations...

Abstract Indentation fracture models of ductile machining in hard and brittle materials are critically appraised. Relations obtained a seminal study for critical depths cut below which is suppressed examined amended. Limitations inherent any such materials‐based analysis, addition to uncertainties empirical measurements underpinning mechanical properties (modulus, hardness, toughness) threshold grinding depths, suggest that caution should be exercised unconditional usage. Notwithstanding...

We report fracture toughness measurements on single crystals of YBa2Cu3Ox, the phase responsible for superconductivity above liquid-nitrogen temperatures. Indentation crack length (010) orthorhombic crystal growth faces revealed (100) and (001) planes as preferred planes. The these is Kc=1.1±0.3 MPa m1/2, hardness H=8.7±2.4 GPa. observed both radial lateral cracks in ambient air suggests that are susceptible to moisture-enhanced nonequilibrium propagation.

Studies of the hardness and toughness minerals have historically focused on Mohs scale, although, with exceptions quartz, orthoclase, calcite, phases are not common rock-forming minerals. We report new (H), (resistance to fracture, K IC ), indentation modulus (E*) data obtained by microhardness depth-sensing (DSI, or nanoindentation) experiments for metamorphic minerals: sillimanite, kyanite, andalusite, garnet, orthoclase feldspar. Because experimental techniques involve indentation-induced...

A theory is formulated for the general fatigue response of brittle flaws which experience residual stress concentrations. The indentation crack taken as a model flaw system purpose setting up basic fracture mechanics equations, but essential results are expected to have wider range applicability in strength characterization ceramics. starting differential equation first set by combining an appropriate intensity factor point‐ or line‐contact with power‐law velocity function. Analytical...

The utility of indentation testing for characterizing a wide range mechanical properties brittle materials is highlighted in light recent articles questioning its validity, specifically relation to the measurement toughness. Contrary assertion by some critics, fracture theory fundamentally founded Griffith–Irwin mechanics, based on model crack systems evolving within inhomogeneous but well‐documented elastic and elastic–plastic contact stress fields. Notwithstanding numerical uncertainty...

Test platforms for the ideal strength of materials are provided by almost defect-free nanostructures (nanowires, nanotubes, nanoparticles, example). In this work, ultimate bending strengths Si nanowires with radii in 20–60 nm range were investigated using a new protocol. Nanowires simply held adhesion on flat substrates bent through sequential atomic force microscopy manipulations. The states prior to failure analyzed great detail measure dynamics and fracture nanowires. An increase from 12...

Variations in the electrical and mechanical properties of silsesquioxane spin‐on‐glass thin films are examined as a function curing time temperature. Particular attention is paid to trade‐off between producing low‐dielectric‐constant films, suitable for advanced microelectronic interconnection structures, mechanically stable able withstand semiconductor wafer fabrication processes. Two critical aspects stability spin‐on glasses shown be positive thermal expansion mismatch with silicon,...