Showing papers on "Indentation published in 1984"
TL;DR: In this paper, a simple technique is presented to obtain the characteristic microhardness values of surface coatings that are too thin for the values to be directly measured, using a physical model of film deformation during indentation.
654 citations
TL;DR: In this article, a fracture analysis of indentation-induced delamination of thin films is presented based on a model system in which the section of film above the delaminating crack is treated as a rigidly clamped disc, and the crack extension force is derived from changes in strain energy of the system as the crack extends.
Abstract: A fracture analysis of indentation‐induced delamination of thin films is presented. The analysis is based on a model system in which the section of film above the delaminating crack is treated as a rigidly clamped disc, and the crack extension force is derived from changes in strain energy of the system as the crack extends. Residual deposition stresses influence the cracking response by inducing buckling of the film above the crack and by providing an additional crack driving force once buckling occurs. A relation for the equilibrium crack length is derived in terms of the indenter load and geometry, the film thickness and mechanical properties, the residual stress level, and the fracture toughness of the interface. The analysis provides a basis for using controlled indentation cracking as a quantitative measure of interface toughness and for evaluating contact‐induced damage in thin films.
438 citations
TL;DR: The physical meaning of Vickers hardness, determined by use of residual indentation measurements, is analyzed in this article, where the roles played by the plasticity and elasticity are discussed.
Abstract: Studies of Vickers hardness of magnesium oxide are presented in the literature for three purposes. They give information about relations between hardness and brittleness, (plasticity and toughness behavior); they show the anisotropical effect of the structure of the material and they are a tool to study the chemomechanical effects (Rebinder effects). Generally, the Vickers hardness is evaluated by measurements of the diagonals of residual indentation. Equipment was built which gives a record of the applied depression depth (h) as a function of the carried load P (in the range 10−1 N to 10+1 N). Investigation of the curves P(h) during loading and unloading and microscopical observations of residual indentation show that phenomena are complex. The contact is elastoplastic. The roles played by the plasticity and elasticity are discussed. The physical meaning of Vickers hardness, determined by use of residual indentation measurements, is analyzed.
384 citations
TL;DR: In this paper, a simple method for measuring frictional stresses between the mairix and individual fibers in a ceramic composite is described, where a standard microhardness indenter is used to apply a force to the end of the fiber and depress it below the matrix surface.
Abstract: A simple method for measuring frictional stresses between the mairix and individual fibers in a ceramic composite is described. A standard microhardness indenter is used to apply a force to the end of the fiber and depress it below the matrix surface. The frictional stress is calculated from measurement of the applied force and the amount of slipping between the fiber and matrix.
207 citations
TL;DR: In this article, the authors measured the strength of indentation flaws and machining damage in both the as-formed and annealed states as a function of flaw orientation relative to an applied uniaxial tension.
Abstract: Mechanisms of failure from surface cracks in combined tension and shear are identified by directly observing the cracks during failure testing. Under the combined influences of residual contact stresses and applied loading, indentation cracks propagate stably and realign normal to the principal applied tension prior to failure. Annealing of indentation flaws causes relaxation of the residual stresses and thereby leads to a change in the mechanics of fracture; unstable propagation occurs from the initial crack at a critical applied loading, with an abrupt change in fracture plane. Strengths of indentation flaws and machining damage in both the as-formed and annealed states are measured as a function of flaw orientation relative to an applied uniaxial tension. Strength variations of indentations and machining flaws are similar. The results are assessed in terms of various proposed mixed-mode fracture criteria, and the implications of the results for nondestructive testing using scattering of surface acoustic waves are discussed.
155 citations
TL;DR: In this article, a fine pointed stylus of tungsten and a single crystal of a softer metal (nickel) was used to measure the friction and adhesion of a model microasperity.
139 citations
TL;DR: In this article, a change in crack path from the interface to the film, accompanied by an increase in crack radius, is observed and interpreted as a buckling-induced stress intensification.
Abstract: Indentation‐induced delamination between thin films of ZnO and Si substrates is examined. Delamination occurs by the growth of lateral cracks, either along the interface or within the film adjacent to the interface. The crack path is determined by the indenter load and the film thickness, as well as by residual stresses formed during deposition. A change in crack path from the interface to the film, accompanied by an increase in crack radius, is observed and is interpreted as a buckling‐induced stress intensification. The interface fracture toughness is estimated from the relative crack lengths in the buckled and unbuckled films.
132 citations
TL;DR: In this article, a model is developed for evaluating stresses in the surfaces of brittle materials from changes in indentation crack dimensions, and the underlying basis of the model is a stress intensity formulation incorporating the solution for a penny-like crack system subjected to a constant stress over a relatively thin surface layer.
Abstract: A model is developed for evaluating stresses in the surfaces of brittle materials from changes in indentation crack dimensions. The underlying basis of the model is a stress intensity formulation incorporating the solution for a penny-like crack system subjected to a constant stress over a relatively thin surface layer. Results from a previous study of surface damage in proton-irradiated glass are used to illustrate the scope of the method. The indentation fracture analysis also provides some fresh insight into the susceptibility of brittle surfaces to spontaneous cracking. Implications of the study concerning the potential effect of surface stresses on mechanical properties, such as strength, erosion and wear, are briefly discussed.
124 citations
TL;DR: In this paper, it was found that low-load microhardness (<50 gf) was sensitive to the thickness of the amorphous layer produced by implantation into both silicon and sapphire.
Abstract: Microhardness indentation testing has been used as a means of introducing controlled localized deformation and fracture in both ion-implanted and unimplanted {1 1 1} silicon and {1 0 ¯1 2} sapphire single crystal surfaces The microstructural alterations due to implantation with N
2
+
and Al+ into silicon and Y+ into sapphire have been characterized using channelled Rutherford backscattering, transmission electron microscopy and electron channelling in the scanning electron microscope It was found that sapphire only became amorphous at doses ⪞3×1016 Y+cm−2 which corresponds to a total energy deposition of ∼3×1023 keV cm−3 (∼44 kJ mm−3) The low-load microhardness (<50 gf) was found to be sensitive to the thickness of the amorphous layer produced by implantation into both silicon and sapphire Compared with the parent crystal, this layer was found both to be softer and to behave in a relatively plastic manner with considerable plastic pile-up occurring around indentations in the higher dose specimens The indentation fracture behaviour was found to be dominated by the presence of implantation-induced compressive stresses The resulting effects were: (a) a decrease in the size of the radial crack traces (henceK
IC is apparently increased when evaluated using indentation fracture mechanics), (b) a decrease in the frequency of occurrence of lateral break-out in silicon and subsurface lateral cracking in sapphire, (c) initiation of lateral cracks further below the surface in both silicon and sapphire Thus in general, it is concluded that hardness and surface plasticity are associated with softer amorphous layers whilst indentation fracture modifications are principally stress related
112 citations
TL;DR: In this article, an extensive literature survey of the evolution of the indentation technique is made and the elastic/plastic solution for the spherical cavity expansion is used to obtain a physical explanation for the quantitative measurement of the radial cracks that occur at the impression corners.
87 citations
TL;DR: In this article, the authors made a study of the effect of experimental variables such as punch spacing, punch contact area, and diamond indentation load on the crack growth and found that the cracks grew to a stable depth, the value of which could be determined by suitable choice of indentation parameters.
Abstract: Bridge indentation involves the initiation of a precrack at thq centre of the top surface of the sample by meajns of diamond indentation (i.e. a Palmqvist crack). Growth of this crack is then induced by pressing either side of it with rectangular punches having their edges parallel with the crack direction. With I increasing load, the crack grows outwards and downwards, and eventually forms a straight-through crack. The present authors have made a study of the effect of experimental variables such as punch spacing, punch contact area, and diamond indentation load on the crack growth. Specimens of a WC–6Co alloy cracked in this way were subsequently used for K 1C measurement. An important result was that the cracks grew to a stable depth, the value of which could be determined by suitable choice of indentation parameters. Numerical analysis using a boundary element method (BEM) was used to explore the stress situation in bridge indentation and provided a qualitative prediction of the experimental r...
TL;DR: In this paper, the effect of room-temperature erosion on material removal from and strength properties of soda-lime glass and sintered alumina was compared to the elastic/plastic indentation fracture model.
Abstract: The effect of room-temperature erosion on material removal from and strength properties of soda-lime glass and sintered alumina was determined. The results were compared to the elastic/plastic indentation fracture model. The dependence of erosion rate and strength of soda-lime glass on the kinetic energy of the impacting particles was in good agreement with predictions. The lack of agreement between theory and experiment for sintered alumina was attributed to microstructural aspects of the erosion damage that are not modeled by indentation fracture.
TL;DR: In this paper, an apparatus is described for the mechanical characterization of extremely thin films by indentation experiments at very low loads, and the penetration depth can be measured as a function of time or load with a resolution of 5 nm.
Abstract: An apparatus is described which is suitable for the mechanical characterization of all kinds of extremely thin films by indentation experiments at very low loads. The penetration depth can be measured as a function of time or load with a resolution of 5 nm. The indentor force can be varied from 10 μN to 5 mN. On the basis of some examples it is demonstrated that the instrument is applicable for ultramicrohardness measurements on metal films as well as for the determination of the viscoelastic properties of polymer coatings. Moreover, it is shown that the apparatus can be used for surface profilometry and ultramicroscratching experiments on relatively soft layers.
TL;DR: In this article, it was shown that, at temperatures above the γ′ solvus, cellular discontinuous recrystallization may be observed in superalloy single crystals with surface grit-blasting or indentation.
Abstract: It is shown that, at temperatures above the γ′ solvus, rapid recrystallization occurs in the surface layers of superalloy single crystals which have been cold worked either by surface grit-blasting or by indentation. At temperatures below the γ′ solvus, cellular discontinuous recrystallization may be observed. By applying a recovery treatment insufficient to cause discontinuous recrystallization, it is possible to suppress the recrystallization of grit-blasted specimens when subsequently heated above the γ′ solvus.
TL;DR: In this article, the authors used a sharp and a truncated wedge in three different rocks to study the continuous development of cracks throughout the tests, and observed that cracks initiated mainly at the edge and corners of wedges but initiation in the interior of the rock was also observed.
TL;DR: In this paper, the fracture properties of several nuclear-waste glasses were determined by indentation techniques and the fracture toughness was calculated from the measurement of radial cracks around Vickers diamond indentations as a function of applied load, and the results agree quite satisfactorily with values obtained by the Hertzian indentation technique.
Abstract: The fracture properties of several nuclear-waste glasses were determined by indentation techniques. The fracture toughness,KIc, was calculated from the measurement of radial cracks around Vickers diamond indentations as a function of applied load, and the results agree quite satisfactorily with values obtained by the Hertzian indentation technique. The fracture toughness of the waste glasses containing simulated fission products ranged from 0.9 to 1.1 MN m−3/2 in air, with slightly higher values measured in dry nitrogen. The hardness was also obtained from the Vickers indentations and the ratioH/E was determined from the elastic recovery of Knoop diamond indentations. The values ofE deduced fromH andH/E were within 15% of values measured by ultrasonic tests. The results along with the limitations of the different techniques are discussed in detail.
TL;DR: In this article, the dependence of hardness on indentation load and anisotropy in hardness in the (011) and (001) planes have been described, and attempts have also been made to understand the nature of the cracks developed around the microindentation.
Abstract: Vickers microhardness measurements have been carried out on flux-grown single crystals of barium molydate. The dependence of hardness on indentation load, and anisotropy in hardness in the (011) and (001) planes have been described. Attempts have also been made to understand the nature of the cracks developed around the microindentation.
TL;DR: In this article, the critical loadP* to cause ring cracking was proportional to the indenter radiusR which is consistent with Auerbach's law, and the values of room temperature fracture surface energy,γ, and fracture toughness,K1C, were derived using the theories of Frank and Lawn and Warren.
Abstract: Hertzian indentation experiments have been performed on sinteredα-Al2O3 using WC-Co spheres with radii in the range 0.5 to 6.5 mm. The critical loadP* to cause ring cracking was proportional to indenter radiusR which is consistent with Auerbach's law. Values of room temperature fracture surface energy,γ, and fracture toughness,K1C, were derived using the theories of Frank and Lawn and Warren.
TL;DR: In this article, the authors use the semi-infinite crack as a short-time model for the case of indentation by a rigid smooth wedge and show that if fracture occurs at the terminus prior to the arrival of wave reflections, it may proceed at a noticeable angle to the undercut plane.
Abstract: Surface obstacle undercuts such as tunnels act as guides for waves produced by rapid indentation of the surface. The diffraction of the waves can produce severe dynamic stresses near the undercut termnini. Utilizing the semi-infinite crack as a short-time model, this article examines these stresses for the case of indentation by a rigid smooth wedge. Although the distance between the terminus and wedge apex gives the problem a characteristic length, the solution can be obtained by summing a dynamically similar solution with respect to a speed parameter. The results show that if fracture occurs at the terminus prior to the arrival of wave reflections, it may proceed at a noticeable angle to the undercut plane.
TL;DR: Estimates of the growth in intensity of tactile sensations were made as functions of indentation depth and rate, with rate as the parameter, and two functions of markedly different slopes were required to describe the estimates.
Abstract: The effects of skin indentation depth and rate on threshold and suprathreshold tactile sensations were investigated. Indentation rates between 0.3 and 10 mm/sec had little effect on the absolute tactile thresholds measured in terms of indentation depth. Slower rates resulted in increased absolute thresholds. Estimates of the growth in intensity of tactile sensations were made as functions of indentation depth and rate. The fastest rate used (10 mm/sec), for a given depth of indentation, produced the most intense sensation; the slowest (0.1 mm/sec), the least intense sensation. The tactile sensation magnitude estimates, with rate as the parameter, could be described by power functions. At the slowest indentation rate the exponent of the function was 1.36. At faster indentation rates (0.4, 1.0, and 10 mm/sec), two functions of markedly different slopes were required to describe the estimates. The exponents of the power functions were between 0.38 and 0.49 for indentation depths up to about 0.9 mm, and between 1.07 and 1.43 for deeper indentation depths.
TL;DR: In this paper, a simple fracture mechanics calculation of the length of subsurface cracks is performed by applying indentation fracture studies of ceramics, demonstrating the influence of material parameters such as fracture surface energy, hardness and elastic constants.
Abstract: Indentation stress fields of one- and two-point loads applied on an ideal elastic half-space are presented. Laboratory observations, although few, are in surprisingly good agreement with long median and cone-type tensile cracks predicted by normal principal stresses. Results indicate that simultaneous loading by multiple indenters offers a possibility partly to control the direction and length of such cracks. This suggests the development of new cutter configurations with a possible increase in efficiency, as compared with present rock boring and rock cutting practice. A simple fracture mechanics calculation of the length of subsurface cracks is performed by applying indentation fracture studies of ceramics. Results demonstrate the influence of material parameters such as fracture surface energy, hardness and elastic constants.
TL;DR: In this paper, the authors show that an indentation load relaxation test is experimentally feasible for thin film testing, such as thin film metallizations, thin films, and contact surfaces.
Abstract: Load relaxation testing has been demonstrated to be useful for characterizing the time dependent plastic properties of metals. However, for testing of small material volumes, such as thin film metallizations, thin films, and contact surfaces, conventional load relaxation techniques cannot be used. For such applications an indentation test offers an attractive means for obtaining data necessary for materials characterization. This work shows that an indentation load relaxation test is experimentally feasible for thin film testing. Experiments on brass and beryllium copper samples with or without a gold/nickel plating illustrate different relaxation properties of the substrates and the surface layers. Furthermore, results of experiments on some fcc metals suggest rather simple relations between the conventional uniaxial load relaxation (LR) test and the indentation load relaxation (ILR) test.
01 Jan 1984
TL;DR: In this article, the authors considered the effect of contact-induced surface flaws along with controlled indentation flaws for construction of toughness and fatigue master maps, fatigue properties of ceramics with natural and controlled flaws, and a statistical analysis of size and stress state effects on the strength of an alumina ceramic.
Abstract: Failure from contact-induced surface flaws is considered along with controlled indentation flaws for construction of toughness and fatigue master maps, fatigue properties of ceramics with natural and controlled flaws, and a statistical analysis of size and stress state effects on the strength of an alumina ceramic. Attention is also given to dynamic and static fatigue of a machinable glass ceramic, the effect of multiregion crack growth on proof testing, and a fracture mechanics analysis of defect sizes. Other topics explored are related to the effect of temperature and humidity on delayed failure of optical glass fibers, subthreshold indentation flaws in the study of fatigue properties of ultrahigh-strength glass, the lifetime prediction for hot-pressed silicon nitride at high temperatures, static fatigue in high-performance ceramics, and requirements for flexure testing of brittle materials.
TL;DR: In this article, the diffraction contrast at the indentations shows that appreciable internal strain energy release has been achieved by dislocations escaping through {1 1 0} crack surfaces, which gives support to the dislocation model of hot spots (very small, high temperature regions) being generated by the collapse of dislo~ cation pileups, particularly, during cracking.
Abstract: Previously, the diffraction constrast in X-ray topographs of diamond pyramid microhardness indentations in MgO crystals was matched with optical microscope observations of cracking and the extent of slip bands made visible by etch pitting [ 1 ]. Results from a further X-ray topography study were correlated with scanning electron microscope observations to determine the three-dimensional arrangement of dislocations surrounding such microhardness indentations [2]. X-ray topographic results for macro-indentations are reported here. Measurement of the extent of diffraction contrast at the indentations shows that appreciable internal strain energy release has been achieved by dislocations escaping through {1 1 0} crack surfaces. The results give support to the dislocation model of "hot spots" (very small, high temperature regions) being generated by the collapse of dislo~ cation pile-ups, particularly, during cracking [3]. Figs. la and b show a matched pair of optical and X-ray topographic pictures of macro-indentations put into an MgO (0 0 1) cleavage surface at 15 and 100kgf load, 147 and 981N, respectively, with a 1.59mm Rockwell spherical steel indenter. Stable support of the load was not obtained at either indentation and so the load was removed after the expiration of a contact period of approximately 15 sec when the rate .of indenter penetration had decreased very appreciably. Diamond pyramid microhardness indentations were placed at 0.1 kgf load (0.981N) around the larger 100kgf indentation to probe the local state of deformation [4]. In Fig. lb, the general appearance of tile white and black diffraction contrast at the 15 kgf indentation relates to previous results reported for the extent of cracking and dislocation etch pits, respectively, centred on microhardness inden-
TL;DR: In this article, the ultramicrohardness of thin alloy films is determined by indentation experiments at very low loads by measuring the hardness of a number of pure metal films, either vapour deposited or magnetron sputtered.
TL;DR: Fracture initiation from Vickers diamond pyramid indentations was investigated for single MnZn ferrite with a 〈110〉 growth direction, having the orientations of the side, [110] and [100] as mentioned in this paper.
01 Nov 1984-International Journal of Human-computer Studies \/ International Journal of Man-machine Studies
TL;DR: An experiment was conducted to study how different methods of indentation affect the ability of programmers to understand programs and found those subjects who received the program written in the departmental standard were better than the other two groups.
Abstract: An experiment was conducted to study how different methods of indentation affect the ability of programmers to understand programs. The subjects were 72 students from an intermediate programming course. Each subject received one of three implementations of a short Pascal program. Each implementation used a different method of source code indentation: no indentation, “excessive indentation”, and Purdue University Department of Computer Science standard (moderate indentation). The subjects answered a 10-question test about the program. The scores of those subjects who received the program written in the departmental standard were better than the scores of the other two groups.
TL;DR: In this paper, the experimental variation of the microhardness of lead with dwell time and temperature is reported, and a period of zero indentation creep of the order of 300 sec is observed.
Abstract: The experimental variation of the microhardness of lead with dwell time and temperature is reported. At homologous temperatures close to 0.5T
m, and using low loads (i.e. 0.1 N), a period of zero indentation creep of the order of 300 sec is observed. This phenomenon, called the incubation period, and the subsequent indentation creep behaviour, are explained in terms of restructuring and recovery of the dislocation network beneath the indenter.