Showing papers on "Indentation published in 1973"
TL;DR: In this paper, an experimental method is described which can measure the direction and magnitude of residual and applied stress in metals using optical interference to measure the permanent surface deformation around a shallow spherical indentation in a polished area on the metal.
Abstract: An experimental method is described which can measure the direction and magnitude of residual and applied stress in metals. The method uses optical interference to measure the permanent surface deformation around a shallow spherical indentation in a polished area on the metal specimen. The deviation from circularly symmetrical surface deformations is measured at known values of applied stress in calibration specimens. This deviation from symmetry can then be used to determine the direction and magnitude of tensile residual stress in specimens of the same material. Determination of compressive residual stress is more limited.
48 citations
TL;DR: In this paper, an explicit expression for the indentation hardness numbers of alkali halide crystals in terms of ionic binding, combined with the theory of plastic indentation, was derived, where the resistance to indentation is caused by the electrostatic faults that exist at the cores of {100} 〈110〉 dislocations.
Abstract: An explicit expression is derived for the indentation hardness numbers of alkali halide crystals in terms of ionic binding, combined with the theory of plastic indentation. The resistance to indentation is caused by the electrostatic faults that exist at the cores of {100} 〈110〉 dislocations. The theoretical hardness is given by (cgs units) H0=0.096(e2/eb4)= 1.2×10−2C44, where e is the electron charge, e is the static dielectric constant, b is the Burgers displacement, and c44 is the elastic shear stiffness. The theoretical hardness for NaCl is 17 kg/mm2 compared with the observed value of 16.7 kg/mm2.
45 citations
TL;DR: The possibility that asperity persistence in indentation experiments is explainable in terms of the plasticity mechanics of as perity interaction has been investigated both theoretically and by conducting experiments with model asperities as discussed by the authors.
43 citations
TL;DR: In this paper, the value of Knoop microhardness was obtained for crystals of BaF2, NaCl and AgCl by indentation in various directions on several crystallographic planes, and it was concluded that hardness anisotropy cannot be used to determine the primary slip mode.
Abstract: The value of Knoop microhardness was obtained for crystals of SrF2, BaF2, NaCl and AgCl by indentation in various directions on several crystallographic planes. In all cases, the hardness is essentially dependent on the crystallographic direction along the long axis of the indentor and independent of the plane of indentation, as first reported by Garfinkle and Garlick for other cubic crystals. In addition, although the absolute value of hardness varies from one crystal to another, the hardness anisotropy was quite similar for all crystals. Since the primary slip mode is different among the crystals tested, it is concluded that hardness anisotropy cannot be used to determine the primary slip mode.
22 citations
TL;DR: In this article, the authors have recently completed some preliminary experiments on this aspect of deformation in the indentation and scratch hardness processes and the results indicate that the cumulative effects, due to repeated loading, may well play an important part in subsequent macro-deformation.
Abstract: WHEN a scratch or indentation hardness measurement is made one is generally more concerned with gross changes in shape, due to macro-deformation or fracture, than in any aspects of small scale or micro-deformation which might also form a part of the permanent deformation process. Consequently, certain guide lines have been established1. The possibility of micro-deformation in a relatively hard crystal due to point contact through a significantly softer indenter or slider may have been assumed but there seems to be little published information on its nature and extent. We have recently completed some preliminary experiments on this aspect of deformation in the indentation and scratch hardness processes and the results indicate that the cumulative effects, due to repeated loading, may well play an important part in subsequent macro-deformation. Most of the experiments were carried out on magnesium oxide because the resultant distribution of dislocations could be readily observed, using the etchant perfected by Gilman and Johnston2, on a (001) plane prepared by cleavage and then chemically polished. Lead, copper and diamond cones, having apical angles of 136°, were used as indenters and sliders. The relevant diamond cone indentation hardness values for the magnesium oxide, copper and lead were 6,000 MN m−2, 980 MN m−2 and 50 MN m−2 respectively and can be assumed to be between 69,000 to 96,000 MN m−2 for diamond3.
21 citations
TL;DR: A remarkable project for a third year physics student at The University of Surrey is described in this paper, where the simple indentation and fracture of perspex blocks with steel ball bearings was discovered, a property which remains unexplained.
Abstract: A remarkable project for a third year physics student at The University of Surrey is described. Through the simple indentation and fracture of perspex blocks with steel ball bearings a new optical property of the material was discovered, a property which remains unexplained.
16 citations
TL;DR: The deformation of the (001) plane of LiF and NaCl by indentation and scratching at high temperatures was performed and the dislocation patterns arising from deformation were sharply different from those observed at room temperature.
Abstract: The deformation of the (001) plane of LiF and NaCl by indentation and scratching at high temperatures was performed. The dislocation patterns arising from deformation were sharply different from those observed at room temperature. It was proposed the explanation of these results.
The model of plastic flow in (001) indentation and scratching were considered. Anisotropy of hardness by the scratch method was revealed clearly at high temperatures. It was proposed the explanation of the anisotropy of hardness. The correlation was established between the dislocation structures observed near the indentations and scratches.
[Russian Text Ignored.]
12 citations
10 citations
01 Nov 1973
TL;DR: In this paper, the deformation behavior of Bi, Sb-Bi, 25 pct SbBi, 50 pct Bi and Sb has been studied under spherical indentation for loads from 50 to 150 kg applied up to 10,000 s from 0.5 to 0.7 of the melting temperature.
Abstract: The deformation behavior of Bi, 10 pct Sb-Bi, 25 pct Sb-Bi, 50 pct Sb-Bi and Sb has been studied under spherical indentation for loads from 50 to 150 kg applied up to 10,000 s from 0.5 to 0.7 of the melting temperature. The softening parameterB and the apparent “activation energy”B’ were calculated from the short-time hardness data, and the true activation energyQc and the stress coefficient for creep α from the long-time indentation data. The α values were found to be greater than five indicating a breakdown of the power law in the range of loads and temperatures utilized. The values ofQc increased slightly with temperature whereas those of α increased with load and decreased with temperature, the observations indicating the effect of stress in the breakdown region.
5 citations
TL;DR: In this paper, the deformation and wear of gramophone records were investigated using both static and sliding indentation tests on vinyl chloride-acetate copolymer and nylon 66.
Abstract: Static and sliding indentation tests on vinyl chloride-acetate copolymer and nylon 66 are described, and form part of a study of the deformation and wear of gramophone records. The vinyl was unusual in showing considerable work softening. Static indentation tests covered the whole range from the fully elastic to the fully plastic condition, and behavior was consistent with the Hertz equations, but the accuracy of the Meyer law is doubtful. Sliding indentation tests included measurement of the depth of track under load on flat and curved surfaces, and observations on the onset of instability, and the formation of a chip. These data will be used for the calculation of distortion on record playback due to deformation of the groove wall under load.
4 citations
Patent•
09 Mar 1973TL;DR: In this article, an elastic profile that projects into a groove-like indentation of the vehicle body covering in which it is secured by a retaining means engaging into a slot provided on the backside of the profile; the slot thereby extends up to the outer area of the elastic profile overlapping the indentation where it receives a reinforcing element extending in the longitudinal direction of the Elastic Profile.
Abstract: A protective strip for motor vehicles, especially for passenger motor vehicles, which includes an elastic profile that projects into a groove-like indentation of the vehicle body covering in which it is secured by a retaining means engaging into a slot provided on the backside of the profile; the slot thereby extends up to the outer area of the elastic profile overlapping the indentation where it receives a reinforcing element extending in the longitudinal direction of the elastic profile.
01 Jan 1973
TL;DR: In this paper, the effect of temperature and normal load on the variation with time of the indentation depth of a rigid spherical indenter in polymeric materials has been investigated with the object of obtaining the dependence of the contact area on the principal parameters of the process.
Abstract: The effect of temperature and normal load on the variation with time of the indentation depth of a rigid spherical indenter in polymeric materials has been investigated with the object of obtaining the dependence of the contact area on the principal parameters of the process. Plexiglas, PVC and polyformaldehyde were selected for study. It is shown that at a given temperature the ratio σm/(a/R)n−2=A is a function of time only and almost independent of the applied load. It is established that the time-temperature superposition principle can be used for investigating metal-thermoplastic contact phenomena. An expression is obtained for calculating the contact area at various temperatures and loading times.
01 Jan 1973
TL;DR: In this article, the detailed mechanics of flat-punch indentation into specimens of finite dimensions under plane-strain conditions were obtained, based on the observed flow patterns of commercially-pure, hard copper specimens.
Abstract: The detailed mechanics of flat-punch indentation into specimens of finite dimensions under plane-strain conditions were obtained, based on the observed flow patterns of commercially-pure, hard copper specimens. Slip-line fields were constructed and a stress calculation was made for some cases. The effects were examined of friction at the interface, and initial dimensions of the specimens, on the deformation characteristics.