Showing papers on "Indentation published in 1968"
TL;DR: In this article, an exact solution to the problem of static indentation by a body whose shape is given by a general polynomial z(r), where r is the distance from the z axis is given.
Abstract: This paper is concerned with the calculation of contact stress distributions, surface displacements and contact radii when an elastic half space z > 0 is indented by a rigid body, symmetrical about the z axis and exerting a prescribed force P normal to the interface, with friction sufficient to prevent any slip between the surfaces of the body and the half space during the application of the load. Within the framework of small displacement theory, an exact solution is obtained to the problem of static indentation by a body whose shape is given by a general polynomial z(r), where r is the distance from the z axis. The solution is worked out in detail for indentors of three simple shapes, namely a flat-faced cylinder, a sphere and a cone (the first two of which have previously been considered by rather different methods by Mossakovski (I954, I963). A closed solution is also obtained to another problem closely related to that of the spherical stamp: that of calculating the indentation and resulting velocity defect when a rigid sphere rolls on an elastic half space. The treatment in all cases is elastostatic, i.e. it is assumed for the stamp problems that the load is applied slowly enough for static equilibrium to prevail at all stages, and correspondingly in the case of the rolling sphere, that its velocity is low enough for the same to be true. .The results for rigid indentors are readily extended to cover the more general case of adhesive contact between two elastic bodies of different material properties by means of a straightforward linear transformation noted by Mossakovski (I963) and recapitulated in the present notation as appendix A, which reduces the general elastic-elastic case to that of a rigid-elastic indentation with suitably adjusted [ 55 ]
234 citations
TL;DR: In this article, the Vickers diamond pyramid hardness measurements have been made on silica glass with varying thermal history using loads up to 1000 g and the hardness was independent of load and source.
Abstract: Vickers diamond pyramid hardness measurements have been made on silica glass with varying thermal history using loads up to 1000 g. Hardness was independent of load and source. From interference photographs and subsequent anneal of the indentations at temperatures belowT
g, it was concluded that indentation leads primarily to densification of a volume of glass in the vicinity of the indenter. A portion of the densification which is recoverable at relatively low temperatures is attributed to molecular entanglement of the glassy network due to high pressure and shear. The other portion which is not recoverable belowT
g represents an approach to the final equilibrium density of the glass. Hardness of silica glass as determined by this method is thus defined as a resistance of the material to densification.
107 citations
TL;DR: In this article, it was shown that the difference in indentation microhardness is due to differential effects of water adsorption on the opposite polar faces rather than being an intrinsic polar mechanical property of the crystal, and the usefulness of such measurements for absolute determinations of crystallographic polarity of non-centrosymmetric crystals is discussed.
Abstract: Marked changes in indentation microhardness have been observed in a wide range of non-metallic materials due to the presence of adsorbed water and other polar species. Opposite polar faces of crystals with non-centrosymmetric structures, including II–VI, III–V and IV–IV compounds, exhibit large differences in microhardness and anomalous indentation creep behaviour. Such differences are shown to be due to differential effects of water adsorption on the opposite polar faces rather than being an intrinsic polar mechanical property of the crystal. The usefulness of microhardness measurements for absolute determinations of crystallographic polarity of non-centrosymmetric crystals is discussed. Effects of environment on the extent of edge dislocation motion away from the indentation are examined. Possible mechanisms to explain the adsorption-induced changes in microhardness and related mechanical properties of non-metallic solids are critically discussed.
89 citations
Journal Article•
41 citations
TL;DR: In this article, it is shown that if a ring is indented across its thickness a plastic zone is formed at the point of indentation, and if the indentation force is sufficiently large, a plastic hinge is formed in the ring, diametrically opposite the point in indentation.
25 citations
01 Sep 1968
TL;DR: In this article, a stress relaxation ball indentation penetrometer was designed and constructed with the intent of measuring the time-dependent stress relaxation modulus of materials incapable of supporting their own weight.
Abstract: A stress relaxation ball indentation penetrometer was designed and constructed with the intent of measuring the time‐dependent stress relaxation modulus of materials incapable of supporting their own weight. An equation is derived to relate the modulus to the geometry of a deformation by a sphere into a plane. The relevance of this equation to creep experiments is discussed.
8 citations
6 citations
TL;DR: Observations of twinning and slip deformation caused by indentation of zinc reveal that extensive slip on the basal and second‐order pyramidal systems takes place at loads up to 5 kg.
Abstract: Observations of twinning and slip deformation caused by indentation of zinc reveal that extensive slip on the basal and second‐order pyramidal systems takes place at loads up to 5 kg. Prismatic punching through 1‐cm crystals is observed at indentation loads in excess of about 2.5 kg. It is concluded that the stress at the tip of the twins cannot be obtained by use of an elastic stress analysis.
5 citations
5 citations
TL;DR: Rubber hardness readings with an indenter depend upon thickness of the rubber specimen as discussed by the authors, and this effect has been known and studied since first attempts to develop precision methods to determine hardness.
Abstract: Rubber hardness readings with an indenter depend upon thickness of the rubber specimen. This effect has been known and studied since first attempts to develop precision methods to determine hardness. Classical elasticity theory accounted satisfactorily for indentation relations with thick rubber but thickness dependence was treated as an empirical correction.
4 citations
TL;DR: Using steel spherical indenters, the relationship between indentation diameter and load was determined for a mature amalgam and Young's modulus and yield point could be calculated.
Abstract: Using steel spherical indenters, the relationship between indentation diameter and load was determined for a mature amalgam. The form of this relationship allowed the regions of elastic and plastic deformation to be identified; hence, Young's modulus and yield point could be calculated. Local contact stresses in the mouth also were estimated.
TL;DR: In this paper, the indentation of the free surface of a semi infinite Newtonian fluid by a rigid right circular cylinder is considered and it is assumed that the weight and inertia effects of the fluid are negligible compared to its viscous effects.
Abstract: The indentation of the free surface of a semi infinite Newtonian fluid by a rigid right circular cylinder is considered. It is assumed that the weight and inertia effects of the fluid are negligible compared to its viscous effects.
01 Jan 1968