The effect of work-hardening upon the hardness of solids: minimum hardness

Gerk, A. P.

doi:10.1007/bf00548163

Cited by 57 publications

(19 citation statements)

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“…In the case of normal ISE, the value of n < 2 has been suggested 3,39,40 to be associated with work-hardening characteristics of the material where generation, mobility, and multiplications of dislocations are involved. A possible cause for the increase in hardness at which n 2 is a decreasing size of the dislocation source.…”

Section: Indentation Size Effectmentioning

confidence: 99%

Atomic force microscopy study of nanoindentation deformation and indentation size effect in MgO crystals

et al. 1999

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The dependences of various nanoindentation parameters, such as depth of penetration d, indentation diameter a, deformation zone radius R, and height h of hills piled up around indents, on applied load were investigated for the initial (unrecovered) stage of indentation of the (100) cleavage faces of MgO crystals by square pyramidal Si tips for loads up to 10 N using atomic force microscopy. The experimental data are analyzed using theories of elastic and plastic deformation. The results revealed that (i) a, R, and h linearly increase with d; (ii) the development of indentation size and deformation zone and the formation of hills are two different processes; (iii) the load dependence of nanohardness shows the normal indentation size effect (i.e., the hardness increases with a decrease in load); and (iv) there is an absence of plastic deformation involving the formation of slip lines around the indentations. It is found that Johnson's cavity model of elastic-plastic boundary satisfactorily explains the experimental data. The formation of hills around indentations is also consistent with a new model (i.e., indentation crater model) based on the concept of piling up of material of indentation cavity as hills.

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Section: Indentation Size Effectmentioning

confidence: 99%

Atomic force microscopy study of nanoindentation deformation and indentation size effect in MgO crystals

et al. 1999

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“…Since hardness has dimensions of pressure or stress, attempts have been made to correlate indentation hardness with other stress properties of solids, for example, elastic modulus E, shear modulus G or uniaxial yield stress Y [1][2][3]. The hardness of a material is usually calculated from the measured value of indentation diameter d produced by an applied load P using relation (1).…”

Section: Introductionmentioning

confidence: 99%

Review: Indentation size effect, indentation cracks and microhardness measurement of brittle crystalline solids – some basic concepts and trends

Sangwal¹

2009

Cryst. Res. Technol.

124

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Indentation size effect, indentation cracks and microhardness measurement of some brittle crystals are reviewed against the background of the existing concepts of indentation deformation of crystalline solids. Several approaches reported in the literature devoted to relationships between applied indentation test load P and indentation diagonal length d are applied to analyze the experimentally observed normal and reverse indentation size effect (ISE) in brittle compounds. Using typical examples of normal and reverse ISE it is shown that the indentation induced cracking model does not give load-independent hardness and the final expression describing the experimental data for various compounds is essentially another form of the Meyer law. Analysis of experiment data on crack lengths and indentation diagonals for different indentation loads suggests that the origin of ISE is associated with the processes of formation of indentation cracks following the general concepts of fracture mechanics. The load-independent hardness H 0 may be determined reliably from plots of P/d against d of the proportional resistance model or of H V against 1/d as predicted by strain gradient plasticity theories. It was found that the load-independent hardness of depends on crystal orientation and state of the indented surface. Finally, some comments on determination of fracture toughness and brittle index of crystals are made. Dedicated to Prof. Wolfgang Neumann on the occasion of his 65th birthday

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“…Dekker and Rieck [10] have observed microhardness variations in manganese aluminate spinels after various annealing times; they conclude that the increase in hardness is due to unobservable preprecipitation. The hardness value depends on many parameters such as indenter orientation, work hardening rate [1,10,11], surface effects [1]... The experiments on cleaved faces of NiO (see section seem to preclude any surface effects on the variation of microhardness with ageing time.…”

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confidence: 99%