Recovered elastic and plastic strains at residual micro-indentations in an MgO crystal

Hammond, B. L.; Armstrong, Ronald W.

doi:10.1080/09500838808227796

Cited by 30 publications

(17 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4, the ratio of elastic-to-plastic strains for diamond pyramid indentations increases significantly as the Hertzian elastic loading curve is approached. Hammond and Armstrong [17] had demonstrated a reduction of the indentation depth on unloading of diamond pyramid microindentations through measured changes in the angle between opposite indentation facets. Woirgard et al have commented on the flat nature of residual nanoindentations made in GaAs as part of a research investigation also involving MgO nanoindentations [22].…”

Section: Nanoindentation Test Measurementsmentioning

confidence: 98%

“…The plastic hardness result compares in Here, we are interested to make a comparison of the preceding hardness evaluations on an effective stress-strain basis. Such log/log hardness stress-strain method of comparison of σ E and σ H stresses was initially reported as a function of (d/D) for MgO crystal measurements by Hammond and Armstrong [17] and updated in reference [10] by addition of the closed circle microindentation results reported previously by Armstrong and Raghuram [18] and by addition of the computed hardness values obtained from Fig. 3.…”

Section: Nanoindentation Test Measurementsmentioning

confidence: 99%

See 1 more Smart Citation

Macro- to Nano-indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors

Armstrong

Elban

2009

Exp Mech

Self Cite

View full text Add to dashboard Cite

Single crystal KCl and MgO indentation hardness test results spanning macroscopic, microstructural, and nanoscale measurements are brought together in a ballindenter-based stress-strain description. For a significant range of hardness measurements made on MgO (001) crystal surfaces, increasingly greater plastic flow stresses are determined at smaller loads applied to smaller effective ball sizes at the rounded tips of Berkovich indenters; and, at the smallest ball diameters of 3,200 nm and 400 nm, the plastic flow stresses are shown to approach the predicted Hertzian elastic loading stresses. The resultant hardness stress-strain description, that is extended to cover the elastic, plastic, and cracking behaviors of MgO crystals, is usefully applied also to a comparison of indentation test results reported for NaCl and RDX crystals. In general, the dislocation-induced cracking stress measurements are shown for MgO and RDX crystals to be lower than cracking stresses evaluated on an (elastic) indentation fracture mechanics (IFM) basis. Comparison is made with metal nanoindentation hardness test results.

show abstract

Section: Nanoindentation Test Measurementsmentioning

confidence: 98%

Section: Nanoindentation Test Measurementsmentioning

confidence: 99%

Macro- to Nano-indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors

Armstrong

Elban

2009

Exp Mech

Self Cite

View full text Add to dashboard Cite

show abstract

“…These reactions lead to the formation of a Lomer lock supposed to be sessile for the aforementioned reasons. This obstacle to further dislocation propagation was associated with crack opening in {110} 45 planes by Keh [147] and Hammond and Armstrong [148]. …”

Section: Micro-indentation In Mgomentioning

confidence: 99%

Dislocations and Plastic Deformation in MgO Crystals: A Review

et al. 2018

View full text Add to dashboard Cite

This review paper focuses on dislocations and plastic deformation in magnesium oxide crystals. MgO is an archetype ionic ceramic with refractory properties which is of interest in several fields of applications such as ceramic materials fabrication, nano-scale engineering and Earth sciences. In its bulk single crystal shape, MgO can deform up to few percent plastic strain due to dislocation plasticity processes that strongly depend on external parameters such as pressure, temperature, strain rate, or crystal size. This review describes how a combined approach of macro-mechanical tests, multi-scale modeling, nano-mechanical tests, and high pressure experiments and simulations have progressively helped to improve our understanding of MgO mechanical behavior and elementary dislocation-based processes under stress.

show abstract

“…The hardness stress is given by the load divided by the projected area of the indentation and the hardness strain is specified as the ratio of contact diameter for a ball indenter divided by the ball diameter. The logarithmic scale for the indentation stress-strain behavior covers a substantial range in stress and strain values that are applicable for the initial (Hertzian) elastic loading response, the onset of progressive plastic flow, and a theoretical limiting elastic cracking condition [27]. …”

Section: Microhardness Assessmentmentioning

confidence: 99%

Dislocation Mechanisms for Shock-Induced Hot Spots

Armstrong

1995

J. Phys. IV France

Self Cite

View full text Add to dashboard Cite

Crystal dislocations provide the ultimate source of localized damage enhancement within solid materials. Vortices are the dislocation counterparts within liquids and gases. For energetic crystals, tubular holes might run along the pre-existent dislocation line lengths and act as shock-induced "in-situ" hot spots. Beyond this consideration, nearly invisible clouds of dislocations are possibly generated at point defects or point defect clusters by the shear stresses at a shock front. Multiple fine scale dislocation movements provide a mechanism for the shock to move to a hydrostatic stress state. Interatomic or intermolecular separations of the order of critical reaction coordinate distances are achievable during the unit dislocation displacements ---without change in material volume. Such nanoscale dislocation predictions connect with microscale experiments in a number of cases where larger scale "defect" considerations are involved. Dislocation pile-ups in slip band avalanches, often associated with cracking, account for very appreciable and localized heating that is deformation rate dependent. Complex dislocation slip band interactions occur within the plastic zones of macroscopic crack tips to control the fracture toughness properties of energetic and related materials.

show abstract

Recovered elastic and plastic strains at residual micro-indentations in an MgO crystal

Cited by 30 publications

References 10 publications

Macro- to Nano-indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors

Macro- to Nano-indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors

Dislocations and Plastic Deformation in MgO Crystals: A Review

Dislocation Mechanisms for Shock-Induced Hot Spots

Contact Info

Product

Resources

About