The effects of hydrostatic pressure on the ductility of metals and alloys

Yajima, Masami; Ishii, Mitsuru; Kobayashi, Masaru

doi:10.1007/bf00189821

Cited by 26 publications

(8 citation statements)

References 7 publications

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“…Since the magnitude of 2 will range between these two cases, the critical hydrostatic pressure will be limited by Equations ( 5) and (6). Since o and f are positive by definition, the critical hydrostatic pressure found by Equation (6) will always be algebraically smaller than the corresponding value found by Equation (5).…”

Section: Discussionmentioning

confidence: 96%

“…From the literature, it has been shown that hydrostatic pressure is a parameter which has great influence on the initiation and propagation of damage in materials [2][3][4][5][6][7]. This has been documented for metal forming processes [19,23] and for MMCs tested in tension with superimposed hydrostatic pressures [8][9][10][11][12][13][14][15][16][17].…”

Section: Discussionmentioning

confidence: 99%

“…The hydrostatic extrusion process permits the pressurization of the die exit such that the forming operation can proceed under superimposed hydrostatic pressure. There is extensive evidence that superimposition of large hydrostatic pressures during plastic deformation of materials suppresses damage events and fracture [3][4][5][6][7]. This effect has been verified for MMCs tested in tension with superimposed hydrostatic pressures [8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 89%

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Hydrostatic Extrusion of Metal Matrix Composites

Lahaie

Embury

2003

Journal of Composite Materials

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The effect of hydrostatic pressure on the formability of a model Cu-W metal matrix composite (MMC) was investigated. The main experimental observation was that damaged and codeformed products were obtained from nominally identical Cu-W billets. A criterion for the suppression of damage during hydrostatic extrusion was developed. The resulting critical hydrostatic pressure criterion was estimated from slip line field theory in order to rationalize the experimental observations. The critical hydrostatic pressure for damage suppression in the W fibers depends on the ratio of fracture stress to flow stress. The analysis suggests a very important effect of both the stress state during hydrostatic extrusion and the previous processing history of the composite.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 89%

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Hydrostatic Extrusion of Metal Matrix Composites

Lahaie

Embury

2003

Journal of Composite Materials

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“…As it can be seen, the scale of the pin deformation is significantly higher than what is possible in the monotonic tension test. The scale of this deformation is likened to the presence of high hydrostatic pressures (typically 1.5 GPa) under the point of contact which is known to make brittle materials more ductile [30,31].…”

Section: Strain Analysismentioning

confidence: 99%

A multiscale finite element model of sliding wear for cobalt-chromium undergoing ratcheting wear

Cross

Limbert

Stewart

et al. 2020

Wear

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Cobalt-chromium alloys are used in reciprocated sliding wear applications where the mated surfaces cannot be lubricated, due to their excellent frictional properties and ability to resist seizure. However, various health risks due to cobalt wear particle generation motivate the replacement of cobalt-based systems. It is suggested that a numerical model of reciprocated dry sliding wear for cobalt-chromium alloys would aid in the development of cobalt-free alternatives to remove any health risks. Therefore, this work focuses on building a mechanistic, i.e. determined purely through physical terms, numerical model of dry reciprocated sliding wear for a specific cobalt-chromium alloy, informed by the experimental literature, to gain an understanding of cobalt wear-rates in response to the tribological loading conditions. A multi-scale method is employed, where the wear is determined by a microscale model of wear, which simulates wear after the material is brought up to a critical strain to failure and material rupture occurs, and the microscale wear-rates are homogenised to the macroscale by use of a statistic model of rough contact. This improves over previous methods by allowing one to observe how material wear-rates are controlled by changes in the elasto-plastic material parameters and geometry of an engineering component. The current numerical model predicts the correct scale of wear, in the range of 1×10 −14 m 3 /Nm or 1×10 −5 mm 3 /Nm, typical for the chosen alloy under dry sliding conditions and is validated against experimental data. The model allows for further development, such as the incorporation of frictional heating, microscale heterogeneity, or the evolution of surface roughness parameters during wear.

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“…The reason behind this seemingly ductile response of a brittle metal can be explained by the presence of high hydrostatic pressures. It has been shown that brittle metals behave as ductile metals when subjected to hydrostatic pressure [22,23], and it is typical under rough surface contact for high stresses generated under the point of contact to cause high hydrostatic pressures in the subsurface [18]. Therefore, one cannot assume the material will necessarily behave in a brittle manner during wear in the presence of these pressures.…”

Section: Wear Testsmentioning

confidence: 99%

Ratcheting wear of a cobalt-chromium alloy during reciprocated self-mated dry sliding

Cross

Limbert

Stewart

et al. 2019

Wear

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Cobalt-chromium alloys find usage in environments where reliable wear and friction properties are required. However, the sliding wear generated presents significant health risks in nuclear and medical applications. Thus, there is great motivation to develop cobalt-free alternatives. These alloys are known to undergo several physical changes at the interface during dry sliding, sensitive to the loading conditions and environment. Due to these physical changes, the wear behaviour of the alloy is modified, which linear Archard-like models do not capture. To better understand the wear performance a cobalt-chromium alloy in-situ, and to aid their replacement, a mechanistic model of wear would be ideal. To understand what physics requires modelling, in order to capture the wear behaviour in response to the loading conditions, a systematic experimental study was performed for a cobalt-chromium hard-facing alloy. Tests were done under various combinations of sliding speed (0.02 m/s to 0.5 m/s) and normal load (40 N to 1000 N). In conjunction with common wear mechanisms, such as oxidative wear, platelet wear was also observed. It is suggested that the platelet wear observed is the consequence of a plastic ratcheting mechanism, known as 'ratcheting wear', owing to the large strains experienced at the wear interface. In addition to this, the stiffness of the wear interface was observed to drop significantly which has previously been unreported for this system. Both of these physical responses have implications for the development of a mechanistic wear model.

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The effects of hydrostatic pressure on the ductility of metals and alloys

Cited by 26 publications

References 7 publications

Hydrostatic Extrusion of Metal Matrix Composites

Hydrostatic Extrusion of Metal Matrix Composites

A multiscale finite element model of sliding wear for cobalt-chromium undergoing ratcheting wear

Ratcheting wear of a cobalt-chromium alloy during reciprocated self-mated dry sliding

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