Transient creep analysis of ball indentation

Ogbonna, Nkem; Fleck, N.A.; Cocks, A.C.F.

doi:10.1016/0020-7403(95)00016-q

Cited by 66 publications

(18 citation statements)

References 14 publications

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“…(6)- (8). In this context it should be mentioned that corresponding investigations were performed in [5,15] for viscoplastic material behavior and essentially the same conclusions, as in [14], could be drawn.…”

Section: Theoretical Background and Problem Formulationmentioning

confidence: 72%

“…[5][6][7][14][15][16] but the overall characteristics of the problem were not fully understood until Olsson and Larsson [17] presented formulae for a general correlation of global contact properties at, in particular, elastic-plastic (level II) spherical contact problems. In [17], the representative stress was determined at a strain value ε = a R 0.2 / , (8) rep as previously suggested in [5,14,15], and high accuracy results were obtained correlating indentation results and, based on the generalization quantities discussed above, also general spherical contact problems.…”

Section: Introductionmentioning

confidence: 99%

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A numerical study of the mechanical behavior at contact between particles of dissimilar elastic–ideally plastic materials

Larsson

Olsson

2015

Journal of Physics and Chemistry of Solids

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Section: Theoretical Background and Problem Formulationmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

A numerical study of the mechanical behavior at contact between particles of dissimilar elastic–ideally plastic materials

Larsson

Olsson

2015

Journal of Physics and Chemistry of Solids

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“…6. Since the m-value of 5.5 is greater than the usual range of 2-4, it is considered that m includes the influence of other mechanisms of time-hardening, which may be related to sub-microstructure usually discussed for primary creep (Derby and Ashby, 1987;Ogbonna et al, 1995). Regardless of the mechanisms, parameter b in Eq.…”

Section: Discussionmentioning

confidence: 99%

Effects of heating history on sintering properties of nickel powder compacts

Shinagawa

Utsunomiya

2015

Mechanical Engineering Journal

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The effects of heating history on the sinterability of nickel powder compacts as a model material are examined from a view point of driving force and flow resistance, that is, the sintering stress and viscosity. Sinter-compression tests were conducted at different constant temperatures for cylindrical specimens, which underwent one-step or two-step heating. In the two-step heating, the specimens were heated up to a higher temperature and cooled down to the test temperatures. After the tests, the microstructure of each specimen was examined and compared with the change in sintering stress and viscosity. For the whole range of test temperatures, viscosity was increased by the two-step heating, which can be explained by the effects of time-hardening. On the other hand, for the lower range of test temperatures, the sintering stress was decreased by the two-step heating. This may be a result of the formation of large pores due to inhomogeneous shrinkage in the unstable state of the powder with small contact in the initial stage of sintering.Key words : Sintering stress, Viscosity, Two step sintering, Sinter compression test, Pore IntroductionSintering as a manufacturing process is used to fabricate many things including ceramic parts, metallic machine components of complex shape, and various functional devices with complicated structures. In order to make the sintering process more effective, however, issues such as shrinkage accompanied with densification, and microstructural evolution in elevated temperatures, should be known and controlled to promote high dimensional accuracy as well as good material properties. The shrinkage as well as the microstructure of sintered materials is sometimes significantly affected by the heating history. In the two-step sintering of nanocrystalline ceramic powder, for example, grain growth is suppressed and densification is promoted, where the triple-point dihedral angle of grain or grain boundary/pore junctions is considered to be changed into a stable state by pre-firing (Chen and Wang, 2000;Wang et al., 2006). During the second step of two-step sintering, the mobility of the junctions may be lower than the grain boundary diffusion rate. The effects of the change in grain boundary/pore junctions on the driving force for densification has not yet been revealed, therefore, the effects of two-step sintering should be clarified from the view point of driving force as well as diffusion rate.Sinter-compression (forging) tests can be used to determine the sintering stress and the viscosity of powder compacts (Venkatachari and Raj, 1986;Rahaman et al., 1986; Zuo et al., 2003a), composites (Bordia andRaj, 1988;Salamone et al., 2003), glass (Ducamp and Raj, 1989), and metal/ceramic mixtures (Shinagawa, 2008(Shinagawa, , 2009. In these studies, microstructural evolutions, such as, grain growth, were considered, but no experiments have been done for the effects of heating history. Even with non-nanocrystalline powders, some effects regarding the sintering stress and viscosity may be o...

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“…Numerous pertinent analyses have been presented concerning this matter, cf., e.g. Hill et al (1989), Hill (1992), Biwa and Storåkers (1995), Ogbonna et al (1995) and Storåkers et al (1997), but here the particular theory laid down in a number of papers by Storåkers and Larsson (1994), Storåkers et al (1997) and Biwa and Storåkers (1995), will be discussed in some detail. In par- ticular, the theoretical framework presented in Storåkers et al (1997) will be adhered to as then the aim of the investigation was to include the geometry of the (rigid) indenter in a general manner.…”

Section: Self-similarity At Indentationmentioning

confidence: 98%

“…Some pertinent investigations to be mentioned explicitly are Hill et al (1989), Hill (1992), Biwa and Storåkers (1995), Ogbonna et al (1995) and Storåkers et al (1997). Often, such analyses include the use of cumulative superposition of incremental fields (based on a flat punch solution) in order to obtain full field solutions corresponding to indentation of different indenter geometries.…”

Section: Introductionmentioning

confidence: 99%

Similarity methods for analysing indentation contact problems—Advantages and disadvantages

Larsson

2008

Journal of Materials Processing Technology

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Transient creep analysis of ball indentation

Cited by 66 publications

References 14 publications

A numerical study of the mechanical behavior at contact between particles of dissimilar elastic–ideally plastic materials

A numerical study of the mechanical behavior at contact between particles of dissimilar elastic–ideally plastic materials

Effects of heating history on sintering properties of nickel powder compacts

Similarity methods for analysing indentation contact problems—Advantages and disadvantages

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