Ultrasonic monitoring of the elastic properties of PMMA bead packings and their rearrangement during pressure sintering

Langlois, Vincent; Jia, Xiaoping

doi:10.1016/j.powtec.2010.08.051

Cited by 9 publications

(4 citation statements)

References 23 publications

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“…and describes well the results obtained in sintered granular materials [28]. Note that all the above models take into account only the material properties of grains, the external load, and the interfacial forces (frictional or adhesive); however, the bulk properties of the binder or cement are ignored (see Sec.…”

Section: A Effective Medium Theory Based On Interfacial Bonding Modelssupporting

confidence: 71%

Acoustic probing of elastic behavior and damage in weakly cemented granular media

Langlois¹,

Jia

2014

Phys. Rev. E

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We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ϕ = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981)] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994)]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces.

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Section: A Effective Medium Theory Based On Interfacial Bonding Modelssupporting

confidence: 71%

Acoustic probing of elastic behavior and damage in weakly cemented granular media

Langlois¹,

Jia

2014

Phys. Rev. E

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“…Modelling of powder metallurgy and sintering processes requires a special constitutive model for particle contact interaction in which the sintering driving forces, viscosity, elasticity, cohesive and thermal interactions play a significant role. Although deformation during sintering itself is governed mainly by the viscosity, the material does maintain certain elasticity [7,8]. Elastic effects influence the distribution of forces in the heterogeneous particulate material and have some importance to the evaluation of stresses during the initial compaction and pressure-assisted sintering process.…”

Section: Introductionmentioning

confidence: 99%

Application of the Hertz formulation in the discrete element model of pressure-assisted sintering

et al. 2017

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This paper presents the numerical modelling of initial powder compaction and pressure-assisted sintering performed by original viscoelastic discrete element model. The research is focused on the influence of the type of the model representing an elastic part of interparticle force. Two elastic contact models-linear and nonlinear Hertz modelhave been implemented and used to analyse interaction of NiAl powder particles during compaction and sintering process. Numerical models have been validated using own experimental results. Microscopic effects (particle penetration) and macroscopic changes (relative density) have been compared. It has been shown that although both models represent properly macroscopic behaviour of the material at the sintering process, the Hertz model produces the results closer to the real experimental ones during the initial compaction stage. Evaluation of macroscopic quantities enables implementation of the discrete element model in the framework of the multiscale modelling framework which is currently developed for sintering processes.

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“…Among others the questions rise on the structure forming processes and the high temperature sintering of the dielectric refractory powders. Some studies revealed the crucial role of the bonding effect on the mechanical behavior of the compacts [7], other point out the importance of number of touching neighbors for each particle, known as the coordination number [8]. However, despite the numerous investigations of the consolidation processes of various nanodispersed powders using the Field Activated Sintering Technique (FAST) [9,10], the main peculiarities of their electric sintering are still not understood in full.…”

Section: Introductionmentioning

confidence: 99%

Structure formation of hot pressed Al2O3 powders under the alternating electric current: experimental observations

Gevorkyan¹,

Lavrynenko²,

Rucki³

2017

Adv. Mater. Lett.

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The paper presents the results of investigations on hot pressure sintering under the alternating current. The powders of different grain sizes were used for the sintering to investigate the impact of the powder on the final sintered structure and relative density. The additional experiments were focused on the kinetics of the Al2O3 nanopowders sintering. They confirmed that the time of the process duration is dependent on the temperature and the applied pressure. However, compared to the powders of tungsten monocarbide, it depends on the temperature rise speed in rather small degree. Discussion of the results pointed out that the obtained data, both theoretical and experimental one, confirmed possibility that during the sintering process the dislocations might appear and spread. It seemed reasonable to assume that in the low voltage regime the activated sliding with diffusion accommodation prevails, while in the high voltage regime the dislocation creep does.

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Ultrasonic monitoring of the elastic properties of PMMA bead packings and their rearrangement during pressure sintering

Cited by 9 publications

References 23 publications

Acoustic probing of elastic behavior and damage in weakly cemented granular media

Acoustic probing of elastic behavior and damage in weakly cemented granular media

Application of the Hertz formulation in the discrete element model of pressure-assisted sintering

Structure formation of hot pressed Al2O3 powders under the alternating electric current: experimental observations

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