Friction and its Measurement in Powder-Compaction Processes

Gethin, D. T.; Solimanjad, N.; Dorémus, P.; Korachkin, D.

doi:10.1007/978-1-84628-099-3_8

Cited by 4 publications

(5 citation statements)

References 8 publications

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“…It seems appropriate to start the present analysis by discussing in some detail, in relation to powder pressing, the two effects of interest currently; rate-dependent frictional effects and time-dependency. Starting with frictional effects, it have been shown that friction between iron powder and die is rate-dependent [10,11]. Previous studies using two-step test methods propose the frictional coefficient between WC-Co powder and die to be 0.2 [14], obviously relying on Coulomb friction and used in previous research [17][18][19][20][21].…”

Section: Frictional Effects and Time-dependencymentioning

confidence: 99%

“…It is important to remember, however, that material related constitutive characteristics are not the only features influencing the mechanics at powder pressing. Previous research [10,11] shows that friction between iron powder and the wall of the pressing tool (die) is dependent on the compaction rate, which could influence the density distribution after compaction and therefore also the shape after sintering. Dynamic simulations at particle level suggest that high compaction rate influences the particle shape [12].…”

Section: Introductionmentioning

confidence: 99%

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On rate-dependence of hardmetal powder pressing of cutting inserts

et al. 2016

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The rate-dependence of hardmetal powder pressing in cutting insert production is investigated experimentally and numerically. In the latter case, the finite element method is relied upon using a continuum mechanics approach. In particular, possible rate-dependency due to creep deformation and rate-dependent friction is discussed with the experimental investigation focusing mainly on dimensional changes during sintering but also pressing forces. The results indicate that rate-dependent frictional effects are the dominating feature and accordingly, it can be argued that for the metal powders investigated here, creep deformations do not have to be accounted for in the constitutive description at the timescales relevant for powder pressing and when the shape after sintering is concerned. For the present powder, the apparent frictional effect decreases at higher pressing rates. Additional details of the friction behavior are studied comparing finite element simulations with experiments.

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Section: Frictional Effects and Time-dependencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On rate-dependence of hardmetal powder pressing of cutting inserts

et al. 2016

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“…During the unloading stage, the punch loads are relaxed and elastic recovery of the press and tool components takes place. The compact itself also experiences some recovery (Gethin et al ., 2008).…”

Section: Discussionmentioning

confidence: 99%

Use of X‐ray micro tomography to study the microstructure of loose‐packed and compacted milk powders

Chawanji

Baldwin

Brisson

et al. 2012

Journal of Microscopy

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SummaryThe use of X-rays to evaluate food microstructure has developed considerably in recent years. In this work we used X-ray micro tomography (XMT) to visualize the microstructure of loose-packed and compacted samples of spray-dried skim milk powder (SMP) and whole milk powder (WMP) and to quantify the proportion of both interstitial and occluded air voids in each sample. Visual scrutiny of the acquired XMT images showed details of the microstructure of the milk powders such as the spherical morphology of the particles, the size of the particles and internal air voids of various sizes. Within loose-packed powders, the proportion of air voids was higher (13% average) in WMP than in SMP. This was reversed in the compacted powders, in which the proportion of air voids was higher in SMP. The disparity in the proportion of air voids in both loose-packed and compacted samples of SMP and WMP was attributed to the size, shape and surface properties of the particles.

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“…In terms of boundary lubrication, the addition of a lubricant in formulations is to reduce the coefficient of wall friction by forming a boundary layer. For example, in a tableting process, the coefficient of friction is derived by the application of a force balance through integration (see Equation (6) and Figure 1) [11].…”

Section: Wall Frictionmentioning

confidence: 99%

Lubricants in Pharmaceutical Solid Dosage Forms

2014

Lubricants

175

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Lubrication plays a key role in successful manufacturing of pharmaceutical solid dosage forms; lubricants are essential ingredients in robust formulations to achieve this. Although many failures in pharmaceutical manufacturing operations are caused by issues related to lubrication, in general, lubricants do not gain adequate attention in the development of pharmaceutical formulations. In this paper, the fundamental background on lubrication is introduced, in which the relationships between lubrication and friction/adhesion forces are discussed. Then, the application of lubrication in the development of pharmaceutical products and manufacturing processes is discussed with an emphasis on magnesium stearate. In particular, the effect of its hydration state (anhydrate, monohydrate, dihydrate, and trihydrate) and its powder characteristics on lubrication efficiency, as well as product and process performance is summarized. In addition, the impact of lubrication on the dynamics of compaction/compression processes and on the mechanical properties of compacts/tablets is presented. Furthermore, the online monitoring of magnesium stearate in a blending process is briefly mentioned. Finally, the chemical compatibility of active pharmaceutical ingredient (API) with magnesium stearate and its reactive impurities is reviewed with examples from the literature illustrating the various reaction mechanisms involved.

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Friction and its Measurement in Powder-Compaction Processes

Cited by 4 publications

References 8 publications

On rate-dependence of hardmetal powder pressing of cutting inserts

On rate-dependence of hardmetal powder pressing of cutting inserts

Use of X‐ray micro tomography to study the microstructure of loose‐packed and compacted milk powders

Lubricants in Pharmaceutical Solid Dosage Forms

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