A Model for Shear Degradation of Lithium Soap Grease at Ambient Temperature

Yuxin Zhou, Rob Bosman, Pieter Martin Lugt

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Abstract

In this paper the shear degradation of lithium 12-hydroxy stearate grease will be measured using an in- house-developed Couette aging machine. In this device the shear rate is well defined. The aging is related to the generated entropy density, as described in Rezasoltani and Khonsari’s work (Tribology Letters, Vol. 56, No. 2, pp. 197–204, 2014 and Ref. 11). The rheological properties of the aged samples were evaluated using a parallel-plate rheometer. The results showed that there are two aging phases with different degradation rates, i.e.—a progressive degradation phase at the early stage, followed by a rather slow deterioration afterwards. Based on this observation an aging equation was
formulated to describe the aging behavior of lithium-thickened grease. Atomic force microscopy results of the fresh and aged greases showed that the variation in thickener microstructure provides a good explanation for the lithium grease degradation mechanism; under shear, the original fibrous network is progressively destroyed and becomes fragmented, leading to the loss of consistency and a change in the rheological properties.
Original languageEnglish
Pages (from-to)38-46
Number of pages9
JournalPower Transmission Engineering
Volume11
Issue number7
Publication statusPublished - 2017

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Soaps (detergents)
Lubricating greases
Lithium
Aging of materials
Degradation
Temperature
Tribology
Rheometers
Shear deformation
Deterioration
Atomic force microscopy
Entropy
Microstructure

Cite this

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title = "A Model for Shear Degradation of Lithium Soap Grease at Ambient Temperature",
abstract = "In this paper the shear degradation of lithium 12-hydroxy stearate grease will be measured using an in- house-developed Couette aging machine. In this device the shear rate is well defined. The aging is related to the generated entropy density, as described in Rezasoltani and Khonsari’s work (Tribology Letters, Vol. 56, No. 2, pp. 197–204, 2014 and Ref. 11). The rheological properties of the aged samples were evaluated using a parallel-plate rheometer. The results showed that there are two aging phases with different degradation rates, i.e.—a progressive degradation phase at the early stage, followed by a rather slow deterioration afterwards. Based on this observation an aging equation wasformulated to describe the aging behavior of lithium-thickened grease. Atomic force microscopy results of the fresh and aged greases showed that the variation in thickener microstructure provides a good explanation for the lithium grease degradation mechanism; under shear, the original fibrous network is progressively destroyed and becomes fragmented, leading to the loss of consistency and a change in the rheological properties.",
author = "Yuxin Zhou and Rob Bosman and Lugt, {Pieter Martin}",
year = "2017",
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A Model for Shear Degradation of Lithium Soap Grease at Ambient Temperature. / Zhou, Yuxin ; Bosman, Rob ; Lugt, Pieter Martin.

In: Power Transmission Engineering, Vol. 11, No. 7, 2017, p. 38-46.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - A Model for Shear Degradation of Lithium Soap Grease at Ambient Temperature

AU - Zhou, Yuxin

AU - Bosman, Rob

AU - Lugt, Pieter Martin

PY - 2017

Y1 - 2017

N2 - In this paper the shear degradation of lithium 12-hydroxy stearate grease will be measured using an in- house-developed Couette aging machine. In this device the shear rate is well defined. The aging is related to the generated entropy density, as described in Rezasoltani and Khonsari’s work (Tribology Letters, Vol. 56, No. 2, pp. 197–204, 2014 and Ref. 11). The rheological properties of the aged samples were evaluated using a parallel-plate rheometer. The results showed that there are two aging phases with different degradation rates, i.e.—a progressive degradation phase at the early stage, followed by a rather slow deterioration afterwards. Based on this observation an aging equation wasformulated to describe the aging behavior of lithium-thickened grease. Atomic force microscopy results of the fresh and aged greases showed that the variation in thickener microstructure provides a good explanation for the lithium grease degradation mechanism; under shear, the original fibrous network is progressively destroyed and becomes fragmented, leading to the loss of consistency and a change in the rheological properties.

AB - In this paper the shear degradation of lithium 12-hydroxy stearate grease will be measured using an in- house-developed Couette aging machine. In this device the shear rate is well defined. The aging is related to the generated entropy density, as described in Rezasoltani and Khonsari’s work (Tribology Letters, Vol. 56, No. 2, pp. 197–204, 2014 and Ref. 11). The rheological properties of the aged samples were evaluated using a parallel-plate rheometer. The results showed that there are two aging phases with different degradation rates, i.e.—a progressive degradation phase at the early stage, followed by a rather slow deterioration afterwards. Based on this observation an aging equation wasformulated to describe the aging behavior of lithium-thickened grease. Atomic force microscopy results of the fresh and aged greases showed that the variation in thickener microstructure provides a good explanation for the lithium grease degradation mechanism; under shear, the original fibrous network is progressively destroyed and becomes fragmented, leading to the loss of consistency and a change in the rheological properties.

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