J. Sicre, Y. Berthier, L. Flamand, P. Reynaud, P. Vergne, M. Godet
Dry lubricants are often used in space because of their excellent behaviour in a vacuum and their thermal stability. However, mechanisms which are heavily loaded, with a high sliding rate, a long life span, or needing a stable friction coefficient cannot use this kind of product. They can be replaced by wet lubricants specially developed for vacuum applications. Such lubricants have a low vapour pressure in order to minimise outgassing losses and avoid contamination. Since European experience in the field of wet lubrication in space is rather limited, the French Space Agency CNES, with the help of the LMC (Laboratoire de Mecanique des Contacts - Contact Mechanics Laboratory), is currently characterising several wet lubricants for use in space applications. The selected lubricants were tested on a vacuum friction test bench which allows the main contact parameters to be controlled: speed, load, and kinematics. The bench is equipped with vacuum facilities and, since it runs under air, neutral gas, or vacuum, it can be used to study the effects of atmosphere. Variations of physical properties (viscosity) versus temperature (−60°C to 100°) and pressure (from atmospheric pressure to 500 MPa) were studied for all the lubricants tested, and these characteristics take into account in the analysis of the tribological test results. This paper briefly lists the characteristics of a space environment (vacuum, microgravity, etc.) and their consequences for lubrication. It describes the equipment used and the tribological and rheological test results obtained on six wet lubricants (three oils and three greases). It also contains conclusions in terms of recommendations about the use of such lubricants.
{"title":"Rheological and tribological characterisation of six wet lubricants for space","authors":"J. Sicre, Y. Berthier, L. Flamand, P. Reynaud, P. Vergne, M. Godet","doi":"10.1002/JSL.3000110104","DOIUrl":"https://doi.org/10.1002/JSL.3000110104","url":null,"abstract":"Dry lubricants are often used in space because of their excellent behaviour in a vacuum and their thermal stability. However, mechanisms which are heavily loaded, with a high sliding rate, a long life span, or needing a stable friction coefficient cannot use this kind of product. They can be replaced by wet lubricants specially developed for vacuum applications. Such lubricants have a low vapour pressure in order to minimise outgassing losses and avoid contamination. \u0000 \u0000 \u0000 \u0000Since European experience in the field of wet lubrication in space is rather limited, the French Space Agency CNES, with the help of the LMC (Laboratoire de Mecanique des Contacts - Contact Mechanics Laboratory), is currently characterising several wet lubricants for use in space applications. \u0000 \u0000 \u0000 \u0000The selected lubricants were tested on a vacuum friction test bench which allows the main contact parameters to be controlled: speed, load, and kinematics. The bench is equipped with vacuum facilities and, since it runs under air, neutral gas, or vacuum, it can be used to study the effects of atmosphere. Variations of physical properties (viscosity) versus temperature (−60°C to 100°) and pressure (from atmospheric pressure to 500 MPa) were studied for all the lubricants tested, and these characteristics take into account in the analysis of the tribological test results. \u0000 \u0000 \u0000 \u0000This paper briefly lists the characteristics of a space environment (vacuum, microgravity, etc.) and their consequences for lubrication. It describes the equipment used and the tribological and rheological test results obtained on six wet lubricants (three oils and three greases). It also contains conclusions in terms of recommendations about the use of such lubricants.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"59 2","pages":"35-44"},"PeriodicalIF":0.0,"publicationDate":"1994-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91498718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the widening use of plastics, it has become an urgent task to study their behaviour in friction systems. The present paper reviews the applications of plastics during the past decades and their function in friction systems. The paper analyses the basic differences between metals and plastics in structure and properties, and points out the limitations, or inapplicability, of using metal tribology to solve problems in plastic friction systems when even different kinds of high-molecular materials have different shapes and applications. The paper also looks at the variety of plastic surfaces, and briefly presents the mechanism, theory, and calculation of the fiction, wear, and lubrication of plastics; theories of plastic wear are summarised. Also presented are the technical functions, simple application techniques, and economic benefits of plastic friction systems.
{"title":"The tribology of plastics — an overview","authors":"Chenghe Wang","doi":"10.1002/JSL.3000110105","DOIUrl":"https://doi.org/10.1002/JSL.3000110105","url":null,"abstract":"With the widening use of plastics, it has become an urgent task to study their behaviour in friction systems. The present paper reviews the applications of plastics during the past decades and their function in friction systems. The paper analyses the basic differences between metals and plastics in structure and properties, and points out the limitations, or inapplicability, of using metal tribology to solve problems in plastic friction systems when even different kinds of high-molecular materials have different shapes and applications. \u0000 \u0000The paper also looks at the variety of plastic surfaces, and briefly presents the mechanism, theory, and calculation of the fiction, wear, and lubrication of plastics; theories of plastic wear are summarised. Also presented are the technical functions, simple application techniques, and economic benefits of plastic friction systems.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"34 1","pages":"45-51"},"PeriodicalIF":0.0,"publicationDate":"1994-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81684033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order for silahydrocarbons to qualify, for use in a broad range of applications (automotive, aerospace, and industrial), the formulated fluid must have good oxidative stability and lubricity. This paper compares the response of a silahydrocarbon, a synthetic hydrocarbon, and a mineral oil to various antiwear and antioxidant additives. A merit rating system is described: it provides a relative ranking of the different formulated fluids according to performance.
{"title":"Improvement of silahydrocarbon performance with additives","authors":"S. Thomas, D. G. Campbell, C. Hsu","doi":"10.1002/JSL.3000100302","DOIUrl":"https://doi.org/10.1002/JSL.3000100302","url":null,"abstract":"In order for silahydrocarbons to qualify, for use in a broad range of applications (automotive, aerospace, and industrial), the formulated fluid must have good oxidative stability and lubricity. \u0000 \u0000This paper compares the response of a silahydrocarbon, a synthetic hydrocarbon, and a mineral oil to various antiwear and antioxidant additives. A merit rating system is described: it provides a relative ranking of the different formulated fluids according to performance.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"33 6","pages":"195-212"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91507467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Research has been undertaken to identify new synthetic basestocks, to be used alone or with polyalphaolefins, for the formulation of high-quality engine oils. Basestock selection was limited to products not normally used in the synthesis of ester-type basestocks. A non-conventional product was identified: a carbonic ester of synthetic alcohols. A complete engine oil has been formulated using this basestock and submitted to a full test programme. The results are reported.
{"title":"Use of a non-conventional synthetic basestock in the formulation of high-quality engine oils","authors":"G. Fisicaro, S. Fattori","doi":"10.1002/JSL.3000100305","DOIUrl":"https://doi.org/10.1002/JSL.3000100305","url":null,"abstract":"Research has been undertaken to identify new synthetic basestocks, to be used alone or with polyalphaolefins, for the formulation of high-quality engine oils. \u0000 \u0000 \u0000 \u0000Basestock selection was limited to products not normally used in the synthesis of ester-type basestocks. A non-conventional product was identified: a carbonic ester of synthetic alcohols. A complete engine oil has been formulated using this basestock and submitted to a full test programme. The results are reported.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"2 1","pages":"237-246"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82291601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rheological properties of two lithium, two lithium complex, and two sodium greases, all with the most common NLGI grade two, have been investigated. The greases are based on a mineral and a synthetic oil. The apparatus used was a cone-and-plate rheometer and an impacting-ball apparatus. The impacting-ball apparatus used a steel ball, which impacted a lubricated sintered carbide plate, to measure the shear stress-pressure coefficient, γ, of the lubricant. At pressures found in elastohydrodynamic contacts this coefficient determined the limiting shear stress. The γ-value thus affects the coefficient of friction and consequently, lower γ-value means less friction. The results from the impacting-ball apparatus showed that the γ-value was lower for the greases with a synthetic base oil and that the lithium greases gave a lower γ-value than the corresponding base oils. Results from the cone-and-plate rheometer showed the characteristic shear thinning behaviour of the greases and the influence of shear history and temperature. The results from the cone-and-plate rheometer have also been fitted to a four parameter rheological model.
{"title":"Rheological properties of lithium, lithium complex, and sodium greases","authors":"H. Åkröm, E. Höglund","doi":"10.1002/JSL.3000100304","DOIUrl":"https://doi.org/10.1002/JSL.3000100304","url":null,"abstract":"The rheological properties of two lithium, two lithium complex, and two sodium greases, all with the most common NLGI grade two, have been investigated. The greases are based on a mineral and a synthetic oil. The apparatus used was a cone-and-plate rheometer and an impacting-ball apparatus. \u0000 \u0000The impacting-ball apparatus used a steel ball, which impacted a lubricated sintered carbide plate, to measure the shear stress-pressure coefficient, γ, of the lubricant. At pressures found in elastohydrodynamic contacts this coefficient determined the limiting shear stress. The γ-value thus affects the coefficient of friction and consequently, lower γ-value means less friction. \u0000 \u0000The results from the impacting-ball apparatus showed that the γ-value was lower for the greases with a synthetic base oil and that the lithium greases gave a lower γ-value than the corresponding base oils. \u0000 \u0000Results from the cone-and-plate rheometer showed the characteristic shear thinning behaviour of the greases and the influence of shear history and temperature. The results from the cone-and-plate rheometer have also been fitted to a four parameter rheological model.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"15 1","pages":"225-236"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73689997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Friction and wear characteristics of a type of polyetheretherketone (PEEK)- based composite were evaluated under two different loading pressures and sliding speeds (P = 1.0 MPa, V = 1.0 m/s and P=2.0 Mpa, V=3.3 m/s). The material was in contact with steel surfaces of two different roughnesses (Ra=0.15 μm and Ra=0.33 μm). Interface temperature, coefficient offriction, depth wear rate, and specific wear rate of the polymer composite changed considerably with the PV value and the counterface roughness. The interface temperature increased with increasing PV value, whereas the friction coefficient decreased. The depth wear rate at the higher PV value was much higher than that at lower PV. In addition, the rougher counterface resulted in a higher friction coefficient, depth wear rate, and specific wear rate, when the PV value was fixed. The effect of counterface roughness on the specific wear rate at the higher PV value was smaller than that at the lower PV. Further variations in friction and wear with testing conditions are discussed along with the corresponding microscopic observations of the worn polymer surfaces and the polymer transferred counterfaces.
{"title":"Effect of testing conditions on friction and wear of a polyetheretherketone-based composite","authors":"Q. Guo, K. Friedrich","doi":"10.1002/JSL.3000100303","DOIUrl":"https://doi.org/10.1002/JSL.3000100303","url":null,"abstract":"Friction and wear characteristics of a type of polyetheretherketone (PEEK)- based composite were evaluated under two different loading pressures and sliding speeds (P = 1.0 MPa, V = 1.0 m/s and P=2.0 Mpa, V=3.3 m/s). The material was in contact with steel surfaces of two different roughnesses (Ra=0.15 μm and Ra=0.33 μm). Interface temperature, coefficient offriction, depth wear rate, and specific wear rate of the polymer composite changed considerably with the PV value and the counterface roughness. The interface temperature increased with increasing PV value, whereas the friction coefficient decreased. The depth wear rate at the higher PV value was much higher than that at lower PV. In addition, the rougher counterface resulted in a higher friction coefficient, depth wear rate, and specific wear rate, when the PV value was fixed. The effect of counterface roughness on the specific wear rate at the higher PV value was smaller than that at the lower PV. Further variations in friction and wear with testing conditions are discussed along with the corresponding microscopic observations of the worn polymer surfaces and the polymer transferred counterfaces.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"1 1","pages":"213-224"},"PeriodicalIF":0.0,"publicationDate":"1993-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90810945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper is a review of the properties and functions of magnetic fluids and their potential use in tribological applications, such as seals and bearings. They offer new possibilities for achieving low friction, low wear, and no leak- age. Magnetic fluids or ferrofluids consist of magnetic particles suspended in a carrier fluid and a coating on the particles. The coating prevents the agglomeration of the particles through magnetic and molecular attraction by keeping the distance between them sufficiently large. The magnetic fluids have the basic properties of liquids and they act like ferromagnetic materials in the presence of an external magnetic field. Shaft sealing is the most promising potential application for ferrofluids. Magnetic seals have zero-leakage and low friction, they are non-stick and they have high-performance properties. Lubrication is another important application of ferrofluids. The advantage over conventional lubricants is the possibility of keeping the lubricant exactly and only where it is needed. They provide the possibility of increasing the life of components. Furthermore, because they do not contaminate, ferrofluids are also used as lubricants in clean environments.
{"title":"Magnetic fluids in sealing and lubrication – a state of the art review","authors":"M. Säynätjoki, K. Holmberg","doi":"10.1002/JSL.3000100203","DOIUrl":"https://doi.org/10.1002/JSL.3000100203","url":null,"abstract":"The paper is a review of the properties and functions of magnetic fluids and their potential use in tribological applications, such as seals and bearings. They offer new possibilities for achieving low friction, low wear, and no leak- age. \u0000 \u0000Magnetic fluids or ferrofluids consist of magnetic particles suspended in a carrier fluid and a coating on the particles. The coating prevents the agglomeration of the particles through magnetic and molecular attraction by keeping the distance between them sufficiently large. The magnetic fluids have the basic properties of liquids and they act like ferromagnetic materials in the presence of an external magnetic field. \u0000 \u0000Shaft sealing is the most promising potential application for ferrofluids. Magnetic seals have zero-leakage and low friction, they are non-stick and they have high-performance properties. Lubrication is another important application of ferrofluids. The advantage over conventional lubricants is the possibility of keeping the lubricant exactly and only where it is needed. They provide the possibility of increasing the life of components. Furthermore, because they do not contaminate, ferrofluids are also used as lubricants in clean environments.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"3 1","pages":"119-132"},"PeriodicalIF":0.0,"publicationDate":"1993-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89498867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A new process has been discovered for the production of low-viscosity PAO fluids in high yield. In particular, the new process can be used to produce a mixture of decene dimers that has low-temperature properties which are superior to the properties of decene dimers produced by the conventional PAO process.
{"title":"A polyalphaolefin with exceptional low‐temperature properties","authors":"K. J. Theriot, R. L. Shubki","doi":"10.1002/JSL.3000100204","DOIUrl":"https://doi.org/10.1002/JSL.3000100204","url":null,"abstract":"A new process has been discovered for the production of low-viscosity PAO fluids in high yield. In particular, the new process can be used to produce a mixture of decene dimers that has low-temperature properties which are superior to the properties of decene dimers produced by the conventional PAO process.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"47 1","pages":"133-142"},"PeriodicalIF":0.0,"publicationDate":"1993-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89085148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High-temperature in-service failure of phosphate ester-based aviation fluids is primarily due to acid-catalysed hydrolysis. The reaction is controlled with epoxides, but careful attention to the other additives is needed to avoid including species which catalyse hydrolysis. From an airline's point of view, water concentration is the critical factor, since it is the only variable that it can control. From a system designer's point of view, minimising fluid temperature should be a goal. Plots relating fluid life to temperature and water level for typical commercial fluids are included.
{"title":"Hydrolysis of phosphate‐based aviation hydraulic fluids","authors":"S. M. Aberathy, J. Laurent","doi":"10.1002/JSL.3000100202","DOIUrl":"https://doi.org/10.1002/JSL.3000100202","url":null,"abstract":"High-temperature in-service failure of phosphate ester-based aviation fluids is primarily due to acid-catalysed hydrolysis. The reaction is controlled with epoxides, but careful attention to the other additives is needed to avoid including species which catalyse hydrolysis. From an airline's point of view, water concentration is the critical factor, since it is the only variable that it can control. From a system designer's point of view, minimising fluid temperature should be a goal. Plots relating fluid life to temperature and water level for typical commercial fluids are included.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"1 1","pages":"107-118"},"PeriodicalIF":0.0,"publicationDate":"1993-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75634859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Srinivasan, C. Corti, L. Montagna, Paolo Savelli
High-performance aerospace systems make severe demands on lubricants. Among the potential candidates, perfluorinated fluids, especially perfluoropolyethers (PFPEs), lead the list. PFPEs are unique in that several of the properties required for the lubrication of these systems, such as thermalloxidation stability, chemical inertness, compatibility with materials of construction, high viscosity index, etc., are inherent to them. However, there is a need to add other characteristics or to improve some of the inherent properties. Research programme to find a solution by preparing PFPEs with different structures as well as developing soluble anticorrosion, antiwear, and stabilising additives has been undertaken. The present paper describes the preliminary results obtained with a few additives and suggests possible action mechanisms.
{"title":"Soluble additives for perfluorinated lubricants","authors":"P. Srinivasan, C. Corti, L. Montagna, Paolo Savelli","doi":"10.1002/JSL.3000100205","DOIUrl":"https://doi.org/10.1002/JSL.3000100205","url":null,"abstract":"High-performance aerospace systems make severe demands on lubricants. Among the potential candidates, perfluorinated fluids, especially perfluoropolyethers (PFPEs), lead the list. PFPEs are unique in that several of the properties required for the lubrication of these systems, such as thermalloxidation stability, chemical inertness, compatibility with materials of construction, high viscosity index, etc., are inherent to them. However, there is a need to add other characteristics or to improve some of the inherent properties. Research programme to find a solution by preparing PFPEs with different structures as well as developing soluble anticorrosion, antiwear, and stabilising additives has been undertaken. The present paper describes the preliminary results obtained with a few additives and suggests possible action mechanisms.","PeriodicalId":17149,"journal":{"name":"Journal of Synthetic Lubrication","volume":"25 1","pages":"143-164"},"PeriodicalIF":0.0,"publicationDate":"1993-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90160260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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