| 1. |
- Basu, Bikramjit, et al.
(författare)
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Friction and Wear of Ceramics : Principles and Case Studies
- 2020
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This book covers the area of tribology broadly, providing important introductory chapters to fundamentals, processing, and applications of tribology. The book is designed primarily for easy and cohesive understanding for students and practicing scientists pursuing the area of tribology with focus on materials. This book helps students and practicing scientists alike understand that a comprehensive knowledge about the friction and wear properties of advanced materials is essential to further design and development of new materials.The description of the wear micromechanisms of various materials will provide a strong background to the readers as how to design and develop new tribological materials. This book also places importance on the development of new ceramic composites in the context of tribological applications. The various sections of the book discuss fundamentals of nature and properties of materials, friction and wear of structural ceramics, bioceramics, biocomposites, and nanoceramics, as well as lightweight composites and friction and wear of ceramics in a cryogenic environment.Some of the key features of the book include: Fundamentals section highlights the salient issues of ceramic processing and mechanical properties of important oxide and non-oxide ceramic systems; State of the art research findings on important ceramic composites are included and an understanding on the behavior of silicon carbide (SiC) based ceramic composites in dry sliding wear conditions is presented as a case study; Erosion wear behavior of ceramics, in which case studies on high temperature erosion behavior of SiC based composites and zirconium diboride (ZrB2) based composites is also covered; Wear behavior of ceramic coatings is rarely discussed in any tribology related books therefore a case study explaining the abrasion wear behavior of WC-Co coating is provided. Finally an appendix chapter is included in which a collection of several types of questions including multiple choice, short answer and long answer ae provided.
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| 2. |
- Bek, Marko, et al.
(författare)
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Long-Term Creep Compliance of Wood Polymer Composites: Using Untreated Wood Fibers as a Filler in Recycled and Neat Polypropylene Matrix
- 2022
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 14:13
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Tidskriftsartikel (refereegranskat)abstract
- Neat (NPP) and recycled (RPP) polypropylene matrix materials were used to prepare wood–polymer composites with untreated wood fibers up to 40 wt.%. Long-term creep properties obtained through the time-temperature superposition showed superior creep resistance of composites with NPP matrix. In part, this is attributed to their higher crystallinity and better interfacial adhesion caused by the formation of a transcrystalline layer. This difference resulted in up to 25% creep compliance reduction of composites with NPP matrix compared to composites with recycled (RPP) polypropylene matrix, which does not form a transcrystalline layer between the fibers and polymer matrix. Despite the overall inferior creep performance of composites with RPP matrix, from the 20 wt.% on, the creep compliance is comparable and even surpasses the creep performance of unfilled NPP matrix and can be a promising way to promote sustainability.
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| 3. |
- Gangwani, Prashant, et al.
(författare)
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Does a Compatibilizer Enhance the Properties of Carbon Fiber-Reinforced Composites?
- 2023
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 15:23
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Tidskriftsartikel (refereegranskat)abstract
- We have evaluated the effectiveness of compatibilizers in blends and composites produced using a solvent manufacturing process. The compatibilizers were two different types of polyethylene (linear low-density and high-density) grafted with maleic anhydride (MAH) and a highly functionalized, epoxy-based compatibilizer with the tradename Joncryl. The selected material combinations were an ultra-high-molecular-weight polyethylene (UHMWPE) with MAH-based materials as compatibilizers and a polyphenylene sulfide plus polytetrafluoroethylene (PPS-PTFE) polymer blend with an epoxy-based compatibilizer. The findings revealed that while the compatibilizers consistently enhanced the properties, such as the impact strength and hardness of PPS-based compositions, their utility is constrained to less complex compositions, such as fibrous-reinforced PPS or PPS-PTFE polymer blends. For fibrous-reinforced PPS-PTFE composites, the improvement in performance does not justify the presence of compatibilizers. In contrast, for UHMWPE compositions, compatibilizers demonstrated negligible or even detrimental effects, particularly in reinforced UHMWPE. Overall, the epoxy-based compatibilizer Joncryl stands out as the only effective option for enhancing mechanical performance. Thermal and chemical characterization indicated that the compatibilizers function as chain extenders and enhance the fiber–matrix interface in PPS-based compositions, while they remain inactive in UHMWPE-based compositions. Ultimately, the incompatibility of the compatibilizers with certain aspects of the manufacturing method and the inconsistent integration with the polymer are the main reasons for their ineffectiveness in UHMWPE compositions.
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| 4. |
- Gangwani, Prashant, et al.
(författare)
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Effect of multi-scale fillers on the tribological behavior of UHMWPE composites in water-lubricated contacts
- 2024
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 196
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the impact of graphite, hexagonal boron nitride and short carbon fibers, acting as micro- and nano-fillers, on the tribological performance of ultra-high-molecular-weight polyethylene (UHMWPE) hybrid composites. The tribological performance is evaluated under boundary-lubrication conditions with distilled water at contact pressures in the range from 5 and 15 MPa. The fillers were found to work synergistically, with the best performance recorded when the compositions incorporated fillers of all scales. The most effective composite, consisting of short carbon fibers, micro-scale graphite, micro-scale hBN and nano-scale hBN, reduced the coefficient of friction by 75 %, reaching a value of 0.06, and the specific wear rate by two orders of magnitude to 2 × 10−7 mm3/Nm, compared to pure UHMWPE. The fillers' size also played an important role. Composites with nano-boron nitride led to 40 % lower friction compared to micro-scale fillers only. However, all the fillers reduced the amount of abrasive wear, especially the boron nitride, as a consequence of the tribochemical reaction between the boron nitride and water at the interface. Additionally, the formation of a transfer film was observed on the steel discs, with only short carbon fibers and graphite contributing to its formation from among the fillers used.
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| 5. |
- Hua, Jing
(författare)
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Friction control in different lubrication regimes
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We often strive to minimize friction but there are also many situations where high friction is desirable. In some cases, something in between, i.e. optimum friction, is attractive. Driven by the broad application prospects, many controllable friction systems regulated with external stimuli such as solvent, pH, temperature, electric potential, and magnetic fields have been designed and fabricated. When external stimuli are imposed on the smart materials, the macroscopic physicochemical properties of the materials are dramatically changed, making controllable friction behavior to become possible. However, most of these exploratory works are in nano/micro size, which cannot be applied in macroscale for industry applications. Lubrication is mainly classified as three regimes: boundary, mixed and full film lubrication. If considering molecular size as well, there exists thin film lubrication between boundary lubrication and elastohydrodynamic lubrication, with the lubricating film thickness of a few nanometers to tens of nanometers. This thesis attempts to find more versatile methods of friction control and tries to find the possibility to achieve friction control at macroscale in all these lubrication regimes.In this thesis, we investigated the possibility of adjusting friction by controlling viscosity in a lubricated contact and it was found that friction of switchable ionic liquids could be controlled in the EHL regime enabled by CO2 absorption and desorption in Paper 1. Glycerol solution formulated with ionic liquid was employed in Paper 2 to obtain superlubricity in thin film lubrication, and it was observed that the lubrication state could be switched between superlubricity and non-superlubricity by adjusting humidity. Friction control of multi-functional green lubricant in mixed lubrication was evaluated in Paper 3. Finally, the macroscopic friction control of ionic liquids in boundary lubrication enabled by environmental humidity was described in Paper 4, and stimuli responsive hydrogel also could be used for achieving friction control in boundary lubrication, studied in Paper 5.
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| 6. |
- Jan, Petra, et al.
(författare)
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Tribological behaviour of green wood-based unrecycled and recycled polypropylene composites
- 2023
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 524-525
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Tidskriftsartikel (refereegranskat)abstract
- In this study we evaluated the tribological performance of polypropylene composites with wood-flour fillers obtained as a by-product from the wood-processing industry, which were based on unrecycled and recycled polypropylene polymer matrices. The mechanical properties of polypropylene-wood composites with wood-filler loadings of 0–40 wt % were determined with tensile tests and their friction and wear behaviours were studied with dry reciprocating ball-on-disc sliding tests against 100Cr6 steel balls at room temperature. The addition of the wood fillers resulted in a significant improvement in the tribological performance compared to the neat, unrecycled, and recycled polypropylene materials: the friction coefficient decreased by up to 30%, while the wear resistance was improved by up to two orders of magnitude. While neat unrecycled polymers have better properties than recycled, addition of 40 wt % wood-filler content in both, recycled and unrecycled composites, resulted in almost the same level of coefficient of friction (∼0.25) and wear coefficient (2 × 10−6 mm3/(Nm) to 3 × 10−6 mm3/(Nm)). Even with the addition of as low as 5 wt % of wood fibres the wear resistance was improved for 63% and 43% for unrecycled and recycled composites, respectively, which indicates that the use of wood fillers could be a sustainable and cost-effective way to improve the polymer tribological performance, and could compensate for the normally poorer properties of recycled materials, making the recycled polypropylene-wood composites a suitable sustainable choice for tribological applications.
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| 7. |
- Kneissl, Lucas M., et al.
(författare)
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Mechanical properties and tribological performance of polyoxymethylene/short cellulose fiber composites
- 2023
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Ingår i: Polymer testing. - : Elsevier Ltd. - 0142-9418 .- 1873-2348. ; 128
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Tidskriftsartikel (refereegranskat)abstract
- Natural fibers are promising bio-based materials to use as reinforcements in polymer composites as often more affordable and accessible alternatives to fossil-based fibers, especially because of their superior sustainability. Polyoxymethylene (POM) is a widely used engineering thermoplastic, which has a melting temperature suitable for processing with natural fibers. In this study, such composites consisting of POM and regenerated cellulose fibers have been developed and studied in terms of their mechanical, thermal, tribological and structural properties. Tensile and flexural moduli increased with incorporation of 30 wt% fibers up to 89% and 79% respectively, crystallinity increased as well by a maximum of approx. 11% at 30% fiber content. Furthermore, the specific wear rate was improved for the composite with 10 wt% fibers, showing a decrease of roughly 80%. This study investigates the processing parameters and tribo-mechanical performance of POM-based natural fiber composites as an important route towards future sustainable polymer composites in load bearing applications.
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| 8. |
- Pusavec, Franci, et al.
(författare)
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Tribology of solid-lubricated liquid carbon dioxide assisted machining
- 2020
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Ingår i: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 69:1, s. 69-72
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Tidskriftsartikel (refereegranskat)abstract
- An investigation is made into the lubrication capabilities of solid-lubricated liquid carbon dioxide (LCO2) in comparison to flood lubrication, straight LCO2 and oil-lubricated LCO2 (MQL). The coefficient of friction is determined via tribological experiments, similar to machining, using an open tribometer which features an uncoated carbide insert sliding against a workpiece. Tribological experiments reveal superior performance of solid-lubricated LCO2. The milling experiments as well indicate that solid-lubricated LCO2 significantly reduces wear. The machined-surface topography is examined using high-magnification SEM, which shows no presence of adhered solid particles on the workpiece surface, providing a completely dry machining process.
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| 9. |
- Vadivel, Hari Shankar, et al.
(författare)
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Do the particle size, molecular weight, and processing of UHMWPE affect its thermomechanical and tribological performance?
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854. ; 12, s. 1728-1737
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Tidskriftsartikel (refereegranskat)abstract
- UHMWPE has exhibited excellent performance when used as contact surfaces in tribological contacts. Traditionally, only UHMWPE grades, with narrow particle size and molecular weight distribution, have been deemed suitable for such applications. Now, various UHMWPE grades are available that are different from each other based on their particle size and molecular weight distribution. The question of whether the particle size of UHMWPE affects its performance and properties presents a research gap. The present study attempts to address this question. Additionally, the effect of processing of the UHMWPE is studied. It is observed that although minor differences were observed in the properties of the various grades of UHMWPE, they are inadequate to conclusively determine that the particle size and processing effect the properties and performance of the material.
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| 10. |
- Vadivel, Hari Shankar, et al.
(författare)
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Time-dependent properties of newly developed multiscale UHMWPE composites
- 2022
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Ingår i: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 105
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-high molecular-weight polyethylene (UHMWPE) composites reinforced with Graphene Oxide (GO), Nanodiamonds (ND), and Short Carbon Fibres (SCF) are characterised for their mechanical performance in tensile and short-term creep tests. A methodology to separate and analyse the materials’ viscoelastic (VE) and viscoplastic (VP) responses is applied and evaluated. The results show a clear dependence of the performance on size scale/morphology of the reinforcements. All composites show time-dependent VP responses that can be expressed by Zapas model and fit the experimental data with high accuracy. The analysed VE strains and creep compliance curves reveal the nonlinear stress-dependent VE behaviour of all composites at all tested creep stresses. Combining multiscale reinforcements results in an improvement that surpasses that of individual reinforcements. The results of this work offer valuable input for the design and selection of polymer-based materials in demanding applications where prolonged use under service conditions is critical to their performance.
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