| 1. |
- Berglund, Kim, 1982-, et al.
(författare)
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A novel reciprocating tribometer for friction and wear measurements with high contact pressure and large area contact configurations
- 2021
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Ingår i: Lubricants. - : MDPI. - 2075-4442. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- There are many moving machine assemblies with conformal tribological contacts at very high contact pressures, e.g., sliding bearings, propeller shaft bearings and machine guideways. Furthermore, applications such as trunnion and guide vane bearing in Kaplan turbines have very low sliding speeds and oscillatory types of motion. Although there is a vast selection of tribology test rigs available, there is still a lack of test equipment to perform friction and wear tests under high contact pressure, reciprocatory sliding and large area contact. The aim of this work is thus to develop a novel reciprocating tribometer and test method that enables friction and wear tests under low-speed reciprocatory sliding with contact pressures up to 90 MPa in a flat-on-flat contact configuration. First, a thorough description of the test rig design is given. Secondly, the influence of contact pressure and stroke length on the tribological properties of a stainless steel and polymer composite material combination is studied. The significance of considering creep, friction during the stroke and contact temperature is specifically highlighted. The novel tribometer can be used to screen different bearing and shaft material combinations and to evaluate the friction and wear performance of self-lubricating bearings for the specific operating conditions found in Kaplan turbines.
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| 2. |
- Mussa, Abdulbaset
(författare)
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A study on wear characteristics of high strength steels under sliding contact
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last decades, significant improvements regarding the design, materials and technology of rock drills have been made. Likewise, in sheet metal forming, forming tools experience very high contact pressures when processing high strength steel sheets. In both applications components operate under extremely tough contact conditions that result in an accelerated component failure. Enhancements on mechanical properties of components material subjected to extreme contact conditions are highly required in order to withstand the application loads and prevent severe wear.The present thesis was focused on understanding of machinery component damage mechanisms under severe contact conditions. A case study of worn components used in rock drilling and sheet metal cold work was carried out. Thread joints from rock drilling and punches from sheet metal pressing were selected for the investigation. For these components, sliding contact under high contact pressure is a common load condition under the components usage. Then, to understand and quantify the influence of contact parameters, load and surface quality on material performance, laboratory simulations were performed. The results were used for a comparative analysis of the typical damage mechanisms observed in the tests and the case study of the components.The case study results showed that the threaded surfaces underwent severe plastic deformation due to the high-pressure sliding contact. The microstructure beneath the worn surface was altered and surface cracks and delamination were frequently observed at the worn surface. The dominant damage mechanism found on the investigated punches was adhesive wear. Material transfer adds friction stresses at the punch surface and ultimately, with repeated punch strokes, it leads to initiation and propagation of fatigue cracks.Wear process in thread joint and punch wear was simulated using the SOFS. The worn specimens tested experimentally showed similar wear mechanisms obtained in the case study. The thread joint wear simulation showed that the total damage at the worn surface was a result of adhesive wear, plastic deformation, and initiation and propagation of fatigue cracks. In addition, the results showed that the type of motion had a significant influence on the worn volume and crack initiation, and more severe wear was observed at reciprocal motion. The punch wear simulation showed that the friction quickly increased as work material from metal sheets transferred to the disc surface. The rate of the material transfer was strongly dependent on the combination of sheet material and tool steel. Further, the present experimental simulations were applicable to characterize and predict wear of components in the application.
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| 3. |
- Almqvist, Andreas, et al.
(författare)
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Selected papers from those presented at the 3rd International Tribology Symposium of IFToMM
- 2014
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 26:5, s. 273-275
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Selected papers presented at the 3rd International Tribology Symposium of the International Federation for the Promotion of Mechanism and Machine Science (IFToMM) are discussed. The 3rd International Tribology Symposium of IFToMM was organized by the Division of Machine Elements of Luleå University of Technology in Sweden from March 19 21, 2013. The symposium was held in the university campus, providing a perfect forum for the tribologists for presenting their latest research and exchange of ideas. The participants were also given the opportunity to experience the snowy landscape during a memorable outdoor dinner. The symposium attracted 146 participants from 26 countries along with 92 papers spread over 32 sessions. These papers covered the fundamental and applied aspects of wide ranging topics such as friction, wear, lubrication, lubricants, tribology in hostile environment, tribomaterials, solid lubricants, surface engineering, and tribotesting.
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| 4. |
- Bara, Özlem, et al.
(författare)
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Adhesion and tribological properties of TiTaBN coatings with a graded interlayer deposited by pulsed DC biased and continuous dc biased magnetron sputtering
- 2015
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Ingår i: Journal of Adhesion Science and Technology. - : Informa UK Limited. - 0169-4243 .- 1568-5616. ; 29:18, s. 2006-2019
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Tidskriftsartikel (refereegranskat)abstract
- The properties of TiBN-based coatings are significantly affected by adding alloying elements and coating parameters. Therefore, in this study, TiTaBN coatings with graded interlayer (CWGIL) were deposited on D2 steel substrates by pulsed DC biased (PDCB) and continuously DC biased (CDCB) closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical, adhesion and tribological properties of the coatings were analysed with EDS, SEM, XRD, microhardness, scratch testing and a pin-on-disc tribo-tester (under various atmospheric conditions). TiTaBN CWGIL deposited by PDCB magnetron sputtering (MS) had a very dense microstructure, high hardness and a high critical load value. TiTaBN CWGIL deposited by PDCB MS had a lower friction coefficient, the wear rate and the penetration depth in all atmospheric conditions. In conclusion, the application of a PDCB substrate instead of a CDCB one dramatically increases the performance of CFUBMS-deposited TiTaBN coatings.
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| 5. |
- Courbon, Cedric, et al.
(författare)
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Adhesion tendency of PVD TiAlN coatings at elevated temperatures during reciprocating sliding against carbon steel
- 2015
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 330-331, s. 209-222
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Tidskriftsartikel (refereegranskat)abstract
- This work focussed on assessing the contact conditions driving the adhesion tendency of PVD TiAlN coated cemented carbide during reciprocating sliding against a normalized AISI 4137 carbon steel. A special emphasis is given to the surface topography of the coating. Results are analysed in terms of friction and material transfer over a large range of temperatures (up to 800 °C) and contact pressures. The post-test surface analysis of the specimens is conducted in order to understand the tribological behaviour and elucidate the formation mechanisms of transfer layers. A numerical model is developed to assess the amount of heat effectively transmitted into the first bodies and the temperature of the surfaces in contact.Whereas temperatures close to 400 °C ensure the formation of a stable tribofilm reducing friction, the highest temperatures lead to unstable frictional behaviour. Coating surface topography has been seen to be a major parameter driving material transfer during the first stages of the contact and the formation of a transfer layer. Thin and homogeneous layers are almost instantaneously formed with a polished surface whereas some time is required with a rougher one to form a film. A large amount of the frictional power is dissipated into these layers and high temperatures can be reached at the surface due to frictional heating. Contact pressure is found to be a parameter promoting transfer and oxidation
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| 6. |
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| 7. |
- Das, Sanjeev, et al.
(författare)
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Effect of static and dynamic ageing on friction and wear behaviour of aluminium 6082 alloy
- 2012
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Ingår i: 15th Nordic Symposium on Tribology - NordTrib 2012. - Trondheim : Department of Geography, Norwegian University of Science and Technology.
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Konferensbidrag (refereegranskat)abstract
- In recent past, warm forming processes have been used successfully to increase the strength of age-hardenable alloys by dynamic precipitation. However, the influence of dynamic age hardening on the wear and friction behaviour of age-hardenable aluminium alloy is not clear. Therefore, in the present investigation the effect of static and dynamic ageing on the friction and wear behaviour of aluminium 6082 alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The aluminium samples used in the present study were in as-cast, solitionised and peak aged conditions. Optical microscope revealed the presence of dendritic structure in both as-cast and solitionised samples. Scanning electron microscope analysis of the debris and worn surfaces revealed the wear mechanism and role of precipitates on the friction and wear results. At low temperature (40 C), the frictional behaviour of as-cast, solitionised and peak aged samples were similar. The wear rates at 40 C increased with increase in the amount of strain inside the specimens due to fine precipitations. At 180 C, a significant variation in the frictional behaviour of different specimens was observed. The wear rate of solitionised specimens at 180 C is higher compared to as-cast and aged specimens. The absence of hard phases at initial stage of the test and subsequent dynamic precipitates restricted to a thin layer were responsible for the increase in wear rate.
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| 8. |
- Das, Sanjeev, et al.
(författare)
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Effect of static and dynamic ageing on wear and friction behavior of aluminum 6082 alloy
- 2013
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 60, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation the effect of static and dynamic ageing on the wear and friction behavior of aluminum alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The AA 6082 alloy samples used in the present study were in as-cast, solutionized and peak aged conditions. Scanning electron microscope analysis of the debris and worn surfaces revealed the role of precipitates on the dry sliding wear behavior. Frictional behavior varies significantly for all the conditions at elevated temperature (180 °C) compared to room temperature (40 °C). Such response was attributed to the dynamic precipitations during elevated temperature test.
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| 9. |
- Decrozant-Triquenaux, Justine, 1994-, et al.
(författare)
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Effect of Surface Engineered Tool Steel and Lubrication on Aluminium Transfer at High Temperature
- 2021
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 477
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Tidskriftsartikel (refereegranskat)abstract
- Hot stamping is characterised by severe contact conditions, especially when forming aluminium components. In order to improve the tool lifetime, process economy, and component quality, understanding the initiation mechanisms behind aluminium transfer onto the tool surface at high temperatures is critical. To date, the tribological interaction between tools and aluminium sheets at high temperature has received limited attention. Lubricants, combined with surface engineering techniques (e.g. coatings, nitriding and surface topography control), show great potential for reducing the severity of material transfer at high temperatures. However, there is still, limited knowledge about their interaction and performance in this tribological context. In this study, high temperature tribological tests were carried out to characterise the synergetic effects of surface coatings/treatments with and without lubrication on friction and wear. A commercially available lubricant was evaluated when used in combination with uncoated, nitrided and CrWN- or DLC ta-C-based PVD coated tool steel. The tests were carried out on a hot strip drawing tribometer, employing an open contact configuration representative of the hot stamping contact conditions at two different temperatures. The counter-material was a 6082 aluminium alloy, heated up following a thermal cycle relevant for the hot stamping process. The results showed that the tribological response was highly dependent on the retention of the lubricant in the contact and the type of surface modification technique. The results show that bonding of the lubricant to the tool surface is critical. In the case of lubricant failure, severe adhesive wear and aluminium transfer onto the tool surface occurred, correlated with an increase in friction. The use of different surface engineering methods led to different results: lower friction levels could be reached when combining use of lubricant and PVD coatings compared to using uncoated or plasma nitrided tool steel. In this study, the best combination to minimise aluminium transfer and friction is the association of the lubricant with CrWN PVD coating in this study.
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| 10. |
- Decrozant-Triquenaux, Justine, 1994-, et al.
(författare)
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Effect of Surface Engineered Tool Steels on Frition and Wear During Sliding Against Aluminium at High Temperatures
- 2018
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Konferensbidrag (refereegranskat)abstract
- Usage of high-strength aluminium alloys is increasing for automotive applications due to high strength-to-weight ratios. Limited formability at room temperature requires hot forming for production of complex geometries. The occurrence of severe adhesion and material transfer negatively affects process economy and there is a need for effective solutions to overcome these issues. This work is focussed on the high-temperature tribological behaviour of Al6016 alloy and uncoated/PVD coated tool steels. Studies were conducted under dry and lubricated conditions using a high-temperature reciprocating tribometer. High friction in dry sliding for uncoated and coated tool steels was observed. Hexagonal boron nitride lubricant was not effective in reducing friction. DLC coating with a polymer lubricant resulted in the lowest friction and minimised material transfer.
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