| 1. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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A note on the pitting life of IQ steel versus 16MnCr5 steel in a back to back gear test rig
- 2018
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Konferensbidrag (refereegranskat)abstract
- IQ-steel is isotropic (i.e. equally strong in all directions), cleaner, and with less inclusions than 16MnCr5 regular gear steel (RS). IQ-steel is used in diesel inlets and for bearings but to date has not been used for gears. Previous studies, has shown good potential to increase the bending fatigue life of gears. The method in this study is a mechanical test procedure to determine the pitting load capacity of gear transmission lubricants, but with the focus on comparing the pitting load capacity of the two steel types IQ-steel with RS. Times to failures, photographs of the fatigue damage are presented in the study. Gear teeth from each steel type were analysed using SEM. The results, which are based on six tests in total (three IQ-steel and three RS-steel gear pairs), indicate that the IQ-steel may have at least similar surface capacity as the regular steel.Keywords: Pitting life, Gear, IQ-steel
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| 2. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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A Wear Detection Parameter for the Wheel–Rail Contact Based on Emitted Noise
- 2019
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Ingår i: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 62:3, s. 496-503
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Tidskriftsartikel (refereegranskat)abstract
- This article describes how a wheel–rail wear detection parameter based on noise was developed by running a rapid transit train instrumented with microphones in a depot with a small curve radius. This full-scale test made use of previous knowledge gained from lab-scale tests. The lab- and full-scale tests showed that noise could be used as an indicator of wear transition, when normal wear turns into severe or catastrophic wear. This transition was accompanied by a significant increase in sound pressure and a broader sound pressure amplitude spectrum; that is, a narrow initial amplitude distribution in the normal wear regime and a broader distribution in the severe wear regime. The measured noise from the inner/low and outer/high rails was analyzed in conjunction with the wear from the outer wheel and comparisons were made between cleaned (exposed to severe wear) and lubricated (no wear) rail. Based on those analyses, a wear detection parameter criterion was developed for this specific train. This wear parameter has been implemented in a real-time condition monitoring system so that warnings of the risk for severe wear could be sent to the maintenance department. Validation of the wear parameter and challenges linked to open system conditions are discussed in this article.
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| 3. |
- Bergseth, Ellen, et al.
(författare)
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Effect of Gear Surface and Lubricant Interaction on Mild Wear
- 2012
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 48:2, s. 183-200
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a twin-disc test machine was used to simulate a rolling/sliding gear contact for three surface finishes, each run with two types of lubricants, thus seeking to develop insight into the tooth flank/lubricant tribological system. The test disc surfaces were case-carburised before the surfaces were produced by: transverse grinding followed by a mechanical abrasive polishing process; transverse grinding only; and transverse grinding followed by preheating as a final finishing step (intended to enhance the build-up of an easily sheared surface boundary layer using a sulphur additive). The twin-disc contact was lubricated with an ester-based environmentally adapted lubricant or a polyalphaolefin-based commercial heavy truck gearbox lubricant. To obtain information about the composition of chemically reacted surface layers, the specimens used were analysed using glow discharge-optical emission spectroscopy. The results indicate that the interactions between different surface finishes and lubricants have different impacts on friction behaviour, wear and the reacted surface boundary layer formed by the lubricant. Running a smooth (polished) surface with the appropriate lubricant drastically reduces the friction. Surface analysis of the ground surfaces gives clear differences in lubricant characteristics. The commercial lubricant does not seem to react chemically with the surface to the same extent as the EAL does. Micropitting was found on all ground discs with both lubricants, though at different rates. The highest amount of wear but less surface damage (i.e. micropits) was found on the preheated surface run with the commercial lubricant.
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| 4. |
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| 5. |
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| 6. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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Effects of thrust washer bearing surface characteristics on planetary gear train wear
- 2019
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 432-433
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Tidskriftsartikel (refereegranskat)abstract
- Thrust washers in spur planetary gears are placed between the planet wheel and planet carrier and act as spacers and wear pads. Metal to metal sliding contact between the planet wheel – washer – carrier causes frictional power losses that, combined with starved lubrication, may cause high contact temperatures and thermo-mechanical effects that potentially trigger thermo-elastic instabilities and excessive local wear. The planetary gear system would benefit from a low-friction interface between the washer and the planet wheel. Five washers with different surface treatments were tested in a full-scale gear rig. These tests were also replicated as closely as possible in a pin-on-disc tribometer. The following types of finishing material treatments were studied: a chemical nickel coating plus polymer on a nitro-carburised surface, a combination of nitro-carburization and solid lubricant layers, electroless deposited chemical nickel coating plus polymer, nitro-carburizing, and manganese phosphating. The frictional results indicate that tribometer tests can be used to compare and classify new washer materials. Lab scale tests show that a new experimental self-lubricating tribomaterial that was applied with laser cladding has a promising potential to increase planetary gear train robustness and service life, especially if the surface is fine grinded.
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| 7. |
- Bergseth, Ellen, 1979-, et al.
(författare)
-
EXPERIENCES OF STUDYING GEAR TRIBOLOGY IN A FZG TEST SET-UP
- 2018
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Konferensbidrag (refereegranskat)abstract
- The main objective of this study is to review the last decade of experimental work in the field of gear pitting life andefficiency of an FZG gear test rig. Located at KTH Machine Design, the FZG rig has led to critical findings with an impacton gear transmissions, such as high efficiency and long fatigue life. The different FZG test set-ups, the sampling methodsand the results (and their limitations) are discussed, and measures are proposed to reduce the limitations. The findingsof this study are used as input to an impact case on how research at a university can provide the major transportindustry in Sweden with the knowledge and the methods to evaluate gear performance.
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| 8. |
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| 9. |
- Bergseth, Ellen, et al.
(författare)
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Influence of real surface topography on the contact area ratio in differently manufactured spur gears
- 2012
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 56, s. 72-80
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Tidskriftsartikel (refereegranskat)abstract
- Surface topography measurements from spur gears produced using four different manufacturing methods were used as input to a contact analysis programme. All test gears were case-hardened, two gears were machined in the hardened state using honing and grinding respectively, and two gears were machined in the non-hardened state using hobbing and hobbing followed by green-shaving respectively. The results show that the surface topography caused by the manufacturing methods has a large influence on the real contact area in the early life of the gear. The green-shaved gear surfaces and the honed gear surfaces have the highest contact area ratio after manufacturing (as-manufactured), which could be advantageous for future gear life with respect to e.g. the running-in process.
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| 10. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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Investigation of pitting resistance in ultra clean IQ-Steel vs commonly used conventional steel; 158Q vs 16MnCr5 : Back-to-back pitting tests
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- KTH Machine Design has conducted pitting tests on gears made out of two different types of steel in a standard back-to-back pitting test rig (FZG). The tested gears were produced from Ovako’s IQ-Steel in grade 158Q and compared to the behaviour of a reference steel, commonly used conventional steel in grade 16MnCr5 (reference steel, RS). The test method is a mechanical test procedure generally used to determine the pitting load capacity of gear transmission lubricants, but in this study the purpose was to compare the pitting load capacity of the two steel types. The report is based on the test procedure described in FVA – Information sheet Research Project No. 371 (Practice Relevant Pitting Test) with minor changes. Time to failure and photographs of the fatigue damages are presented in this report. One gear tooth from each steel type was analysed using SEM. The results, which are based on six tests in total (three gear pairs IQ-Steel and three RS-steel), indicate that the IQ-Steel has better surface durability than the reference steel. To better understand the mechanisms involved, further tests are suggested.
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| 11. |
- Bergseth, Ellen, et al.
(författare)
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Logarithmical Crowning for Spur Gears
- 2010
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Ingår i: Strojniski vestnik. - 0039-2480. ; 56:4, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalignment (e.g. assembly deviations). Lead crowning means that the tooth centre is slightly thicker than the tooth edges and is usually described as a circular arc profile. The use of crowning shifts the peak load from the tooth flank edges and, therefore, reduces the risk for high contact pressures at the edges, which can otherwise result in a shortened service life. In this study a logarithmical lead profile was compared with traditional lead profile modifications for gears. The profiles were applied on a spur gear pair and a numerical method for contact analysis was used to calculate the contact pressure distribution at the pitch diameter. All lead profiles were optimised with respect to low contact pressure at a specific normal load, a specified maximum misalignment in the plane of action and a tooth flank edge contact criteria. The results show that the logarithmical profile responds differently to misalignments compared to the traditional lead profile modifications. The logarithmical profile resulted in lower maximum contact pressures for small misalignments and is, therefore, of further interest in terms of achieving a robust gear design. (C) 2010 Journal of Mechanical Engineering. All rights reserved.
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| 12. |
- Bergseth, Ellen, 1979-
(författare)
-
On tribological design in gear tooth contacts
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The correct tribological design will have a considerable effect on a gear’s service life and efficiency. The purpose of this thesis is to clarify the impact of variation in the gear tooth flank tribological system on the gear contact load capacity – to increase the understanding of how surface topography and lubricant interact.In this thesis the variation in surface topography inherent in the manufacturing method has been shown, by experimental work and computer simulations, to be an important factor for the contact condition in the early life of gears. Surface analysis revealed that the formation and composition of surface boundary layers depends strongly on the chemical composition of the lubricant, but also on pre-existing surface boundary layers. Additionally, surface boundary layers play a major role in frictional behaviour, wear and in allowing the lubricant to react properly with the surfaces.Paper A presents the current ISO 6336 calculation of surface durability. A robust design approach was used to investigate the extent to which the current standard for calculation of surface durability allows for manufacturing variations and the choice of lubricant.Paper B investigates the extent to which a logarithmical profile modification can increase gear contact pressure robustness compared to traditional lead profiles for gears.Paper C compares different gear manufacturing methods and their as-manufactured (fresh unworn) surface topographies, using measured surface topographies as input to a contact simulation program.Paper D examines surface boundary layer formation and the corresponding wear in relation to different anti-wear additives in an environmentally adapted base oil.Papers E and F make use of specimens with surface topographies imitating two gear manufacturing methods (grinding and superfinishing) to be used in a twin-disc and barrel-on-disc machine respectively. The contacts are analysed by friction measurements and simulations combined with methods for surface analysis.
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| 13. |
- Bergseth, Ellen, 1979-, et al.
(författare)
-
Study of surface roughness and surface orientation on friction in rolling/sliding contacts: barrel-on-disc versus twin-disc
- 2017
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Konferensbidrag (refereegranskat)abstract
- Gears are one of the most important means of mechanical power transmission. Even though the efficiency is high for a gear pair today, further decrease in friction can contribute to lower the fuel consumption. A barrel-on-disc machine (same setup as ball-on-disc) to simulate a rolling/sliding gear contact was used to study the impact of manufacturing method, grinding and superfinishing, on friction. To evaluate the extent to which friction and wear can be diminished by reducing surface roughness and changing surface orientation. Measurement results showed that the change of lubricant had an impact on friction in the mixed to boundary lubrication regimes similar to that of the change of main surface orientation. The results were compared with those from a parallel study involving a twin-disc machine, also used to simulate rolling/sliding contacts (see Figure). Measurements and simulations showed that the barrel-on-disc and twin-disc setups reflected the same friction trends. However, the friction coefficient using the barrel-on-disc setup was almost twice as large as that found using the twin-disc machine. The wear mechanisms also differed: micropits occurred on discs used in the twin-disc set-up whereas normal or no wear was found on the barrel-on-disc specimens. The difference in contact geometry is believed to be the main reason for the higher friction level in the barrel-on-disc machine. A computer contact analysis was used to clarify the differences using perfectly smooth and computer-generated textured surfaces.
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| 14. |
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| 15. |
- Bergseth, Ellen, 1979-, et al.
(författare)
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Study of Surface Roughness on Friction in Rolling/Sliding Contacts : Ball-on-Disc Versus Twin-Disc
- 2020
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 68:2
-
Tidskriftsartikel (refereegranskat)abstract
- Although the efficiency of a gear pair is currently high, a better understanding of surface/lubricant contribution on efficiency is critical. Electrified drivelines will, for example, impose higher speed and alternate loading, and it is expected that these new conditions will, to a greater extent, rely on the surface/lubricant characteristics. Phenomena taking place in the gear contact is often measured using ball-on-disc and twin-disc tribometers. In this study, these two test set-ups were compared in order to assess differences in the behaviour of surface/lubricant interactions. Results showed that ball-on-disc and twin-disc set-ups reflect the same friction trends. However, the friction results differed by a factor of roughly two, even though the tribometers were set-up to run at the same contact pressure. The wear mechanisms also differed: micropits occurred on discs used in the twin-disc set-up, whereas normal or no wear was found on the ball-on-disc specimens. The contact conditions for the two test set-ups were also analysed using a numerical model. The comparison of these two machines may aid gear designers in selecting the proper experimental set-up for their purpose.
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| 16. |
- Bergseth, Ellen
(författare)
-
Virtual Hobbing
- 2007
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Hobbing is a widely used machining process to generate high precision external spur and helical gears. The life of thehob is determined by wear and other surface damage. In this report, a CAD approach is used to simulate the machiningprocess of a gear tooth slot. Incremental removal of material is achieved by identifying contact lines. The paper presentsan example of spur gear generation by means of an unworn and a worn hob. The two CAD-generated gear surfaces arecompared and showed form deviations.
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| 17. |
- Bergseth, Ellen, et al.
(författare)
-
Wear in environmentally adapted lubricants with AW/EP technology
- 2008
-
Ingår i: Tech. Akad. Esslingen Int. Tribol. Colloq. Proc.. - 3924813736 - 9783924813734
-
Konferensbidrag (refereegranskat)abstract
- Mineral oil based lubricants are dominating the market still. However, there is now a broad range of environmentally adapted lubricants (EAL) based on both natural and synthetic esters. Wear was studied in a pin-on-disc-machine giving the wear coefficient. The surface reactions formed by the additives were examined. The studied lubricants were formulated with a complex ester as the base fluid. The wear number decreased with increasing reacted surface layer depth as well as with increasing oxide layer. A highly polar base fluid gave relatively low wear numbers even without additives. This is an abstract of a paper presented at the 16th International Colloquium Tribology Lubricants Materials and Lubrication Engineering (Stuttgart/Ostfildern, Germany 1/15-17/2008).
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| 18. |
- Bergseth, Ellen, et al.
(författare)
-
Wear in environmentally adapted lubricants with AW technology
- 2008
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 1557-6841 .- 0265-6582. ; 25:4, s. 137-158
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to examine the tribofilm formation and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants, i.e. when using synthetic ester base fluids with different anti-wear additives. AW additives of the following types were studied: phosphorus, sulphur–phosphorus and sulphur–nitrogen together with an additive based on carbon, hydrogen, oxygen and nitrogen chemistry. In addition, the base fluid itself was tested.Wear was studied in a pin-on-disc-machine giving the wear coefficient. The surfaces were analysed by glow discharge-optical emission spectroscopy, revealing the surface reactions formed by the additives. The results indicate that the wear number decreases with increasing reacted surface layer depth as well as with increasing oxide layer depth. Also, the results indicate that a highly polar base fluid give relatively low wear numbers even without additives.
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| 19. |
- Bergstedt, Edwin, et al.
(författare)
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Gear micropitting initiation of ground and superfinished gears : Wrought versus pressed and sintered steel
- 2021
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 160
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with CPT gears. The materials are wrought steel (16MnCr5) and a commercial powder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding and superfinishing. Experimental results show that the superfinishing prevented micropitting, but led to premature failure due to cracks in the root caused by tip-to-root interference. Micropitting was initiated at a higher load stage for the powder metallurgical steel compared to the ground wrought steel. The failure mechanisms were similar between materials with the same surface finish. The powder metallurgical steel showed subsurface initiated fatigue compared to the wrought ground steel having surface-initiated fatigue. Testing new finishing methods and materials, one has to be aware of the influence of the gear micro geometry.
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| 20. |
- Bergstedt, Edwin, 1986-, et al.
(författare)
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Gear Micropitting Initiation of Ground and Superfinished Gears: Wrought versus Pressed and Sintered Steel
-
Ingår i: Tribology International. - 0301-679X .- 1879-2464.
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with C-PT gears. The materials are wrought steel (16MnCr5) and a commercialpowder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding andsuperfinishing. Experimental results show that the superfinishing prevented micropitting, but ledto premature failure due to cracks in the root caused by tip-to-root interference. Micropitting wasinitiated at load stage 8, and 9 for the ground wrought, and powder metallurgical steel respectively.The failure mechanisms were similar between materials with the same surface finish. The powdermetallurgical steel showed subsurface initiated fatigue compared to the wrought groundsteel having surface-initiated fatigue. Testing new finishing methods and materials, onehas to be aware of the influence of the gear micro geometry.
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| 21. |
- Hjelm, Rikard, et al.
(författare)
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A multi-perspective method for gear efficiency and contact analysis
- 2023
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Ingår i: Results in Engineering (RINENG). - : Elsevier BV. - 2590-1230. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Modern gearing applications, in particular electrification, impose new challenges in many different fields of engineering and research. In specific, new demands are imposed on gears, including higher rotational speed, lower noise acceptance, and increased efficiency, as well as increased resistance against pitting and scuffing. To meet these demands, a better understanding of gear contacts is needed. The Eurostars project Effigears proposes a novel multi-perspective methodology for assessment of gear efficiency and contact analysis. The methodology consists of using a novel surface treatment method, Triboconditioning (R), implemented in a streamfinishing process, surface measurements using a scattered light method, experimental testing using the standardized FZG test rig, and contact simulations using a novel thermal elasto-hydrodynamic lubrication tool. It is found, in preliminary tests, that enhanced gear performance may be enhanced due to Triboconditioning (R) surface treat-ment. Findings also include better understanding of how surface characteristics and lubricants affect scuffing and pitting, and the effect of load distribution on gearset behavior.
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| 22. |
- Höjer, M., et al.
(författare)
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A noise related track maintenance tool for severe wear detection of wheel-rail contact
- 2016
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Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110
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Tidskriftsartikel (refereegranskat)abstract
- An on-board measurement system has been developed that in real time identifies the probability for occurrence and also the exact location of severe wear in the wheelrail contact. Noise generated by the wheel-rail contact is a troublesome side effect both when railway vehicles negotiate curves and run on straight tracks. The concept behind this project is to use this noise as an indicator of the transition from the mild wear regime to the severe/catastrophic wear regime that implies high maintenance cost. At first tribometers were used in a laboratory study to investigate the relationships between wear and the emitted noise. Wear transitions from mild to severe wear were always accompanied by an increase in sound pressure of about 10 dB. The transitions also changed the sound pressure amplitude distribution from a narrow banded to a broader banded distribution. Secondly a full scale test in a small radius curve in a depot was carried out using a metro train, type C20. In agreement with the laboratory tests, the same kind of transfer from mild to severe wear was identified on the full scale tests in the depot. In addition, the sound pressure changed significantly, both in amplitude and in distribution, when transferring from mild to severe wear. By comparing the noise from the inner wheel-rail contact to noise from the outer wheel-rail contact a wear detection parameter for the outer wheel-rail contact is suggested. The third part of this project involves validation of the maintenance tool by operating the instrumented train in normal metro traffic, while at the same time collecting wear particles and making replicate casts of the rail at critical locations in the metro. Further comparison with weather data and a maintenance log has also been performed.
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| 23. |
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| 24. |
- Kumar, Mayank, 1991-
(författare)
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Friction in threaded fasteners : Influence of materials and tooling
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Threaded fasteners represent the most common type of machine element, with a unique function that facilitates ease of assembly and disassembly. This ease of disassembly allows machine parts to be reused, refurbished, and recycled. Easy as these components are to assemble, several factors must be considered to achieve the desired clamp force and to utilize the fastener to its full load capacity. The research presented in the thesis compares different tightening strategies and assembly tools to show that the clamp force and it´s scatter are influenced by the variation in the coefficient of friction (CoF) to a much larger extent than by the accuracy of an assembly tool. The research therefore focus on understanding the frictional response in a threaded fastener joint during tightening.A range of design and assembly factors are considered to identify how to increase reliability of the threaded fastener joints. These factors include tightening speed, coating, surface topography, fastener storage conditions, cutting fluid residue and joint material. A torque-controlled, two-step tightening method was mainly used in the studies as it is widely practiced across the production floor of the motor vehicle and general industries to tighten threaded fastener joints. A state-of-the-art friction test rig (FTR) was built to quantify variations in the CoF in the thread and under-head contacts during tightening. Coatings and contact surfaces are also characterized using SEM, FIB, indenters, and optical microscopes to gain an insight to find the likely reasons behind CoF variation. Fasteners with different Zn-based coatings were tightened on plates with surface topographies similar to those found in the motor vehicle industry. The samples were not cleaned before the testing but used "as-received" from the supplier. The degree of damage to the joint surface and fastener thread from the tightening depends on the hardness of the coating. The hardest coating (Zn-Ni) remained relatively unchanged but gave twice as high CoF in the under-head contact compared to the softest coating (Zn-flake). The under-head friction often dominates the tightening process and may be significantly affected by the joint surface topography and the level of cleanliness. In the automotive industry, many parts to be assembled are not thoroughly cleaned, increasing the risk of cutting fluid residue on the joint surface. Different types of cutting fluids were compared in a study with fasteners tightened against “as-received" and cleaned plates. It was shown that CoF might drastically decrease depending on the coating and cutting fluid types. An ester-based fluid performed best, providing the lowest CoF in the under-head contact due to its higher viscosity and polarity. A water-based fluid showed a significantly larger scatter. Water can also influence friction due differences in humidity and temperature. Sometimes fasteners are stored outside a factory which could lead to water diffusion in the coating in hot-humid climate or condensation of water on the fastener surface when it is brought from the outside storage at sub-zero temperatures into the production hall. Water on the coating and inside of it could lead to low CoF, with overtightening and fastener failure as a result. Four Zn-based coatings were compared and showed different response depending on the coating structure and topcoat. Another way to reduce CoF is to use variable speed tightening. It will also increase productivity, as it is faster. It will also improve operator ergonomics, as it gives much lower reaction torque. Much higher CoF was found for EPZ coating when tightened at a constant and very low speed, 5 rpm, due to cohesion that resulted in material transfer, compared to CoF during high, variable speed tightening. At the same time, speed had negligible influence on the CoF when using soft Zn-flake coating as the coating easily sheared off, acting as a solid lubricant.A soft coating is also practical when used in contact with parts made using additive manufacturing (AM). The AM parts are often rough, but a soft coating can mitigate an increase in the under-head CoF. An interesting finding was that the cheapest solution of using an uncoated fastener works very well. An anti-corrosion oil on the plain fastener helped in achieving low CoF. When the AM plate was machined, the CoF and surface damage significantly increased due to the lay of the surface topography created by machining. The findings presented in the thesis increase understanding of how various design and assembly factors govern friction in the thread and under-head contacts. The under-head contact dominates friction response. A proper selection and adjustment of these factors will help design engineers to optimize joint designs and achieve high fastener strength utilization.
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| 25. |
- Li, Xinmin, et al.
(författare)
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Pin-on-Disc Study of Tribological Performance of Standard and Sintered Gear Materials Treated with Triboconditioning Process: Pre-treatment by Pressure-induced Tribo-film formation
- 2017
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Ingår i: Tribology Transactions. - : Taylor & Francis Group. - 1040-2004 .- 1547-397X. ; 60:1, s. 47-57
-
Tidskriftsartikel (refereegranskat)abstract
- oating is one of the innovative approaches used to improve the wear resistance and load-carrying capacity of surfaces in rolling-sliding contact, such as gears and rolling element bearings. In this study, the tribological performance of standard gear material (16MnCr5) and two kinds of powder metallurgy (PM) gear material (Distaloy AQ + 0.2% C and Astoloy 85Mo +0.2% C) with and without tribofilms formed by a pre-treatment were evaluated. Specimens treated with the pre-treatment and the substrate is subjected to pin-on-disc tests under boundary lubrication conditions. The friction and wear performance of the two different PM gear materials with the pre-treatment formed tribo-film were compared to RS-RS (16MnCr5 material disc and pin combination) for reference. It was found that the pre-treatment lowers the friction coefficient and enhances the wear resistance of pins because of the tribo-film formed. The tribo-film caused good running-in due to the existing of and Fe and W oxides. Mo-Mo (Astoloy 85Mo + 0.2% C material disc and pin combination) and Mo-RS (Astoloy 85Mo + 0.2% C disc and 16MnCr5 pin combination) showed statistically significant higher wear resistance.
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| 26. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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A pin-on-disc study on the tribology of cast iron, sinter and composite railway brake blocks at low temperatures
- 2019
-
Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; , s. 48-52
-
Tidskriftsartikel (refereegranskat)abstract
- Most freight wagons in the EU use cast iron brake blocks. Cast iron brake blocks have a stable braking capability in different environmental conditions, but wear down the wheel tread quickly. Therefore, there is a need to understand the tribology of other brake block materials. A pin-on-disc tribometer placed in a temperature-controlled chamber is used to investigate the tribology of cast iron, sinter and composite railway brake blocks at low ambient temperatures. Pins made from different brake blocks are tested with discs made from steel wheels. Both friction coefficient and wear are evaluated at five different temperatures from + 10 to − 30 °C. The cast iron block demonstrated the greatest wear at − 10 and − 20 °C, due to the ductile-to-brittle transition at low temperatures. The worn graphite from cast iron is likely to become a solid lubricant, reducing the friction at − 10 and − 20 °C. For the composite brake block, a gradual decrease in friction with decreasing temperature was found. The sinter brake block was not sensitive to changes in ambient temperature. The sliding speed in the current study is relatively low and further study at higher speed is suggested in order to evaluate the tribological performance of different brake blocks.
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| 27. |
- Lyu, Yezhe, et al.
(författare)
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Development of a noise related track maintenance tool
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track maintenance tool, in the form of an on-board measurement system. As a first step, lab scale tests using a pin-on-disc tribometer were used in order to distinguish how noise changes when the wear mechanism in a sliding contact shifts from normal wear to severe and catastrophic wear. Once the potential for using sound as an indication of severe wear transitions was established, full scale tests were carried out with a rapid transit (metro) train, type C20. The train was equipped with microphones that continuously measured the sound pressure near the wheel rail contact. In order to provoke severe/catastrophic wear, the test train was run in a curve with small radius, and the rails and wheels were carefully cleaned before the tests. The same kind of transfer from mild to severe/catastrophic wear was identified on the full scale test as in the laboratory scale test, confirmed by studying the surface topography and the morphology of the wear particles. Moreover, the full scale test results showed that the sound pressure changed significantly when transferring from mild to severe wear in agreement with the pin-on-disc test results. By comparing noise from the inner wheel/rail contact to noise form the outer wheel/rail contact a wear indication value for the outer wheel/rail contact is suggested in this study. This value can be seen as an advanced parameter from which the probability of severe wear, in the wheel flange/rail gauge face contact of the outer contact, can be estimated. At present, a real time condition monitoring system is set up in Stockholm (Metro line 1) in order to validate the results.
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| 28. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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Effect of humidity on the tribological behaviour and airborne particle emissions of railway brake block materials
- 2018
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 118, s. 360-367
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Tidskriftsartikel (refereegranskat)abstract
- A pin-on-disc tribometer placed in a one-way ventilated chamber was used to investigate the effect of relative humidity on the tribology and airborne particle emission of three commercial railway brake block materials (grey cast iron, organic composite, and sintered). Cast iron showed the highest friction coefficient, particle emission and wear loss and organic composite exhibited the lowest. The generation of oxide layers on the worn cast iron surface resulted in a decrease in friction, particle emission and wear. Moisture adsorption by the organic composite leads to decreased friction coefficient and particle emission with increasing humidity. Relative humidity does not affect the friction coefficient of the sintered brake block, whose particle emission and wear loss significantly decline with increasing relative humidity.
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| 29. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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On the relationships among wheel–rail surface topography, interface noise and tribological transitions
- 2015
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 338-339, s. 36-46
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Tidskriftsartikel (refereegranskat)abstract
- Noise from the wheel-rail interface is a troublesome side effect when railway vehicles negotiate rail curves and straight tracks. A laboratory study using two pin-on-disc tribometers to simulate the pure sliding process in a wheel-rail contact investigated the relationships between surface topographies, tribological aspects and emitted noise. The influence of five different initial surface topographies manufactured by polishing and grinding (transverse and circular) was studied. Polished samples yielded the highest friction coefficient and wear rate because of strong adhesion. Samples with manufacturing traces vertical to the sliding direction produced the lowest friction coefficient and wear rate, and were dominated by ploughing and abrasion. Samples with manufacturing marks parallel to the sliding direction exhibited a medium level in both fiction coefficient and wear rate; the wear mechanism was combined ploughing-adhesion. Noise emission followed the same pattern as the friction coefficients: the highest sound pressure levels occurred for the polished samples and the lowest for the samples with transverse manufacturing marks. Wear transitions from mild to severe wear were always accompanied by an increase in sound pressure of about 10 dB. The transitions also changed the sound pressure amplitude distribution from a narrow banded to a broader banded.
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| 30. |
- Lyu, Yezhe, et al.
(författare)
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Open System Tribology and Influence of Weather Condition
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The tribology of an open system at temperatures ranging between 3 degrees C and -35 degrees C, with and without snow, was investigated using a pin-on-disc tribometer mounted in a temperature-controlled environmental chamber. The relationship between the microstructure and ductility of the materials and the tribology at the contacting surfaces was investigated. The study shows that during continuous sliding, pressure causes snow particles to melt into a liquid-like layer, encouraging the generation of oxide flakes on the contact path. The friction coefficient and wear rate are dramatically reduced through an oxidative friction and wear mechanism. In the absence of snow, the tribological process is controlled by the low temperature brittleness of steel in the temperature range from 3 degrees C to -15 degrees C. At these temperatures, cracks are prone to form and extend on the worn surfaces, resulting in the spalling of bulk scraps, which are crushed into debris that increases the friction coefficient and wear rate due to strong abrasion. When the temperature falls to -25 degrees C, an ice layer condenses on the metal surfaces and relaxes the tribological process in the same way as the added snow particles, which significantly decreases the friction and wear.
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| 31. |
- Lyu, Yezhe, et al.
(författare)
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The effect of Subzero temperature and snow on the tribology of wheel-rail contact
- 2016
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Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110
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Tidskriftsartikel (refereegranskat)abstract
- The wheel-rail system operates in an open environment where the weather condition varies constantly. In this laboratory study, an investigation using a pin-on-disc tribometer placed in a temperature-controlled room was conducted to examine the effect of subzero temperature and snow on friction and wear at the wheel-rail contact. In temperature range from 3 to-15 °C (without snow) friction and wear were dominated by low temperature brittleness, which led to an increase in friction and wear. When temperature decreased down to-25 °C, an ice layer condensed on the pin and disc surfaces, which then melted during sliding and acted as a lubricant, leading to the sharp decrease of friction and wear. When snow crystals were added into the contact they melted into water droplets during sliding because of pressure melting and reduced the friction and wear following the boundary lubrication mechanism. With increasing temperature from-25 to 3 °C, friction performed monotonously decreasing because of the increasing thickness of the water layer. A large area of oxide flakes generated on the worn surfaces also significantly protected the contacting wheels and rails from severe wear.
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| 32. |
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| 33. |
- Lyu, Yezhe, 1987-, et al.
(författare)
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TRIBOLOGY OF THREE RAILWAY BRAKE BLOCK MATERIALS TESTED AGAINST RAILWAYWHEEL AT LOW TEMPERATURES
- 2018
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Konferensbidrag (refereegranskat)abstract
- Three railway brake block materials, i.e. cast iron, sintered and organic composite, were tested against railway wheel at10, 3, -10, -20 and -30 °C using a pin-on-disc tribometer with regards to the friction and wear performance. At -10 and -20 °C, cast iron tests yielded very high wear losses both on pin and disc samples and low friction coefficient. The largeamount of graphite worn off from the cast iron sample acted as a lubricant. Friction and wear of sintered material arenot sensitive to the change of temperature. Disc sample tested against organic composite at -30 °C showed negativewear loss, indicating that materials were added onto the surface.
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| 34. |
- Mahmood Reza, Khabbazi, 1972-, et al.
(författare)
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Assembly Feature Data Instance Modeling : Prototype Implementation and Outputs
- 2017
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Ingår i: 2017 INTERNATIONAL CONFERENCE ON MECHANICAL, SYSTEM AND CONTROL ENGINEERING (ICMSC). - : IEEE. - 9781509065301 ; , s. 343-347
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Konferensbidrag (refereegranskat)abstract
- This paper introduces the assembly feature data schema instance modeling to pre-examine the schema functionality and output- as the preliminary step for data modeling. In order to link assembly with product design, it is essential to determine which entities of product design are involved at the automated assembly planning and operations. It is possible to assign meaningful attributes (assembly features) to the part model entities in a systematic and structured way. Using object-oriented design, the assembly feature data structure and its relationships are modeled. As a part of the research on product and assembly system data integration within the evolvable production system platform, the instance models for proposed assembly feature data structure provide a deeper understanding and error reduction that might possibly occur at the development of the database. Moreover through instance modeling, the assembly feature data query output format from the database prototype is simulated. An industrial assembly model example with its 3DPart models is chosen to demonstrate the realized assembly feature data set with string data type. The models support the desired simplicity at the database prototype implementation. The output format envisions the interoperability factor between product models and the assembly planning systems.
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| 35. |
- Olofsson, Ulf, 1962-, et al.
(författare)
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Nanoparticle emissions from the transport sector: health and policy impacts - the nPETS concept
- 2023
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Ingår i: 2022 Conference Proceedings Transport Research Arena, TRA Lisbon 2022. - : Elsevier BV. ; 72, s. 248-255
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Konferensbidrag (refereegranskat)abstract
- Road, rail, air, and sea transport generate a major fraction of outdoor ultrafine particles. However, there is no common methodology for comparable sub 100 nm particle emissions measurement. This paper presents the nPETS (grant agreement No 954377) concept to understand and mitigate the effects of emerging non-regulated nanoparticle emissions. This paper presents the concept and selected results. For example, nucleation and condensation mechanisms occur more frequently in the urban background site, leading to new particle formation, while mostly fresh emissions are measured in the traffic site.
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| 36. |
- Sannellappanavar, G., et al.
(författare)
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Towards real time automated early gear failure detection
- 2022
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Ingår i: Tribologia. - : The Finnish Society for Tribology. - 0780-2285 .- 1797-2531. ; 39:3-4, s. 42-44
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Tidskriftsartikel (refereegranskat)abstract
- The ability to stop a gear fatigue test before catastrophic failure has many advantages. However, today, a wide-ly accepted approach is not available. This case study applies a vibration-based condition monitoring methodologyto detect early gear failures. The gear studied takes part in an all-wheel-drive drivetrain system. Vibration signalsfrom four run-to-failure fatigue tests at two constant torque-speed combinations were used as input to time-synchronous averaging and autoregression model generation. The applied methodology shows promising resultsfor early failure detection, and the process is feasible for implementation in an automated environment. Real timeanalysis is also possible since the autoregression model generates a healthy state TSA signal during the early tes-ting stages. However, the time to failure detection varies with operating conditions, with low sensitivity at high-speed and low-torque conditions.
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| 37. |
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