| 1. |
- Andersson, Kjell, 1959-, et al.
(author)
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Design, analysis and testing of a 5-axis solution for water jet cutting
- 2012
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In: NordDesign 2012 - Proceedings of the 9th NordDesign Conference. - : Center for Industrial Production, Aalborg University and Design Society, University of Strathclyde.
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Conference paper (peer-reviewed)abstract
- Abrasive water jet cutting is a technique which utilizes water mixed with abrasives, projected at high velocities to cut a wide range of materials. With a 5-axis solution for angled cutting chamfered cuts of material e.g. for parts that later are going to be welded and thus reducing one manufacturing step can be performed. This paper reports project work made in the MF2004 Machine Design advanced course at KTH. It describes the design and analysis of a first prototype (alpha prototype) of a 5-axis solution as well as the design of a second prototype (beta prototype). The selected concept is a tool center point (TCP) solution where the chamfer angle is realised by two rotations and the TCP position is independent of these rotations.
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| 2. |
- Andersson, Martin, et al.
(author)
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Efficiency and temperature of spray lubricated superfinished spur gears
- 2022
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In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 236:11, s. 2283-2291
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Journal article (peer-reviewed)abstract
- Gearboxes are one of the most power dense systems used today, and in certain instances their limiting factor is the ability to evacuate heat from the gear contact. This work analyses the efficiency (i.e. heat generation) and tooth temperature in the three lubricating conditions dip, into mesh spray and out of mesh spray for superfinished gears which are then compared to ground gears. A back-to-back gear test rig is employed to test maximum contact pressures at the pitch of 0.59 to 0.96 GPa and pitch velocities from 0.5 to 20 m/s at a controlled lubricant temperature of 90 °C. The results show superfinished gears have higher mesh efficiency and lower gear tooth and bulk temperatures, hence lower heat flux compared to ground gears in all lubricating conditions.
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| 3. |
- Bergseth, Ellen, 1979-, et al.
(author)
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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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Conference paper (peer-reviewed)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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| 4. |
- Lindholm, Per, et al.
(author)
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The effect of elasticity in powder metal gears on tooth loading and mean coefficient of friction
- 2018
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In: Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science. - : Sage Publications. - 0954-4062 .- 2041-2983. ; 232:11, s. 2023-2031
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Journal article (peer-reviewed)abstract
- Powder metal gears have a lower density than conventional steel gears due to their intrinsic porosity from the manufacturing process. This also results in a lower elasticity leading to larger deformations and lower contact pressure in a gear contact. By using different modelling tools (namely FEA and available commercial software), the load behavior along the line of action is studied to compare the influence of lower elasticity with standard wrought steel elasticity for FZG-C type gears. A further step is taken analyzing this effect on the mean coefficient of friction through the recalculation of the gear mesh power loss factor. Conclusions observed are differences in load distribution and marginal differences in the gear mesh power loss factor when comparing sintered and wrought steel FZG-C type gears. Sintered steel showed a marginally longer line of action and simultaneously a decrease of the single tooth contact length when compared to wrought steel, while differences in the gear mesh power loss factor proved non-essential due to the spread in previously measured experimental data.
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| 5. |
- Mallipeddi, Dinesh, 1987, et al.
(author)
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Effect of Running-In (Load and Speed) on Surface Characteristics of Honed Gears
- 2019
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In: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 62:3, s. 412-418
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Journal article (peer-reviewed)abstract
- The initial running-in cycles alter the surface integrity characteristics and influence gear performance. This article shows how the surface characteristics of honed spur gears evolved due to the combined effect of running-in load (0.9 or 1.7 GPa) and speed (0.5 or 8.3 m/s) in Forschungsstelle fur Zahnräder und Getriebebau tests. Running-in affected the surface layers to a depth of 5 µm. High running-in load promoted plastic deformation of asperities, created microstructural changes associated with surface cracks, and relaxed residual stresses. It also enhanced the amount of phosphorous from extreme pressure (EP) additives at the surface. The surface contact fatigue failure—that is, micropitting—was promoted by running-in speed rather than load.
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| 6. |
- Mallipeddi, Dinesh, 1987, et al.
(author)
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The effect of manufacturing method and running-in load on the surface integrity of efficiency tested ground, honed and superfinished gears
- 2019
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In: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 131, s. 277-287
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Journal article (peer-reviewed)abstract
- This study compares gear surface characteristics generated by grinding, honing and superfinishing of case-hardened steel, including the evolution during efficiency testing with two different prior running-in loads (0.9 GPa and 1.7 GPa). The most influential factor was surface roughness. Micro-pitting was associated with surface asperities and hence only seen in ground and honed gears, while being absent for super-finished gears. The micro-pitting was enhanced by running-in load, but only for rough surfaces. Deformation-induced localized microstructure impact was associated with cracks. Residual stresses reached similar levels after efficiency testing. Phosphorous content in the gear surface was connected to surface roughness and running-in load.
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| 7. |
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| 8. |
- Sosa, Mario, 1986-, et al.
(author)
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Gear Web Design with focus on Powder Metal - Sound characteristics and web design : Sound characteristics and web design
- 2013
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In: International Conference on Gears. - : VDI Verlag. - 9783180921990 ; , s. 1199-1208
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Conference paper (peer-reviewed)abstract
- The presented work focuses on gear web design using powder metal (PM) by utilizing the finite element method (FEM) to reduce weight and inertia taking into account root bending strength and tooth deflection.A topological optimization is used to determine feasible candidates for different web designs which have as objective to reduce volume. Similar geometric topologies were shown during different loading conditions; and hence, this topology was chosen as a suitable candidate. This candidate was further developed into a parametric model which incorporated the same overall shape shown in the topological optimization. A shape optimization procedure was used utilizing the parametric model having as state variables root bending strength and tooth deflection; and as objective the decrease in inertia, and in consequence weight, of the gear. To analyze a gear which is thoroughly studied, a similar gear to the FZG C type gear is used.Another aspect studied in this paper is the damping properties of three different gears, wrought, conventional PM and double density. Their damping properties are measured using their reverberation time and their frequency response function.Sound characteristics results show that a significant increase in dampening can be observed in PM gears when compared to conventional wrought gears. Finally results from the shape optimizations show how gears can be designed with PM to reduce weight and inertia, with marginal effects on strength and stiffness.
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| 9. |
- Sosa, Mario, 1986-
(author)
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Running-in of gears from a surfacetransformation and efficiency point of view
- 2015
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Licentiate thesis (other academic/artistic)abstract
- Requirements today for machines have moved beyond functionality intoefficiency and reliability, gears are no exception. The presented work focuseson the analysis of the measurement, evolution and effect of running-in on geardrives from a surface roughness and efficiency point of view. With no consen-sus on a definition or observation of running-in of gear drives, measurementsof both efficiency and surface transformation during the predefined running-inis explored. A verified methodology on how to separate form, waviness androughness is presented. Two finishing methods, namely generation groundand superfinished, are analyzed in terms of efficiency and surface characteris-tics as manufactured, after running-in and after efficiency testing in order todetermine the effects of load level during running-in.Results show that separation of form can be achieved with a carefullychosen polynomial, while waviness is more subject to how the user definesa cut-off wavelength for the surface roughness. Ground gears show distinctsmoothening in terms of surface roughness at high running-in load, and nogeneral trend for low load. This behavior is also reflected in the efficiencysince higher loads gave overall lower efficiency after running-in when com-pared to lower loads. Superfinished gears in contrast show no running-in ef-fects in terms of efficiency. Additionally, ground gears exhibit general changein friction and surface roughness during the first cycles of running-in whenanalyzing high load. Overall gains in efficiency can be obtained from running-in; however, at most speeds improvements from polishing a surface, in thiscase superfinishing, proved to lead to higher efficiency.
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| 10. |
- Sosa, Mario, 1986-
(author)
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Running-in of gears - surface and efficiency transformation
- 2017
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Doctoral thesis (other academic/artistic)abstract
- With ever shorter development times and market demands on overall system performance such as efficiency, reliability and low maintenance, accurate predictive tools are necessary and gear drives prove to be no exception. All these characteristics have an impact on a process which has remained a riddle: running-in. Even though no consensus on a definition of this phenomena is readily available, this thesis examines efficiency, surface roughness and simulation through the optics of running-in.Geared transmissions are known for their formidable efficiency and their extreme reliability. However, with an ever increasing power density, the ability to accurately predict mesh losses becomes of utmost importance. The accurate quantification of bearing losses as well as efficiency of ground and superfinished gears under dip lubrication are examined with respect to running-in. Results show a considerable influence on the calculation of gear mesh losses originating from which bearing loss model is chosen. Furthermore, when a larger running-in load is used on ground gears, an increase in efficiency can be observed during working operation, while for superfinished no significant changes are found. These efficiency/frictional changes are also shown to occur in the initial cycles of the running-in phase.From a surface transformation point of view running-in is shown to be a reduction of asperity tips in case hardened ground gears, while in superfinished gears no changes were seen. These gear surface changes were measured with a novel method with a surface profilometer in-situ before, after running-in and after efficiency testing. Results also show that such changes in ground gear roughness profile occur during the very initial cycles.In order to predict running-in, a simulation method was developed. Such method utilizes a 2D surface integral method to simulate contact between rough surfaces, but requires the use of surface hardness and an accurate lower cutoff wavelength. This cutoff wavelength proved to play a pivotal role in determining an accurate contact pressure at the proper level of granularity, hence a well defined real contact area. The predicted and measured run-in surfaces are compared and are found to be in accordance with each other.
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| 11. |
- Sosa, Mario, 1986-
(author)
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The hunt for the correct cell size: Lower wavelength cutoff effect on contact simulation with a focus on running-in
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Other publication (other academic/artistic)abstract
- With the ever increasing drive for higher power density, efficiency and reliability the need to properly predict properties such as real contact area and pressure have become a necessity. These two properties are intrinsically linked to a lowercutoff wavelength, or the level of discretization, used when performing a contact simulation. This article exposes amethod to determine the minimum cutoff wavelength (utilized here in a rough gear contact employing surface hardness)using an initial and a run-in surface. Results in this article show the cutoff wavelength for different gear manufacturingmethods as well as the similarities found between the apparent contact area.
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