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- John, Shobin, 1991-, et al.
(författare)
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Friction between pin and roller of a truck's valvetrain
- 2019
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Ingår i: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics Publishing (IOPP). - 2051-672X. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- In order to minimize the fuel consumption in internal combustion engines, the frictional losses must be minimized between the moving parts such as the sliding bearings. In this study, the sliding friction between the pin and roller in a heavy duty truck engine's valvetrain has been investigated. Three combinations of production components with different surface treatment were used: steel pin with steel roller, steel pin with WS2 coating inside the roller and PVD coated steel pin with steel roller. In-house test rig was used, enabling controlled conditions close to the real engine. A new method for alignment using a laser scanner was introduced together with high resolution tactile measurements of radial displacement during test. Surface topography of pins and rollers was measured before test with a mechanical stylus instrument. The WS2 showed 3.1 times and the PVD showed 2.5 times lower friction than the steel type at low speeds. Even though the friction reduction of WS2 over the PVD is not large, the important advantage is that the WS2 can be manufactured at lower costs than the PVD one. Good correlations among the friction, initial roughness and radial displacements were also found.
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| 4. |
- Vallhagen, Johan, 1965, et al.
(författare)
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Robustness in aerospace components manufacturing and fabrication – a case study
- 2011
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Ingår i: Proceedings of ISABE2011.
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Konferensbidrag (refereegranskat)abstract
- One approach to light weight designs of jet engine components is to fabricate structures instead of making large complex castings. This needs other methodology to design, plan and verify the joining processes and geometry dimensioning and tolerancing of the parts. This case study has used methods and tools for robust design developed for use in the automotive industry. The purpose of the study was to evaluate the methodology on jet engine components.With virtual geometry models, assembly modeling can be done based on locating schemes, describing the kinematics relations of the assembly. The effect of locator disturbances and part error on critical assembly dimensions can be analyzed with respect to three-dimensional effects. The locating schemes have also been evaluated through a measuring process analyzing the repeatability.The conclusion is that the Robust Design and Tolerancing methodology can be applied to the type of fixturing of joining needed for fabrication of parts in the case study and that great improvements can be made optimising the placement of reference points.
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| 6. |
- Bergquist, Annika, et al.
(författare)
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Increased risk of primary sclerosing cholangitis and ulcerative colitis in first-degree relatives of patients with primary sclerosing cholangitis
- 2008
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Ingår i: Clinical Gastroenterology and Hepatology. - New York : Elsevier. - 1542-3565 .- 1542-7714. ; 6:8, s. 939-943
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: The importance of genetic factors for the development of primary sclerosing cholangitis (PSC) is incompletely understood. This study assessed the risk of PSC and inflammatory bowel disease (IBD) among first-degree relatives of patients with PSC, compared with the first-degree relatives of a cohort without PSC. Methods: Subjects from the national Swedish cohort of PSC patients (n = 678) were matched for date of birth, sex, and region to up to 10 subjects without a diagnosis of PSC (n = 6347). Linkage through general population registers identified first-degree relatives of subjects in both the PSC and comparison cohorts (n = 34,092). Diagnoses among first-degree relatives were identified by using the Inpatient Register. Results: The risk of cholangitis was statistically significantly increased in offspring, siblings, and parents of the PSC patient cohort, compared with relatives of the comparison cohort, with the hazard ratios and 95% confidence intervals, 11.5 (1.6–84.4), 11.1 (3.3–37.8), and 2.3 (0.9–6.1), respectively. The hazard ratios for ulcerative colitis (UC) among first-degree relatives of all PSC patients was 3.3 (2.3–4.9) and for Crohn's disease 1.4 (0.8–2.5). The risk of UC for relatives of PSC patients without IBD was also increased, 7.4 (2.9–18.9). Conclusions: First-degree relatives of patients with PSC run an increased risk of PSC, indicating the importance of genetic factors in the etiology of PSC. First-degree relatives of PSC patients without IBD are also at an increased risk of UC, which might indicate shared genetic susceptibility factors for PSC and UC.
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| 7. |
- Dimkovski, Zlate, 1974-, et al.
(författare)
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Functional parameter screening for predicting durability of rolling sliding contacts with different surface finishes
- 2018
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Ingår i: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics Publishing (IOPP). - 2051-672X. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- The reliability and lifetime of machine elements such as gears and rolling bearings depend on their wear and fatigue resistance. In order to screen the wear and surface damage, three finishing processes: (i) brushing, (ii) manganese phosphating and (iii) shot peening were applied on three disc pairs and long-term tested on a twin-disc tribometer. In this paper, the elastic contact of the disc surfaces (measured after only few revolutions) was simulated and a number of functional and roughness parameters were correlated. The functional parameters consisted of subsurface stresses at different depths and a new parameter called 'pressure spikes' factor'. The new parameter is derived from the pressure distribution and takes into account the proximity and magnitude of the pressure spikes. Strong correlations were found among the pressure spikes' factor and surface peak/height parameters. The orthogonal shear stresses and Von Mises stresses at the shallowest depths under the surface have shown the highest correlations but no good correlations were found when the statistics of the whole stress fields was analyzed. The use of the new parameter offers a fast way to screen the durability of the contacting surfaces operating at similar conditions. © 2018 IOP Publishing Ltd.
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| 9. |
- Edholm, Peter, 1974, et al.
(författare)
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Robust Tolerance Design Applied on Robot Concept Development
- 2010
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Ingår i: 8th International NordDesign Conference, NordDesign 2010; Goteborg; Sweden; 25 August 2010 through 27 August 2010. ; , s. 21-30
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Konferensbidrag (refereegranskat)abstract
- A robust tolerance design concept based on locating schemes (for example, used in the car industry for sheet metal parts) and the methods and tools connected to that concept are applied on a new robot development. A case study of a robot assembly is performed in a new robot development project. The robot is mainly designed using machined parts, and traditionally these parts are toleranced using feature-to-feature based tolerances and linear dimensioning. The goal of this case study is to see if there are any advantages to using a new approach when designing robots to enable high geometric quality at a low cost. With limitations, the study shows that it seems possible to effectively use the tolerance design concept in robot development with assemblies consisting of machined parts.
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| 10. |
- El-Ghoul, Zoel-Fikar, et al.
(författare)
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Wear analysis of pin and roller surfaces
- 2019
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Ingår i: 16th International Conference on Metrology and Properties of Engineering Surfaces (Met and Props 2017). - Bristol, UK : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- In this paper three different combinations were evaluated: (i) steel pin vs steel roller, (ii) steel pin vs tungsten disulfide (WS2) coated roller and (iii) PVD pin vs steel roller. The aim of this paper is to properly quantify the topographical variations of the pin/roller surfaces and asses the appropriateness of the measuring technique before and after the tribological tests primarily performed for friction reduction. In-house tribometer was used to test the friction/wear performance of the three different combinations. Surface topographies were measured by white light interferometer (3D) and mechanical stylus (2D). To enable fast relocation on the stylus and interferometer, a 3D printed mask was used. Regarding the pins, Sa, Sk and Svk have been found to follow the wear changes: the lowest wear change for the combination (ii) and highest for the combination (i) but less for the combination (iii). Regarding the changes of Ra on the pin locations where edge contact occurs, the largest changes were found to be for combination (i), followed by combination (ii) and (iii). Ra and Rk change less significantly for the roller surfaces. Good correlations among the friction, initial/final roughness and radial displacements were also found.
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