| 1. |
- Alemani, Mattia, et al.
(författare)
-
Dry sliding of a low steel friction material against cast iron at different loads : Characterization of the friction layer and wear debris
- 2017
-
Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 376-377, s. 1450-1459
-
Tidskriftsartikel (refereegranskat)abstract
- Pin-on-disc testing was used to investigate the sliding behavior and the wear products of a low-steel friction material against a cast iron disc at different applied loads, to investigate the effect of the temperature rise induced by frictional heating. The testing rig was operated in a clean chamber with a purified incoming air flux. The outgoing flux carries the wear particles to an impactor that counted and sorted them by average diameter and weight. At increasing applied loads, corresponding to a proportional increase of the pin-disc contact temperature, the coverage of both the pin and disc surface by a friction layer was found to increase too. The relevant X-Ray diffraction patterns revealed the presence of a large amount of graphite and different compounds originating from the friction material and from the counterface disc, mainly iron oxides, as concerns this latter. After the test at the lowest investigated load, i.e., 1 kg, the disc worn surface exhibited abrasive grooves and a discontinuous friction layer mainly made of compacted iron oxide particles. After the test at higher loads, i.e., 5 and 7 kg, the disc surface was covered by a compact friction layer. As concerns the friction layer on the pins, most of the ingredients from the friction material were detected, in association with the iron oxides from the disc. These results can be interpreted in terms of the temperature stability range of the phenolic resin used as a binder of the friction material. The characterization of the collected airborne wear debris showed that the particles produced by the low temperature (i.e., low load) test were mostly equiaxed; whereas those produced by the high temperature (i.e., high loads) tests, predominantly displayed a plate-like morphology. The mechanisms of their formation in relation to the characteristics of the friction layers are illustrated and discussed.
|
|
| 2. |
- Alemani, Mattia, et al.
(författare)
-
On the influence of car brake system parameters on particulate matter emissions
- 2018
-
Ingår i: Wear. - : ELSEVIER SCIENCE SA. - 0043-1648 .- 1873-2577. ; 396, s. 67-74
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of car brake system parameters on particulate matter emissions was investigated using a pin-on-disc tribometer. Samples from a low-steel friction material and a cast iron disc were tested for different sliding velocities, nominal contact pressures and frictional powers. Disc temperatures were also measured. Their impact on total concentration, size distribution, particle coefficient and transition temperature was analysed. Results show that frictional power is the most significant brake system parameter. However, temperature, as a response parameter, is the most influential, inducing a shift towards the ultrafine particulate fraction and raising emissions. A transition temperature, independent of the system parameters, was identified.
|
|
| 3. |
- Alemani, Mattia, et al.
(författare)
-
Scaling effects of measuring disc brake airborne particulate matter emissions – A comparison of a pin-on-disc tribometer and an inertia dynamometer bench under dragging conditions
- 2018
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : Sage Publications. - 1350-6501 .- 2041-305X. ; 232:12, s. 1538-1547
-
Tidskriftsartikel (refereegranskat)abstract
- An important contributor to non-exhaust emissions in urban areas is airborne particulate matter originating from brake systems. A well-established way to test such systems in industry is to use inertia dynamometer benches; although they are quite expensive to run. Pin-on-disc tribometers, on the other hand, are relatively cheap to run, but simplify the real system. The literature indicates promising correlations between these two test stands with regard to measured airborne number distribution. Recent studies also show a strong dependency between the airborne number concentration and the disc temperature. However, a direct comparison that also takes into account temperature effects is missing. The aim of this paper is, therefore, to investigate how the transition temperature is affected by the different test scales, under dragging conditions, and the effects on total concentration and size distribution. New and used low-steel pins/pads were tested against cast iron discs/rotors on both the aforementioned test stands, appositely designed for particulate emission studies. A constant normal load and constant rotational velocity were imposed in both test stands. Results show that a transition temperature can always be identified. However, it is influenced by the test scale and the frictional pair status. Nevertheless, emissions are assessed similarly when an equivalent frictional pair status is analysed (e.g. run-in). Further investigations for fully run-in samples on the pin-on-disc should be performed in order to finally assess the possibility of using the tribometers for the initial assessment of different friction materials.
|
|
| 4. |
- Andersson, Martin, et al.
(författare)
-
Efficiency and temperature of spur gears using spray lubrication compared to dip lubrication
- 2017
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE PUBLICATIONS LTD. - 1350-6501 .- 2041-305X. ; 231:11, s. 1390-1396
-
Tidskriftsartikel (refereegranskat)abstract
- Increased machine efficiency is a requirement in today's world and geared transmissions are no exception. A back-to-back gear test rig was used to compare dip lubrication with spray lubrication regarding gearbox efficiency, mesh efficiency, gear temperature and surface roughness. Gears lubricated at the inlet of the mesh show a lower measured temperature when compared to spray lubrication at the outlet of the mesh. Spray lubrication, when compared to dip lubrication, yields the same efficiency for both rotating directions at the tested speeds of 0.5 to 20 m/s. Spray lubrication shows a significantly higher total gearbox efficiency at higher speeds, higher measured tooth temperature and no measurable change in surface roughness.
|
|
| 5. |
- Bergseth, Ellen, 1979-, et al.
(författare)
-
A note on the pitting life of IQ steel versus 16MnCr5 steel in a back to back gear test rig
- 2018
-
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
|
|
| 6. |
- Bergseth, Ellen, 1979-, et al.
(författare)
-
A Wear Detection Parameter for the Wheel–Rail Contact Based on Emitted Noise
- 2019
-
Ingår i: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 62:3, s. 496-503
-
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.
|
|
| 7. |
- Bergseth, Ellen, 1979-, et al.
(författare)
-
EXPERIENCES OF STUDYING GEAR TRIBOLOGY IN A FZG TEST SET-UP
- 2018
-
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.
|
|
| 8. |
- 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
-
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.
|
|
| 9. |
- Borg, Sixten, et al.
(författare)
-
Patient-reported outcome and experience measures for diabetes: development of scale models, differences between patient groups and relationships with cardiovascular and diabetes complication risk factors, in a combined registry and survey study in Sweden
- 2018
-
Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose The Swedish National Diabetes Register (NDR) has developed a diabetes-specific questionnaire to collect information on individuals' management of their diabetes, collaboration with healthcare providers and the disease’s impact on daily life. Our main objective was to develop measures of well-being, abilities to manage diabetes and judgements of diabetes care, and to detect and quantify differences using the NDR questionnaire.Design, setting and participants The questionnaire was analysed with using responses from 3689 participants with type 1 and 2 diabetes, randomly sampled from the NDR population, combined with register data on patient characteristics and cardiovascular and diabetes complication risk factors.Methods We used item response theory to develop scales for measuring well-being, abilities to manage diabetes and judgements of diabetes care (scores). Test–retest reliability on the scale level was analysed with intraclass correlation. Associations between scores and risk factor levels were investigated with subgroup analyses and correlations.Results We obtained scales with satisfactory measurement properties, covering patient reported outcome measures such as general well-being and being free of worries, and patient reported experience measure, for example, access and continuity in diabetes care. All scales had acceptable test–retest reliability and could detect differences between diabetes types, age, gender and treatment subgroups. In several aspects, for example, freedom of worries, type 1 patients report lower than type 2, and younger patients lower than older. Associations were found between some scores and glycated haemoglobin, but none with systolic blood pressure or low-density lipoprotein cholesterol. Clinicians report positive experience of using scores, visually presented, in the patient dialogue.Conclusions The questionnaire measures and detects differences in patient well-being, abilities and judgements of diabetes care, and identifies areas for improvement. To further improve diabetes care, we conclude that patient-reported measures are important supplements to cardiovascular and diabetes complication risk factors, reflecting patient experiences of living with diabetes and diabetes care.
|
|
| 10. |
- Borg, Sixten, et al.
(författare)
-
Quality of life in chronic conditions using patient-reported measures and biomarkers: a DEA analysis in type 1 diabetes
- 2019
-
Ingår i: Health Economics Review. - : Springer Science and Business Media LLC. - 2191-1991. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background A chronic disease impacts a patient's daily life, with the burden of symptoms and managing the condition, and concerns of progression and disease complications. Such aspects are captured by Patient-Reported Outcomes Measures (PROM), assessments of e.g. wellbeing. Patient-Reported Experience Measures (PREM) assess patients' experiences of healthcare and address patient preferences. Biomarkers are useful for monitoring disease activity and treatment effect and determining risks of progression and complications, and they provide information on current and future health. Individuals may differ in which among these aspects they consider important. We aimed to develop a measure of quality of life using biomarkers, PROM and PREM, that would provide an unambiguous ranking of individuals, without presuming any specific set of importance weights. We anticipated it would be useful for studying needs and room for improvement, estimating the effects of interventions and comparing alternatives, and for developing healthcare with a broad focus on the individual. We wished to examine if efficiency analysis could be used for this purpose, in an application to individuals with type 1 diabetes. Results We used PROM and PREM data linked to registry data on risk factors, in a large sample selected from the National Diabetes Registry in Sweden. Efficiency analysis appears useful for evaluating the situation of individuals with type 1 diabetes. Quality of life was estimated as efficiency, which differed by age. The contribution of different components to quality of life was heterogeneous, and differed by gender, age and duration of diabetes. Observed quality of life shortfall was mainly due to inefficiency, and to some extent due to the level of available inputs. Conclusions The efficiency analysis approach can use patient-reported outcomes measures, patient-reported experience measures and comorbidity risk factors to estimate quality of life with a broad focus on the individual, in individuals with type 1 diabetes. The approach enables ranking and comparisons using all these aspects in parallel, and allows each individual to express their own view of which aspects are important to them. The approach can be used for policy regarding interventions on inefficiency as well as healthcare resource allocation, although currently limited to type 1 diabetes.
|
|
