No description available.

<p>Numerical procedures for reliable wheel and rail wear prediction are rare. Recent development of simulation techniques and computer power together with tribological knowledge do however suggest computer aided wear prediction as possible. The present objective is to devise a numerical procedure able to simulate profile evolution due to uniform wear sufficiently accurate for application to vehicle dynamics simulation. Such a tool should be useful for maintenance planning, optimisation of the railway system and its components as well as trouble-shooting. More specifically, the field of application may include estimation of reprofiling frequency, optimisation of wheel – rail profile match, optimisation of running gear suspension parameters, and recognition of unfavourable profile evolution influencing the dynamic response of the vehicle.</p><p>The research contribution accounted for in this thesis includes, besides a literature review, modelling of the wheel – rail interface, benchmarking against traditional methods, and validation with respect to full-scale measurements.</p><p>The first part addresses wheel – rail contact conditions in the context of wear simulation as well as tribological environment and tractive forces. The current approach includes Archard’s wear model with associated wear maps, vehicle dynamics simulation, and railway network definition. One objective is to be able to include variations in operation conditions in the set of simulations instead of using scaling factors. In particular the influence of disc braking and varying lubrication conditions have been investigated. Both environmental factors like moist and contamination and deliberate lubrication need to be considered. As part of the associated contact analysis the influence of tangential elastic deformation of the contacting surfaces has been investigated and found to be essential in case of partial slip contact conditions. The influence on the calculated wear of replacing the Hertzian contact by a non-elliptic semi-Hertzian method has been investigated, showing relocation of material loss towards increased profile curvature.</p><p>In the second part comparisons have been carried out with traditional methods, where the material loss is assumed to be directly related to the energy dissipated in the contact. Attention has been paid to the understanding of the principle differences between the investigated methods, comparing the distribution of friction energy, sliding velocity, and wear depth. As a prerequisite, contact conditions with dependence on wheelset guidance and curving performance as well as influence of tractive forces have been investigated.</p><p>In the final part validation of the developments related to wheel wear simulation is addressed. Disc braking has been included and a wear map for moist contact conditions based on recent tests has been drafted. Good agreement with measurements from the reference operation, is achieved. Further a procedure for simulation of rail wear and corresponding profile evolution has been formulated. A simulation set is selected defining the vehicles running on the track to be investigated, their operating conditions, and contact parameters. Trial calculations of a few curves show qualitatively good results in terms of profile shape development and difference in wear mechanisms between gauge corner and rail head. The wear rates related to traffic tonnage are however overestimated. The impact of the model improvements accounted for in the first part of the thesis has been investigated, indicating directions for further development.</p>

Numerical procedures for reliable wheel and rail wear prediction are rare. Recent development of simulation techniques and computer power together with tribological knowledge do however suggest computer aided wear prediction as possible. The present objective is to devise a numerical procedure able to simulate profile evolution due to uniform wear sufficiently accurate for application to vehicle dynamics simulation. Such a tool should be useful for maintenance planning, optimisation of the railway system and its components as well as trouble-shooting. More specifically, the field of application may include estimation of reprofiling frequency, optimisation of wheel – rail profile match, optimisation of running gear suspension parameters, and recognition of unfavourable profile evolution influencing the dynamic response of the vehicle. The research contribution accounted for in this thesis includes, besides a literature review, modelling of the wheel – rail interface, benchmarking against traditional methods, and validation with respect to full-scale measurements. The first part addresses wheel – rail contact conditions in the context of wear simulation as well as tribological environment and tractive forces. The current approach includes Archard’s wear model with associated wear maps, vehicle dynamics simulation, and railway network definition. One objective is to be able to include variations in operation conditions in the set of simulations instead of using scaling factors. In particular the influence of disc braking and varying lubrication conditions have been investigated. Both environmental factors like moist and contamination and deliberate lubrication need to be considered. As part of the associated contact analysis the influence of tangential elastic deformation of the contacting surfaces has been investigated and found to be essential in case of partial slip contact conditions. The influence on the calculated wear of replacing the Hertzian contact by a non-elliptic semi-Hertzian method has been investigated, showing relocation of material loss towards increased profile curvature. In the second part comparisons have been carried out with traditional methods, where the material loss is assumed to be directly related to the energy dissipated in the contact. Attention has been paid to the understanding of the principle differences between the investigated methods, comparing the distribution of friction energy, sliding velocity, and wear depth. As a prerequisite, contact conditions with dependence on wheelset guidance and curving performance as well as influence of tractive forces have been investigated. In the final part validation of the developments related to wheel wear simulation is addressed. Disc braking has been included and a wear map for moist contact conditions based on recent tests has been drafted. Good agreement with measurements from the reference operation, is achieved. Further a procedure for simulation of rail wear and corresponding profile evolution has been formulated. A simulation set is selected defining the vehicles running on the track to be investigated, their operating conditions, and contact parameters. Trial calculations of a few curves show qualitatively good results in terms of profile shape development and difference in wear mechanisms between gauge corner and rail head. The wear rates related to traffic tonnage are however overestimated. The impact of the model improvements accounted for in the first part of the thesis has been investigated, indicating directions for further development. / QC 20110124

No description available.

Metal on metal wear at high sliding speeds and high contact pressures results in the melting of one or both of the sliding solid bodies due to heat generated at the contact interface. Understanding the influence of sliding speeds, contact pressures and material properties on wear rates is important in developing predictive models for designing more efficient and effective engineering system components. Typical engineering applications subjected to these extreme conditions include ultrahigh speed machining, rocket sleds, large caliber cannon, and electromagnetic launchers. Sliding speeds on the order of 1,000 m/s and contact pressures in excess of 100 MPa are common in these applications and difficult to replicate in a laboratory environment. A unique wedge experiment using a minor caliber electromagnetic launcher has been developed and implemented to characterize wear deposition of a 6061-T6 aluminum sliding body on several different guider materials of varying mechanical and thermal properties at sliding speeds from 0 – 1,200 m/s and contact pressures from 100 – 225 MPa. Optical microscopy and 3D profilometry were used to characterize and quantify the slider wear. Three distinct wear regions, plasticity dominated, severe plastic deformation and melt lubrication were observed. Test results provided evidence that the aluminum slider contact interface was molten. Modeling of the experimental wear data showed a dependence on pressure and velocity and guider material properties, density and specific heat. A predictive wear model was developed for the melt lubrication region as a tool for designing components subjected to similar operating conditions.

<p>Numerical procedures for reliable wheel and rail wearprediction are rare. Recent development of simulationtechniques and computer power together with tribologicalknowledge do however suggest computer aided wear prediction.The objective of the related research field at the RoyalInstitute of Technology (KTH) is to arrive at a numericalprocedure able to simulate profile evolution due to uniformwear to a degree of accuracy sufficient for application tovehicle dynamics simulation. Such a tool would be useful formaintenance planning as well as optimisation of the transportsystem and its components.</p><p>The research contribution accounted for in this thesisincludes, in addition to a literature review, refinement ofmethods applied to uniform wheel wear simulation by inclusionof braking and improvement of the contact model. Further atentative application to uniform rail wheel simulation has beenproposed and tested.</p><p>The first part addresses issues related to braking andwheel-rail contact conditions in the context of wheel wearsimulation. The KTH approach includes Archard’s wear modelwith associated wear maps, vehicle dynamics simulation andrailway network definition. In previous work at KTH certainvariations in operating conditions have been accounted forthrough empirically estimated average scaling factors. Theobjective of the current research is to be able to include suchvariations in the set of simulations. In particular theinfluence of disc braking and varying friction and lubricationconditions are investigated. Both environmental factors likemoist and contamination and deliberate lubrication need to beconsidered. As part of the associated contact analysis theinfluence of tangential elastic deformation of the contactingsurfaces on the sliding velocity has been separatelyinvestigated and found to be essential in case of partial slipcontact conditions.</p><p>In the second part validation of the improvements related towheel wear simulation is addressed. Disc braking has beenincluded in the simulation set and a wear map for moist contactconditions based on recent tribometer tests has been draftedand tested. It has been shown that the previously used brakingfactor accounts for the combination of the contributions fromsurface elasticity and braking. Good agreement withmeasurements from the Stockholm commuter service is achieved.It is concluded that the model improvements accounted for aresufficient for adequate simulation of tread wear but thatfurther development of the flange / gauge corner contactmodelling may be needed.</p><p>In the final part a procedure for simulation of rail wearand corresponding profile evolution has been formulated. Asimulation set is selected defining the vehicles running on thetrack to be investigated, their operating conditions, andcontact parameters. Several variations of input data may beincluded together with the corresponding occurrenceprobability. Trial calculations of four non-lubricated curveswith radii from 303 m to 802 m show qualitatively reasonableresults in terms of profile shape development and difference inwear mechanisms between gauge corner and rail head. The wearrates related to traffic tonnage are however overestimated. Itis believed that model refinements in terms of environmentalinfluence and contact stress calculation are useful to improvethe quantitative results.</p> / QC 20100531

WEAR ANALYSIS OF HOT FORGING DIES ABACHI, Siamak M. S., Department of Mechanical Engineering Supervisor: Prof. Dr. Metin AKK&Ouml / K Co-Supervisor: Prof. Dr. Mustafa lhan G&Ouml / KLER December 2004, 94 pages The service lives of dies in forging processes are to a large extent limited by wear, fatigue fracture and plastic deformation, etc. In hot forging processes, wear is the predominant factor in the operating lives of dies. In this study, the wear analysis of a closed die at the final stage of a hot forging process has been realized. The preform geometry of the part to be forged was measured by Coordinate Measuring Machine (CMM), and the CAD model of the die and the worn die were provided by the particular forging company. The hot forging operation was carried out at a workpiece temperature of 1100&deg / C and die temperature of 300&deg / C for a batch of 678 on a 1600-ton mechanical press. The die and the workpiece materials were AISI L6 tool steel and DIN 1.4021, respectively. The simulation of forging process for the die and the workpiece was carried out by Finite Volume Method using MSC.SuperForge. The flow of the material in the die, die filling, contact pressure distribution, sliding velocities and temperature distribution of the die have been investigated. In a single stroke, the depth of wear was evaluated using Archard&rsquo / s wear equation with a constant wear coefficient of 1&yen / 10-12 Pa-1 as an initial value. The depth of wear on the die surface in every step has been evaluated using the Finite Volume simulation results and then the total depth of wear was determined. To be able to compare the wear analysis results with the experimental worn die, the surface measurement of the worn die has been done on CMM. By comparing the numerical results of the die wear analysis with the worn die measurement, the dimensional wear coefficient has been evaluated for different points of the die surface and finally a value of dimensional wear coefficient is suggested. As a result, the wear coefficient was evaluated as 6.5&yen / 10-13 Pa-1 and considered as a good approximation to obtain the wear depth and the die life in hot forging processes under similar conditions.

Numerical procedures for reliable wheel and rail wearprediction are rare. Recent development of simulationtechniques and computer power together with tribologicalknowledge do however suggest computer aided wear prediction.The objective of the related research field at the RoyalInstitute of Technology (KTH) is to arrive at a numericalprocedure able to simulate profile evolution due to uniformwear to a degree of accuracy sufficient for application tovehicle dynamics simulation. Such a tool would be useful formaintenance planning as well as optimisation of the transportsystem and its components. The research contribution accounted for in this thesisincludes, in addition to a literature review, refinement ofmethods applied to uniform wheel wear simulation by inclusionof braking and improvement of the contact model. Further atentative application to uniform rail wheel simulation has beenproposed and tested. The first part addresses issues related to braking andwheel-rail contact conditions in the context of wheel wearsimulation. The KTH approach includes Archard’s wear modelwith associated wear maps, vehicle dynamics simulation andrailway network definition. In previous work at KTH certainvariations in operating conditions have been accounted forthrough empirically estimated average scaling factors. Theobjective of the current research is to be able to include suchvariations in the set of simulations. In particular theinfluence of disc braking and varying friction and lubricationconditions are investigated. Both environmental factors likemoist and contamination and deliberate lubrication need to beconsidered. As part of the associated contact analysis theinfluence of tangential elastic deformation of the contactingsurfaces on the sliding velocity has been separatelyinvestigated and found to be essential in case of partial slipcontact conditions. In the second part validation of the improvements related towheel wear simulation is addressed. Disc braking has beenincluded in the simulation set and a wear map for moist contactconditions based on recent tribometer tests has been draftedand tested. It has been shown that the previously used brakingfactor accounts for the combination of the contributions fromsurface elasticity and braking. Good agreement withmeasurements from the Stockholm commuter service is achieved.It is concluded that the model improvements accounted for aresufficient for adequate simulation of tread wear but thatfurther development of the flange / gauge corner contactmodelling may be needed. In the final part a procedure for simulation of rail wearand corresponding profile evolution has been formulated. Asimulation set is selected defining the vehicles running on thetrack to be investigated, their operating conditions, andcontact parameters. Several variations of input data may beincluded together with the corresponding occurrenceprobability. Trial calculations of four non-lubricated curveswith radii from 303 m to 802 m show qualitatively reasonableresults in terms of profile shape development and difference inwear mechanisms between gauge corner and rail head. The wearrates related to traffic tonnage are however overestimated. Itis believed that model refinements in terms of environmentalinfluence and contact stress calculation are useful to improvethe quantitative results. / QC 20100531

Non-exhaust PM10 is an issue in the urban environment linked to health issues. Emissions of non-exhaust PM10 is relatable to pavement properties. Also of importance is resuspension of road dust stored from surfaces. This depends on the traffic and metrological conditions. Given this, the purpose of the thesis was to give an overview limited to Sweden and the Nordic countries regarding non-exhaust PM10 emissions and road dust. The overview includes how particles are related to human health. Also included is the principle of how particles are emitted from road surface and tyre interaction, both directly and through resuspension of road dust. This thesis also includes an overview of how the use of studded tyres impact on asphalt surfacings and how the properties of the materials used impact on the abrasion wear. This is then linked to the emissions of non-exhaust particles. Further described is how measurements can be done of ambient particles and road dust, followed on two major models for road abrasion wear and non-exhaust PM prediction. Also included is how road operation, e.g. traction sanding and dust binding, influence the particle emissions together with other options to reduce the emissions through, e.g. limiting the use of studded tyres. One special issue discussed in this thesis is the lack of holistic view regarding the environmental problems in the urban environment with focus on particle emissions and road noise emissions, both from the road surface and tyre interaction. Currently the most problematic issue is prioritized and the resulting solution to that specific problem might increase other problems. This thesis shows that much knowledge is available regarding non-exhaust PM10 emissions and road dust, but also that several knowledge gaps exists. Several suggestions on further studies is given together with a brief overview on the continued work forward from this thesis. / Icke-avgasemissioner av PM10 är ett problem i urbana miljöer länkat till flera hälsoaspekter. Dessa emissioner kan relateras till beläggningars egenskaper. Även resuspension av vägdamm från ytor är av betydelse och beror på både trafiken och meterologin. Baserat på detta är syftet med denna avhandling att ge en översikt kring icke-avgas PM10 emissioner och vägdamm, begränsat till Sverige och de övriga nordiska länderna. Denna översikt inkluderar hur partiklar relaterar till människans hälsa. Annat som inkluderas är hur partiklarna emitteras från vägyta-däckinteraktionen, både direkt och genom resuspension av vägdamm. Avhandlingen inkluderar även en översikt kring hur användandet av dubbdäck inverkar på vägbeläggningar och hur dess egenskaper inverkar på nötningsslitage. Detta länkas därefter till partikelemissioner. Vidare beskrivs även hur mätningar kan genomföras av partiklar samt vägdamm vilket följs upp av beskrivningar kring två större modeller kring prediktion av nötningsslitage och prediktion av icke-avgasemissioner. Även hur driftåtgärder inverkar på emissionerna tillsammans med alternativ för att minska emissionerna tas upp. Ett särskilt problem som tas upp i avhandlingen är bristen på helhetssyn beträffande miljöproblem i den urbana miljön med fokus på partikel- och bulleremissioner från vägyta-däckinteraktionen. För närvarande brukar det värsta problemet prioriteras och lösningen till det detta problem kan i sin tur medföra att andra miljöproblem istället förvärras. Denna avhandling visar på att mycket kunskap existerar kring icke-avgasemissioner av PM10 och kring vägdamm, men även att flertalet kunskapsluckor existerar. Flertalet förslag på vidare studier ges tillsammans med en överblick kring det fortsatta arbetet. / <p>QC 20180202</p>