This Master's thesis project was provided by Epiroc Rock Drills AB and conducted at Camatec Industriteknik AB in Karlstad, Sweden. The project is centered around the cutter wheel in the mechanical rock excavator Mobile Miner 40V.  This cutter wheel is equipped with cutter discs that grind rock into debris as the wheel rotates and thrusts forward. The internal system consisting of a bearing constellation and the components in its vicinity has experienced a certain degree of wear in the form of scuffing and this was detected on the surfaces of some of the components in the system. The reasons for this occurrence are unknown and per the request of the thesis provider, this was to be determined. The thesis provider also requested a new Finite Element Analysis (FEA) model of the system along with feasible load cases that can be applied to said model. The project was deemed extensive and was therefore decided to be conducted by two students. This thesis covers the determination of the load cases as well as the optimization of the current design of the system inside the cutter wheel. During the pre-study, relevant background data was obtained for the cutter wheel and the internal system. Methods and models considered to potentially be useful were also gathered. The system in question was divided into two separate models; one consisted of a tribo-system with two components in sliding contact and the other consisted of the bearing constellation along with the outer-most section of the cutter wheel. The purpose of the first model was to use it to determine the contact pressure between the tribo-surfaces and by doing so, be able to determine the expected lubrication regime for the oil in the tribo-system. A material selection process was also conducted on the tribo-surface that had experienced the most severe surface damage. Additionally, minor reconstructions were made with the purpose of optimizing the system. The purpose of the second model was to apply the calculated load cases to the cutter disc attachments located on the outer-most section of the cutter wheel and then determine the contact pressures that develop on the bearing roller elements. The results of the thesis work consist of five potential material options, two reconstructions and 60 different load cases for the FEA model. With the load cases, the largest contact pressures on the bearing roller elements was determined. In addition, the cause of the severe surface damage that had occurred in the system is believed to have been identified. Further work on the project work is believed to be required. Future work of interest are determining load cases that incorporate multiple cutter discs simultaneously in contact with the rock, reconstruction solutions for the oil inlet and outlet pipes, a more thorough materials selection process and a criterion for the expected lubrication regime in the tribo-system based on tests performed with materials that are more identical to the ones in this project. / Detta examensarbete tillhandahölls av Epiroc Rock Drills AB och genomfördes hos Camatec Industriteknik i Karlstad, Sverige. Projektet är centrerat kring cutterhjulet i maskinen Mobile Miner 40V som är avsedd för mekanisk bergavverkning. Cutterhjulet är utrustat med cutter discar som maler berget till mindre flisor genom att hjulet roterar och trycks framåt. Det inre systemet bestående av en lagring med närliggande komponenter har utsatts för en viss grad av nötning i form av scuffing och detta upptäcktes på ytorna hos vissa av komponenterna i systemet. De bakomliggande anledningarna för denna förekomst är okända och utifrån begäran från projektgivaren skulle dessa anledningar fastställas. Projektgivaren eftersökte även en ny FEM-modell av systemet tillsammans med rimliga lastfall som ska kunna appliceras på modellen i fråga. Projektet ansågs tämligen omfattande och det bedömdes därför att två studenter krävdes för att genomföra arbetet. Denna uppsats behandlar framtagningen av lastfallen såväl som optimeringen av den nuvarande designen av systemet inuti cutterhjulet. Under förstudien hämtades relevant bakgrundsdata för cutterhjulet och det interna systemet. Metoder och teorier som ansågs vara potentiellt användbara samlades även in. Systemet i fråga delades in i två separata modeller; en bestod av ett tribo-system bestående av två tribo-ytor i glidande kontakt och den andra bestod av lagringen tillsammans med den yttersta sektionen hos cutterhjulet. Syftet med den förstnämnda modellen var att använda den för att bestämma kontakttrycket mellan tribo-ytorna, och genom detta kunna fastställa den förväntade smörjningsregimen hos oljan i tribo-systemet. En materialvalsprocess utfördes även för tribo-ytan som hade utsatts för den mest allvarliga skadan. Även smärre omkonstruktioner utfördes med syftet att optimera systemet. Syftet hos den andra modellen var att kunna applicera de beräknade lastfallen på cutter discarnas infästningar som återfinns i den yttersta sektionen hos cutterhjulet och sedan bestämma kontakttrycken som uppstår på rullarna i lagren. Resultaten från arbetet består av fem potentiella materialval, två konstruktionsändringar och 60 olika lastfall för FEM-modellen. Genom att applicera lastfallen bestämdes de största kontakttrycken på lagrens rullar. Utöver detta anses det att anledningen för den allvarliga ytskadan som hade skett i systemet har identifierats. Det anses att fortsatt arbete krävs för projektet. Kompletterande arbete som anses vara av intresse är lastfall som inkluderar flera cutter discar i ingrepp samtidigt med berget, konstruktionslösningar för tillförsel och bortförsel av oljan, en mer djupgående materialvalsprocess och ett kriterium för förväntad smörjningsregim hos tribo-systemet baserat på tester utförda med material som är mer identiska med dem som förekommer i projektet.

Working at elevated temperature has its challenges due to the high level of complexity whenthe tribosystems operate under harsh conditions, commonly resulting in an increase on thefriction and thermal softening that goes into severe adhesion, severe abrasion and materialtransfer. Despite considerable research, there is a lack of research on tribology applied to hightemperature processes.  The aim of this project is to understand the tribological behavior of tool steel sliding againstaluminum under lubrication conditions working at high temperature. Salt-based, graphite-based, and polymer-based lubricants were evaluated as they are commonly used for aluminum forming. The cleanability of the lubricants after being subjected to elevated temperatures is also studied. High temperature tribological tests were carried out in a reciprocating sliding flat-on-flat configuration for 15 seconds. Optical microscope, SEM and EDS were performed to analyze the specimens after the tribological tests. Then a cleanability study was done to evaluate the cleanability of the lubricants and the effect of temperature on the cleanability of the lubricant. The concentration of the lubricants played an important role in the lubricant’s friction stability and dispersion, particularly for the polymer-based and graphite-based lubricants. Under the tested conditions the salt-based lubricant was ineffective as it showed high and unstable friction. The 10 wt.% polymer-based lubricant concentration presented severe adhesion and material transfer from the aluminum onto the tool steel.  The effect of temperature on the cleanability of the lubricants was correlated to the temperature in which the lubricants start to degrade. Nevertheless, the best cleanability was achieved when using ethanol as a cleaning agent in combination with high pressure spraying, and wirebrush techniques. Mild and high alkaline agents had poor cleanability abilities resulting insurface damage and corrosion on the tool steel.

The purpose of the project work was to build knowledge of the tribological behaviour of self-lubricating laser cladding, with and without external solid lubricant during conditions relevant for hot metal forming of aluminium. The materials used during the project were plates coated with a Ni-based self-lubricating clad and a reference sample of work tool steel. The self-lubricating laser clad was applied using a high power direct diode laser. The external solid lubricant used was a graphite dispersion. The external solid lubricant was applied on the samples using a spraying technique, leaving a dry layer of solid graphite on the plates. To test the tribological behaviour of the plates, linear reciprocating friction and wear tests were performed both under lubricated and dry conditions. During the dry tests, different surface roughness of the plates where investigated. The pins for the tribological test were made of AA7075. Parameters chosen for the tribological tests were based on conditions during hot forming of aluminium. After having taken images of the plates using scanning electron microscopy, and using a 3D optical profiler, the wear volume and material transfer was evaluated, and wear mechanism analysis was performed.   The tribological behaviour of polished Ni-based laser clad under dry conditions is comparable to that of the reference sample at its best performance. Using a mirror polished Ni-based laser clad under dry condition can be an option to not using external solid lubricant during hot forming of aluminium. Also, the surface roughness of the self-lubricating clad under dry conditions does not affect the coefficient of friction.

Detta examensarbete utfördes på Scania CV AB och behandlar delar i lastbilens avgassystem som utsätts för korrosion och nötning. Huvudmålet med detta arbete är att utveckla en provmetod för livslängdsundersökning av flexibla slangar. En serie tester utfördes för att förstå grundorsakerna till brott och en FE-analys utfördes för att verifiera resultaten till dessa prov. En stor del av den flexibla slangen blir stel på grund av höga avgastemperaturer och som leder till plastisk deformation av slangen. Men de tre första lindningarna som ligger närmast motorn behåller sin flexibilitet på grund av kontinuerliga motorvibrationer. Slutsatsen är att huvudorsaken som gör att de flexibla slangarna går av, är slitage som leder till sprickinitiering. Den sprickan sprider sig i form av lågcykelutmattning d.v.s att det tar ganska kort tid tills brott sker i den flexibla slangen. Korrosion initierar mellan de icke-flexibla delar av slangen Korrosionshastigheten ökar med tiden och det orsakar små hål på ytorna. Baserat på testresultaten är den mest lämpliga stället för livslängdsundersökningar Scanias komponentprovceller. Genom att mäta slitagedjupet under repeterbara förhållanden som rekommenderas i rapporten och med hjälp av data från kundutfall, kan en livslängd uppskattas. För att kunna förbättra livslängden för de flexibla slangarna, rekommenderas att använda rostfritt stål typ 1.4828 vid tillverkning av dessa slangar bör varmformning användas, samt att avståndet mellan lagrena respektive tjockleken ökas. Flera tester med olika teststidsintervall behöver göras för att ta reda på nötningshastigheten. / This thesis was conducted at Scania CV AB with information based on corrosion and wear. The main goal of this work is to develop a test method to investigate the stripwounded hose’s lifetime. A series of tests were performed to understand the reasons of their failure and a FE analysis was performed to verify the results obtained from these tests. It was observed that a large part of stripwounded hose becomes stiff due to high temperatures of the exhaust gas. The high temperature leads to plastic deformation of the hose. In contrast, the three first windings closest to the engine keep their flexibility due to continuously engine vibrations while there is sign of wear between the layers in these three windings more than other parts of the stripwounded hose. Hence, it is concluded that the main reason for stripwounded hose’s unpredictable failures is wear which leads to crack initiation. The crack propagation is in type of low cycle fatigue which means that it takes a short time until the stripewounded hose breaks. Corrosion is initiated between the non-flexible parts of the hose. The rate of corrosion is increased by time and causes small holes on the surfaces. According to results from the experiments the most suitable location for the lifetime investigation is Scania’s component test cells . Several tests with different time spans needs to be performed. By measuring the wear depth rate under repeatable test conditions and bycomparing with stripwounded hoses from customer trucks, a lifetime can be estimated. To improve the fatigue lifetime of the stripwounded hoses, it is recommended to use stainless steel of type 1.4828, manufactured through hot-forming with larger distance between layers and thicker layers to find out the wear rate.

Efficient transmissions systems are key to producing competitive motor vehicles that have a smaller environmental impact. Gears are the main components in vehicle transmissions and although they are already highly efficient, there is still room for improvement. In this study, the focus falls on the lubricant used to create separating films between gears and todissipate heat. When driving, the gears churn this lubricant, giving rise to power losses that are related to the amount and properties of the lubricant. However, any attempt to reduce these losses must not compromise the required lubrication and heat dissipation. Paper A reports on the use of an FZG gear test rig to investigate power losses and heat generation for different gear immersion depths, surface roughness and coatings. The results show that lower gear roughness reduces gear mesh losses and heat generation. A polishing affect was obtained when a non-coated gear ran against a coated gear.The aim of the research reported in paper B was to increase the accuracy of efficiency testing. It investigated how and whether repeated disassembly and re-assembly of the same test equipment, as well as test performance and rig conditions, affect the measured torque loss in an FZG gear test rig. It was shown that the measured torque loss changes between one assembly and another. Repeatability between tests is crucial for accurate conclusions.The aim of the research reported in paper C was to study whether gear efficiency could be increased by a running-in procedure, which would reduce the need for a coolant. A back-to-back gear test rig was used to test two running-in loads. Higher gear mesh efficiency was seen when a higher running-in load was used. / <p>QC 20141006</p>

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. / <p>QC 20150922</p>

A common choice of bearing for industrial applications such as turbomachinery and rotating compressors is the Tilting-Pad Journal Bearing (TPJB) due to its excellent stability properties. TPJB's are however limited by the reduction of damping in the fluid film at high velocities. In order to overcome this, the Active Tilting-Pad Journal Bearing (ATPJB) has been developed. By adding the possibility of high-pressure radial oil injection through servo-valves which can be controlled via a feedback-loop control system, the classically purely mechanical TPJB becomes a mechatronic device called ATPJB.  The objective of this project is to conduct an experimental evaluation of the dynamical behavior of the ATPJB test rig located at the Technical University of Denmark, use the experimental results to modify the previously developed dynamical model which is used for the calculation of a model-based control system. The control system is to be implemented and experimentally validated at high velocities. Improvements made to the test rig in order to achieve high velocities have been documented and described in this work. The mathematical modeling of the individual components, reduction methods, and the global system assembly is covered with an extensive overview. Parameters of the model have been made frequency dependant in order to have an accurate model, resulting in good agreement with experimental data over a wider operational range. With the implemented Linear Quadratic Gaussian controller it is shown that ATPJB has extended operational range compared to TPJB and shows reduction of vibrations over rotational speeds spanning from 1000 RPM to 10,000 RPM. The ATPJB-technology, as it is implemented in this project, does not improve frictional losses in the system. It is argued that the added sensing and actuating systems inherited in the ATPJB technology make the technology highly suitable for the ideas of Industry 4.0 and also allows for the implementation of Early Fault Diagnosis which gives an economical incitement to invest in ATPJB-technology.

This report covers the work and results of the thesis project in Mechanical Engineering from Luleå university of technology performed by Niklas Ydebäck. The objective of the thesis project is to research if it is possible, with general principles of fluid flow between components and the corresponding geometric constraints between them and just a few channels of data, to model the leakage of a radial piston hydraulic motor. The model is of the grey box kind which makes use of both numerical and statistical methods together with known physical properties of a system in order to model the system. The unknown parameters of this system that are estimated using the least squares method are the three different gap heights of the system as well as the two different eccentricities in the system. The model contains the physical properties of the system, stated in equations for the leakage in the relevant lubrication interfaces, but no relational properties for the dynamics and affects between the individual lubricating interfaces. The model developed is due to the model generality together with the data quality accessible not able to model the system with reliable quality. The model is however able to capture the general trend of the leakage in the system over the applied time series datasets. / Den här rapporten presenterar arbetsgången och resultatet av examensarbetet för en civilingenjörsexamen i Maskinteknik från Luleå tekniska universitet utförd av Niklas Ydebäck. Målet med examensarbetet är att utvärdera och undersöka om det är möjligt, med generella och vedertagna principer av fluidflöde mellan smorda komponenter tillsammans med de geometriska begränsningarna som hör dem till och några få kanaler av data, att modellera läckaget för en radialkolvsmotor. Modellen är en grålådemodell som med hjälp av numeriska och statistiska metoder och kända fysikaliska principer av ett system bildar en modell av systemet. De okända parametrarna av systemet som estimeras med hjälp av minsta kvadrat metoden är de tre olika typerna av spalthöjderna och de två olika eccentricitetstyperna som finns i systemets smorda kontakter. Modellen består av de fysikaliska egenskaperna i systemet, formerade i ekvationer för läckaget i de relevanta smorda kontakterna, men inga relationella egenskaper för dynamiken och effekterna mellan de olika smorda kontakterna. Den utvecklade modellen är på grund av den generella karaktären av modellen tillsammans med kvaliteten på den data som finns tillgänglig inte möjlig att modellera läckaget i systemet med tillräcklig noggrannhet. Modellen är trots detta kapabel att fånga de generella trender som återfinns i den uppmätta datan på läckaget för de applicerade dataseten.

With the increasing restrictions in emission legislations, the automotive industry aims to improve the efficiency of the lubricating system and to decrease fuel consumption. In the power cylinder unit (PCU), the piston rings are the major contributor to these consumptions. Hence, focus on the dynamic behaviour of the rings to reduce lube oil consumption (LOC) becomes a key factor in thriving towards sustainability. Several studies have been conducted on the piston ring-pack specifically using a 2D ring dynamics approach. This study focuses on developing a 3D ring dynamics model, in the software tool AVL EXCITE™ Piston&amp;Rings, which is capable of observing the behaviour of the ring along the third dimension i.e. circumferential direction. A coordinated approach used in the methodology gives an insight into the parameters affecting the model behaviour. Within the PCU, wear on the cylinder liner surface and in the piston ring grooves can lead to accelerated LOC. This study further focuses on using the 3D model to analyse the friction and wear on the piston rings. Factors contributing towards LOC are individually studied and the results obtained are compared to the experimental engine test data. The outcome of the 3D numerical model developed shows promising results. The model can therefore be used to simulate different piston ring-packs and analyse the behaviour of the piston ring with a better prediction of friction, wear and LOC. Thus, the model will contribute to reducing the number of physical tests conducted, the expense involved in conducting those tests and would provide satisfactory products to the customer and would manage future emission requirements.

Over the last decade, the application of ultra-high strength steel as safety components and structural reinforcements in automobile applications has increased due to their favourable high-strength-to-weight ratio. The complex shaped components are widely produced using hot stamping. However, this process encounters problems such as galling and increased wear of the tools due to harsh operating conditions associated to the elevated temperatures. Moreover, quenching is a critical step that affects the hot formed components. Slow cooling rates results in inhomogeneous mechanical properties and increased cycle time. Therefore, fast and homogeneous quenching of the formed components in combination with reduction of wear rates during hot forming are important targets to ensure the quality and efficiency of the process. The use of additive manufacturing (AM) technologies opens up potential solutions for novel tooling concepts. The manufacturing of complex shape cooling channels and integration of high-performance alloys at the surface could benefit the tribological performance in the forming operation. However, the research into high temperature tribological behaviour of AM materials in hot forming applications is very limited. The aim of this work is to study the tribological performance of additively manufactured materials. Two steels were used – a maraging steel and modified H13 tool steel. The hot work tool steel H13 is commonly applied for dies in metal forming processes. In this thesis it was used to study additive manufacturing as the processing route instead of conventional casting. The choice of a maraging steel is motivated by a possible application of high-performance alloys as a top layer on dies. The materials were post-machined and studied in milled, ground and shot-blasted conditions. The different post-machining operations were applied to study the effect of surface finish on the tribological behaviour and also to evaluate different methods of post-machining an AM surface. As fabricated dies are usually manufactured with milled surface. During its use, the dies undergo refurbishment after certain number of cycles and the surface condition is changed to a ground surface. These surface finishes are commonly tested for hot forming applications. The shot blasted operation was chosen as alternative surface finish. The process allows to prepare large sized tools easily and the surface has beneficial compressive stresses. The tribological behaviour of AM steels was studied using a hot strip drawing tribometer during sliding against a conventional Al-Si coated 22MnB5 steel. The workpiece temperature during the tests was 600 and 700°C. The results of the tribological performance of AM materials were compared to conventionally cast tool steel QRO90.The results have shown that the friction behaviour of both maraging and H13 steels at 600°C was stable and similar whereas at 700°C the COF was more unstable and resulted in an earlier failure of the tests due to increased material transfer of Al-Si coating from the workpiece surface.The main wear mechanisms for AM materials were galling and abrasion at both temperatures. Abrasion is more severe for the AM steels in comparison to cast tool steel QRO90. The galling formation on milled and ground surfaces showed similar behaviour to cast steel and it increased with higher workpiece temperatures. The shot-blasted surfaces showed less build-up of transferred material on the surface but folding of asperities and entrapment of Al-Si particles within surface defects generated during shot-blasting.