Grease-lubricated journal bearings are widely used in heavy duty applications, such as construction equipment, agriculture- and forest machines. The main purpose of the grease-lubricated journal bearing is solely to create sustainable rotation of a given application. However, purpose seldom decides complexity of journal bearing design. Depending on application, parameters such as Load , Material  and Lubrication immensely increase complexity of the design. Tribology is a highly interdisciplinary subject, which requires knowledge concerning physics, chemistry, metallurgy and solid mechanics. Tribological aspects of a design are frequently regarded as irrelevant. Tribological issues are commonly enlightened in combination with structural design weaknesses. The main aim of the thesis was to analyze two cylinder joints found in a Komatsu Forest 951 crane and establish root cause to the structural and tribological issues. Outline of the approach was divided into three main targets: 1. Investigate mechanical and tribological aspects of the crane design. 2. Understand how these aspects influence the life time of the bearings. 3. Summarize the analysis and suggest improvements based on the discovery. Fundamental structural and tribological design guidelines regarding grease-lubricated journal bearings have been presented in this thesis. Damaged components such as cylinders, pins and journal bearings have been examined at Komatsu Forest’s factory in Umeå. Further, a scanning electron microscopy study has been done at Luleå University of Technology, to determine predominant wear mechanisms in the harvester crane joints. A non-linear finite element model of the crane has been designed to represent pressure distribution in the contact between bearing and pin. The finite element analysis gives a good approximation of the contact but leaves room for further refinements. Temperatures, in the contacts, have not been identified and will be measured outside the time frame of the master’s thesis. Design changes, with respect to discovered structural and tribological issues have been suggested. The suggested improvements can potentially increase the life time of lift cylinders, pins and journal bearings.

This diploma work is performed at Sandvik Mining and Rock Technology, Rock Tools division, a world-leading mining equipment manufacturer. The aim is to study the wear of cemented carbide rock drill inserts worn against granite and sandstone countersurfaces, with focus on the impact of binder phase composition and flushing agent chemistry. A brief introduction to rock drilling, cemented carbides and the wear and degradation mechanisms of cemented carbides in rock drilling is given. Wear is induced in a lab test by sliding cemented carbide inserts against granite and sandstone countersurfaces while flushing with deionized water or synthetic mine water. The wear is quantified by measuring material weight loss, and worn inserts are studied by SEM. All wear marks feature crushed, fragmented and heavily deformed WC grains and cavities left after individually removed WC grains. Rock adhere strongly on inserts worn against both granite and sandstone, and adhered material from both rock types sometimes endure the mechanical contact between insert and rock without significant spalling. Inserts tested with deionized water against sandstone wear 2.2 - 5.1 times more relative to against granite, and the only distinct difference observed is the distribution of adhered rock. The use of synthetic mine water relative to deionized water impacts the wear of all inserts, though corrosion products are only found on some of them. Further, the tribological contact greatly impacts the corrosive attack. The relative wear difference using different water chemistries is larger for inserts with a smaller relative amount of binder. In most cases, increased wear is measured for inserts tested with synthetic mine water. For reasons yet unknown, this trend is reversed for inserts with a high relative amount of binder tested against sandstone, where a decrease in wear is measured instead. / Detta examensarbete har utförts åt Sandvik Mining and Rock Technology, Rock Tools avdelningen, som är en världsledande utrustningstillverkare inom gruvindustrin. I arbetet undersöks nötningen av så kallade bergborrstift av hårdmetall. Berg är generellt ett mycket hårt och sprött material, och borrning i berg går därför i huvudsak ut på att krossa och spola bort krossad sten. Längst fram på bergborrar sitter borrkronor som till största del är gjorda i stål. Då stål är för mjukt för att effektivt kunna avverka berg monterar man in stift av hårdmetall längst fram på borrkronan. Hårdmetall är ett kompositmaterial av mycket hårda men spröda wolframkarbidkorn (WC) som hålls ihop av en, jämfört med WC, mjuk och formbar metall som kallas bindefas. Resultatet är ett mycket hårt men fortfarande relativt segt material som dessutom klarar de mycket höga temperaturer som uppstår vid bergborrning. Traditionellt används kobolt som bindefas, men nu tros det finnas hälsorisker med kobolt och dessutom sker en stor del av världens koboltutvinning under oetiska förhållanden i konfliktländer i Afrika. Detta i kombination med att koboltpriserna ökat dramatiskt de senaste åren leder till att man nu söker efter alternativa bindefaser. Bland annat undersöker man olika legeringar av nickel och järn. I detta arbete jämförs nötningen av stift med nickel-, järn- och olika koboltbindefaser. I ett labtest fås nötning genom att stiften trycks mot en roterande stencylinder av antingen granit eller sandsten. I verkliga förhållanden används ofta så kallat gruvvatten som sipprar in i gruvan som spolvatten för att ta bort stenkrosset och kyla borrkronan. För att se hur kemin i spolvattnet påverkar nötningen spolas kontaktytan mellan stift och stencylinder med antingen avjoniserat vatten eller syntetiskt gruvvatten under testerna. Stiftens materialförlust under provningen beräknas genom att mäta deras vikt innan och efter. För att se om skillnader i nötningshastighet mellan olika stifttyper eller testvillkor avspeglas i olika utseenden på slitytorna undersöks stiften med hjälp av ett svepelektronmikroskop (SEM). Från SEM-bilderna ser man att alla stift från alla testvillkor har krossade och fragmenterade WC-korn på ytan och att stora delar av slitytorna täckts av påkletat berg. Bergpåsmetningarna är ibland mycket tunna (< 1 μm) och delvis inblandade i bindefasen, och ibland betydligt tjockare (flertal μm). De tjockare påsmetningarna är bundna så pass hårt till ytan att de kan upprätthålla delar av kontakten mellan stiftet och berget under testningen utan att lossna. Huruvida detta skyddar hårdmetallen från att nötas eller om det påkletade berget reagerar med, och därmed ökar den kemiska nedbrytningen av stiftet är inte utrett. Berget skyddar dock den underliggande hårdmetallen mot den korrosion som uppstår i kontakt med spolvattnet. Resultaten visar att stiften nöts betydligt mer mot sandsten än mot granit. Förutom att bergpåsmetningarna har en annan fördelning över ytan så syns inga tydliga skillnader mellan stiften testade mot de båda bergarterna. De flesta stiften nöts mer när de testas med gruvvatten än med avjoniserat vatten. Detta gäller alla stift utom de som har hög relativ mängd bindefas och som testats mot sandsten. Dessa stift nöts tvärt om mindre när de testas med gruvvatten än med avjoniserat vatten. Hittills har ingen anledning till denna konsekventa avvikelse hittats.

This thesis summarizes the work done on tribological characterization of multifunctional hardfacing coatings with self-lubricating properties, intended for use in mechanical components operating in high temperature applications for which conventional lubricants are no longer effective. Deposition techniques like laser cladding have a great potential in reworking/repair of high value industrial components in order to extend their lifetime. It is expected that the use of self-lubricating laser claddings could be useful in high temperature applications like metal forming, leading to decreased friction and wear. In this study, the tribological behavior of self-lubricating claddings has been studied against steel and aluminum counter surfaces, using ASI52100 bearing steel in addition to AA6082 and AA2007 aluminum flat pins as the counter bodies. Nickel- and iron-based powders have been chosen for the preparation of claddings. Self-lubricating properties of Ag/MoS2 have been compared to an untreated reference cladding and grade 1.2367 tool steel. For steel counter surfaces, tribological properties in the temperature range between RT and 600⁰C have been investigated and at 300°C for aluminum counter surfaces. Tribological tests were done by a high frequency linear oscillation (SRV) test machine under reciprocating conditions. The wear scar and volume of coatings were measured by using a 3D optical profilometer. SEM/EDS analysis were additionally performed for the characterization of microstructure and wear scar. The results indicated that MoS2 reduced friction and wear of the Fe-based cladding material when tested against steel at room temperature compared to the reference alloy and grade 1.2367 tool steel, and that the addition of silver further decreased wear in addition to early stage friction. It was also observed that the tribolayer, which was formed during the sliding of Ni-based - 5 Ag - 10 MoS2 and against aluminium under lubricated conditions, was protective and provided low and steady friction.

Additive manufacturing is gaining popularity at a rapid rate and has been a resourceful production process to reduce material usage, wastage (scrap) and manufacturing costs for various applications. The project conducted, emphasizes on Thermoplastic Elastomer (TPE SE6300C-65A) material, which is a highly versatile compound, and has the ability to exhibit properties of both rubber (Elastomers) in terms of flexibility and plastic (Polymers) in terms of recyclability. Cost reduction without compromising quality is one of the important factors for industries. The project involves the use of TPE pellets to extrude filaments that could be used for 3D Printing. Filament extrusion involves process variables like Nozzle Temperature, De-humidification of pellets, Diameter of the nozzle, Distance of collection, Cooling and Angle of inclination of the extruder. These process variables are optimized to accomplish the desired quality of filament. The filament produced through extrusion is further used to make products using Fused Deposition Modeling (FDM). FDM also involves numerous process variables like Layer Thickness, Build Orientation, Print Infill, Print Speed etc. In this study, different test specimens, in terms of geometrical shapes are printed from the material, TPE SE6300C-65A and tested in order to understand how the surface features as well as the dimensional accuracy change with different process variables. It is observed that the surface topography produced throughout FDM process is majorly affected by the angle of orientation of the printed part. The main goal of this thesis is to give the reader a better understanding on which process variable, such as layer thickness, temperature and print speed affect the surface roughness of the models and also a comparison between these three variables, highlighting which is more or less affecting. It is also observed the dimensional accuracy of the real specimen deviate from the value input into the CAD software. The results obtained in this study clearly suggest that there is a lot of opportunities for future improvements especially regarding the dimensional accuracy, it is imperative to achieve the highest precision possible in order to have commercial values for the FDM 3D printing.

The addition of lead to the copper alloys increases its machinability and reducesthe overall production cost, despite copper being expensive, which makes achallenging task to replace lead. But the alarming effects of lead on human healthand the recycling problems has led to the increase in concern forreducing/eliminating the use of lead in brass and other copper alloys. Manymaterials are considered to replace lead in brass; silicon is one such alternative.The turned brass sample are investigated using the state of the artequipments at Halmstad University. The results obtained are controlled readingsof surface parameters and is categorized using surface imaging and mappingsoftware, Mountains Map.This thesis characterizes the lead and the lead free brass's surfaceintegrity for a certain cutting data. The study deals with the evaluation ofselection of appropriate surface integrity parameters and summarizes theappropriate combination of cutting data to maintain the surface of the ecobrass/unleaded brass on par with the leaded brass surface. The 2D and 3Dsurface parameters illustrates the surface functionality and its effect on thematerial in contact.The research results suggest a detailed methodology for the analysis ofsurface topography and a comparison exemplifying differences between the twomaterials under study. The research provides a perplexed results and forms thebasis for further investigations of the samples machined at different cutting data.Second set of test includes comparing the Leaded brass with the unleaded brasssamples machined at 0.06, 0.1, 0.15 and 0.2mm/rev respectively. The studyfocuses on the correlation of cutting feed and the surface parameters. Comparingthe results of two tests, the unleaded brass machined @ feed rate 0.2mm/rev,200m/min, 1.5mm depth of cut posses similar surface functionality as leadedbrass.

The ease of manufacturing complex geometries using fused deposition modeling (FDM) 3D-Printing reduces the overall production cost compared with the traditional manufacturing techniques. Because of the benefits of 3D printing technologies, it is proposed to be used in the manufacturing of different products. But there is still no definite characterization of the surface quality of objects manufactured by 3D printing. Hence in order to define the texture of the surfaces produced, measurements from different samples are taken and quantified.In this study, a 3D test model consisting of various slopes is printed at different layer thicknesses and different print speeds using different 3D printers.Thus, the effect of the surface orientation on the surface roughness was studied in relation to the different layer thicknesses and different print speeds. The study samples are measured using the state of the art equipment at Halmstad University.This thesis studies the surface roughness at different slopes of FDM models.A related study on the dimensional variation between the CAD model and the actual3D printed model, and causes/reasons for the variations are analyzed.It is observed that FDM produced part surface topography is directly affected by the orientation of the surface. Also, the surface roughness increases with increase in layer thickness. The observed correlations between surface roughness and layer thickness and surface orientation could be used to better understand the behavior of FDM surfaces, thus to better quantify the surface roughness. To improve quality, it must first be quantified. It is well observed that dimensional inaccuracy exists between the CAD model and the printed part. These results suggest that there is a lot of work and improvements to be done in order to close the gap of dimensional inaccuracy and achieve a high precision commercial FDM 3Dprinting.

Increasing environmental awareness has driven a lot of research to look into various environmentally friendly lubricants which can replace more conventional mineral oil based lubricants. This is true in particular for marine and hydropower applications where the risk of lubricant leakage can be damaging to the local environment. Glycerol is an organic compound produced as a byproduct when producing Biodiesel. It is environmentally friendly and has been used by the pharmaceutical and food industries for a long time. Recent research has shown that glycerol has very good tribological properties and can be used as a lubricant in some applications. However, its high viscosity and high static friction are disadvantageous and needs improvement. The purpose of this study is to investigate possible surface active environmentally adapted additives in glycerol and water solutions. 14 additives have been selected for testing and were tested in a pin-on-disc start-stop friction test to see their effect on the static and dynamic friction coefficients. From these 14 additives two were selected due to their superior performance and were further studied. The effect of concentration of water and additive in glycerol was also investigated using the same test conditions. A phosphor based additive has been found to be the best performing.

Improving vehicle efficiency and complying to stricter exhaust emission legislations are some of the driving factors to advancement in technology of engine components. The main bearings in an internal combustion engine contribute significant amount of friction. These bearings support engine loads and allow free rotation of the crankshaft. The bearings consist of a steel backing, a lining material and an optional overlay. The overlays help to minimize friction and enhance seizure resistance during adverse operating conditions. The aim of the thesis is to study the friction and wear performance of five multi-layered bearings with various overlays. A bi-metal bearing is used as the reference for comparison. Additionally, influence of two shaft surface textures are also studied comparing to the standard shaft surface finish. A modified twin-disc test rig is used to evaluate tribological performance of the bearing system. Forced misalignment tests were also performed to simulate edge contact conditions, which occur in an engine due to shaft deflection, asymmetrical loading and other factors. The bearing surface profiles were measured using an optical interferometer. The test setup showed good repeatability and consistent results. Relative friction and wear performance are compared and the bearings are ranked accordingly. One bearing type with a polymer and MoS2 overlay showed the best overall performance. This bearing combined with a plateau textured shaft further lowered the friction coefficient by 3 % in boundary and mixed lubrication regime.

På Volvo Group Trucks Operations (GTO) i Skövde tillverkas cylinderblock, cylinderhuvud och svänghjul genom gjutning med sandformar. Då formverktygen som formar sandformarna fylls uppkommer slitage där sandpartiklarna träffar, vilket leder till att formverktygen behöver underhållas regelbundet.Målet med denna studie är att hitta alternativa material som formverktygen kan tillverkas i alternativt förstärkas eller beläggas med för att minska slitaget i formverktygen och på så sätt minska kostnader genom att förlänga underhållsintervallen. Problemet analyseras och en litteraturstudie kring erosiv och abrasiv nötning genomförs.Ett antal material tas fram genom en materialvalsprocess som lämpliga kandidater baserat på litteraturstudien, materialkartor och diskussion. Materialprover testas med en standardmetod för erosion med gasburna partiklar. Resultat från tidigare empiriska studier tyder på att erosion påverkas starkt av materialegenskaper så som hårdhet och seghet men även de eroderande partiklarnas infallsvinkel och hastighet.Erosionstestet utförs för 30 och 90 graders infallsvinkel. Testet visar att de mjukare stålen, Holdax och Sverker 21, har högre beständighet mot erosion vid låga infallsvinklar och det hårdare stålet Nimax har högre beständighet vid höga infallsvinklar. Nimax anses vara ett lämpligt material till formverktyget då Nimax har den totalt lägsta erosionstakten vid hopslagning av den totala erosionstakten över båda infallsvinklarna. Nimax har den lägsta erosionstakten vid 30 graders infallsvinkel och anses även ha god beständighet mot erosion vid 90 graders infallsvinkel.Rekommendation ges kring upprepade erosionstester för att säkerställa resultatet. Rekommendationer finns också kring materialprovning i formverktyget för att se om ett materialbyte skulle leda till besparingar. Undersökning av möjligheter att konstruera bort nötning i formverktyget genom ändring av infallsvinklar mellan den inblåsta sanden och formverktyget, samt ändring av lufttryck rekommenderas. / At Volvo Group Trucks Operations (GTO) in Skövde, cylinder blocks, cylinder heads and flywheels are manufactured through sandcasting. As the forming tools that forms the sand forms are filled with sand, wear occurs where the sand particles hit the tool surface. The forming tool thus needs to be regularly maintained. The aim of this study is to evaluate alternative materials that the forming tools can be manufactured in to reduce wear, and thereby reducing costs by extending maintenance intervals. The problem is analyzed and a literature study on erosive and abrasive wear is carried out. A number of materials are presented as suitable candidates based on the literature study, material charts and discussion. Material samples are tested using a standard method for solid particle erosion using gas jets. Results from previous empirical studies indicate that erosion is strongly influenced by material properties such as hardness and toughness but also the angle of impingement and velocity of the erosive particles.The erosion test is performed at 30 and 90 degree angle of impingement. The test shows that the softer steel, Holdax and Sverker 21 have higher resistance to erosion at low angles of impingement and the harder steel Nimax has higher resistance at high angles of impingement. Nimax is considered a suitable material for the forming tool, as Nimax has the overall lowest erosion rate when adding the total erosion over both angles of impingement. Nimax has the lowest erosion rate at 30 degrees angle and is also considered to have good resistance to erosion at 90 degrees angle. Recommendation is given on repeated erosion tests to validate the results. There are also recommendations regarding material testing in the forming tool to see if a material change would lead to savings. Examination of possibilities to make changes in the sand filling process, altering angle of impingement between the sand blown and the forming tool as well as air pressure is recommended.

Thermal fatigue is a serious problem in todays power plants. A large amount of damages around the world circles around that subject. The damage can come from the mechanism of two flows mixing with different temperatures in a T-junction. It is a fundamental prerequisite that these T-junctions are frequently tested for damages. An amount of criterias steers the rate of testings. This guide/document will provide the process of rating the T-junctions resistance with valid information and ease the course. If a T-junction is stated as very sensetive for thermal fatigue, it will be graded with a low damage index. This value is reliant of the temperature difference between the two flows and can be changed with different actions, for example by adding a mixer to the T-junction. The mixer will blend the two flows so the thermal fatigue reduces or doesn’t occour at all. The T-junction can be tested with several methods, ultra sonic testing or eddy-current testing. The ultra sonic testing method is the most used method and can test the inside of the T-junction pipe without access of the inside.