Grinding is a commonly used finishing process to produce components of desired shape, size and dimensional accuracy. The ultimate goal is to have the maximum workpiece quality, minimum machining time and high economic efficiency by making a selective adaptation of the possible process strategy and chosen parameter selection. The focus of this study arose from a limitation that challenges the grinding industry. The production rate of the ground parts is generally constrained by surface topography and subsurface damage appearing as residual tensile stress, localized burns, and phase transformation induced micro and macro-cracking. This motivates the need for a reliable numerical modelling to simulate the grinding process. The numerical model sought should be able to predict not only the required grinding residual stresses but also the deformation history. The objective of this thesis is to build up a reliable finite element model for grinding-induced residual stress analysis and thus to explore thoroughly the mechanisms in terms of grinding conditions. The variations of the residual stresses and strains at integration points have been examined, and the effects of the friction coefficient (µ), Peclet number (Pe), non dimensional heat transfer coefficient (H) and different magnitudes of input heat flux (Q) on both the microstructure and the residual stress state are analyzed. Finally, based on the new findings in this research, a more comprehensive methodology is suggested for further study.

Detta examensarbete har utförts på Ovako Bar i Hällefors i syfte att kontrollera möjligheterna att automatisera en slipningsprocess på stänger med ytdefekter. Det största skälet till arbetets uppkomst är de vibrationsskador som uppstår i operatörers händer vilket i sin tur leder till sjukskrivningar. Arbetet inleddes med en nulägesanalys på Kontrollstation 7 för att kontrollera hur processen går till, hur operatörerna upplever situationen och få en större förståelse för situationen. Information om nuvarande utrustning inhämtas i syfte att kunna utvärdera möjligheter. Kontakter med potentiella leverantörer togs också, i syfte att få ytterligare bollplank. Efter nulägesanalysen inleddes förbättringsförslagsprocessen. Lösningar till problemet uppkom ur brainstorming efter kravspecifikationen. De lösningar som blev godkända skickades ut till diverse leverantörer som tidigare kontaktats för vidare idéutbyte och möjlighet till utförande. De leverantörer som kontaktades var IM Teknik och Robotslipning AB. Investeringsanalysen visar att lösningen ”robotslipning med visionssystem” är den mest kostnadseffektiva för att uppnå de krav och önskemål som skulle uppfyllas. / This thesis has been carried out on Ovako Bar in Hellefors in order to check the possibility of automating the manual grinding process on bars with surface defects. The biggest reason for the occurrence of this thesis is the vibration damages in operators' hands, which in turn leads to sick leave. Work began with a current situation analysis of KS-7 to observe how the process works, how operators perceive the situation and get a better understanding of the situation as well as acquiring information on the current equipment. Contacts with potential suppliers were taken as well in order to obtain additional exchange about the potential products. After the current situation analysis the improvement suggestions phase took place. Solutions to the problem arose out of brainstorming according to the specifications. The solutions that were approved were sent to various vendors for further exchange of ideas and the possibility of execution. IM Teknik and Robotslipning are the companies that were contacted. Investment analysis shows that the solution with robotic grinding with vision system is the most cost efficient to meet the demands and requirements to be fulfilled.

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Using a Panasonic MG-72 Micro Electro-Discharge Machine, techniques and procedures are developed to fabricate complex microstructures in conductive materials and engineered ceramics.

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Rails play a significant role in transport of goods and passengers. In Australia railway transport industry contributes 1.6% of GDP with goods and services worth $AUD 8 billion each year which includes $ AUD 0.5 billion per year in exports (Australasian Railway Authority Inc, 2002). Rail track maintenance plays an important role in reliability and safety. The Office for Research and Experiments (ORE) of the Union International des Chemins de Fer (UIC) has noted that maintenance costs vary directly (60-65 per cent) with change in train speed and axle load. It was also found that the increase in these costs with increased speed and axle load was greater when the quality of the track was lower (ORR, 1999). Failures during operation are costly to rail players due to loss of service, property and loss of lives. Maintenance and servicing keep rail tracks in operating, reliable and safe condition. Therefore, technical and economical analysis is needed by rail players to reduce maintenance cost and improve reliability and safety of rail networks. Over the past few years, there have been major advances in terms of increased speed, axle loads, longer trains, along with increased traffic density in corridors. This has led to increased risks in rail operation due to rolling contact fatigue (RCF) and rail wear. The infrastructure providers have less incentive to maintain a given infrastructure standard if its access charges are rigid and rolling stock standard is not achieved. It has been estimated that between 40 to 50 per cent of wagon maintenance costs and 25 per cent of locomotive maintenance costs are related to wheel maintenance (Railway Gazette International, 2003). The economic analysis of Malmbanan indicates that about 50% of the total cost for maintenance and renewal were related to traffic on rails and 50% not related to traffic, such as signaling, electricity and snow-clearance. The results from the analysis have made it possible for the mining company LKAB to start up the 30 Tonnes traffic with new wagons and locomotives on the Malmbanan line in year 2001 (Åhrén et al 2003). The rail infrastructure providers have challenges to maintain infrastructure due to government control on access charges and limited control on rail operations. The aim of the research is to: · Develop a maintenance cost model for optimal rail grinding for various operating conditions; and · Develop integrated rail grinding and lubrication strategies for optimal maintenance decisions. In this research real life data has been collected, new models have been developed and analysed for managerial decisions. Simulation approach is used to look into the impact on various costs such as rail grinding, operating risk, down time, inspection, replacement, and lubrication. The results of the models for costs and the effect of rail grinding and lubrication strategies are provided in this thesis. In this research rail track degradation, rail failures and various factors that influence rail degradation are analysed. An integrated approach for modelling rail track degradation, rail wear, rail grinding and lubrication is developed. Simulation model and cost models for rail grinding are developed and analysed. It has been found through this research that rail grinding at 12 MGT interval is economic decision for enhancing rail life. It was also found that lubrication is most effective compared to stop/start and no lubrication strategies in steep curves. Rail grinding strategies developed in this research have been considered by Swedish National Rail for analysing the effectiveness of their existing policies on grinding intervals. Optimal grinding and lubrication decisions have huge potential for savings in maintenance costs, improving reliability and safety and enhancing rail life.

Doctor of Philosophy / This research aimed to develop new cooling methods to replace, or at least minimise, the use of currently used grinding coolants which are known to be harmful to the environment. The methods used involved the application of a cold air and vegetable oil mist mixture (CAOM), and the use of liquid nitrogen as cooling media. Allied research focused on the development of a segmented grinding wheel equipped with a coolant chamber. The feasibility of a grinding system using CAOM was assessed on the surface grinding of plain carbon steel 1045. It was found that at low material removal rates, ground surfaces were obtained with a quality comparable to that from grinding with a conventional coolant in association with a reduction of grinding forces. There was no significant difference in the subsurface hardness of the components using CAOM, although the latter method showed a stronger dependence of surface residual stresses on the depth of cut due to the limit in cooling capacity of CAOM. The effects of using liquid nitrogen as a cooling medium on the microstructure of quenchable steel were explored. It was found that a martensite layer was induced on the ground surface. The microstructure featured a dispersion of very fine carbides within the martensite lattice, resulting in a remarkable increase in hardness and high compressive residual stresses within the layer. The topography of the ground surfaces indicated that the material was predominantly removed by brittle fracture. Furthermore surface oxidisation was suppressed. In the interest of coolant minimisation, a segmented wheel equipped with a pressurized coolant chamber was developed. A higher quality ground surface was obtained in conjunction with a coolant saving of up to 70%. In addition, the adhesion of ground chips on the wheel surface largely disappeared. Furthermore, surface tensile residual stresses caused by thermal deformation were minimised. The mechanism of coolant disintegration to form mists using this type of wheel system was studied. The Weber theory for Newtonian jet instability was applied to quantitatively determine the contribution of coolant flow rate to mist and ligament modes. A semi-analytical model was then developed to predict the mist flow rate by taking into account both grinding parameters and coolant properties. The model prediction was in agreement with experimental measurements. Based on the principles of fluid motion and the mechanisms of spin-off and splash, analytical models for both conventional and segmented wheels were established to provide a physical understanding of the mechanisms of coolant penetration into the grinding zone. Coolant minimisation was evident using the segmented wheel where the coolant pumping power into the grinding zone increased with wheel speed, but for the conventional wheel it decreased. A quantitative analysis was developed that accounted for the coolant properties and system design characteristics governing the penetration mechanism revealed by the theory established above. In conjunction with the mist formation analysis, the developed model offers a practical guideline for the optimal use of grinding coolants in achieving a balance between the demands of productivity and care for the environment.