The present work was conducted in Sandvik Coromant to enhance the knowledge and understanding of general flank wear growth and specifically in this case flank wear growth on the cutting edge of the coated (Ti(C, N)/ Al2O3/ TiN) tool inserts.   Reliable modeling of tool life is always a concern for machining processes. Numbers of wear models studies predicting the tool life length have been created throughout the metal-cutting history to better predict and thereby control the tool life span, which is a major portion of the total cost of machining.   A geometrical contact model defining the geometry of the flank wear growth on the cutting tool inserts was proposed and then compared with four suggested models, which estimates flank wear. The focus of this work is on the initial growth of flank wear process and thereby short cutting-time intervals are measured.   Wear tests on cutting tool inserts were performed after orthogonal turning of Ovako 825 B steel and were analysed by optical instrument, 3D optical imaging in Alicona InfiniteFocus and EDS in SEM. Force measurements for cutting speeds, Vc, 150, 200, and 250 m/min and feed rate, fn, 0.15 mm/rev were recorded as well.   Results show that initial flank wear land, VB, growth is dominated by sliding distance per cutting length for different cutting speeds. A good correlation between the geometrical contact model and estimation models is indentified. The cutting force measurements compared with the flank wear land show proportionality between two parameters. For the machining data in the present study the flank wear rate per sliding distance, dW/dL, is estimated to 2x103 (μ3/m).

Despite a large demand from industry, a realistic chatter modeling for hard turning has not been available due to the complexity of the problem, which is mainly caused by flank wear and nonlinearity in hard turning. This thesis attempts to develop chatter models for predicting chatter stability conditions in hard turning with the considerations of the effects of flank wear and nonlinearity. First, a linear model is developed by introducing non-uniform load distribution on a tool tip to account for the flank wear effect. Second, a nonlinear model is developed by further incorporating nonlinearity in the structure and cutting force. Third, stability analysis based on the root locus method and the describing function approach is conducted to determine a critical stability parameter. Fourth, to validate the models, a series of experiment is carried out to determine the stability limits as well as certain characteristic parameters for facing and straight turning. From these, it is shown that the nonlinear model provides more accurate predictions than the linear model, especially in the high-speed range. Furthermore, the stabilizing effect due to flank wear is confirmed through a series of experiments. Fifth, to fully account for the validity of linear and nonlinear models, an empirical model is proposed to fit in with the experimental stability limits in the full range of cutting speed. The proposed linear and nonlinear chatter models will help to improve the productivity in many manufacturing processes. In addition, chatter experimental data will be useful to develop other chatter models in hard turning.

This study includes examination of the machinability characteristics of two medium carbon steel types (SAE 1040 and SAE 1050) as a result of spherodizing treatment. Both steel types were handled into four categories according to their spherodizing treatment parameters (temperature and time). Microstructural investigation, hardness and ultrasonic sound velocity measurement (with both longitudinal and transverse waves) of these steels were performed, and effect of applied heat treatments on microstructure, hardness and ultrasonic sound velocity was investigated. Pulse-echo method has been used for ultrasonic sound velocity measurements, and measurements were performed with 5 and 10 MHz longitudinal and 5 MHz transverse wave probes. Tool life criterion was used for determining the machinability characteristics of the steels. For this purpose, flank wear land measurements were performed on the cutting tools. Results have showed that, by appliying heat treatment it is possible to change the microstructure, hardness, ultrasonic sound velocity and machinability characteristics of a steel.

Classical orthogonal and oblique cutting are the fundamental material removal or machining processes to which other practical machining processes can be related in the study and modelling of the machining processes. In the last century, a large amount of research and development work has been done to study and understand the various machining processes with a view to improving the processes for further economic (cost and productivity) gains. However, many aspects of the cutting processes and cutting performance remains to be fully understood in order to increase the cutting capability and optimize the cutting processes; in particular, there is little study to understand the effects of the inevitable tool wear on the machining processes. This thesis includes an extensive literature review on the mechanics of cutting analysis. Considerable work has been carried out in past decades on the fundamental analysis of 'sharp' tool cutting. Although some work has been reported on the effects of tool flank wear on the cutting performance, there is a general lack of the fundamental study of the effects of the flank wear on the basic cutting or chip formation process. It has been well documented that tool flank wear results in an increase in the cutting forces. However, it was not known if this force increase is a result of the change in the chip formation process, and/or the rubbing or ploughing forces between the tool flank and the workpiece. In work carried out since the early 1980s, the effects of the so-called edge forces have been considered when the tool is not absolutely sharp. Little has been reported to further develop fundamental cutting theories to understand applications to more relevant the practical situation, i.e. to consider the tool wear effects. Based on the findings of the literature review, an experimental investigation is presented in the first part of the thesis to study the effects of tool flank wear on the basic cutting or chip formation process by examining the basic cutting variables and performance in the orthogonal cutting process with tool flank wear. The effects of tool flank wear on the basic cutting variables are discussed by a comprehensive analysis of the experimental data. It has been found that tool flank wear does not affect the basic cutting variables (i.e. shear angle, friction angle and shear stress). It is therefore deduced that the flank wear does not affect the basic chip formation process in the shear zone and in the tool-chip interface. The study also finds that tool flank wear causes an increase in the total cutting forces, as can be expected and such an increase is entirely a result of the rubbing or ploughing forces on the tool wearland. The significance of this finding is that the well-developed machining theories for 'sharp' tools can be used in modelling the machining processes when tool flank wear is present, rather than study the machining process and develop machining theories from scratch. The ploughing forces can be modelled for incorporation into the overall cutting force prediction. The experimental study also allows for the forces on the wearland (or wearland force) and edge forces to be separated from the total measured forces. The wearland force and edge force models are developed in empirical form for force prediction purpose. In addition, a database for the basic cutting variables or quantities is established for use in modelling the cutting forces. The orthogonal cutting force model allowing for the effects of flank wear is developed and verified by the experimental data. A comprehensive analysis of the mechanics of cutting in the oblique cutting process is then carried out. Based on this analysis, predictive cutting force models for oblique cutting allowing for the effects of flank wear are proposed. The wearland force and edge force are re-considered by analysing the oblique cutting process and the geometrical relation. The predictive force models are qualitatively and quantitatively assessed by oblique cutting tests. It shows that the model predictions are in excellent agreement with the experimental data. The modelling approach is then used to develop the cutting force models for a more general machining process, turning operation. By using the concept of an equivalent cutting edge, the tool nose radius is allowed for under both orthogonal and oblique cutting conditions. The wearland forces and edge forces are taken into consideration by the integration of elemental forces on the tool flank and the cutting edge, respectively. The cutting forces in turning operations are successfully predicted by using the basic cutting quantity database established in the orthogonal cutting analysis. The models are verified by turning operation tests. It shows that the model predictions are in excellent agreement with the experimental results both qualitatively and quantitatively. The major findings, research impacts and practical implications of the research are finally highlighted in the conclusion. The modelling approach considering the flank wear effects in the classical orthogonal and oblique cutting and turning operations can be readily extended to other machining operations, such as drilling and milling.

This dissertation thesis is focused on the analysis of specific cutting forces and accompanying effects during machining of the new materials, composite materials. The experimental part is split up to two main chapters. In the first chapter, the development of specific cutting forces is analyzed in detail when cutting conditions are changing. The experimental machining of glass/polyester and carbon/epoxy composites is described for fibers orientations 0 a 90 (ie, the orientation of the fibers in the feed rate direction and perpendicular to the feed rate direction). The influence of the cutting tool flank wear on the specific cutting force is investigated further. The last section compares the values of specific cutting forces when machining with carbide milling tools deposited by different types of coating. The second chapter describes the measurement of sound spectrums generated by cutting process, sound maps creating and finding possible correlations between dominant frequencies of the sound and the specific cutting forces, or the cutting tool flank wear. The measurements are described for the cases of machining steel 15 260.7 and glass-polyester composite material.

The usage of titanium alloys in many industries has increased significantly over the years due to their superior properties. However, they are extremely difficult to machine because of their distinctive characteristics such as their high temperature strength, low thermal conductivity, and high chemical affinity for tool materials. Hence, despite their increased usage, they are still expensive to machine when compared to other metals. The current research aims to address the machinability issues of titanium alloys by developing novel compositions of a new generation of self-adaptive Physical Vapor Deposition (PVD) coatings that function by forming beneficial tribo-films through their interaction with the environment. These tribo-films form during cutting and provide enhanced lubricity, hardness, strength, and thermal barrier characteristics to the cutting tool. It was found that during Ti6Al4V machining, significant BUE and crater wear formation occurs; however, one is dominant over the other depending on the cutting conditions. Therefore, the coatings investigated were designed by taking into consideration the dominant tool wear mechanisms and the complex tribological phenomena that occur in the cutting zone. The current research investigated monolayer TiB2 and CrN self-adaptive PVD coatings for the rough (cutting speed - 45 m/min, feed -0.15 mm/rev, and depth of cut – 2 mm) and finish (cutting speed - 150 m/min, feed -0.1225 mm/rev, and depth of cut – 0.25 mm) turning of Ti6Al4V alloy. Detailed experimental studies were performed to study the effectiveness of the coatings during machining. Micro-mechanical characteristics of the coatings were also studied to understand how coating properties affect the coatings performance in machining and tribo-film formation. The results obtained show that both the TiB2 and CrN coatings significantly improve tool performance during the rough turning of Ti6Al4V alloy compared to the current industrial standard, which is due to certain micro-mechanical coating properties and the beneficial tribo-films formed. A coating of CrN coating was found to increase tool life during finish turning. It was also established that for machining applications where intensive adhesive interaction occurs at the tool-chip interface, coatings with lower hardness values perform significantly better than harder ones. / Thesis / Doctor of Philosophy (PhD) / Titanium alloys are increasingly becoming the material of choice for many industrial applications due to their superior properties. However, they are very difficult to machine since they have high chemical affinity towards tool materials, low thermal conductivity, and high temperature strength. These properties cause rapid failure of the tool. The objective of the current research is to address machinability issues during Ti6Al4V machining and improve tool performance. One effective strategy to minimize tool wear is to apply self-adaptive PVD tool coatings that can form beneficial tribo-films through their interaction with the environment and provide enhanced lubricity, hardness, strength, and thermal barrier characteristics to the cutting tool. In the current research, two self-adaptive PVD coatings were developed that offset the dominant tool wear mechanisms prevalent during the rough and finish turning of Ti6Al4V alloy and reduced the tool wear rate by more than 60% compared to the current industrial standard.

Various nitrides, such as chromium nitride and titanium nitride, find extensive use in cutting tools, micromechanical devices, and medical implants due to their exceptional physical, mechanical, and chemical properties. These coatings exhibit superior hardness compared to high-speed steel and cemented carbide along with notable protective capabilities against corrosion and wear. These coatings have been successfully used to enhance the properties of cemented carbide and steel tools while safeguarding their surfaces. By adjusting deposition parameters like N2 gas pressure, the properties of PVD coatings can be tailored to effectively withstand specific dominant wear modes during machining. The study investigates and demonstrates that CrN coatings can be specifically engineered to have distinct mechanical and tribological properties by adjusting the N2 gas pressure, which enhances machining performance in cases where BUE formation occurs. A comprehensive coating characterization was conducted for each CrN coating studied. Wear performance assessments of the various CrN-coated WC tools were carried out during dry finish turning of SS 304. Additionally, high temperature coating characterization was performed for the best-performing in house deposited coating (nitrogen gas pressure of 4 Pa, bias voltage of -50 V) and a commercial coating, up to 450°C. The results highlighted the influence of N2 gas pressure on the structural, mechanical, and tribological properties of CrN coatings. The findings indicate that coatings with a comparatively low H/E ratio (while maintaining higher elastic modulus values), low roughness, moderate residual stress, high plasticity index, and high toughness exhibited superior performance when machining sticky materials and in high-temperature applications prone to adhesive wear and built-up edge (BUE) formation. Furthermore, high-temperature studies confirmed that the in-house coating retained a low H/E ratio, high plasticity index, high toughness, and low roughness, without compromising the hardness or elastic modulus values. In contrast, the commercial coating failed to retain its properties at higher temperatures. These high-temperature studies provide valuable insights for selecting CrN coatings tailored for machining materials that tend to adhere to the cutting tool and for high-temperature applications. / Dissertation / Master of Applied Science (MASc) / Coating properties such as hardness, residual stress, adhesive behaviour, elastic modulus, and roughness significantly affect tool performance and wear patterns, besides machining parameters and conditions. This research focuses on CrN coatings deposited by PVD cathodic arc deposition, adjusting the N2 gas pressure while keeping bias voltage constant. The research investigates and illustrates that CrN coatings can be specifically tailored (by adjusting the N2 gas pressure) to possess unique mechanical, and tribological properties that ameliorate machining performance in scenarios involving BUE formation. Three CrN coatings were deposited using the PVD technique by varying the N2 gas pressure. A thorough coating characterization was conducted for each of three in house deposited coatings and one commercially available coating. The wear behaviour of different CrN-coated WC tools was evaluated during dry finish turning of SS 304 to identify the best-performing coating. Lastly, high-temperature coating characterization was performed up to 450 ˚C for one in-house deposited coating (nitrogen gas pressure of 4 Pa, bias voltage of -50 V) and one commercial coating. The results showed that a coating that has low H/E ratio (without compromising elastic modulus), high plasticity index, high toughness, moderate residual stress and low roughness effectively minimizes issues related to sticking and BUE formation and retains coating properties at high temperatures.

Den ökande efterfrågan på högre produktkvalitet inom tillverkningsindustrin kräver hög stabilitet och lång livslängd på borrverktyg under borrningbearbetningsprocessen. En metod för att öka produktkvaliteten och därmed förlänga livslängden på borrverktyg är skäreggpreparering. Skäreggpreparering används för att skapa en kantgeometri som ger borrverktyget både en bättre styrka och högre tålighet mot slitage. Det mest förekommande slitaget på borrverktyg är fasförslitning och det utvecklas snabbt under den initiala slitningsperioden under borrens livslängd. Syftet med det här examensarbetet var att genom flerfaktorförsök undersöka hur skäreggprepareringsprocessen kan förbättras för att minska fasförslitning under den initiala slitningsperioden på belagda hårdmetallborrar. Skäreggprepareringsprocessen studerades som en fallstudie på Scania Motorbearbetning. Fallstudien genomfördes efter problemlösningsmetodiken DMAIC (Define, Measure, Analyse, Improve och Control) som inkorporerade försöksplanering, vilket medförde att två ytterligare faser tillkom: Pre-analyze och Experiment. Datainsamlingen bestod av både kvalitativ och kvantitativ data. Den kvalitativa datan erhölls från intervjuer under Measure-fasen och den kvantitativa datan erhölls från det genomförda experimentet under Experiment-fasen, som sedan analyserades i Analyze-fasen. Baserat på litteraturstudien, nulägesbeskrivningen och intervjuerna bestämdes försöksfaktorerna till processtid, borrens djup i slipmedel, rotationsriktning på rotor och rotationshastighet på spindel samt responsvariablerna till skäreggradie och total fasförslitning. Försöksfaktorerna testades i ett fullständigt tvånivåers faktorförsök med 4 faktorer och 4 centrumpunkter. Analysen av resultaten från experimentet visade att korrelationen mellan responsvariablerna var försumbar under den initiala slitningsperioden. Vidare identifierades inte några signifikanta effekter baserade på responsvariabeln total fasförslitning. Däremot kunde det konstateras att de försöksfaktorer som påverkade responsvariabeln skäreggradie var processtid, borrens djup i slipmedel och rotationsriktning på rotor. En optimeringsmodell togs fram i Improve-fasen för att optimera skäreggprepareringsprocessen med avseende på skäreggradie. Optimeringen utgick från att ha en stor skäreggradie under förutsättningen att den nuvarande processtiden halveras. Optimeringsmodellen kunde inte bekräftas, därför togs en rekommendation fram som beskriver stegen för att bekräfta den framtagna optimeringsmodellen. Vidare togs två ytterligare rekommendationer fram med syfte att undersöka skäreggprepareringsprocessen med avseende på andra typer av slitage samt undersöka verktygsslitage under verktygets fulla livslängd. I Control-fasen togs en kontrollplan fram som stöd för att kontrollera rekommendationerna. Avslutningsvis bidrog det här examensarbetet med nya insikter och slutsatser om utveckling av fasförslitningen under den initiala slitningsperioden under en borrs livslängd. / The increasing demand for higher product quality in the manufacturing industry requires high stability and long service life of drilling tools during the drilling process. One method of increasing product quality and thus extending the tool life for drills is cutting edge preparation. Cutting edge preparation is used to create an edge geometry that gives the drilling tool both better strength and higher resistance to wear. The most common wear on drill tools is flank wear that develops rapidly during the initial wear period of the drill's life. The purpose of this thesis was to investigate how the cutting edge preparation process can be improved by factorial design in order to reduce flank wear during the initial wear period on coated solid carbide drills. The cutting edge preparation process was studied as a case study at Scania's motor processing department. The case study followed problem-solving methodology DMAIC (Define, Measure, Analyze, Improve and Control) incorporating design of experiments. This resulted in two additional phases: Pre-Analyze and Experiment. Data collection consisted of both qualitative and quantitative data. The qualitative data were obtained from interviews during the Measure phase and the quantitative data was obtained from the experiment conducted during the Experiment phase, which was later analyzed in the Analyze phase.     Based on a literature study, current description, and interviews, the identified experimental factors were process time, depth in the grinding granulate, rotational direction of the rotor, and rotational speed of spindle. The identified response variables were cutting edge radius and total flank wear. The experimental factors were tested in a full two-level factorial design with 4 factors and 4 center points. The analysis of the results from the experiment showed that the correlation between the response variables was negligible during the initial wear period. Furthermore, no significant effects could be found based on the response variable total flank wear. However, it was found that the experimental factors that influenced the response variable cutting edge radius were process time, depth in grinding granulate, and direction of rotation of the rotor. An optimization model was developed during the Improve phase to optimize the cutting edge preparation process in regards to the cutting edge radius. The optimization was based on generating a large cutting edge radius and at the same time reducing the current process time by half. The optimization model could not be confirmed; therefore, a recommendation was developed outlining the steps to confirm the optimization model. Furthermore, two additional recommendations were made to investigate the cutting edge preparation process concerning other types of wear and to examine tool wear during the tool’s full life. A control plan was developed in the Control phase to help to control the recommendations. In conclusion, this thesis contributed new insights and conclusions on the development of flank wear during the initial wear period during the tool life.

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&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.