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  • 101.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Tricoire, Aurélien
    Volvo Aero, Trollhättan.
    Dorfman, Mitch
    Sulzer Metco, Westbury, United States.
    Next generation thermal barrier coatings for the gas turbine industry2011In: Journal of Thermal Spray Technology, Vol. 20, no 1-2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings. © 2010 ASM International.

  • 102.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång.
    Dorfman, Mitch
    Sulzer Metco, Westbury, USA.
    Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems2013In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 22, no 6, p. 864-872Article in journal (Refereed)
    Abstract [en]

    The aim of this study was the further development of dysprosia stabilised zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial stan dard thermal barrier coating. Two morphologies of ceramic top coat were studied; one using a dual layer systems and the second using a polymer to generate porosity. Evaluations were carried out using laser flash technique to measure thermal properties. Lifetime testing was conducted using thermal shock testing and thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis used to characterise porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

  • 103.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Tang, Zhaolin
    Northwest Mettech Corp., Vancouver, Canada.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of Bond Coat Surface Roughness on the Structure of Axial Suspension Plasma Spray Thermal Barrier Coatings - Thermal and Lifetime Performance2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, no April, p. 15-23Article in journal (Refereed)
  • 104.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA .
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings2014In: Coatings, ISSN 2079-6412, Vol. 4, no 3, p. 630-650Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM

  • 105.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Treibacher Industrie AG, Althofen 9330, Austria.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Susnjar, Johann
    Treibacher Industrie AG, Althofen 9330, Austria.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Performance Testing of Suspension Plasma Sprayed Thermal Barrier Coatings Produced with Varied Suspension Parameters2015In: Coatings, ISSN 2079-6412, Vol. 5, no 3, p. 338-356Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying has become an emerging technology for the production of thermal barrier coatings for the gas turbine industry. Presently, though commercial systems for coating production are available, coatings remain in the development stage. Suitable suspension parameters for coating production remain an outstanding question and the influence of suspension properties on the final coatings is not well known. For this study, a number of suspensions were produced with varied solid loadings, powder size distributions and solvents. Suspensions were sprayed onto superalloy substrates coated with high velocity air fuel (HVAF) -sprayed bond coats. Plasma spray parameters were selected to generate columnar structures based on previous experiments and were maintained at constant to discover the influence of the suspension behavior on coating microstructures. Testing of the produced thermal barrier coating (TBC) systems has included thermal cyclic fatigue testing and thermal conductivity analysis. Pore size distribution has been characterized by mercury infiltration porosimetry. Results show a strong influence of suspension viscosity and surface tension on the microstructure of the produced coatings.

  • 106. DAS, D.K.
    et al.
    Singh, Vakil
    Joshi, Shrikant V.
    High temperature oxidation behaviour of directionally solidified nickel base superalloy CM–247LC2003In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 19, no 6, p. 695-708Article in journal (Refereed)
    Abstract [en]

    The present paper describes the isothermal and cyclic oxidation behaviour of the technologically important nickel base directionally solidified superalloy CM-247LC in air in the temperature range 1000-1200°C. This superalloy behaves as a transition nickel base alloy under isothermal oxidation conditions and exhibits a fairly long transient oxidation period (~20 h at 1100°C). Irrespective of the temperature of exposure and nature of oxidation (isothermal or cyclic), a composite oxide scale develops on CM-247LC. While the outer portion of the oxide scale consists of either spinel (NiAl2O4) or a mixture of spinel and NiO, depending on oxidation temperature, the inner portion is always constituted of alumina. Beyond the transient period, the alloy is found to follow parabolic oxidation kinetics. The oxide layer that forms is invariably very non-uniform in thickness, and is dispersed with two types of oxide particles. While tantalum rich oxide particles are found scattered in the outer zone of the oxide layer, hafnium rich oxide particles lie close to the oxide/metal interface. Results also reveal that the nature of oxidation associated with the CM-247LC superalloy causes entrapment of metal islands in the oxide layer.

  • 107.
    Das, Kallol
    et al.
    University West, Department of Engineering Science.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Effect of tool wear on quality in drilling of titaniumalloy Ti6Al4V, Part II: Microstructure and Microhardness2017In: High speed machining, E-ISSN 2299-3975, Vol. 3, p. 11-22Article in journal (Refereed)
    Abstract [en]

    Drilling of Ti6Al4V with worn tools can introduce superficial and easily measured features such as increase of cutting forces, entry and exit burrs and surface quality issues and defects. Such issues were presented in the part I of this paper. In part II, subsurface quality alterations,such as changes of the microstructure and microhardness variation is considered by preparing metallographic sections and measurement, mapping of the depth of grain deformation, and microhardness in these sections. Drastic changes in the microstructure and microhardness were found in sections drilled with drills with large wear lands,particularly in the dry cutting tests. These measurements emphasize the importance of detection of tool wear and ensuring coolant flow in drilling of holes in titanium components.

  • 108.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Robotic Friction Stir Welding for Flexible Production2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Friction Stir Welding (FSW) is a modern welding process that joins materials by frictional heat, generated by a rotating tool. Unlike other welding processes, the material never melts, which is beneficial for the weld properties. FSW is already widely adopted in several industries but the applications are limited to simple geometries like straight lines or circular welds, mostly in aluminium. The welding operation is performed by rigid FSW machines, which deliver excellent welds but puts limitations on the system in terms of flexibility and joint geometries. Therefore, several research groups are working on the implementation of the FSW process on industrial robots. A robot allows welding of three-dimensional geometries and increases the flexibility of the whole system. The high process forces required for FSW, in combination with the limited stiffness of the robot brings some extra complexity to the system.  The limitations of the robot system are addressed in this licentiate thesis.

    One part of the thesis studies the effect of robot deflections on the weld quality. A sensor-based solution is presented that measures the path deviation and compensates this deviation by modifying the robot trajectory. The tool deviation is reduced to an acceptable tolerance and root defects in the weld are hereby eliminated. The sensor-based method provided better process understanding, leading to a new strategy that uses existing force-feedback for path compensations of the tool. This method avoids extra sensors and makes the system less complex. Another part of this work focuses on the extra complexity to maintain a stable welding process on more advanced geometries. A model is presented that allows control of the heat input in the process by control of the downforce. Finally, the robot’s limitations in terms of maximal hardness of the materials to be welded are investigated. Parameter tuning and implementation of preheating are proposed to allow robotic FSW of superalloys.

  • 109.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Three-dimensional friction stir welding of inconel 718 using the ESAB Rosio FSW-Robot2013In: ASM Proceedings of the International Conference: Trends in Welding Research, Chicago, IL, 2013, p. 829-833Conference paper (Refereed)
    Abstract [en]

    Robotic Friction Stir Welding (FSW) facilitates for increased welding flexibility, and allows for studies of forces in three dimensions without having the high cost of a stiff 5-axes FSW machine. Recent developments in tool materials and welding equipment motivate this study on FSW of high-strength alloys by a robot in a three dimensional workspace. New concepts of aircraft engines suggest higher temperatures to increase engine efficiency, requiring more durable materials such as the nickel-based alloy 718. The ESAB Rosio™ FSW robot, used in this study, can deliver up to 15kN downforce and 90Nm torque. This is sufficient for welding high-strength alloys of limited thickness. This study focuses on the process forces during friction stir welding of Inconel 718 with thickness up to 3mm in butt-joint configuration. A newly developed threaded Poly-Crystalline Boron Nitride (PCBN) tool with convex shoulder is used in a local argon-shielded atmosphere. Initial tests are performed in a stiff FSW machine in position controlled mode. The measured process forces in position control are later on used as parameters on the force-controlled robot. Different backing bar materials are investigated with the aim to decrease the risk of root defects. Tool steel and regular inconel backing bars are proven to be too soft for this purpose and alternatives are suggested. The optimal welding parameters are tuned to combine a good weld quality with the process forces that can be obtained by the robot. Preheating is used to further decrease the need of high process forces. Copyright © 2013 ASM International® All rights reserved.

  • 110.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Thermoelectric method for temperature measurement in friction stir welding2013In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 18, no 7, p. 541-550Article in journal (Refereed)
    Abstract [en]

    Previous research within friction stir welding (FSW) has demonstrated that online control of welding parameters can improve the mechanical properties and is necessary for certain applications to guarantee a consistent weld quality. One approach to control the process is by adapting the heat input to maintain a stable welding temperature, within the specified operating boundaries. This requires accurate in-process temperature measurements. This paper presents a novel method to measure the temperature at the interface of the FSW tool and workpiece. The method is based on the thermoelectric effect between dissimilar materials. The measurements are compared to thermocouple measurements and to a physical model and show good correspondence to each other. Experiments demonstrate that the method can quickly detect temperature variations, due to geometrical variations of the workpiece or due to parameter changes. This allows use of the method for online control of robotic FSW.

  • 111.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Temperature control of robotic friction stir welding using the thermoelectric effect2014In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 70, no 1-4, p. 375-383Article in journal (Refereed)
    Abstract [en]

    Friction stir welding (FSW) of non-linear joints receives an increasing interest from several industrial sectors like automotive, urban transport and aerospace. A force-controlled robot is particularly suitable for welding complex geometries in lightweight alloys. However, complex geometries including three-dimensional joints, non-constant thicknesses and heat sinks such as clamps cause varying heat dissipation in the welded product. This will lead to changes in the process temperature and hence an unstable FSW process with varying mechanical properties. Furthermore, overheating can lead to a meltdown, causing the tool to sink down into the workpiece. This paper describes a temperature controller that modifies the spindle speed to maintain a constant welding temperature. A newly developed temperature measurement method is used which is able to measure the average tool temperature without the need for thermocouples inside the tool. The method is used to control both the plunging and welding operation. The developments presented here are applied to a robotic FSW system and can be directly implemented in a production setting.

  • 112.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation Systems.
    Surface Quality and Strength in Robotic Friction Stir Welding of Thin Automotive Aluminium Alloys2011In: The 4th International Swedish Production Symposium / [ed] Jan-Eric Ståhl, The Swedish Production Academy , 2011, p. 554-562Conference paper (Refereed)
    Abstract [en]

    Friction Stir Welding (FSW) is a novel method for joining materials without using consumablesand without melting the materials. It uses a rotating tool that creates frictionalheat and mixes the materials mechanically together. Robotic application of FSW allowsthree-dimensional welding of light-weight metals in e.g. the automotive industry. TheStiRoLight project is driven by Saab Automobile AB and performed at University Westfor investigation of robotic FSW of three-dimensional welding seams. It aims to introduceFSW in the automotive production line. This paper describes the effect of penetrationdepth of the FSW tool during force controlled robotic welding of thin (< 2 mm) aluminium inoverlap configuration. The influence of pin length on strength of welded aluminium sheetsis investigated using tensile and peel tests. The main limiting factor for penetration depthis the surface quality on the backside of the weld, which often is important in automotiveapplications. Further, the roughness of the plates on the backside is measured and relatedto pin length and backing bar properties. This paper shows a relation between penetrationdepth and tensile strength, and suggests an optimal pin length to guarantee a good weldquality while maintaining an acceptable surface quality. The influence of sheet thicknesstolerance is also discussed. Knowledge is fed back to designers and manufacturingengineers to facilitate for use in production with guaranteed product quality.

  • 113.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Production System. TWI Ltd, Cambridge, UK.
    Martin, Jonathan
    TWI Ltd, Cambridge, UK.
    Wei, Sam
    TWI Ltd, Cambridge, UK.
    Robotic Stationary Shoulder FSW: benefits and limitations2016In: Conference proceedings of the 11th International Symposium on Friction Stir Welding, 2016Conference paper (Refereed)
  • 114.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Soron, Mikael
    ESAB Welding AB .
    Ilar, Torbjörn
    University West, Department of Engineering Science, Division of Production Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Process and Product Development.
    Friction stir welding with robot for light vehicle design2010In: Proceedings from the 8th International Friction Stir Welding Symposium: Timmendorfer Strand, Germany 18-20 May 2010, The Welding Institute , 2010Conference paper (Other academic)
    Abstract [en]

    Reducing weight is one of the enablers to design more environmentally friendly vehicles. Friction Stir Welding (FSW) supports low weight design through its capability to join different combinations of light weight materials, e.g. different aluminium alloys, but also through its possibilities in producing continuous joints. StiRoLight is a recently started project for robotised FSW for joining of light weight materials emphasising on the vehicle industry, an industry with a long-time experience of robotic welding. The first task involves investigation of force feedback for maintaining the desired contact force. Another important aspect in robotised FSW is the compliance of the robot, which may result in deviations from the pre-programmed path as a result of the high process forces experienced during the welding operation. The further exploration of three-dimensional FSW seams and definition of the process windows will be part of further research within this project.

  • 115.
    de Souza Amaral, Thiago
    et al.
    CBMM, Araxá, MG, Brasil.
    Carboneri Carboni, Marcelo
    CBMM, São Paulo, SP, Brasil.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Welding Technology. Universidade Federal de Uberlândia – UFU, Uberlândia, MG, Bras.
    Avaliação da Aplicação de um Atlas de Soldagem de um Aço Bainítico Microligado ao Nióbio: Application Assessment of a Welding Atlas of a Niobium Microalloyed Bainitic Steel2017In: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 22, no 2, p. 163-173Article in journal (Refereed)
    Abstract [en]

    Niobium microalloyed steels have shown to be an excellent solution for fabrication of structural beams, employing concepts already developed for the oil and gas industry. However, the definition of the actual welding related needs of this family of bainite steels is not well described in the welding standards mostly used in the structural construction sector. This paper demonstrates the construction and assessment of a Welding Atlas, built from using physical simulations (Gleeble and dilatrometry) and mechanical tests of the simulated specimens. The objective is to have the Atlas as a guiding tool to improve the parametrization for welding this class of steels. The proposal methodology was applied to a HSLA bainitic steel class 65 ksi. It was possible to determine with more accuracy the recommended energy range of the weld, including the need or not of preheating, and show that they were comparable with actual welds. The methodology shows benefits including a safer parametrization and cost savings resulting from unnecessary preheating elimination.

  • 116.
    Devotta, Ashwin
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    FE Modelling and Characterization of Chip Curl in Nose Turning processIn: International Journal of Machining and Machinability of Materials, ISSN 1748-572XArticle in journal (Refereed)
  • 117.
    Devotta, Ashwin Moris
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Characterization & modeling of chip flow angle & morphology in 2D & 3D turning process2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within manufacturing of metallic components, machining plays an important role and is of vital significance to ensure process reliability. From a cutting tool design perspective,  tool macro geometry  design  based on physics based  numerical modelling  is highly needed  that can predict chip morphology.  The chip morphology describes the chip shape geometry and the chip curl geometry. The prediction of chip flow and chip shape is vital in predicting chip breakage, ensuring good chip evacuation and lower surface roughness.  To this end, a platform where such a  numerical model’s chip morphology prediction  can be compared with experimental investigation is needed and is the focus of this work. The studied cutting processes are orthogonal cutting process and nose turning process. Numerical models that simulate the chip formation process are employed to predict the chip morphology and are accompanied by machining experiments. Computed tomography is used  to scan the chips obtained from machining experiments and its ability to capture the variation in  chip morphology  is evaluated.  For nose turning process,  chip  curl parameters during the cutting process are to be calculated. Kharkevich model is utilized in this regard to calculate the  ‘chip in process’ chip curl parameters. High speed videography is used to measure the chip side flow angle during the cutting process experiments and are directly compared to physics based model predictions. The results show that the methodology developed provides  the framework where advances in numerical models can be evaluated reliably from a chip morphology prediction capability view point for nose turning process. The numerical modeling results show that the chip morphology variation for varying cutting conditions is predicted qualitatively. The results of quantitative evaluation of chip morphology prediction shows that the error in prediction is too large to be used for predictive modelling purposes.

  • 118.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Characterization of Chip Morphology in Oblique Nose Turning employing High Speed Videography and Computed Tomography Technique2016In: Proceedings International Conference on competitive Manufacturing: 27 January - 29 January 2016 Stellenbosch, South Africa organised By The department Of Industrial Engineering Stellenbosch University / [ed] Dimiter Dimitrov & Gert Adriaan Oosthuize, Department of Industrial Engineering Stellenbosch University , 2016, p. 249-254Conference paper (Refereed)
    Abstract [en]

    Simulation of industrial cutting processes employing physics based numerical models provide valuable insights into its deformation mechanics. Evaluating such models through chip studies require characterizing complex geometric features like chip shape, and chip curl. In this study, a characterization methodology is developed employing tools like computed tomography (CT) and high speed imaging. The methodology is used to characterize chip curl parameters such as chipside flow angle, chip up curl and chip side curl in oblique nose turning process. To evaluate the methodology, AISI 1045 steel is machined over a range of machining parameters and the chips obtained are characterized. The study shows that the employed methodology can be used to characterize varying chip curl geometries in nose turning process. CT technique is additionally employed when the chips are significantly deformed. The study also shows that the developed characterization methodology could be used to evaluate physics based numerical models.

  • 119.
    Devotta, Ashwin Moris
    et al.
    Sandvik Coromant AB, Sandviken, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Simulation-Based Product Development Framework for Cutting Tool Geometry Design2019In: Conference Proceedings: International Conference on Competitive Manufacturing, COMA19, presented at Stellenbosch Univerisy, January 30 - February 1 2019, Stellenbosch University, Stellenbosch, South Africa. / [ed] Dimitrov, D., Hagedorn-Hansen, D. & Von Leipzig, K., Stellenbosch University , 2019, p. 47-52Conference paper (Refereed)
    Abstract [en]

    Cutting tool geometry design has traditionally relied on experimental studies; while engineering simulations, to the level of industrial deployment, have been developed only in the last couple of decades. With the development of simulation capability across length scales from micro to macro,cutting tool geometry development includes engineering data development for its efficient utilization. This calls for the design of a simulation-based approach in the design of cutting tool geometry so that the engineering data can be generated for different machining applications (e.g.digital twin). In this study, the needs for engineering model development of different stages of cutting tool design evaluation is assessed. To this end, some of the previously developed engineering models have been evaluated for evaluation of chip form morphology in industrially relevant nose turning process, work piece material behavior modeling and damage modeling for the prediction of chip shape morphology. The study shows the possibility for the developed models to act as building blocks of a digital twin. It also shows the need for engineering model development for different aspects of cutting tool design, its advantages, limitations, and prospects.

  • 120.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. R&D Turning, Sandvik Coromant, Sandviken.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Löf, Ronnie
    R&D Turning, Sandvik Coromant, Sandviken.
    Finite element modelling and characterisation of chip curl in nose turning process2017In: International Journal of Machining and Machinability of Materials, E-ISSN 1748-572X, Vol. 19, no 3, p. 277-295Article in journal (Refereed)
    Abstract [en]

    Finite element (FE) modelling of machining provide valuable insights into its deformation mechanics. Evaluating an FE model predicted chip morphology requires characterisation of chip shape, chip curl and chip flow angles. In this study, a chip morphology characterisation methodology is developed using computed tomography (CT), high-speed imaging and Kharkevich model equations enabling evaluation of FE model’s chip morphology prediction accuracy. Chip formation process in nose turning of AISI 1045 steel is simulated using a 3D FE model for varying feed rate and depth of cut and evaluated against experimental investigations using the employed methodology. The study shows that the methodology is able to characterise chip morphology in nose turning process accurately and enables evaluation of FE model’s chip morphology prediction accuracy. This can enable the finite element model to be deployed in cutting tool design for chip breaker geometry design.

  • 121.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    Modeling of Chip curl in Orthogonal Turning using Spiral Galaxy describing Function2016In: Proceedings International Conference on competitive Manufacturing: 27 January - 29 January 2016 Stellenbosch, South Africa organised By The department Of Industrial Engineering Stellenbosch University / [ed] Dimiter Dimitrov & Gert Adriaan Oosthuizen, Global Competitiveness Centre in Engineering Department of Industrial Engineering Stellenbosch University , 2016, p. 33-38Conference paper (Refereed)
    Abstract [en]

    With advances in modeling of machining process, a methodology for quantitative evaluation of the chip curl shape in orthogonal turning process is highly desired. To achieve this, a function to fit the varying chip curl was required. A mathematical function which is used to describe spiral galaxies is employed in this work which is able to accurately model wide variety of chip curl shapes. The function is employed to compare the chip curl predicted by numerical models with experimental investigations and it should be able to capture the variation of chip curl for varying cutting conditions ranging from tightly wound springs to comma shapes and the transition between them. This provides insights into the evaluation of cutting models from a practical view point. Finite element simulations were performed to predict the chip shape for varying tool rake angles and feed rates in orthogonal cutting process. The results show that the mathematical function was capable to model the wide variety of chip curl shapes encountered in orthogonal turning process.The chip curl predicted by the simulations show that numerical simulations need advanced models to depict work piece material behaviour, heat transfer behaviour and friction behaviour to predict the variation in chip curl shapes accurately for an orthogonal turning process.

  • 122.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Sandvik Coromant AB, Sandviken, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    Espes, Emil
    Sandvik Coromant AB, Stockholm, Sweden.
    Quantitative Characterization of Chip Morphology Using Computed Tomography in Orthogonal Turning Process2015In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 33, p. 299-304Article in journal (Refereed)
    Abstract [en]

    Abstract The simulation of machining process has been an area of active research for over two decades. To fully incorporate finite element (FE) simulations as a state of art tool design aid, there is a need for higher accuracy methodology. An area of improvement is the prediction of chip shape in FE simulations. Characterization of chip shape is therefore a necessity to validate the FE simulations with experimental investigations. The aim of this paper is to present an investigation where computed tomography (CT) is used for the characterization of the chip shape obtained from 2D orthogonal turning experiments. In this work, the CT method has been used for obtaining the full 3D representation of a machined chip. The CT method is highly advantageous for the complex curled chip shapes besides its ability to capture microscopic features on the chip like lamellae structure and surface roughness. This new methodology aids in the validation of several key parameters representing chip shape. The chip morphology’s 3D representation is obtained with the necessary accuracy which provides the ability to use chip curl as a practical validation tool for FE simulation of chip formation in practical machining operations. The study clearly states the ability of the new CT methodology to be used as a tool for the characterization of chip morphology in chip formation studies and industrial applications.

  • 123.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Siriki, Ravendra
    Sandvik Materials Technology, Sandviken, Sweden.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Finite Element Modeling and Validation of Chip Segmentation in Machining of AISI 1045 Steel2017In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 499-504Article in journal (Refereed)
    Abstract [en]

    The finite element (FE) method based modeling of chip formation in machining provides the ability to predict output parameters like cutting forces and chip geometry. One of the important characteristics of chip morphology is chip segmentation. Majority of the literature within chip segmentation show cutting speed (vc) and feed rate (f) as the most influencing input parameters. The role of tool rake angle (α) on chip segmentation is limited and hence, the present study is aimed at understanding it. In addition, stress triaxiality’s importance in damage model employed in FE method in capturing the influence of α on chip morphology transformation is also studied. Furthermore, microstructure characterization of chips was carried out using a scanning electron microscope (SEM) to understand the chip formation process for certain cutting conditions. The results show that the tool α influences chip segmentation phenomena and that the incorporation of a stress triaxiality factor in damage models is required to be able to predict the influence of the α. The variation of chip segmentation frequency with f is predicted qualitatively but the accuracy of prediction needs improvement. © 2017 The Authors.

  • 124.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. R&D Turning, Sandvik Coromant AB, Sandviken, 811 81, Sweden.
    Sivaprasad, Palla Venkata
    R&D, Sandvik Materials Technology AB, Sandviken, 811 81, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Magnevall, Martin
    R&D, Sandvik Coromant AB, 811 81 Sandviken, Sweden; Blekinge Institute of Technology, Department of Mechanical Engineering, SE-371 41 Karlskrona, Sweden .
    Lundblad, Mikael
    R&D, Sandvik Coromant AB, 811 81 Sandviken, Sweden.
    A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime2019In: Metals, ISSN 2075-4701, Vol. 9, no 5, article id 528Article in journal (Refereed)
    Abstract [en]

    In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s-1, 5 s-1, and 60 s-1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

  • 125.
    dos Santos Paes, Luiz Eduardo
    et al.
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil.
    Pereira, Milton
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil.
    Weingaertner, Walter Lindolfo
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Welding Technology. Federal University of Uberlandia, Center for Research and Development of Welding Processes (Laprosolda), Uberlândia Brazil.
    Souza, Tiago
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil.
    Comparison of methods to correlate input parameters with depth of penetration in LASER welding2019In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 101, no 5-8, p. 1157-1169Article in journal (Refereed)
    Abstract [en]

    Despite the industrial relevance of LASER welding, determination of sustainable parameterization is still a challenge. Trial and error, or even not totally justified methodologies, are frequently applied on LASER welding parametrization. This approach potentially leads to a decrease of the process tolerance and, consequently, increasing the likelihood of imperfections, which means extra operational time and raising of the final cost. The present paper addresses a comparative discussion about five factors experimentally determined and frequently used to predict depth of penetration in LASER welding. The experiments were performed with a 10-kW fiber LASER. In a first batch, power was varied while welding speed was fixed at 1 m/min. In a second batch, welding speed was varied and power was kept at 10 kW. The first demonstrated concern on using these popular factors is the definition and quantification of LASER energy. For evidencing this aspect, two samples were processed with the same welding energy of 120 kJ/m, yet resulting in completely different penetrations. Eventually, an empirical model based on power as a factor allowed a more reliable prediction of the depth of penetration.

  • 126.
    Draxler, Joar
    et al.
    Luleå University of Technology, Luleå, 97187, Sweden.
    Edberg, Jonas
    Luleå University of Technology, Luleå, 97187, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Lindgren, Lars -Erik
    Luleå University of Technology, Luleå, 97187, Sweden.
    Modeling and simulation of weld solidification cracking part I: A pore-based crack criterion2019In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 5, p. 1489-1502Article in journal (Refereed)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair and, if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

  • 127.
    Draxler, Joar
    et al.
    Luleå University of Technology, Luleå, 97187, Sweden.
    Edberg, Jonas
    Luleå University of Technology, Luleå, 97187, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Lindgren, Lars -Erik
    Luleå University of Technology, Luleå, 97187, Sweden.
    Modeling and simulation of weld solidification cracking part II: A model for estimation of grain boundary liquid pressure in a columnar dendritic microstructure2019In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 5, p. 1503-1519Article in journal (Refereed)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of Alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

  • 128.
    Draxler, Joar
    et al.
    Luleå University of Technology, Luleå, 97187, Sweden.
    Edberg, Jonas
    Luleå University of Technology, Luleå, 97187, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Lindgren, Lars-Erik
    Luleå University of Technology, Luleå, 97187, Sweden.
    Modeling and simulation of weld solidification cracking part III: Simulation of solidification cracking in Varestraint tests of alloy 7182019In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 6, p. 1883-1901Article in journal (Refereed)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model required to compute the pressure and thickness of the liquid film required in the crack criterion. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

  • 129.
    Edberg, Jonas
    et al.
    Luleå University of Technology, 971 87 Luleå, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Use of Indicators for Hot and Warm Cracking in Welded Structures2017In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 7, p. 145-150Article in journal (Refereed)
    Abstract [en]

    Weight reduction of mechanical components is becoming increasingly important as a way to provide more environment friendly production and operation of different equipment. This is true in almost any manufacturing industry, but is especially important to the aerospace industry. Casting has often been replaced by hot and cold metal working operations and welding, usually including an additional heat treatment. This gives components better material properties and provides components with less weight and cost but with increased strength and efficiency. This may even be true for rotating Ni- based superalloy components, and is enabled by welding methods. However, weld cracking of precipitation hardening Ni-based superalloys is a serious problem, both in manufacturing and overhaul since it endangers component life if cracks are allowed to propagate. Cracks can appear in a weld and in it’s surroundings. The triggering mechanisms depend on its location and when it is nucleated. Generally saying, weld cracking in precipitation hardening Ni-based superalloys consists of two different types of cracking, hot cracking and warm cracking which may be further divided into heat affected zone (HAZ) liquation cracking, solidification cracking and strain age cracking, respectively. Finite element simulations of welding and heat treatment processes started in the seventies for small laboratory set-up cases and have today matured, and are now used on large-scale structures like aerospace components. But FE-based crack criteria that can predict the risk of cracking due to welding or heat treatments are rare. In a recent study both hot cracking and warm cracking have been investigated in Ni-based superalloys, and two FE-based indicators showing the risk of hot and warm cracks have been proposed. The objective of the investigation presented in this paper is to compare results from FE-simulations with experimental results from weldability tests, like the Varestraint test and the high temperature mechanical Gleeble test. © 2016

  • 130.
    Edstorp, Marcus
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    A Simplifed Finite Element Formulation for Spray Transfer GMA Weld Pools2008In: Progress in Industrial Mathematics at ECMI 2006: European Consortium for Mathematics in Industry, ECM, Springer , 2008, p. 822-826Conference paper (Refereed)
    Abstract [en]

    This chapter is concerned with the matter of mathematically modelling and computationally simulating the thermo and fluid dynamical phenomena occuring in the workpiece during a gas metal arc welding (GMAW) process, and does so by employing a continuum mechanical approach and a finite element formulation for approximating the solution of equations expressing the continuity of mass, the balance of linear momentum, the conservation of energy and the motion of the weld pool surface. GMAW is an electrode arc fusion welding process. The designation arc fusion signifies that an electric arc is struck between the welding electrode and the workpiece, and this causes the base material to melt on either side of the joint. During the subsequent solidification this will cause fusion between the workpiece parts. The electrode consist in a filler metal, and it is hence consumed during the process and molten droplets are, under the influence of electromagnetical and gravitational forces, transferred to the liquid weld pool. Mass is thus added to the workpiece and this causes a reinforcement of the joint.

  • 131.
    Edstorp, Marcus
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Charles, Corinne
    University West, Department of Engineering Science, Division of Production Engineering.
    A Finite Element Methodology for Simulating the Influence of Process Parameters on the Phase Transitions in a GTA weld2009In: Proceedings of the 15th International Conference on the Joining of Materials, 2009Conference paper (Other academic)
  • 132.
    Eggertsen, P. -A
    et al.
    University of Technology, Div. of Material and Computational Mechanics, Dept. of Applied Mechanics Chalmers.
    Mattiasson, Kjell
    University of Technology, Div. of Material and Computational Mechanics, Dept. of Applied Mechanics Chalmers.
    Larsson, Mats
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    A comprehenisve analysis of benchmark 4: Pre-strain effect on springback of 2D draw bending2011In: AIP Conference Proceedings, Seoul, 2011, Vol. 1383, p. 1064-1071Conference paper (Refereed)
    Abstract [en]

    In order to be able to form high strength steels with low ductility, multi-step forming processes are becoming more common. Benchmark 4 of the NUMISHEET 2011 conference is an attempt to imitate such a process. A DP780 steel sheet with 1.4 mm thickness is considered. In order to understand the pre-strain effect on subsequent forming and springback, a 2D draw-bending is considered. Two cases are studied: one without prestrain and one with 8% pre-stretching. The draw-bending model is identical to the "U-bend" problem of the NUMISHEET'93 conference. The purpose of the benchmark problem is to evaluate the capability of modern FE-methods to simulate the forming and springback of these kinds of problems. The authors of this article have previously made exhaustive studies on material modeling in applications to sheet metal forming and springback problems, [1],[2],[3]. Models for kinematic hardening, anisotropic yield conditions, and elastic stiffness reduction have been investigated. Also procedures for material characterization have been studied. The material model that mainly has been used in the current study is based on the Banabic BBC2005 yield criterion, and a modified version of the Yoshida-Uemori model for cyclic hardening. This model, like a number of other models, has been implemented as User Subroutines in LS-DYNA. The effects of various aspects of material modeling will be demonstrated in connection to the current benchmark problems. The provided material data for the current benchmark problem are not complete in all respects. In order to be able to perform the current simulations, the authors have been forced to introduce a few additional assumptions. The effects of these assumptions will also be discussed. © 2011 American Institute of Physics.

  • 133.
    Ekberg, Johanna
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Ganvir, Ashish
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Creci, Simone
    Chalmers University of Technology, Department of Chemistry and Chemical Engineering, Gothenburg, Sweden.
    Nordstierna, Lars
    Chalmers University of Technology, Department of Chemistry and Chemical Engineering, Gothenburg, Sweden.
    The Influence of Heat Treatments on the Porosity of Suspension Plasma-Sprayed Yttria-Stabilized Zirconia Coatings2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 391-401Article in journal (Refereed)
    Abstract [en]

    Suspension plasma-sprayed coatings are produced using fine-grained feedstock. This allows to control the porosity and to achieve low thermal conductivity which makes the coatings attractive as topcoats in thermal barrier coatings (TBCs). Used in gas turbine applications, TBCs are exposed to high temperature exhaust gases which lead to microstructure alterations. In order to obtain coatings with optimized thermomechanical properties, microstructure alterations like closing of pores and opening of cracks have to be taken into account. Hence, in this study, TBC topcoats consisting of 4 mol.% yttria-stabilized zirconia were heat-treated in air at 1150 °C and thereafter the coating porosity was investigated using image analysis (IA) and nuclear magnetic resonance (NMR) cryoporometry. Both IA and NMR cryoporometry showed that the porosity changed as a result of the heat treatment for all investigated coatings. In fact, both techniques showed that the fine porosity decreased as a result of the heat treatment, while IA also showed an increase in the coarse porosity. When studying the coatings using scanning electron microscopy, it was noticed that finer pores and cracks disappeared and larger pores grew slightly and achieved a more distinct shape as the material seemed to become more compact.

  • 134.
    Ekberg, Johanna
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology,Göteborg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology,Göteborg, Sweden.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Analysis of single splats produced by axial suspension plasma spraying2018In: Surface Engineering, ISSN 0267-0844, E-ISSN 1743-2944, Vol. 34, no 5, p. 407-411Article in journal (Refereed)
    Abstract [en]

    Axial suspension plasma spraying (ASPS) is a relatively new, innovative technique with which microstructures have been produced that are similar to the ones produced by electron beam physical vapor deposition. They have a columnar structure and consist of nm- and µm-sized pores. However, so far the formation of the microstructure is not fully understood because fragmentation and vaporisation of the liquid significantly affects the deposition process. Analysis of single splats can provide important information on the phenomena controlling the coating formation process and the final coating properties. Therefore, the present study aims at providing first results of 8 wt-% yttria-stabilised zirconia single splats sprayed onto a steel substrate by use of ASPS. Scanning electron microscopy and atomic force microscopy have been used to characterise the splats with respect to appearance, shape, and size distribution. © 2017 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute

  • 135.
    Eklund, Johan
    et al.
    Chalmers University of Technology, Energy and Materials, Department of Chemistry and Chemical Engineering, Göteborg, 412 96, Sweden.
    Phother, J.
    Chalmers University of Technology, Energy and Materials, Department of Chemistry and Chemical Engineering, Göteborg, 412 96, Sweden.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Liske, Jesper
    Chalmers University of Technology, Energy and Materials, Department of Chemistry and Chemical Engineering, Göteborg, 412 96, Sweden.
    High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications2019In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 91, no 5-6, p. 729-747Article in journal (Refereed)
    Abstract [en]

    The present study investigates the initial corrosion behaviour of HVAF-sprayed NiCr, NiAl and NiCrAlY coatings in two different environments, O 2 + H 2 O and O 2 + H 2 O + KCl at 600 °C for up to 168 h in order to evaluate the possibility of utilizing such coatings in biomass- and waste-fired boilers. SEM/EDX analysis showed that all coatings displayed a protective behaviour in O 2 + H 2 O. Upon addition of KCl (O 2 + H 2 O + KCl), the corrosion behaviour of the NiCr coating drastically changed as it formed a thick oxide layer and displayed major chlorine diffusion down to the substrate. The NiCrAlY coating displayed a significantly better corrosion resistance with only minor oxide formation. The NiAl coating exhibited a protective behaviour similar to when exposed in the absence of KCl indicating that a thin protective oxide has formed on the coating surface. The performance of the NiAl and NiCrAlY coatings is promising for future studies with long-term exposures in more corrosive environments such as in a biomass- and waste-fired boiler. © 2019, The Author(s).

  • 136.
    Elefante, Arianna
    et al.
    University of Bari, Physics Department, Via Amendola 173, 70126 Bari, Italy.
    Nilsen, Morgan
    University West, Department of Engineering Science, Division of Production Systems.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Maggipinto, Tommaso
    University of Bari, Physics Department, Via Amendola 173, 70126 Bari, Italy.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. IFN-CNR Institute for Photonics and Nanotechnologies, Physics Department, Via Amendola 173, 70126 Bari, Italy.
    Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal2019In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, p. 178-185Article in journal (Refereed)
    Abstract [en]

    Robotized laser beam welding of closed-square-butt joints is sensitive to the positioning of the laser beam with respect to the joint since even a small offset may result in a detrimental lack of sidewall fusion. An evaluation of a system using a photodiode aligned coaxial to the processing laser beam confirms the ability to detect variations of the process conditions, such as when there is an evolution of an offset between the laser beam and the joint. Welding with different robot trajectories and with the processing laser operating in both continuous and pulsed mode provided data for this evaluation. The detection method uses wavelet analysis of the photodetector signal that carries information of the process condition revealed by the plasma plume optical emissions during welding. This experimental data have been evaluated offline. The results show the potential of this detection method that is clearly beneficial for the development of a system for welding joint tracking.

  • 137.
    Ericson Öberg, Anna
    et al.
    Material- och Tillverkningsteknik, Chalmers.
    Johansson, Martin
    Holm, Erik
    Hammersberg, Peter
    Material- och Tillverkningsteknik, Chalmers.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    The Influence of Correct Transfer of Weld Information on Production Cost2012In: 5th Swedish Production Symposium 2012, SPS12: 6-8 nov 2012, Linköping / [ed] Mats Björkman, Linköping, 2012, p. 295-302Conference paper (Other academic)
    Abstract [en]

    This study aims at identifying the causes for deviations between actual and theoretical weld weight. Previous performed studies have shown examples of up to 40% extra weld consumables used in some cases. One consequence is of course higher production cost but it can also give increased weight leading to higher fuel consumption and decreased payload. An interesting aspect is that generous margins on specific production measures dilute important feedback of process variation information preventing and prolonging structural root cause analysis.

    The causes for the observed deviations can heritage from several areas, both technical and within the information handling. The investigation shows that single components of the information structure and system, such as unsuitable demands as well as incapable evaluation methods, significantly influences the reliability of the entire manufacturing process. The common factor concerning when problems occur, seems to be the ability of correct information transfer between different functions in the organisation preventing the mismatch to appear in the interface. Suggestions for improving this situation include cross functional agreements as well as new measuring methods.

  • 138.
    Ericson Öberg, Anna
    et al.
    Chalmers, Gothenburg, Sweden.
    Åstrand, Erik
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Volvo Construct Equipment, Braås, Sweden.
    Improved productivity by reduced variation in gas metal arc welding (GMAW)2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 92, no 1-4, p. 1027-1038Article in journal (Refereed)
    Abstract [en]

    The purpose of the research conducted is to describe the consequences of variation in the welding industry and the effect it has on manufacturing productivity. The potential has shown to be hidden in unnecessarily stringent requirements and over-processing. This has been studied in steps: customer requirements, design and analysis, preparation, welding, and assessment. The effect of variation in each step has been analyzed including estimations of its productivity improvement potential. Theoretically, in a perfect situation, with customized requirements and eliminated variation, more than half of all welding could be removed. Such a reduction is certainly neither practical nor possible. However, a sensible, controlled reduction could still have a very high impact. The financial implications are therefore substantial. The improved productivity of the manufacturing resources could be used for business development and increased production. To be able to realize the potential, interdisciplinary efforts are necessary. Management across different functions need to agree on the intended product life and make decisions thereafter.

  • 139.
    Ericsson, Mikael
    University West, Department of Technology.
    Simulation of robotic TIG-welding2003Licentiate thesis, comprehensive summary (Other academic)
  • 140.
    Ericsson, Mikael
    et al.
    University West, Department of Technology, Mathematics and Computer Science.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science.
    A look at the optimization of robot welding speed based on process modelling2007In: Welding Journal, ISSN 0043-2296, Vol. 86, no 8, p. 238-244Article in journal (Refereed)
    Abstract [en]

    Simulation tools to search for optimal process parameters are of great interest to reduce the number of experiments and thereby reduce cost and production time. In this paper, robot simulation has been used in combination with finite element simulations to optimize robot speed in order to minimize distortion while keeping complete joint penetration. In an earlier work performed by the authors, a finite element model was developed to predict heat transfer and residual stresses of parts with complex shapes. An interface between a robot simulation model and a finite element analysis model was also constructed. In this paper, an iterative method for robot speed optimization has been developed using MATLAB. The algorithm is designed to maintain complete joint penetration while maximizing productivity by utilizing the fastest weld speed. The method makes it possible to optimize the heat input to the component and thereby minimize component deformation for parts with complex shapes. The system was evaluated on stainless steel plates with varying thicknesses. Robot weld paths were defined off line and automatically downloaded to the finite element software where the optimization was performed. Simulations and experimental validations are presented.

  • 141.
    Ericsson, Mikael
    et al.
    University West, Department of Technology, Mathematics and Computer Science.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science.
    Berglund, D.
    Ling-Peng, R.
    Three dimensional simulation of robot path, heat transfer and residual stresses of a welded part with complex geometry2005In: International jourrnal for the joining of materials, ISSN 0905-6866, Vol. 17, no 2, p. 42-51Article in journal (Refereed)
    Abstract [en]

    In this article a simulation system is presented that combines computer aided robotics software used to define the welding operation, with a finite element model that predicts temperature-time histories and residual stress distributions for welding applications. The objective is to develop a tool for engineering processes in which robot trajectories and welding process parameters can be optimized off-line on parts with complex geometries. The system was evaluated on a stainless steel gas turbine component. Temperature dependent properties and phase change were included in the analysis. The turbine component was welded using an in-house TIG welding cell. The assumptions and principles that underpin the modeling techniques are presented together with predicted temperature histories, residual stresses, and fixture forces. Predicted residual stresses were compared with neutron diffraction measurements.

  • 142.
    Ericsson, Mikael
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zhang, Xiaoxiao
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Virtual Commissioning of Machine Vision Applications in Aero Engine Manufacturing2018In: Proceedings of The 15th International Conference on Control,Automation, Robotics and Vision, November 18-21, 2018, 2018, p. 1947-1952, article id 0293Conference paper (Refereed)
    Abstract [en]

    New aero engine design puts new demands on the manufacturing methods with increased automation level. Therefore, the use of vision sensors for control and guiding of industrial robots is being increasingly used. In such system, it is need to customise the machine vision system with real components in the real environment which is normally done close to the start-up of the production. This paper addresses a new concept for designing, programming, analysing, testing and verifying a machine vision application early in the design phase, called Virtual Machine Vision. It is based on a robot simulation software where the real machine vision application is simulated before the implementation in the production line. To verify the Virtual Machine Vision concept an advanced stereo vision application was used. Using two captured images from the robot simulated environment, camera calibration, image analysis and stereo vision algorithms are applied to determine a desired welding joint. The information of the weld joint, i.e. robot position and orientation for the weld path, are sent from the machine vision system to the robot control system in the simulation environment and the weld path is updated. The validation of the Virtual Machine Vision concept using the stereo vision application is promising for industrial use, and it is emphasised that the same programs are used in the virtual and real word.

  • 143.
    Eriksson, Robert
    et al.
    Siemens AG, Large Gas Turbines, Huttenstr. 12, 10553, Berlin, Germany.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Broitman, Esteban
    Linköping University. IFM, 58183, Linköping, Sweden.
    Jonnalagadda, Krishna Praveen
    Linköping University, IEI, 58183, Linköping, Sweden.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Lin Peng, Ru
    Linköping University, IEI, 58183, Linköping, Sweden.
    Stresses and Cracking During Chromia-Spinel-NiO Cluster Formation in TBC Systems2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 1002-1014Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young’s moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO. © 2015 ASM International

  • 144. Eriksson, Robert
    et al.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Broitman, Esteban
    Linköping University.
    Jonnalagadda, Krishna Praveen
    Linköping University.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Peng, Ru Lin
    Linköping University.
    Stress and Cracking during Chromia-Spinel-NiO Cluster Formation in Thermal Barrier Coating Systems2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 1002-1014Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young's moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO.

  • 145.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Frequency Domain Study of Vibrations above and under Stability Lobes in Machining Systems2014In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 14, p. 164-169Article in journal (Refereed)
    Abstract [en]

    Using modified Nyquist contours, the dominant poles of the closed loop delay-differential equation for machining systems such as milling are identified. Contours with constant damping ratio of the dominant poles are constructed using this method. These contours are similar in shape to the stability lobes, but move upwards and to the right as the instability parameter increases. Additionally, it is possible to study the movement of the dominant poles to the right-hand side of the complex plane as the system becomes unstable by increasing the depth of cut at a constant spindle speed. The movement of the dominant pole is shown to be towards the right (unstable) and upward (higher vibration frequency) of the complex plane. In some cases, there would be a jump of vibration frequency due to the change of the lobe number. It is also shown that the damping ratio of the structure strongly affects both the vibration frequency and the damping ratio of the dominant poles in the closed loop system. Finally, in two milling experiments with two different spindle speeds and continuously increasing depth of cuts, vibration frequencies are measured and compared to the theoretical predictions. The measurements agree with the theoretical predictions, particularly in the unstable cutting conditions.

  • 146.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    In-process identification of modal parameters using dimensionless relationships in milling chatter2019In: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 143, p. 49-62Article in journal (Refereed)
    Abstract [en]

    Machining parameters needed for stable, high-performance high-speed machining could be found using mathematical models that need accurate measurements of modal parameters of the machining system. In-process modal parameters, however, can slightly differ from those measured offline and this can limit the applicability of simple measurement methods such as impact hammer tests. To study and extract the in-process modal parameters, mathematical models are used to define two key dimensionless parameters and establish their relationships with each other and the modal parameters. Based on these relationships, the modal parameters are extracted using two analytical methods, the two-point method (TPM), and the regression method (RM). As shown with experimental studies, the RM extracts the modal parameters successfully and while being much faster than the existing iteration-based methods, it provides stability lobe predictions that match well the experimental results. Furthermore, it is noted that the natural frequency parameter is estimated with much better relative precision compared to the damping ratio and the modal stiffness parameters. © 2019 Elsevier Ltd

  • 147.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Prediction of vibration frequencies in milling using modified Nyquist method2015In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 11, no November, p. 73-81Article in journal (Refereed)
    Abstract [en]

    Study of the vibration frequencies at different cutting conditions is an alternative to the use of impact hammer test for identification of natural frequencies of the machining structure and calculation of stability lobe diagrams. Vibration frequencies not only depend on the natural frequencies of the structure, but also they are dependent on the spindle speed, damping ratio of the structure and the depth of cut. Ignoring these additional parameters would lead to errors in identification of the natural frequencies of the system and considerable deviation of the calculated stability lobe diagrams from actual cutting tests. In this study modified Nyquist method is used to investigate the effects of spindle speed, depth of cut and damping ratio of the structure on vibration frequencies. The quality of frequency prediction is compared to linear and nonlinear time domain simulations and machining experiments.

  • 148.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vibration frequencies in stable and unstable milling2015In: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 90, p. 44-49Article in journal (Refereed)
    Abstract [en]

    Vibration frequencies in machining may be employed for calculation of natural frequencies of the dominant modes in chatter and selection of chatter-free spindle speeds with large material removal rates. In this approach, it is important to investigate the relationship between the vibration frequencies, the natural frequencies, spindle speeds and depth of cuts for both stable and unstable cutting conditions. In this paper, the dominant poles of the closed loop time delay differential equation of a milling operation are calculated by successive sectioning of the complex plane and using Cauchy's argument principle. Vibration frequency and damping ratio of the closed loop machining system for each cutting condition is calculated based on the position of the dominant pole on the complex plane which provides 3D plots of the vibration frequency and closed loop damping ratio over any range of depth of cuts and spindle speeds. Finally, the findings of the analytical approach are compared to a machining experiment and a time domain simulation and differences and similarities in their predictions are discussed.

  • 149.
    Eynian, Mahdi
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Altintas, Y
    University of British Columbia, Department of Mechanical Engineering, Manufacturing Automation Laboratory.
    Analytical Chatter Stability of Milling With Rotating Cutter Dynamics at Process Damping Speeds2010In: Journal of manufacturing science and engineering, ISSN 1087-1357, E-ISSN 1528-8935, Vol. 132, no 2Article in journal (Refereed)
    Abstract [en]

    Thispaper presents a chatter stability prediction method for milling flexibleworkpiece with end mills having asymmetric structural dynamics. The dynamicchip thickness regenerated by the vibrations of the rotating cutterand the fixed workpiece is transformed into the principle modaldirections of the rotating tool. The process damping is modeledas a linear function of vibration velocity. The dynamics ofthe milling system is modeled by a time delay matrixdifferential equation with time varying directional factors and speed dependentelements. The periodic directional factors are averaged over a spindleperiod, and the stability of the resulting time invariant butspeed dependent characteristic equation of the system is investigated usingthe Nyquist stability criterion. The stability model is verified withtime domain numerical simulations and milling experiments.

  • 150.
    Eynian, Mahdi
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Das, Kallol
    University West, Department of Engineering Science.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Effect of tool wear on quality in drilling of titaniumalloy Ti6Al4V, Part I: Cutting Forces, BurrFormation, Surface Quality and Defects2017In: High speed machining, E-ISSN 2299-3975, Vol. 3, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Titanium's Ti6Al4V, alloy is an important material with a wide range of applications in the aerospace industry.Due to its high strength, machining this material for desired quality at high material removal rate is challenging and may lead to high tool wear rate. As a result,this material may be machined with worn tools and the effects of tool wear on machining quality need to be investigated.In this experimental paper, it is shown how drills of various wear levels affect the cutting forces, surface quality and burr formation. Furthermore, it is shown that high cutting forces and high plastic deformation, along with high temperatures that arise in cutting with worn tools may lead to initiation of microscopic cracks in the workpiece material in proximity of the drilling zone.

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