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  • 1.
    Agic, Adnan
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Hägglund, S.
    Seco Tools, Fagersta, Sweden.
    Ståhl, Jan-Eric
    Lund University, Production and Materials Engineering, Lund, Sweden.
    Beno, Tomas
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Influence of radial depth of cut on dynamics of face milling application2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-9Conference paper (Refereed)
    Abstract [en]

    The choice of milling cutter geometry and appropriate cutting data for certain milling application is of vital importance for successful machining results. Unfavourable selection of cutting conditions might give rise to high load impacts that cause severe cutting edge damage. The radial depth of cut in combination with milling cutter geometry might under some circumstances give unfavourable entry conditions in terms of cutting forces and vibration amplitudes. This phenomenon originates from the geometrical features that affect the rise time of the cutting edge engagement into work piece at different radial depths of cut. As the radial depth of cut is often an important parameter, particularly when machining difficult to cut materials, it is important to explore the driving mechanism behind vibrations generation. In this study, acceleration of the work piece is measured for different radial depths of cut and cutting edge geometries. The influence of the radial depth of cut on the dynamical behaviour is evaluated in time and frequency domains. The results for different radial depths of cut and cutting geometries are quantified using root mean square value of acceleration. The outcome of this research study can be used both for the better cutting data recommendations and improved tool design.

  • 2.
    Agic, Adnan
    et al.
    Seco Tools, Fagersta, Sweden ; University West, Department of Engineering Science, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Hägglund, S.
    Seco Tools, Fagersta, Sweden.
    Ståhl, J.-E.
    Lund University, Production and Materials Engineering, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Influence of radial depth of cut on entry conditions and dynamics in face milling application2017In: Journal of Superhard Materials, ISSN 1063-4576, Vol. 39, no 4, p. 259-270Article in journal (Refereed)
    Abstract [en]

    The choice of milling cutter geometry and appropriate cutting data for certain milling application is of vital importance for successful machining results. Unfavorable selection of cutting conditions might give rise to high load impacts that cause severe cutting edge damage. Under some circumstances the radial depth of cut in combination with milling cutter geometry might give unfavorable entry conditions in terms of cutting forces and vibration amplitudes. This phenomenon is originated from the geometrical features that affect the rise time of the cutting edge engagement into workpiece at different radial depths of cut. As the radial depth of cut is often an important parameter, particularly when machining difficult-to-cut materials, it is important to explore the driving mechanism behind vibrations generation. In this study, acceleration of the workpiece is measured for different radial depths of cut and cutting edge geometries. The influence of the radial depth of cut on the dynamical behavior is evaluated in time and frequency domains. The results for different radial depths of cut and cutting geometries are quantified using the root mean square value of acceleration. The outcome of this research study can be used both for the better cutting data recommendations and improved tool design.

  • 3.
    Agic, Adnan
    et al.
    Seco Tools, Fagersta, Sweden ; Department of Engineering Science, University West, Trollhättan, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Ståhl, Jan-Erik
    Production and Materials Engineering, Lund University, Sweden.
    Beno, Tomas
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries2019In: International Journal on Interactive Design and Manufacturing, ISSN 1955-2513, E-ISSN 1955-2505, Vol. 13, no 2, p. 557-565Article in journal (Refereed)
    Abstract [en]

    Understanding the influence of the cutting edge geometry on the development of cutting forces during the milling process is of high importance in order to predict the mechanical loads on the cutting edge as well as the dynamic behavior on the milling tool. The work conducted in this study involves the force development over the entire engagement of a flute in milling, from peak force during the entry phase until the exit phase. The results show a significant difference in the behavior of the cutting process for a highly positive versus a highly negative cutting edge geometry. The negative edge geometry gives rise to larger force magnitudes and very similar developments of the tangential and radial cutting force. The positive cutting edge geometry produces considerably different developments of the tangential and radial cutting force. In case of positive cutting edge geometry, the radial cutting force increases while the uncut chip thickness decreases directly after the entry phase; reaching the peak value after a certain delay. The radial force fluctuation is significantly higher for the positive cutting edge geometry. The understanding of such behavior is important for modelling of the milling process, the design of the cutting edge and the interactive design of digital applications for the selection of the cutting parameters.

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  • 4.
    Agic, Adnan
    et al.
    Seco Tools, Fagersta, Sweden ; University West, Department of Engineering Science, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Ståhl, J.-E.
    Lund University, Production and Materials Engineering, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Experimental analysis of cutting edge effects on vibrations in end milling2019In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 24, p. 66-74Article in journal (Refereed)
    Abstract [en]

    The ability to minimize vibrations in milling by the selection of cutting edge geometry and appropriate cutting conditions is an important asset in the optimization of the cutting process. This paper presents a measurement method and a signal processing technique to characterize and quantify the magnitude of the vibrations in an end milling application. Developed methods are then used to investigate the effects of various cutting edge geometries on vibrations in end milling. The experiments are carried out with five cutting edge geometries that are frequently used in machining industry for a wide range of milling applications. The results show that a modest protection chamfer combined with a relatively high rake angle has, for the most of cutting conditions, a reducing effect on vibration magnitudes. Furthermore, dynamics of a highly positive versus a highly negative cutting geometry is explored in time domain and its dependency on cutting conditions is presented. The results give concrete indications about the most optimal cutting edge geometry and cutting conditions in terms of dynamic behavior of the tool.

  • 5.
    Agic, Adnan
    et al.
    Seco Tools AB, Fagersta, Sweden ; Department of Engineering Science, University West, Trollhättan, Sweden.
    Gutnichenko, Oleksandr
    Division of Production and Materials Engineering, Lund University, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Ståhl, Jan-Eric
    Division of Production and Materials Engineering, Lund University, Sweden.
    Influence of cutting edge geometry on force build-up process in intermittent turning2016In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 46, p. 364-367Article in journal (Refereed)
    Abstract [en]

    In the intermittent turning and milling processes, during the entry phase the cutting edges are subjected to high impact loads that can give rise to dynamical and strength issues which in general cause tool life reduction. In this study the effect of geometrical features of the cutting tool on the force generation during the entry phase is investigated. Cutting forces are measured by a stiff dynamometer at a high sampling frequency. In addition, the chip load area is analyzed and related to the measured cutting force. The results show that micro-geometrical features, in particular the protection chamfer, significantly affect the force generation during the entry phase.

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  • 6.
    Alasttal, Reema
    et al.
    University of Skövde, School of Engineering Science.
    Nizam, Ali
    University of Skövde, School of Engineering Science.
    Karakterisering av kopparytor för att optimera kvaliteten vid lasersvetsning av hairpins2022Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Development of electric motors in recent years has led to major changes in the automotive industry. This means that the industry is constantly in need of development in order to be able to adapt to new methods and materials. The thesis examines part of this. Laser welding of copper rods, called hairpins, is an important part of the production of an electric motor. During laser welding of copper hairpins, defects occur in the material which results in a poor welding quality which in turn leads to poorer current flow in the electric motor. In this work, a literature review is performed together with experiments to determine which coatings and how the roughness / surface fineness affects the laser welding of copper hairpins. 10 different samples are selected, where contaminated, oxidized and black-painted surfaces are examined with sanded and polished surfaces. The results show that hairpins with a rough surface without any coating have the best welding quality, while hairpins in their original milled shape show the second best welding quality. The conclusion is that coatings increase the porosity, which results in a lower welding quality. More tests need to be performed to ensure the result.

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  • 7.
    Altintas, Yusuf
    et al.
    Manufacturing Automation Laboratory, Department of Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada.
    Eynian, Mahdi
    Manufacturing Automation Laboratory, Department of Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada.
    Onozuka, H.
    Production Engineering Research Laboratory, Hitachi, Ltd., Yokohama, Japan.
    Identification of dynamic cutting force coefficients and chatter stability with process damping2008In: CIRP annals, ISSN 0007-8506, E-ISSN 1726-0604, Vol. 57, no 1, p. 371-374Article in journal (Refereed)
    Abstract [en]

    This paper presents a cutting force model which has three dynamic cutting force coefficients related to regenerative chip thickness, velocity and acceleration terms, respectively. The dynamic cutting force coefficients are identified from controlled orthogonal cutting tests with a fast tool servo oscillated at the desired frequency to vary the phase between inner and outer modulations. It is shown that the process damping coefficient increases as the tool is worn, which increases the chatter stability limit in cutting. The chatter stability of the dynamic cutting process is solved using Nyquist law, and compared favourably against experimental results at low cutting speeds.

  • 8.
    Amouzgar, Kaveh
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Ng, Amos H. C.
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment. Division of Industrial Engineering and Management, Uppsala University, Sweden.
    Ljustina, Goran
    Volvo Car Corporation, ME PS Research and Technology, Skövde, Sweden.
    Optimizing index positions on CNC tool magazines considering cutting tool life and duplicates2020In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 93, p. 1508-1513Article in journal (Refereed)
    Abstract [en]

    Minimizing the non-machining time of CNC machines requires optimal positioning of cutting tools on indexes (stations) of CNC machine turret magazine. This work presents a genetic algorithm with a novel solution representation and genetic operators to find the best possible index positions while tool duplicates and tools life are taken in to account during the process. The tool allocation in a machining process of a crankshaft with 10 cutting operations, on a 45-index magazine, is optimized for the entire life of the tools on the magazine. The tool-indexing time is considerably reduced compared to the current index positions being used in an automotive factory. 

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  • 9.
    Andersson Lassila, Andreas
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Svensson, Daniel
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Wang, Wei
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Andersson, Tobias
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Numerical evaluation of cutting strategies for thin-walled parts2024In: Scientific Reports, E-ISSN 2045-2322, Vol. 14, no 1, article id 1459Article in journal (Refereed)
    Abstract [en]

    Static form errors due to in-process deflections is a major concern in flank milling of thin-walled parts. To increase both productivity and part geometric accuracy, there is a need to predict and control these form errors. In this work, a modelling framework for prediction of the cutting force-induced form errors, or thickness errors, during flank milling of a thin-walled workpiece is proposed. The modelled workpiece geometry is continuously updated to account for material removal and the reduced stiffness matrix is calculated for nodes in the engagement zone. The proposed modelling framework is able to predict the resulting thickness errors for a thin-walled plate which is cut on both sides. Several cutting strategies and cut patterns using constant z-level finishing are studied. The modelling framework is used to investigate the effect of different cut patterns, machining allowance, cutting tools and cutting parameters on the resulting thickness errors. The framework is experimentally validated for various cutting sequences and cutting parameters. The predicted thickness errors closely correspond to the experimental results. It is shown from numerical evaluations that the selection of an appropriate cut pattern is crucial in order to reduce the thickness error. Furthermore, it is shown that an increased machining allowance gives a decreased thickness error for thin-walled plates.

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  • 10.
    Andersson, Tobias
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Svensson, Daniel
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Andersson Lassila, Andreas
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Trujillo Vilches, Francisco Javier
    Department of Civil, Materials and Manufacturing Engineering, EII, University of Malaga, Spain.
    Bermudo Gamboa, Carolina
    Department of Civil, Materials and Manufacturing Engineering, EII, University of Malaga, Spain.
    3D-Simulation of Heat Flow in Indexable Drilling2023In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 955, p. 53-62Article in journal (Refereed)
    Abstract [en]

    In machining, the heat flow into the workpiece during the cutting process is often a major concern. The temperature rise can lead to substantial residual stresses or elastic in-process deformations which may result in the dimensional tolerance requirements being violated. In the present study a modelling strategy is developed for determination of the heat load during indexable drilling. The heat load on the workpiece is determined from 3D thermomechanical Coupled Eulerian Lagrangian analyses of orthogonal turning for various chip thicknesses and cutting speeds. The determined heat load is then transferred to a 3D transient heat transfer analysis of the indexable drilling process for the determination of the temperature field. Thereby, this modelling technique avoids the complex cutting process that is performed in real cutting simulations and thereby reducing the computational complexity of the problem considerably. The simulated temperatures are compared with experimentally measured temperatures and some conclusions are drawn regarding the modelling approach.

  • 11.
    Bergström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Luleå, Sweden.
    Fergusson, Michael
    Xtura AB, Kungsbacka, Sweden.
    Folkesson, Patrik
    Xtura AB, Kungsbacka, Sweden.
    Runnemalm, Anna
    Production Technology, University West, Trollhättan, Sweden.
    Ottosson, Mattias
    Production Technology, University West, Trollhättan, Sweden.
    Andersson, Alf
    Chalmers University of Technology, Department of Product and Production Development, Gothenburg, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Luleå, Sweden.
    Automatic in-line inspection of shape based on photogrammetry2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-9Conference paper (Refereed)
    Abstract [en]

    We are describing a fully automatic in-line shape inspection system for controlling the shape of moving objects on a conveyor belt. The shapes of the objects are measured using a full-field optical shape measurement method based on photogrammetry. The photogrammetry system consists of four cameras, a flash, and a triggering device. When an object to be measured arrives at a given position relative to the system, the flash and cameras are synchronously triggered to capture images of the moving object.From the captured images a point-cloud representing the measured shape is created. The point-cloud is then aligned to a CAD-model, which defines the nominal shape of the measured object, using a best-fit method and a feature-based alignment method. Deviations between the point-cloud and the CAD-model are computed giving the output of the inspection process. The computational time to create a point-cloud from the captured images is about 30 seconds and the computational time for the comparison with the CAD-model is about ten milliseconds. We report on recent progress with the shape inspection system.

  • 12.
    Bermudo Gamboa, Carolina
    et al.
    Department of Civil, Material and Manufacturing Engineering, EII, University of Malaga, Spain.
    Andersson, Tobias J.
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Svensson, Daniel
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Trujillo Vilches, Francisco Javier
    Department of Civil, Material and Manufacturing Engineering, EII, University of Malaga, Spain.
    Martín-Béjar, Sergio
    Department of Civil, Material and Manufacturing Engineering, EII, University of Malaga, Spain.
    Sevilla Hurtado, Lorenzo
    Department of Civil, Material and Manufacturing Engineering, EII, University of Malaga, Spain.
    Modeling of the fracture energy on the finite element simulation in Ti6Al4V alloy machining2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 18490Article in journal (Refereed)
    Abstract [en]

    One of the main problems that exists when working with Finite Element Methods (FEM) applied to machining processes is the lack of adequate experimental data for simulating the material properties. Moreover, for damage models based on fracture energy, the correct selection of the energy value is critical for the chip formation process. It is usually difficult to obtain the fracture energy values and requires complex tests. In this work, an analysis of the influence of this fracture energy on the cutting force and the chip generation process has been carried out for different sets of cutting parameters. The aim is to present an empirical relationship, that allows selecting the fracture energy based on the cutting force and cutting parameters. The work is based on a FEM model of an orthogonal turning process for Ti6Al4V alloy using Abaqus/Explicit and the fracture energy empirical relation. This work shows that it is necessary to adjust the fracture energy for each combination of cutting conditions, to be able to fit the experimental results. The cutting force and the chip geometry are analyzed, showing how the developed model adapts to the experimental results. It shows that as the cutting speed and the feed increase, the fracture energy value that best adapts to the model decreases. The evolution shows a more pronounced decrease related to the feed increment and high cutting speed. 

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  • 13.
    Broberg, Patrik
    et al.
    University West, Trollhättan, Sweden.
    Runnemalm, Anna
    University West, Trollhättan, Sweden.
    Analysis algorithm for surface crack detection by thermography with UV light excitation2016In: Quantitative InfraRed Thermography 2016: Abstracts / [ed] Mariusz Kaczmarek; Adam Bujnowski, Gdańsk, Poland: Gdańsk University of Technology , 2016, p. 160-165Conference paper (Refereed)
    Abstract [en]

    Surface crack defects can be detected by IR thermograpgy due to the high absorption of energy within the crack cavity. It is often difficult to detect the defect in the raw data, since the signal easily drowns in the background. It is therefore important to have good analysis algorithms that can reduce the background and enhance the defect. Here an analysis algorithm is presented which significantly increases the signal to noise ratio of the defects and reduces the image sequence from the camera to one image.

  • 14.
    Broberg, Patrik
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Sjödahl, Mikael
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Runnemalm, Anna
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Comparison of NDT-methods for automatic inspection of weld defects2015In: International journal of materials & product technology, ISSN 0268-1900, E-ISSN 1741-5209, Vol. 50, no 1, p. 1-21Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to investigate different NDT–methods for weld inspection in an objective manner. Test objects are produced with known variation of flaws: internal pores, surface and internal cracks, toe radius and weld depth. The NDT–methods compared are: phased array ultrasound, radiography, eddy current, thermography and shearography. The results show that radiography is the better method for volumetric defects in thin plates while ultrasound is better for flat defects and thicker, non–flat plates. The thermography was shown to have good surface defect detection abilities. A combination of ultrasound and thermography results in a detection of all the non–geometrical defects is investigated in this study.

  • 15.
    Das, Kallol
    et al.
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part II: Microstructure and Microhardness2017In: High Speed Machining, E-ISSN 2299-3975, Vol. 3, no 1, 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.

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  • 16.
    De Vin, Leo J.
    University of Skövde, School of Technology and Society.
    Air Bending of Sheet Metal2005In: FAIM 2005: Volume I: Proceedings of the 15th International conference on flexible automation and intelligent manufacturing, July 18th-20th, 2005 / [ed] Esther Alvarez; Jalal Ashayeri; William G. Sullivan; Munir Ahmad, Bilbao: University of Deusto , 2005, p. 465-473Conference paper (Refereed)
  • 17.
    Devotta, Ashwin Moris
    et al.
    Sandvik Coromant AB, Sandviken, Sweden.
    Beno, Tomas
    University West, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    Simulation-Based Product Development Framework for Cutting Tool Geometry Design2019In: International Conference on Competitive Manufacturing (COMA 19) Proceedings: 30 January 2019 – 1 February 2019 Stellenbosch, South Africa / [ed] Dimiter Dimitrov; Devon Hagedorn-Hansen; Konrad von Leipzig, 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.

  • 18.
    Devotta, Ashwin Moris
    et al.
    Sandvik Coromant AB, Sandviken, Sweden ; University West, Department of Engineering Science, Trollhättan, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Siriki, Ravendra
    Sandvik Materials Technology, Sandviken, Sweden.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    Eynian, Mahdi
    University West, Department of Engineering Science, Trollhättan, Sweden.
    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.

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  • 19.
    Devotta, Ashwin Moris
    et al.
    R&D Turning, Sandvik Coromant AB, Sandviken, Sweden.
    Sivaprasad, P. V.
    R&D, Sandvik Materials Technology AB, Sandviken, Sweden.
    Beno, Tomas
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling2020In: Metals, ISSN 2075-4701, Vol. 10, no 4, article id 519Article in journal (Refereed)
    Abstract [en]

    Machining process modeling has been an active endeavor for more than a century and it has been reported to be able to predict industrially relevant process outcomes. Recent advances in the fundamental understanding of material behavior and material modeling aids in improving the sustainability of industrial machining process. In this work, the flow stress behavior of C45E steel is modeled by modifying the well-known Johnson-Cook model that incorporates the dynamic strain aging (DSA) influence. The modification is based on the Voyiadjis-Abed-Rusinek (VAR) material model approach. The modified JC model provides the possibility for the first time to include DSA influence in chip formation simulations. The transition from continuous to segmented chip for varying rake angle and feed at constant cutting velocity is predicted while using the ductile damage modeling approach with two different fracture initiation strain models (Autenrieth fracture initiation strain model and Karp fracture initiation strain model). The result shows that chip segmentation intensity and frequency is sensitive to fracture initiation strain models. The Autenrieth fracture initiation strain model can predict the transition from continuous to segmented chip qualitatively. The study shows the transition from continuous chip to segmented chip for varying feed rates and rake angles for the first time. The study highlights the need for material testing at strain, strain rate, and temperature prevalent in the machining process for the development of flow stress and fracture models.

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  • 20.
    Devotta, Ashwin Moris
    et al.
    R&D Turning, Sandvik Coromant AB, Sandviken, Sweden ; Department of Engineering Science, University West, Trollhättan, Sweden.
    Sivaprasad, Palla Venkata
    R&D, Sandvik Materials Technology AB, Sandviken, Sweden.
    Beno, Tomas
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Hurtig, Kjell
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Magnevall, Martin
    R&D, Sandvik Coromant AB, Sandviken, Sweden ; Department of Mechanical Engineering, Blekinge Institute of Technology, Karlskrona, Sweden.
    Lundblad, Mikael
    R&D, Sandvik Coromant AB, 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.

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  • 21.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    Analytical Stability Prediction in Five Axis Ball-End Milling2013In: Proceedings of the International Conference on Advanced Manufacturing Engineering and Technologies NEWTECH 2013: Stockholm, Sweden 27-30 October 2013 / [ed] Andreas Archenti; Antonio Maffei, Stockholm: KTH Royal Institute of Technology , 2013, Vol. 1, p. 189-198Conference paper (Refereed)
    Abstract [en]

    In five axis ball-end milling, the cutting edge is a continuous curve and the engagement with workpiece changes as the cutting tool rotates. Therefore the sensitivity to vibration varies along the cutting edge and as the tool rotates. In this paper, the vibration-force relationship (VFR) is obtained for infinitesimal length of cutting edge as a function of tool’s rotation angle. Numerical integration results in the VFR of the whole cutting edge and the tool. VFR of the tool is coupled to the dynamic vibration model of the tool and the workpiece to predict the possibility of vibrational instability. This algorithm is then used to predict the effects of changing the lead angle in a test setup with a flexible depth of cut direction. The analytical results, along with experiments demonstrate that the large lead angles considerably improve the stability of the process.

  • 22.
    Eynian, Mahdi
    The Faculty of Graduate Studies (Mechanical Engineering), The University of British Columbia, Canada.
    Chatter stability of turning and milling with process damping2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The prediction of chatter instability in machining steel and thermal-resistant alloys at low ‎cutting speeds has been difficult due to unknown process damping contributed by the ‎contact mechanism between tool flank and wavy surface finish. This thesis presents ‎modeling and measurement of process damping coefficients, and the prediction of chatter ‎stability limits for turning and milling operations at low cutting speeds. ‎ The dynamic cutting forces are separated into regenerative and process damping ‎components. The process damping force is expressed as a product of dynamic cutting ‎force coefficient and the ratio of vibration and cutting velocities. It is demonstrated that ‎the dynamic cutting coefficient itself is strongly affected by flank wear land. In ‎measurement of dynamic cutting forces, the regenerative force is eliminated by keeping ‎the inner and outer waves parallel to each other while the tool is oscillated using a piezo ‎actuator during cutting. ‎Classical chatter stability laws cannot be used in stability prediction for general turning ‎with tools cutting along non-straight cutting edges; where the direction and magnitude of ‎the dynamic forces become dependent on the depth of cut and feed-rate. A new dynamic ‎cutting force model of regeneration of chip area and process damping, which considers ‎tool nose radius, feed–rate, depth of cut, cutting speed and flank wear is presented. The ‎chatter stability is predicted in the frequency domain using Nyquist stability criterion.‎ The process damping is considered in a new dynamic milling model for tools having ‎rotating but asymmetric dynamics. The flexibility of the workpiece is studied in a fixed ‎coordinate system but the flexibility of the tool is studied in a rotating coordinate system. ‎The periodic directional coefficients are averaged, and the stability of the dynamic ‎milling system is determined in the frequency domain using Nyquist stability criterion. ‎The experimentally proven, proposed stability models are able to predict the critical ‎depth of cut at both low and high cutting speeds.‎ 

  • 23.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    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.

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  • 24.
    Eynian, Mahdi
    University West, Department of Engineering Science, Trollhättan, Sweden.
    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

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  • 25.
    Eynian, Mahdi
    University West, The Department of Engineering Sciences, Trollhättan, Västra Götaland, Sweden.
    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.

  • 26.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Selection of chatter-free milling conditions using vibration frequency measurements2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Unwanted vibration of the tool with respect to the workpiece, known as chatter, can damage machine tool, cutting tool, and the surface finish of the workpiece in a machining operation such a milling. These vibrations could be avoided by reducing the depth of cut, but this approach hurts the productivity and reduces material removal rate. Previous studies have established methods, known as stability prediction methods that provide that enable using large depth of cuts while avoiding chatter. The calculation of stability lobes commonly starts by measurement of dynamic properties of the machining structure. This paper investigates an alternative approach, in which vibration frequencies gathered during test cuts with the target machining system are used to identifying the modal parameters of the machining system in its operational condition. An earlier method that was based on a one dimensional dynamics model is modified to use relationships developed for a two dimensional model that describes the dynamics of spindles and tools with axisymmetric dynamics. This approach improves the stability lobe prediction considerably as shown in results.

  • 27.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    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.

  • 28.
    Eynian, Mahdi
    et al.
    Department of Mechanical Engineering, Manufacturing Automation Laboratory, University of British Columbia, Vancouver, BC, Canada.
    Altintas, Y.
    Department of Mechanical Engineering, Manufacturing Automation Laboratory, University of British Columbia, Vancouver, BC, Canada.
    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 2, article id 021012Article in journal (Refereed)
    Abstract [en]

    This paper presents a chatter stability prediction method for milling flexible workpiece with end mills having asymmetric structural dynamics. The dynamic chip thickness regenerated by the vibrations of the rotating cutter and the fixed workpiece is transformed into the principle modal directions of the rotating tool. The process damping is modeled as a linear function of vibration velocity. The dynamics of the milling system is modeled by a time delay matrix differential equation with time varying directional factors and speed dependent elements. The periodic directional factors are averaged over a spindle period, and the stability of the resulting time invariant but speed dependent characteristic equation of the system is investigated using the Nyquist stability criterion. The stability model is verified with time domain numerical simulations and milling experiments.

  • 29.
    Eynian, Mahdi
    et al.
    Manufacturing Automation Laboratory, University of British Columbia, Vancouver, BC, Canada.
    Altintas, Yusuf
    Manufacturing Automation Laboratory, University of British Columbia, Vancouver, BC, Canada.
    Chatter Stability of General Turning Operations With Process Damping2009In: Journal of manufacturing science and engineering, ISSN 1087-1357, E-ISSN 1528-8935, Vol. 131, no 4, article id 041005Article in journal (Refereed)
    Abstract [en]

    The accurate prediction of chatter stability in general turning operations requires the inclusion of tool geometry and cutting conditions. This paper presents regenerative chip and regenerative chip area/cutting edge contact length based dynamic cutting force models, which consider cutting conditions and turning tool geometry. The cutting process is modeled as it takes place along the equivalent chord length between the two end points of the cutting edge. The regenerative chip model is simple, and the stability can be solved directly. However, the three-dimensional model considers the effect of tool vibrations at the present and previous spindle revolutions on the chip area, chord length, and force directions and is solved using Nyquist stability criterion. The penetration of worn tool flank into the finish surface is considered as a source of process damping. The effects of the nose radius, approach angle of the tool, and feedrate are investigated. The proposed stability model is compared favorably against the experimental results.

  • 30.
    Eynian, Mahdi
    et al.
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Das, Kallol
    University West, Department of Engineering Science, Trollhättan, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part I: Cutting Forces, Burr Formation, Surface Quality and Defects2017In: High speed machining, E-ISSN 2299-3975, Vol. 3, no 1, 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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  • 31.
    Eynian, Mahdi
    et al.
    University West, Trollhättan, Sweden.
    Magnevall, Martin
    University West, Trollhättan, Sweden ; Sandvik Coromant AB, Sandviken, Sweden.
    Cedergren, Stefan
    GKN Aerospace Sweden AB, Trollhättan, Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB, Trollhättan, Sweden.
    Lundblad, Mikael
    Sandvik Coromant AB, Sandviken, Sweden.
    New methods for in-process identification of modal parameters in milling2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 77, p. 469-472Article in journal (Refereed)
    Abstract [en]

    Chatter vibrations encountered in machining can degrade surface finish and damage the machining hardware. Since chatter originates from unstable interaction of the machining process and the machining structure, information about vibration parameters of the machining structure should be used to predict combinations of cutting parameters that allow stable machining. While modal test methods, for example those with impact hammers, are widely used to identify structural parameters; the need for sophisticated test equipment is prohibitive in their use. Furthermore, dynamic properties of critical components of a machine tool may change as they get affected by cutting loads, material removal and spindle rotation. Recently few algorithms have been proposed that identify the in-process dynamic parameters by frequency measurements, thus avoiding these problems. In this paper, some of these algorithms are reviewed and their capabilities and limitations in processing am experimental data set are compared and discussed. © 2018 The Authors. Published by Elsevier Ltd.

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  • 32.
    Eynian, Mahdi
    et al.
    Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.
    Onozuka, Hideaki
    Production Engineering Research Laboratory, Hitachi, Ltd., Yokohama, Japan.
    Altintas, Yusuf
    Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.
    Chatter in turning with process damping2007In: Proceedings of the 22nd Annual ASPE Meeting, ASPE 2007, American Society for Precision Engineering , 2007Conference paper (Refereed)
  • 33.
    Eynian, Mahdi
    et al.
    University West, Sweden.
    Usino, Sunday Ogheneochuko
    University West, Sweden.
    Bonilla Hernández, Ana Esther
    GKN Aerospace Engine Systems AB, Sweden.
    Studies on surface roughness in stable and unstable end-milling2020In: SPS2020: Proceedings of the Swedish Production Symposium, October 7-8, 2020 / [ed] Kristina Säfsten; Fredrik Elgh, IOS Press, 2020, p. 465-474Conference paper (Refereed)
    Abstract [en]

    Surface roughness is an important aspect of a machined piece and greatly influences its performance. This paper presents the surface roughness of end-milled aluminium plates in stable and unstable machining conditions at various spindle speed and depth of cuts machined with cylindrical end-mills. The surface roughness is measured using high-resolution surface replicas with a white light interferometry (WLI) microscope. The measurements of the end-milled floors show that the surface roughness as long as the cutting is performed in stable conditions is insensitive to the depth of cut or spindle speed. In contrast, within chattering conditions, which appear according to stability lobes, surface roughness values increase almost 100%. While at the valleys of the stability lobe diagram, there is a gradual increase in roughness, at the peaks of the stability lobe, the transition from the stable to unstable condition occurs with a sudden increase of the roughness values. In the study of down-milled walls, while the roughness increases with the depth of cut within both the stable and the chattering regions, the transition from the stable to chattering condition can lead to a much larger increase in the surface roughness. These results could be used for strategic selection of operation considering the needs of robustness and possible variation of dynamic parameters that can affect the position of the cutting conditions within the stability lobe diagrams.

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  • 34.
    Eynian, Mahdi
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Sensitivity of Axis Tracking Errors of Machine Tools to Tool Wear in Drilling2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Axis Tracking Errors (ATEs) of the active and inactive axis of numerically controlled machine tools are presented as new means of detection of tool wear that forgo expensive sensors or modifications of the machining structure, however, very little has been published about their capabilities or limitations as signal source for monitoring. In this paper the ATEs and cutting forces in drilling tests in two different machine tools, with drills of varying wear levels are measured. The sensitivity to wear is compared by introducing Percent Deviation from New Tool (PDFNT) factor, which is applied to the peak-to-peak values of the signals. While the ATEs are very small in magnitude, they are highly sensitive to wear levels, with PDFNTs reaching to 1000% for some axis. In addition, the standard deviation of PDFNTs calculated in drilling of seven holes with the same tool represents the repeatability of ATEs. The PDFNTs for ATEs are rather repeatable, but less repeatable than the PDFNTs of the axial drilling force. Furthermore it is shown that ATEs of different machine tools have different levels of sensitivity to wear levels which necessitates calibrating of monitoring systems using ATEs for each machine tool separately.

  • 35.
    Ghasemi, Rohollah
    KTH, Materialvetenskap.
    Hydrogen-assisted stress corrosion cracking of high strength steel2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this work, Slow Strain Rate Test (SSRT) testing, Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) were used to study the effect of microstructure, corrosive environments and cathodic polarisation on stress corrosion cracking (SCC) of two grades of high strength steels, Type A and Type B. Type A is manufactured by quench and tempered (Q&T) method. Type B, a normalize steel was used as reference. This study also supports electrochemical polarisation resistance method as an effective testing technique for measuring the uniform corrosion rate. SSRT samples were chosen from base metal, weld metal and Heat Affected Zone (HAZ). SSRT tests were performed at room temperature under Open Circuit Potential (OCP) and cathodic polarisation using 4 mA/cm2 in 1 wt% and 3.5 wt% NaCl solutions. From the obtained corrosion rate measurements performed in 1 wt% and 3.5 wt% NaCl solutions it was observed that increased chloride concentration and dissolved oxygen content enhanced the uniform corrosion for all tested materials. Moreover, the obtained results from SSRT tests demonstrate that both Q&T and normalized steels were not susceptible to SCC in certain strain rate (1×10-6 s-1) in 1 wt% and 3.5 wt% NaCl solutions under OCP condition. It was confirmed by a ductile fracture mode and high reduction in area. The weld metal of Type A with acicular ferrite (AF), pro-eutectoid (PF) and bainite microstructure showed higher susceptibility to hydrogen assisted stress corrosion cracking compared to base metal and HAZ. In addition, typical brittle intergranular cracking with small reduction in area was observed on the fracture surface of the Type A due to hydrogen charging.

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  • 36.
    Ghasemi, Rohollah
    et al.
    Department of Mechanical Engineering, Materials and Manufacturing - Casting, School of Engineering, Jönköping University, Sweden.
    Elmquist, Lennart
    Department of Mechanical Engineering, Materials and Manufacturing - Casting, School of Engineering, Jönköping University, Sweden.
    The relationship between flake graphite orientation, smearing effect, and closing tendency under abrasive wear conditions2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 317, no 1–2, p. 153-162Article in journal (Refereed)
    Abstract [en]

    Abstract Plastic deformation of the matrix during the wear process results in closing the graphite flakes. In this study, the relationship between the deformation of the matrix and the closing tendency of flake graphite was investigated, both qualitatively and quantitatively. Two representative piston rings, which belonged to the same two-stroke marine engine but were operated for different periods of time, were studied. Initial microstructural observations indicated a uniform distribution of graphite flakes on unworn surfaces, whereas worn surfaces demonstrated a tendency towards a preferred orientation. Approximately 40% of the open flakes of the unworn surfaces were closed during sliding, which may result in the deterioration of the self-lubricating capability of cast iron. Moreover, flakes within the orientation range of 0 to 30° relative to the sliding direction showed a maximum closing tendency when subjected to sliding. The closing tendency gradually decreased as the angle increased, approaching a minimum between 30 and 70°. A slight increase in the closing tendency was observed for flakes with orientations between 70 and 90°. A similar trend was observed on both rings. Furthermore, SEM and EDS analysis indicated substantial deformation of the matrix in the area around the flakes. An insignificant corrosion attack was observed on both worn piston ring surfaces.

  • 37.
    Lönn, Dan
    et al.
    University of Skövde, School of Engineering Science.
    Spångberg, David
    University of Skövde, School of Engineering Science.
    Study of process parameters in laser beam welding of copper hairpins2022Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study had the purpose to further the use of industrial lasers in the manufacturing of hairpin electric motors by optimizing the process of contacting the hairpins. A problem with laser beam welding of copper is the porosity created in the process which can lead to increased resistance of the welded region along with degraded mechanical properties. By experiment this study aimed to find the optimal parameters to reduce the porosity while maintaining all other requirements for the weld. The track of achieving a satisfactory simulation was done to minimize the need of physical experiments which can be argued as a sustainable development aspect. A set of parameters was found that achieved a low volume of pores, a sufficient weld depth and a desirable bead geometry. Some pores still remained, mostly at the endpoint of the laser path which could be caused by the laser shut-off leading to a keyhole collapse enclosing some pores in that region. The simulation showed promising results in welding depth and melt region. Further work on ramping the laser power at the endpoint could be beneficial for eliminating the remaining porosity as well as refining the simulation in terms of porosity.

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  • 38.
    Malakizadi, Amir
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Ghasemi, Rohollah
    Jönköping University, School of Engineering, Department of Materials and Manufacturing, Jönköping, Sweden.
    Behring, Carsten
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Olofsson, Jakob
    Jönköping University, School of Engineering, Department of Materials and Manufacturing, Jönköping, Sweden.
    Jarfors, Anders E. W.
    Jönköping University, School of Engineering, Department of Materials and Manufacturing, Jönköping, Sweden.
    Nyborg, Lars
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Krajnik, Peter
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 410-411, p. 190-201Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to investigate the tool performance when machining compacted graphite iron (CGI) alloys. A comparison was made between solid solution strengthened CGI including various amounts of silicon (Si-CGI) and the pearlitic-ferritic CGI as a reference material. The emphasis was on examining the influence of microstructure and mechanical properties of the material on tool wear in face milling process. Machining experiments were performed on the engine-like test pieces comprised of solid solution strengthened CGI with three different silicon contents and the reference CGI alloy. The results showed up-to 50% lower flank wear when machining Si-CGI alloys, although with comparable hardness and tensile properties. In-depth analysis of the worn tool surfaces showed that the abrasion and adhesion were the dominant wear mechanisms for all investigated alloys. However, the better tool performance when machining Si-CGI alloys was mainly due to a lower amount of abrasive carbo-nitride particles and the suppression of pearlite formation in the investigated solid solution strengthened alloys.

  • 39.
    Meena, Akash
    et al.
    Department of Civil and Mechanical Engineering, Technical University of Denmark, Lyngby, Denmark.
    Andersson Lassila, Andreas
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Lönn, Dan
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Salomonsson, Kent
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Wang, Wei
    University of Skövde, School of Engineering Science. University of Skövde, Virtual Engineering Research Environment.
    Nielsen, Chris Valentin
    Department of Civil and Mechanical Engineering, Technical University of Denmark, Lyngby, Denmark.
    Bayat, Mohamad
    Department of Civil and Mechanical Engineering, Technical University of Denmark, Lyngby, Denmark.
    Numerical and experimental study of the variation of keyhole depth with an aluminum alloy (AA1050)2024In: Journal of Advanced Joining Processes, E-ISSN 2666-3309, Vol. 9, article id 100196Article in journal (Refereed)
    Abstract [en]

    The keyhole depth is a key measurement characteristic in the laser welding of busbar to battery tabs in battery packs for electric vehicles (EV), as it directly affects the quality of the weld. In this work, experiments are carried out with controlled and adjusted laser power and feed rate parameters to investigate the influence on the keyhole width, keyhole depth and porosities. A 3D numerical model of laser keyhole welding of an aluminum alloy (A1050) has been developed to describe the porosity formation and the keyhole depth variation. A new integration model of the recoil pressure and the rate of evaporation model is implemented which is closer to the natural phenomena as compared to the conventional methods. Additionally, major physical forces are employed including plume formation, upward vapor pressure and multiple reflection in the keyhole. The results show that keyhole depth is lower at higher feed rate, while lower feed rates result in increased keyhole depth. This study reveals that low energy densities result in an unstable keyhole with high spattering, exacerbated by increased laser power. Mitigating incomplete fusion is achieved by elevating laser energy density. The findings emphasize the critical role of keyhole depth in optimizing laser welding processes for applications like busbar-to-battery tab welding.

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  • 40.
    Parsian, Amir
    et al.
    AB Sandvik Coromant, Sandviken, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Magnevall, Martin
    Department of Mechanical Engineering, Blekinge Institute of Technology, Karlskrona, Sweden.
    Beno, Tomas
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Minimizing the Negative Effects of Coolant Channels on the Torsional and Torsional-Axial Stiffness of Drills2021In: Metals, ISSN 2075-4701, Vol. 11, no 9, p. 1473-1473Article in journal (Refereed)
    Abstract [en]

    Coolant channels allow internal coolant delivery to the cutting region and significantly improve drilling, but these channels also reduce the torsional and torsional-axial stiffness of the drills. Such a reduction in stiffness can degrade the quality of the drilled holes. The evacuation of cutting chips and the delivery of the cutting fluid put strict geometrical restrictions on the cross-section design of the drill. This necessitates careful selection and optimization of features such as the geometry of the coolant channels. This paper presents a new method that uses Prandtl’s stress function to predict the torsional and torsional-axial stiffness values. Using this method drills with one central channel are compared to those with two eccentric coolant channels, which shows that with the same cross-section area, the reduction of axial and torsional-axial stiffness is notably smaller for the design with two eccentric channels compared to a single central channel. The stress function method is further used to select the appropriate location of the eccentric coolant channels to minimize the loss of torsional and torsional-axial stiffness. These results are verified by comparison to the results of three-dimensional finite element analyses.

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  • 41.
    Parsian, Amir
    et al.
    AB Sandvik Coromant, Sandviken, Sweden ; University West, Trollhättan, Sweden.
    Magnevall, Martin
    AB Sandvik Coromant, Sandviken, Sweden.
    Beno, Tomas
    University West, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    A Mechanistic Approach to Model Cutting Forces in Drilling with Indexable Inserts2014In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 24, p. 74-79Article in journal (Refereed)
    Abstract [en]

    Holes are made in many industrial parts that need screws, pins or channels for passing fluids. The general method to produce holes in metal cutting is by drilling operations. Indexable insert drills are often used to make short holes at a low cost. However, indexable drills are prone to vibrate under certain circumstances, causing vibrations that affect tool life. Therefore, a good prediction of cutting-forces in drilling is important to get a good description of the cutting process for optimization of tool body and insert design. Reliable simulations of dynamic forces also aid in prediction of chatter vibrations that have significant effects on the quality of the manufactured parts as well as the tool life. In this paper, a mechanistic approach is used to model the cutting-forces. Cutting-force coefficients are identified from measured instantaneous forces in drilling operations. These coefficients are used for simulating torque around drill-axis, axial force and cutting-forces in the plane perpendicular to drill-axis. The forces are modeled separately for peripheral and central insert, which results in a detailed description of the cutting-forces acting on each insert. The forces acting on each insert are estimated by dividing the cutting edges into small segments and the cutting-forces acting on each segment are calculated. The total forces are predicted by summation of the forces acting on each segment. Simulated torque and forces are compared to measured cutting-forces for two different feeds. A good agreement between predicted and experimental results, especially in torque and axial-force, is observed.

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  • 42.
    Parsian, Amir
    et al.
    Sandvik Coromant, Sandviken, Sweden ; University West, Trollhättan, Sweden.
    Magnevall, Martin
    Sandvik Coromant, Sandviken, Sweden ; University West, Trollhättan, Sweden.
    Beno, Tomas
    University West, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    Sound Analysis in Drilling, Frequency and Time Domains2017In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 411-415Article in journal (Refereed)
    Abstract [en]

    This paper proposes a guideline for interpreting frequency content and time history of sound measurements in metal drilling processes. Different dynamic phenomena are reflected in generated sound in cutting processes. The footprint of such phenomena including torsional, lateral regenerative chatter and whirling in sound measurement results are discussed. Different indexable insert drills, at several cutting conditions, are covered. The proposed analysis could be used for studying, online monitoring and controlling of drilling processes. © 2017 The Authors.

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  • 43.
    Parsian, Amir
    et al.
    Sandvik Coromant, Sandviken, Sweden ; University West, Trollhättan, Sweden.
    Magnevall, Martin
    Sandvik Coromant, Sandviken, Sweden.
    Beno, Tomas
    University West, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    Time-Domain Modeling of Torsional-Axial Chatter Vibrations in Indexable Drills with Low Damping2015Conference paper (Refereed)
    Abstract [en]

    In drills with helical chip flutes the coupling between axial and rotational degrees-of-freedom can cause chatter vibrations. These torsional-axial chatter vibrations can lead to a high frequency and unpleasant noise. It is desirable to design tools which are less prone to chatter vibrations and thus also makes less noise during operation. Dynamics of chatter vibrations in drilling is due to changes in chip-thickness that causes dynamic loads on the structure. These loads in return contribute and sustain vibrations. In this paper a simulation routine is proposed that can be used to model these chatter vibrations in drilling when damping of the drill-body is low. In case of low damping, the drill rotates backward in some instants. The importance of modeling of this phenomenon is emphasized in this paper and a method is proposed to model loads in case of backward rotations. The generated chip is calculated in each time-step and obtained chip-thickness is used to calculate dynamic loads. The structural responses are calculated in form of displacements by loading the drill with predicted dynamic loads based on the calculated chip thickness. Obtained displacements are used to calculate chip-thickness in the next time-step. Spectrum of simulated vibrations is compared with spectrum of measured noise and a good agreement between measurements and simulations is observed.

  • 44.
    Parsian, Amir
    et al.
    AB Sandvik Coromant, Sandviken, Sweden ; University West, Trollhättan, Sweden.
    Magnevall, Martin
    AB Sandvik Coromant, Sandviken, Sweden ; University West, Trollhättan, Sweden.
    Eynian, Mahdi
    University West, Trollhättan, Sweden.
    Beno, Tomas
    University West, Trollhättan, Sweden.
    Time Domain Simulation of Chatter Vibrations in Indexable Drills2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 89, no 1-4, p. 1209-1221Article in journal (Refereed)
    Abstract [en]

    Regenerative chatter vibrations are common in drilling processes. These unwanted vibrations lead to considerable noise levels, damage the quality of the workpiece, and reduce tool life. The aim of this study is to simulate torsional and axial chatter vibrations as they play important roles in dynamic behavior of indexable insert drills with helical chip flutes. While asymmetric indexable drills are not the focal points in most of previous researches, this paper proposes a simulation routine which is adapted for indexable drills. Based on the theory of regenerative chatter vibration, a model is developed to include the asymmetric geometries and loadings that are inherent in the design of many indexable insert drills. Most indexable insert drills have two inserts located at different radial distances, namely central and peripheral inserts. Since the positions of the central and peripheral inserts are different, the displacement and thereby the change in chip thickness differs between the inserts. Additionally, the inserts have different geometries and cutting conditions, e.g., rake angle, coating, and cutting speed, which result in different cutting forces. This paper presents a time-domain simulation of torsional and axial vibrations by considering the differences in dynamics, cutting conditions, and cutting resistance for the central and peripheral inserts on the drill. The time-domain approach is chosen to be able to include nonlinearities in the model arising from the inserts jumping out of cut, multiple delays, backward motions of edges, and variable time delays in the system. The model is used to simulate cutting forces produced by each insert and responses of the system, in the form of displacements, to these forces. It is shown that displacements induced by dynamic torques are larger than those induced by dynamic axial forces. Finally, the vibration of a measurement point is simulated which is favorably comparable to the measurement results.

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  • 45.
    Pejryd, Lars
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden ; Production Technology Centre, Innovatum AB, Trollhättan, Sweden ; Volvo Aero Corporation, Trollhättan, Sweden.
    Eynian, Mahdi
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Beno, Tomas
    Department of Engineering Science, University West, Trollhättan, Sweden ; Volvo Aero Corporation, Trollhättan, Sweden.
    Minimization of chatter in machining by the use of mobile platform technologies2012In: Proceedings of the 5th International Swedish Production Symposium, SPS12: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping, 2012, p. 179-189Conference paper (Refereed)
    Abstract [en]

    The risk of vibration in machining can be estimated by identification of the transfer functions of the system. Traditionally the transfer functions may be identified through the use of an impact hammer and a force transducer. This technology needs wiring and therefore cannot be easily used in a production environment. Through the use of the sound that is picked up from the running process, the simplified stability diagram of the system can be deduced. Mobile platforms, like phones and pads can be used to record the sound of the process. The computational capability of these devices are now enough to render the possibility to include the theory and modelling into these devices to make it possible to analyze the process in question as it is running and from that give recommendations to modify the process for minimization of the chatter vibrations. The paper outlines the theoretical considerations and strategy employed to make it possible to develop a useful solution for end-users on the shop floor.

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  • 46.
    Runnemalm, Anna
    et al.
    Division of Engineering Science, University West, Trollättan, Sweden.
    Ahlberg, Jörgen
    Department of Electrical Engineering, Linköping University, Linköping, Sweden.
    Appelgren, Anders
    Division of Engineering Science, University West, Trollättan, Sweden.
    Sjökvist, Stefan
    Termisk Systemteknik AB, Linköping, Sweden.
    Automatic Inspection of Spot Welds by Thermography2014In: Journal of nondestructive evaluation, ISSN 0195-9298, E-ISSN 1573-4862, Vol. 33, no 3, p. 398-406Article in journal (Refereed)
    Abstract [en]

    The interest for thermography as a method for spot weld inspection has increased during the last years since it is a full-field method suitable for automatic inspection. Thermography systems can be developed in different ways, with different physical setups, excitation sources, and image analysis algorithms. In this paper we suggest a single-sided setup of a thermography system using a flash lamp as excitation source. The analysis algorithm aims to find the spatial region in the acquired images corresponding to the successfully welded area, i.e., the nugget size. Experiments show that the system is able to detect spot welds, measure the nugget diameter, and based on the information also separate a spot weld from a stick weld. The system is capable to inspect more than four spot welds per minute, and has potential for an automatic non-destructive system for spot weld inspection. The development opportunities are significant, since the algorithm used in the initial analysis is rather simplified. Moreover, further evaluation of alternative excitation sources can potentially improve the performance.

  • 47.
    Runnemalm, Anna
    et al.
    University West, Trollhättan, Sweden.
    Broberg, Patrik
    University West, Trollhättan, Sweden.
    Garcia de la Yedra, Aitor
    IK4-LORTEK, Ordizia, Spain.
    Fuente, Raquel
    IK4-LORTEK, Ordizia, Spain.
    Beizama, Ane Miren
    IK4-LORTEK, Ordizia, Spain.
    Fernandez, Erik
    IK4-LORTEK, Ordizia, Spain.
    Thorpe, Nigel
    Tecnitest ingenieros, Madrid, Spain.
    Henriksson, Per
    GKN Aerospace Engine Systems Sweden, Trollhättan, Sweden.
    Automated inspection of welds with limited access by use of active thermography with laser line excitation2016Conference paper (Refereed)
    Abstract [en]

    Inspection of welds for detecting surface breaking defects is traditionally performed by using NDT methods such as Fluorescent Penetrant Inspection, Visual Inspection or Eddy Current. All those well-known techniques have drawbacks, as they need access to the surface, either for preparation with e.g. liquids or for using contact probes. Traditional methods also require a skilled operator to carry out the inspection, and moreover to analyse the obtained results. Furthermore, for the inspection of welds with limited access, the use of those traditional methods is even more complex, resulting in increased inspection time and reduced detection capability or in worst case, areas impossible to inspect. Therefore, the development of a fully automated non-contact method overcoming these limitations is desired. ;Active thermography is a novel NDT technique for weld inspection. The method has shown promising results for replacing traditional techniques when it comes to detection of surface breaking defects in metals. The method make use of an excitation source in order to heat the sample in a controlled manner during the test, and an infrared thermal camera for recordings of the thermal evolution. ;In this work, an automated solution developed and demonstrated for inspection of welds in a jet-engine component with limited access is presented. The NDT system is mounted on an industrial robot, making it possible to automatic scan the inspected area. The system consists of a, continuous laser-line excitation source together with a FLIR SC 655 microbolometer thermographic camera. In order to access limited areas, two polished aluminium mirrors have been used for both infrared radiation monitoring and laser excitation respectively. A solution for automatic analysing, defect detection and sizing is also included and presented.

  • 48.
    Runnemalm, Anna
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Broberg, Patrik
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Henrikson, Per
    GKN Aerospace Engine System, Trollhättan, Sweden.
    Ultraviolet excitation for thermography inspection of surface cracks in welded joints2014In: Nondestructive Testing and Evaluation, ISSN 1058-9759, E-ISSN 1477-2671, Vol. 29, no 4, p. 332-344Article in journal (Refereed)
    Abstract [en]

    Infrared thermography is a non-contact and full field inspection method which has proven to be suitable for automatic surface crack detection. For automatic analysis of the inspection results, a high signal-to-noise ratio (SNR) is required. In this paper an alternative excitation method, using ultraviolet (UV) illumination, is presented and evaluated. Artificial surface defects, so-called notches, in a titanium plate are detected both in the weld seam and in the heat affected zone. Notches with a size from 80 μm in width and 250 μm in length are detected. The SNR using UV illumination is compared with that using flash lamp excitation. The results show that UV illumination using a mercury lamp is a good alternative as excitation source for thermography when detecting surface cracks. To validate the excitation method, results from real surface cracks are included.

  • 49.
    Sikström, Fredrik
    et al.
    Högskolan Väst, Avdelningen för produktionssystem (PS).
    Runnemalm, Anna
    Production Technology, University West, Trollhättan, Sweden.
    Broberg, Patrik
    Production Technology, University West, Trollhättan, Sweden.
    Nilsen, Morgan
    Production Technology, University West, Trollhättan, Sweden.
    Svenman, Edvard
    Production Technology, University West, Trollhättan, Sweden.
    Evaluation of non-contact methods for joint tracking in a laser beam welding application2016In: The 7th International Swedish Production Symposium, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Symposium , 2016, p. 1-6Conference paper (Refereed)
    Abstract [en]

    The use of automated laser welding is a key enabler for resource efficient manufacturing in several industrial sectors. One disadvantage with laser welding is the narrow tolerance requirements in the joint fit-up. This is the main reason for the importance of joint tracking systems. This paper describes anevaluation of four non-contact measurement methods to measure the position, gap width and misalignment between superalloy plates. The evaluation was carried out for increased knowledge about the possibilities and limitations with the different methods. The methods are vision-, laser-line-,thermography- and inductive probe systems which are compared in an experimental setup representing a relevant industrial application. Vision is based on a CMOS camera, where the image information is used directly for the measurements. Laser-line is based on triangulation between a camera and a projected laserline. Thermography detects the heat increase in the gap width due to external heat excitation. Inductive probe uses two eddy current coils, and by a complex response method possibilities to narrow gap measurement is achieved. The results, evaluated by comparing the data from the different systems, clearly highlights possibilities and limitations with respective method and serves as a guide in the development of laser beam welding.

  • 50.
    Svenman, Edvard
    et al.
    GKN Aerospace, Sweden ; University West, Sweden.
    Rosell, Anders
    GKN Aerospace, Sweden ; Chalmers University of technology, Sweden.
    Runnemalm, Anna
    University West, Sweden.
    Christiansson, Anna-Karin
    University West, Sweden.
    Henrikson, Per
    GKN Aerospace, Sweden.
    Weld gap position detection based on eddy current methods with mismatch compensation2015In: Proceedings of JOM 18 International Conference on Joining Materials, Helsingør, Denmark, April 26-29, 2015, JOM-institute , 2015, p. 1-9Conference paper (Refereed)
    Abstract [en]

    The paper proposes a method for finding the accurate position of narrow gaps, intended for seam tracking applications. Laser beam welding of butt joints, with narrow gap and weld width, demand very accurate positioning to avoid serious and difficult to detect lack of fusion defects. Existing optical and mechanical gap trackers have problems with narrow gaps and surface finish. Eddy current probes can detect narrow gaps, but the accuracy is affected by mismatch in height above the surface on either side of the gap. In this paper a non-contact eddy-current method, suitable for robotic seam tracking, is proposed. The method is based on the resistive and inductive response of two absolute eddy current coils on either side of the gap to calculate a position compensated for height variations. Additionally, the method may be used to estimate the values of height and gap width, which is useful for weld parameter optimization. To investigate the response to variations in height, the method is tested on non-magnetic metals by scanning one commercially available eddy current probe across an adjustable gap and calculating the expected response for a two-probe configuration. Results for gap position are promising, while mismatch and gap width results need further investigation.

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