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  • 1.
    Adawi, Rahim
    University of Skövde, School of Engineering Science.
    Preventing fatal effects of overworking: Product design solution2018Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    “Overworking to death” is a phenomenon that has been noticeable in developing countries. The cause of death is mainly through ischemic strokes. While the victims’ occupations differed, they all shared a common characteristic, being positioned in a sedentary work, ranging from IT workers to doctors. This project’s aim was to develop a product that prevented or decreased the strokes that derived from sedentary overwork. This was mainly tackled by preventing one of the three causes of developing blood props, slowed blood flow. In order to gather rich data of the phenomenon, a qualitative study was conducted in China, during two months. By doing an extensive structured sampling, information rich data could be gathered during a short period of time. Data were derived from observations, questionnaires and an interview, which then was interpreted to customer needs and the final product specification. The final product became a trouser with an in built dynamic compression mechanic, that can compress the veins mostly during sitting activities, in order to prevent blood stasis. The compression mechanic works like the Chinese finger trap; compressing the calves while sitting and stretching the legs forward. It is made only out of polysaccharides fibres; cotton and corn.

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    PREVENTING FATAL EFFECTS OF OVERWORKING – PRODUCT DESIGN SOLUTION / Rahim_Adawi
  • 2.
    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.

  • 3.
    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.

  • 4.
    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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    FULLTEXT01
  • 5.
    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.

  • 6.
    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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  • 7.
    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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  • 8.
    Alfredsson, K. Svante
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Gawandi, A. A.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Gillespie, J. W., Jr.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Carlsson, L. A.
    Department of Mechanical Engineering, Florida Atlantic University, Boca Raton, USA.
    Bogetti, T. A.
    Army Research Laboratory, Aberdeen Proving Ground, MD, USA.
    Stress analysis of axially and thermally loaded discontinuous tile core sandwich with and without adhesive filled core gaps2011In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 93, no 7, p. 1621-1630Article in journal (Refereed)
    Abstract [en]

    An analytical study is performed to investigate the stress states in an axially and thermally loaded sandwich structure with a discontinuous ceramic tile core. General and simplified models are developed to determine stresses in the constituents of the sandwich structure with and without adhesive in the gaps between adjacent tiles. A general model that allows local bending of the face sheet and a simplified model which assumes uniform through-thickness stress distribution in the face sheets are developed. It is shown that the normal stress in the face sheet decreases when the gap is filled by adhesive, although the tile stress increases. The analytical model shows that normal and shear stresses at the face/core interface can be reduced by filling the gaps between tiles. Filled gaps also elevate the axial stiffness of the structure. Model results are verified by comparison to a previously developed analytical model and finite element analysis. (C) 2011 Elsevier Ltd. All rights reserved.

  • 9.
    Alfredsson, K. Svante
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Gawandi, A. A.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Gillespie Jr., J. W.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Carlsson, L. A.
    Department of Mechanical Engineering, Florida Atlantic University, Boca Raton, USA.
    Bogetti, T. A.
    Army Research Laboratory, Aberdeen Proving Ground, USA.
    Flexural analysis of discontinuous tile core sandwich structure2012In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 94, no 5, p. 1524-1532Article in journal (Refereed)
    Abstract [en]

    Three-point flexure loading of sandwich beams with a core consisting of discrete ceramic tiles (DTSS) is considered. The tile gaps may be bonded or unbonded (open gaps). The analysis utilizes a layer-wise beam theory approach. The general formulation for the displacements and stresses in the face sheets, face/core adhesive layer, and core is derived. Solutions for stresses and displacements of the beam constituents are obtained from finite element formulation based on analytical solution of the face sheet/tile unit cell. The approach is verified by comparison to stress results obtained from ordinary finite element analysis where each layer is modeled discretely. Effects of load introduction and support conditions on the effective flexural stiffness are examined. It is demonstrated that the face sheets experience substantial stress concentrations at the tile joint locations, especially if the gaps are unfilled. Analysis of beam compliance reveals sensitivity to details of load introduction and support conditions, especially when the span length becomes comparable to the tile length.

  • 10.
    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.

  • 11.
    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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  • 12.
    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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  • 13.
    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.
    Modelling and simulation of heat flow in indexable insert drilling2024In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015Article in journal (Refereed)
    Abstract [en]

    In machining, the heat generated during the process deforms the components and the final shape might not meet specified tolerances. There is therefore a need for a compensation strategy which requires knowledge of the workpiece temperature field and the associated thermal distortions. In this work, a methodology is presented for the determination of the heat load for indexable insert drilling of AISI 4140. Compared to previous research, this work has introduced a varying heat load. The heat load is extracted from thermo-mechanical finite element simulations for different nominal chip thicknesses and cutting speeds using the coupled Eulerian-Lagrangian formulation of an orthogonal turning process. The heat load is then transferred to a simplified 2D axisymmetric heat transfer model where the in-process temperature field in the workpiece is predicted. To verify the methodology, the predicted temperatures are compared to the experimentally measured temperatures for various feed rates. It is found that the model is capable of predicting the workpiece temperatures reasonably well. However, the methodology needs to be further explored to validate its applicability.

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  • 14.
    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.

  • 15.
    Aragón Martín, Laura
    University of Skövde, School of Engineering Science.
    Alternative materials for the horseshoe2014Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This thesis is a research-focused work on a study of alternative materials for horseshoes. Within this thesis the objectives and functions of a compliant horseshoe are identified, based on a literature study of the work of previous researches, and they are linked to the properties of material. After identifying these objectives, a number of methods are implemented with the aim of detecting the most suitable materials for horseshoes taking into account the properties linked with the objectives. In order to determine whether the selected material is suitable or not, a comparison with a traditional forged steel horseshoe is carried out. Whenever an appropriate material is found, a most exhaustive study is performed and finally, a decision is elected based on the further investigation. The last chapter of this thesis is comprised of a document destined for future researches where suggestions about how to get more reliable results in the field are explained.

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  • 16.
    Atarijabarzadeh, Sevil
    et al.
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden.
    Nilsson, Fritjof
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden / ABB, Corp Res, Västerås, Sweden.
    Hillborg, Henrik
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden / ABB, Corp Res, Västerås, Sweden.
    Karlsson, Sigbritt
    University of Skövde. KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden.
    Strömberg, Emma
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden.
    Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling2015In: International Journal of Polymer Science, ISSN 1687-9422, E-ISSN 1687-9430, article id 390292Article in journal (Refereed)
    Abstract [en]

    This study focuses on how the texture of the silicone rubber material affects the distribution of microbial growth on the surface of materials used for high voltage insulation. The analysis of surface wetting properties showed that the textured surfaces provide higher receding contact angles and therefore lower contact angle hysteresis. The textured surfaces decrease the risk for dry band formation and thus preserve the electrical properties of the material due to a more homogeneous distribution of water on the surface, which, however, promotes the formation of more extensive biofilms. The samples were inoculated with fungal suspension and incubated in a microenvironment chamber simulating authentic conditions in the field. The extent and distribution of microbial growth on the textured and plane surface samples representing the different parts of the insulator housing that is shank and shed were determined by visual inspection and image analysis methods. The results showed that the microbial growth was evenly distributed on the surface of the textured samples but restricted to limited areas on the plane samples. More intensive microbial growth was determined on the textured samples representing sheds. It would therefore be preferable to use the textured surface silicone rubber for the shank of the insulator.

  • 17.
    Bae, Juhee
    et al.
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Li, Yurong
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Ståhl, Niclas
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Mathiason, Gunnar
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Kojola, Niklas
    Group function R&I, SSAB, Stockholm, Sweden.
    Using Machine Learning for Robust Target Prediction in a Basic Oxygen Furnace System2020In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 51, no 4, p. 1632-1645Article in journal (Refereed)
    Abstract [en]

    The steel-making process in a Basic Oxygen Furnace (BOF) must meet a combination of target values such as the final melt temperature and upper limits of the carbon and phosphorus content of the final melt with minimum material loss. An optimal blow end time (cut-off point), where these targets are met, often relies on the experience and skill of the operators who control the process, using both collected sensor readings and an implicit understanding of how the process develops. If the precision of hitting the optimal cut-off point can be improved, this immediately increases productivity as well as material and energy efficiency, thus decreasing environmental impact and cost. We examine the usage of standard machine learning models to predict the end-point targets using a full production dataset. Various causes of prediction uncertainty are explored and isolated using a combination of raw data and engineered features. In this study, we reach robust temperature, carbon, and phosphorus prediction hit rates of 88, 92, and 89 pct, respectively, using a large production dataset. © 2020, The Author(s).

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  • 18.
    Bae, Juhee
    et al.
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Mathiason, Gunnar
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Li, Yurong
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Kojola, Niklas
    Group R and I, SSAB, Stockholm, Sweden.
    Ståhl, Niclas
    University of Skövde, School of Informatics. University of Skövde, Informatics Research Environment.
    Understanding Robust Target Prediction in Basic Oxygen Furnace2021In: IEIM 2021: The 2nd International Conference on Industrial Engineering and Industrial Management, New York, NY: Association for Computing Machinery (ACM), 2021, p. 56-62Conference paper (Refereed)
    Abstract [en]

    The problem of using machine learning (ML) to predict the process endpoint for a Basic Oxygen Furnace (BOF) process used for steelmaking has been largely studied. However, current research often lacks both the usage of a rich dataset and does not address revealing influential factors that explain the process. The process is complex and difficult to control and has a multi-objective target endpoint with a proper range of heat temperature combined with sufficiently low levels of carbon and phosphorus. Reaching this endpoint requires skilled process operators, who are manually controlling the heat throughout the process by using both implicit and explicit control variables in their decisions. Trained ML models can reach good BOF target prediction results, but it is still a challenge to extract the influential factors that are significant to the ML prediction accuracy. Thus, it becomes a challenge to explain and validate an ML prediction model that claims to capture the process well. This paper makes use of a complex and full production dataset to evaluate and compare different approaches for understanding how the data can determine the process target prediction. One approach is based on the collected process data and the other on the ML approach trained on that data to find the influential factors. These complementary approaches aim to explain the BOF process to reveal actionable information on how to improve process control.

  • 19.
    Belov, Ilja
    et al.
    Jönköping University, School of Engineering, Jönköping, Sweden.
    Nordh, Andreas
    ZiGrid AB, Nora, Sweden.
    Salomonsson, Kent
    Jönköping University, School of Engineering, Jönköping, Sweden.
    Leisner, Peter
    Jönköping University, School of Engineering, Jönköping, Sweden / SP Technical Research Institute of Sweden, Borås, Sweden.
    Fin‐Tube and Plate Heat Exchangers: Evaluation of Transient Performance2017In: 18th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    A methodology for evaluation of transient performance of, and comparison between plate heat exchanger and plate-fin-and-tube heat exchanger was developed and realized, including experiment and 3-D simulation. Heat transfer from water to a gas medium was addressed. The heated gas volume was the same for both heat exchanger designs. This was achieved by placing the plate-fin-and-tube heat exchanger into enclosure. The volume average temperature of the gas as function of time was computed. Estimated material cost for the studied designs was at least seven times lower than for the stainless steel plate heat exchanger. The performance of the selected plate-fin-and-tube heat exchanger design was found comparable to the plate heat exchanger, when both fin and tube materials were set to Al, and the enclosure was a light-weight thermal insulator. Transient behavior of the studied heat exchangers should be of interest for micro-grid applications, but also for thermal management in electronic cabinets and data centers.

  • 20.
    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.

  • 21.
    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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  • 22.
    Biel, Anders
    University of Skövde, School of Technology and Society.
    Cohesive laws for adhesives at repeated loading: an experimental methodManuscript (Other academic)
  • 23.
    Biel, Anders
    University of Skövde, School of Technology and Society.
    Mechanical behaviour of adhesive layers: experimental methods, cohesive laws, and fracture mechanics2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Adhesive joining is today viewed as one of the key technologies to achieve decreased emissions in the automobile industry. To decrease weight, optimal material selection often results in different materials for different parts. This leads to the necessity to join mixed material. Here, the use of adhesives is the most promising joining technology. For a rational design process, good models for strength analysis of adhesively joined structures are essential. With cohesive modelling, fracture of the adhesive layer is modelled with a stress-deformation law. This law - often denoted a cohesive law - gives the traction exerted on the adherends due to the deformation of the adhesive layer. This thesis is concerned with experimental methods to measure cohesive properties of engineering adhesives and standardized methods to measure the fracture energy of adhesives. A new method to measure cohesive laws is developed. With this method, the cohesive law of an epoxy adhesive is measured in shear. In peel loading, with elastically deforming adherends, the cohesive law is shown to be independent of the geometry of the specimen. If the adherends deform plastically the fracture energy increases. Experiments are performed in order to determine the temperature dependence of the cohesive layer for an epoxy adhesive. It is shown that the peak stress is strongly dependent on the temperature while the fracture energy shows only small temperature dependence. Experiments are also performed to study the influence of strain rate in peel and shear loading. The experiments show that the peak stress increases with an increasing strain rate and that the fracture energy increase in peel loading and decreases in shear with increasing strain rate. A new method to experimentally determine the relation between damage and plasticity in the adhesive during the fracture process is developed. For the present adhesive, it is shown that only minor plasticity occurs during the fracture process in peel loading. For peel, several commonly used methods to evaluate the fracture energy using the double cantilever beam specimen are critically studied. For some methods the error in evaluated fracture energy is larger than 40 %. It is shown that the evaluated fracture energy is more dependent on the choice of method than on the cohesive properties of the adhesive layer.

  • 24.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Carlberger, Thomas
    SAAB Automobile AB, SE-461 80 Trollhättan, SWEDEN.
    Influences of temperature on cohesive parameters for adhesives2007In: Interface design of polymer matrix composites - mechanics, chemistry, modelling and manufacturing: Proceedings of the 28th Risø International Symposium on Materials Science / [ed] Bent F. Sørensen, Lars Pilgaard Mikkelsen, Hans Lilholt, Stergios Goutianos, Fadhil Shareef Abdul-Mahdi, Roskilde: Risø National Laboratory , 2007, p. 143-148Conference paper (Refereed)
    Abstract [en]

    Experiments are performed to evaluate the temperature dependence of the stress-elongation relation for an engineering epoxy adhesive. Seven temperatures from -40ºC to 80ºC are considered. At each temperature, about seven experiments are performed with a double cantilever beam specimen. The experiments are evaluated using an inverse solution. The results show that the peak stress decreases monotonically with temperature, from about 55 MPa at -40ºC to about 11 MPa at 80ºC. Thus, the shape of the stress-elongation relation varies with the temperature. At higher temperatures, the fracture energy decreases slightly.

  • 25.
    Biel, Anders
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Chaudhry, Mobina
    Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden.
    Gustafsson, Stefan
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Nygren, Håkan
    Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden.
    The use of MgO-paste as a biodegradeable bone cement2016In: Materials Today: Proceedings, E-ISSN 2214-7853, Vol. 3, no 2, p. 556-561Article in journal (Refereed)
    Abstract [en]

    The use of MgO-paste as bone cement was tested on titanium cylinders implanted into rat tibia. The evaluation of bone healingwas made with the retention force (pull-out) test, light microscopy and ESEM/ EDX. Preimplantation of the MgO-paste into drillperforations of rat tibia increased the retention of the titanium implant 6-fold. The error was expressed as the 95% confidenceinterval of means (n=10 bones in each group). The observed difference between 3.46+/-0.71 N/mm2 for Ti-cylinders implantedwith MgO-paste and 0.56+/-0.26 N/mm2 for Ti-cylinders implanted directly into the bone, is statistically significant (p<0.01).The increase of retention force, caused by MgO is parallel to an increased thickness of the compact bone surrounding the implantand closer contact between bone and implant.Histological examination of the implant-related bone showed that the MgO-induced bone growth is mediated by the formation ofa bone-inducing matrix. The matrix contains organic substance, most likely proteins.

  • 26.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, School of Technology and Society.
    An analysis of the evaluation of the fracture energy using the DCB-specimen2007In: Archives of Mechanics, ISSN 0373-2029, Vol. 59, no 4-5, p. 311-327Article in journal (Refereed)
    Abstract [en]

    The methods to estimate the fracture energy using DCB-specimens as advocated in common standards. For instance, ASTM D 3433 and BS 7991:2001 are based on a compliance method, i.e. on linear elastic fracture mechanics (LEFM). Since the mechanical properties of almost all adhesives are non-linear, errors are generated. In some of the standards, the non-linear behaviour is compensated for by the use of correction terms generated from the experiments. An analysis of the methods of evaluation the fracture energy from experiments is performed. This analysis is performed first by simulating an experiment using realistic data for an engineering adhesive and then, by analysing the results with different methods. In this way, the correct fracture energy is known beforehand and the error in the evaluated fracture energy can be determined. In the present work it is shown that the magnitude of this error depends on the length of the crack. The results show that some commonly  used methods generate substantial errors when a large region of non-linear deformation precedes the crack tip. It is also shown that methods based on nonlinear fracture methods do not produce this kind of error.

  • 27.
    Biel, Anders
    et al.
    University of Skövde, School of Technology and Society.
    Stigh, Ulf
    University of Skövde, School of Technology and Society.
    Effects of constitutive parameters on the accuracy of measured fracture energy using the DCB-specimen2008In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, no 10, p. 2968-2983Article in journal (Refereed)
    Abstract [en]

    Several methods exist to estimate the fracture energy for adhesive joints using the double cantilever beam specimen and linear elastic fracture mechanics. Since the mechanical properties of all adhesives are non-linear, errors are generated. By use of an exact solution experiments are simulated. These are evaluated with eight different methods. The influence of the constitutive parameters is systematically studied. This influence is small for most methods. The error due to the choice of evaluation method is considerably larger. One of the commonly used methods gives accurate results; the error is less than 3%. However, most methods yield substantial errors.

  • 28.
    Biel, Anders
    et al.
    Department of Wind Energy, Technical University of Denmark.
    Stigh, Ulf
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Measurement of tensile properties of fibres using a DCB-specimen2015In: 20th International Conference on Composite Materials: Copenhagen, 19-24th July 2015 / [ed] Ole Thybo Thomsen, Bent F. Sørensen, Christian Berggreen, 2015Conference paper (Refereed)
    Abstract [en]

    Constitutive data are needed at extreme strains to increase the understanding of fracture processes. Ordinary tensile tests ends prematurely due to localization and large amounts of elastic energy stored in the specimens prior to fracture. A novel method is proposed to perform tensile tests using a double cantilever beam specimen. To verify the method a large specimen is developed and tested. Similar results are achieved with the present method as with more standardized methods giving confidence in the method. The specimen should be possible to minimise to provide data with small specimens.

  • 29.
    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.

  • 30.
    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.

  • 31.
    Bäckström, Ammie
    et al.
    University of Skövde, School of Engineering Science.
    Werner, Nicklas
    University of Skövde, School of Engineering Science.
    Utredning av sprickorsakerna i infästningarna till kylelement2021Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The assignment handed out by Cementa in Skövde is to investigate why crack formation and propagation emerge in the fixed attachment clamps and propose solutions against it. The fixed attachments are part of the cooling element suspension, used in the cement production to cool the material coming out of the oven. There is also an attachment clamp for the cooling elements with a clearance around the cooling elements which allows some movement in all directions.

    Since Cementa has not performed any former research for this case, a thorough literature study is conducted. Material properties, manufacturing, fracture types and fracture mechanisms are subjects examined in the literature study. Hypotheses are formed using the gathered information and are tested by calculations and analyses.

    The two main hypotheses formed are:

    • Stresses greater than the tensile strength for the steel causes crack formation.
    • Fatigue causes crack formation.

    The methods used to investigate the hypotheses are calculations by hand and FE-analysis. The results from calculations and analyses shows that the clearance in the movable attachment had great influence on the stresses obtained in the fixed attachment and is the probable cause for crack formation and propagation. The most likely fracture mechanism is fatigue and corrosion, bad welds and thermal tension could be contributing factors for crack formation. 

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  • 32.
    Carlberger, Thomas
    University of Skövde, School of Technology and Society.
    Adhesive joining for crashworthiness: material data and explicit FE-methods2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, crash simulations replace crash testing in the product development phase in theautomotive industry. High quality simulations enable shorter product development time andhigher competitiveness. However, increasing requirements regarding emissions andcrashworthiness are demanding optimised material choice in the parts constituting the carbody structure. Lightweight materials are becoming frequently used. Joining dissimilarmaterials is difficult using common joining techniques like spot welding. To this end,adhesive joining is currently gaining popularity not only due to the ability to join dissimilarmaterials, joint integrity and structural stiffness both increase by the use of adhesive joining.Moreover, the number of spot welds may be reduced in hybrid joints.In this thesis, adhesive joints are studied with respect to crashworthiness of automotivestructures. The main task for the adhesive is not to dissipate the impact energy, but to keep thejoint integrity so that the impact energy can be consumed by plastic work of the basematerials. Fracture of adhesives can be accurately modelled by cohesive zones. The dynamicbehaviour of finite element structures containing cohesive zones is studied using a simplifiedstructure. An amplified strain rate is found in the adhesive as compared to the base material.The cohesive zone concept is used in the development of a 2D interphase element. Theaccuracy and time step influence of the interphase element is compared to solutions based oncontinuum element representation of the adhesive. The interphase element is found to predictfracture of the adhesive joint with engineering accuracy and has a small effect on the timestep of the explicit FE method.The cohesive laws for use in the material models of the adhesive have been determined usingdedicated test methods. The double cantilever beam specimen and the end notched flexurespecimen are used with inverse methods to determine cohesive laws in peel and shear,respectively. The cohesive laws are determined for varying temperature, strain rate andadhesive layer thickness. A built up bimaterial beam is designed for testing and simulation ofjoints consisting of bolts, adhesives and combinations of bolts and adhesives, i.e. hybridjoints. The model of the hybrid beam developed was found to be able to predict results fromimpact tests, quantified as maximum load and deformed shape of the beam.

  • 33.
    Carlberger, Thomas
    et al.
    University of Skövde, School of Technology and Society.
    Biel, Anders
    University of Skövde, School of Technology and Society.
    Influence of temperature and strain rate on cohesive properties of a structural epoxy adhesiveManuscript (Other academic)
  • 34.
    Chauhan, H. S.
    et al.
    Department of Physics, University of Rajasthan, Jaipur, India.
    Ilver, L.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Nilsson, P. O.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Kanski, J.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Karlsson, Krister
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Direct- and inverse-photoemission investigations of the electronic structure of Cd(0001)1993In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 48, no 7, p. 4729-4734Article in journal (Refereed)
    Abstract [en]

    Photoemission and inverse angle-resolved photoemission spectra are presented for Cd(0001). The data are interpreted in terms of interband transitions, density-of-states effects, and excitations of surface states.

  • 35.
    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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  • 36.
    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)
  • 37.
    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.

  • 38.
    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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  • 39.
    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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  • 40.
    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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  • 41.
    Dong, Xixi
    et al.
    Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University London, Uxbridge, United Kingdom.
    Feng, Lingyun
    Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University London, Uxbridge, United Kingdom.
    Wanga, Shihao
    Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University London, Uxbridge, United Kingdom.
    Wang, Feng
    School of Metallurgy and Materials, University of Birmingham, Birmingham, United Kingdom.
    Ghasemi, Rohollah
    Husqvarna AB, Huskvarna, Sweden.
    Ji, Gang
    Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, Lille, France.
    Nyberg, Eric A.
    Kaiser Aluminum, Spokane Valley, WA, United States.
    Ji, Shouxun
    Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University London, Uxbridge, United Kingdom.
    A quantitative strategy for achieving the high thermal conductivity of die-cast Mg-Al-based alloys2022In: Materialia, E-ISSN 2589-1529, article id 101426Article in journal (Refereed)
    Abstract [en]

    A quantitative strategy was reported to design and develop Mg-Al-based alloys to achieve high thermal conductivity, in which the specific RE elements can be introduced to reduce the Al concentration in Mg matrix and to suppress the formation of Mg17Al12 phase through the formation of new intermetallic phases. Based on quantitative calculations, the strategy was demonstrated by a novel die-cast Mg3.2Al4.4La0.4Nd (in wt.%) alloy, which provided the thermal conductivity of 114.3 W/(m∙K) at ambient temperature and 137.5 W/(m∙K) at 300 °C, ∼25% higher than the commercial Mg4Al4RE (AE44) alloy. Meanwhile, the alloy also offered excellent ambient yield strength of 143.2 MPa and elongation of 8.2%, and superior strength and ductility than the AE44 alloy at elevated temperatures.

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  • 42.
    España Giner, Jose Manuel
    et al.
    Polytechnic University of Valencia, Alcoy, Spain.
    Fages, Eduardo
    Textile Research Institute, Alcoy, Spain.
    Boronat Vitoria, Teodomiro
    Polytechnic University of Valencia, Alcoy, Spain.
    Moriana Torró, Rosana
    Textile Research Institute, Alcoy, Spain.
    Balart Gimeno, Rafael Antonio
    Polytechnic University of Valencia, Alcoy, Spain.
    Antioxidant effects of natural compounds on green composite materials2012In: Plastics Research Online, p. 1-3Article in journal (Other academic)
    Abstract [en]

    Naturally-occurring antioxidant compounds can improve the thermal resistance of a bio-composite, increasing the degradation temperature of the material by as much as 130%.

  • 43.
    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.

  • 44.
    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.‎ 

  • 45.
    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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  • 46.
    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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  • 47.
    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.

  • 48.
    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.

  • 49.
    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.

  • 50.
    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.

123 1 - 50 of 134
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