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  • 551.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Economical Viability of Laser Metal Deposition2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Reports on large economic savings using Additive Manufacturing (AM) has been found in literature when exploiting the positive capabilities of AM. This paper evaluates the economic potential of, the AM method, laser metal deposition (LMD) in production of add-on features compared to conventional manufacturing methods. This is done by theoretical case studies, which explore factors critical to the cost of manufacturing a jet engine flange. LMD has the potential to be an economical viable alternative to conventional manufacturing methods when the manufactured component has a high buy-to-fly ratio, the component is small and complex, if the operator time can be kept to a minimum, and/or when the design freedom of LMD can be capitalized into lighter and more efficient components.

  • 552.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Evaluation of a temperature measurement method developed for laser metal deposition2017In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 22, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Measuring temperatures in the material during laser metal deposition (LMD) has an inherent challenge caused by the laser. When thermocouples are radiated by the high intensity laser light overheating occurs which causes the thermocouple to fail. Another identified difficulty is that when the laser passes a thermocouple, emitted light heats the thermocouple to a higher temperature than the material actually experience. In order to cope with these challenges, a method of measuring temperatures during LMD of materials using protective sheets has been developed and evaluated as presented in this paper. The method has substantially decreased the risk of destroying the thermocouple wires during laser deposition. Measurements using 10 mm2 and 100 mm2 protective sheets have been compared. These measurements show small variations in the cooling time (∼0.1 s from 850°C to 500°C) between the small and large protective sheets which indicate a negligible effect on the temperature measurement. © 2016 Institute of Materials, Minerals and Mining.

  • 553.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Evaluation of the effect of process parameters on microstructural characteristics in laser metal deposition of Alloy 7182015In: Journal of optics and laser technologyArticle in journal (Refereed)
  • 554.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of Heat Input on Grain Structure in Thin-Wall Deposits using Laser Metal Powder Deposition2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. -7Conference paper (Refereed)
    Abstract [en]

    Laser metal deposition (LMD) is an additive manufacturing method which is used to deposit material directly onto a metal surface layer upon layer until a final component is achieved. The material used in this study is the nickel iron based superalloy Alloy 718. There is a strong thermal gradient associated with this method which generally produces columnar grains growing in the build-up direction. The preferred solidification orientation of the FCC matrix is in the (001) direction which makes it possible to build directionally solidified structures with epitaxial grains growing through the layers. In this study LMD with powder as additive has been used to build thin walled samples, multiple layers high. The main objectives of this research are to assess the influence of the heat input on the grain structure in LMD builds and evaluate how the morphology and texture of the grains are affected by the changes in process parameters. Two different parameter sets are compared where a high and a low heat input have been used. The two samples with different heat inputs have been evaluated using a scanning electron microscope coupled to an electron back scatter diffraction detector in order to obtain quantitative grains size measurements as well as crystallographic information. It was shown that the grain structure was considerably affected by the heat input where the high heat input produced a strong texture with columnar grains growing in the build-up direction. With a low heat input the grains became finer and, although elongated, the grains became more equiaxed.

  • 555.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Investigation of laser metal deposited Alloy 718 onto an EN 1.4401 stainless steel substrate2017In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 97, no Supplement C, p. 144-153Article in journal (Refereed)
    Abstract [en]

    This paper focuses on how process parameters affect the deposition of Alloy 718 onto an EN 1.4401 stainless steel substrate in terms of secondary phase formation, dilution and hardness. A columnar solidification structure with elongated grains growing in the direction normal to the substrate was observed for all parameters. In the interdendritic regions, phases with a high content of Niobium were identified. Scanning Electron Microscopy imaging and Energy Dispersive Spectroscopy measurements revealed these phases to most likely be Laves phase and Nb-carbides. Temperature measurements indicated no significant aging in the deposits. Considerable enrichment of iron was found in the initially deposited layers due to dilution from the substrate. The increased content of iron seemed to aid in forming constituents rich in niobium which, in turn, influenced the hardness. The highest mean hardness was noted in the sample with the lowest area fraction of Nb-rich constituents.

  • 556.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Ojo, Olanrewaju
    University of Manitoba, Department of Mechanical Engineering,Winnipeg, R3T 5V6, Canada.
    Effect of Process Parameters on the Crack Formation in Laser Metal Powder Deposition of Alloy 7182018In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 10, p. 5042-5050Article in journal (Refereed)
    Abstract [en]

    Cracking in Alloy 718 using laser metal powder deposition has been evaluated in this study. It is found that the material is susceptible to cracking when the laser power is high, the scanning speed is high and the powder feeding rate is low. Almost all the cracks are located close to the center of the deposited wall and propagates in the normal direction to the substrate. Evidence of liquation are found at the cracked surfaces and since all cracks reside in regions which are reheated several times, the cracks are determined to mostlikely be heat affected zone liquation cracks. The influence of respective process parameter was evaluated using a design of experiment approach. It is shown that, when the powder feeding rate is incorporated as avariable, the heat input is not a suitable indicator for the hot cracking susceptibility in laser metal powder deposition of Alloy 718. A combinatory model using the power ratio together with the heat input is therefore proposed.

  • 557.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Ojo, Olanrewaju
    University of Manitoba,Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Microstructural Characterization of Laser Metal Powder Deposited Alloy 7182018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 142, p. 550-559Article in journal (Refereed)
    Abstract [en]

    A microstructural study of Laser Metal Powder Deposition (LMPD) of Alloy 718, using a low (40 J/mm) and high (100 J/mm) heat inputs (HIs) was performed. The microstructure was characterized in as-deposited condition as well as after a standard heat-treatment, using optical microscope (OM), scanning electron microscope (SEM) and Transmission Electron Microscope (TEM). Laves, MC-carbides, γ' and γ'' are observed in the interdendritic areas of both conditions. However, the dendritic core only consists of γ-matrix. The high HI condition shows a slightly larger Primary Dendrite Arm Spacing (PDAS) as compared to the low HI condition. Additionally, the particle size of the Nb-rich constituents in the interdendriticregions (Laves-phase and Niobium carbide) are larger in the high HI sample. After heat-treatment, the Laves phase dissolves and is replaced by δ-phase in the interdendritic regions, while γ', γ'' and MC-carbideremain in the interdendritic regions. However, the γ'' precipitates seems to be less developed in the dendritic core as compared to the interdendritic regions, especially in the high HI sample. This can be attributed to a heterogeneous distribution of Nb in the microstructure, with a lower Nb content in the dendritic core as compared to close to the interdendritic regions.

  • 558.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Modeling and simulation for welding automation2010Doctoral thesis, comprehensive summary (Other academic)
  • 559.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Automation Systems.
    Operator bias in the estimation of arc efficiency in gas tungsten arc welding2015In: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 20, no 1, p. 128-133Article in journal (Refereed)
    Abstract [en]

    In this paper the operator bias in the measurement process of arc efficiency in stationary direct current electrode negative gas tungsten arc welding is discussed. An experimental study involving 15 operators (enough to reach statistical significance) has been carried out with the purpose to estimate the arc efficiency from a specific procedure for calorimetric experiments. The measurement procedure consists of three manual operations which introduces operator bias in the measurement process. An additional relevant experiment highlights the consequences of estimating the arc voltage by measuring the potential between the terminals of the welding power source instead of measuring the potential between the electrode contact tube and the workpiece. The result of the study is a statistical evaluation of the operator bias influence on the estimate, showing that operator bias is negligible in the estimate considered here. On the contrary the consequences of neglecting welding leads voltage drop results in a significant under estimation of the arc efficiency. © 2015, Universidade Federal de Uberlandia. All rights reserved.

  • 560.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Automation Systems.
    Operator influence on the estimation of arc efficiency in gas tungsten arc welding2013In: JOM-17 - International Conference on Joining Materials, 5-8 May 2013, Helsingør, Denmark. Proceedings / [ed] Osama Al-Erhayem, JOM-Institute , 2013Conference paper (Other academic)
    Abstract [en]

    In this paper the operator bias in the measurement process of arc efficiency in stationary direct current electrode negative gas tungsten arc welding is discussed. An experimental study involving 15 operators (enough to reach statistical significance) has been carried out with the purpose to estimate the arc efficiency from a specific procedure for calorimetric experiments. The measurement procedure consists of three manual operations which introduces operator bias in the measurement process. An additional relevant experiment highlights the consequences of estimating the arc voltage by measuring the potential between the terminals of the welding power source instead of measuring the potential between the electrode contact tube and the workpiece. The result of the study is a statistical evaluation of the operator bias influence on the estimate, showing that operator bias is negligible in the estimate considered here. On the contrary the consequences of neglecting welding leads voltage drop results in a significant under estimation of the arc efficiency.

  • 561.
    Sikström, Fredrik
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Christiansson, Anna-Karin
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Simulated Feedback Control of Metal Fusion Welding2007In: Proceedings of the ninth IASTED International Conference on Control and Applications: Montreal, Canada 2007, ACTA Press , 2007, p. 2263-2270Conference paper (Refereed)
  • 562.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation Systems.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Automation Systems. University West, Department of Engineering Science, Division of Production Systems. Chalmers University of Technology, Department of Signals and Systems,Gothenburgh, Sweden.
    Model based feedback control of gas tungsten arc welding: An experimental study2015In: Automation Science and Engineering (CASE), 2015 IEEE International Conference on, IEEE conference proceedings, 2015, p. 411-416Conference paper (Refereed)
    Abstract [en]

    In order to obtain high structural integrity and joint performance in welding a transient heat conduction model has been utilized to design a model based feedback controller.Gas tungsten arc welding of work-pieces of austenitic steel have been simulated by the finite element method. The basis for controller design is a low order model obtained from parametric system identification. The identification has been performed both on the finite element simulation and on physical welding. The low order model responses show a good agreement with both the finite element simulation result and the physical process response. An experimental study has been performed to verify the approach. This study also explores what experiments are needed for a successful design. It is shown that model based control successfully mitigates perturbations that occur during welding.

  • 563.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Process and Product Development. University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Process and Product Development. University West, Department of Engineering Science, Division of Production Systems.
    Model order reduction methods applied to a welding model2012In: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering, ISSN 0959-6518, E-ISSN 2041-3041, Vol. 226, no 7, p. 972-984Article in journal (Refereed)
    Abstract [en]

    A  finite element representation modelling transient heat conduction of gas tungsten arc welding of stainless steel is used to evaluate different methods for model order reduction. The focus is on establishing a linear low-order model of the dynamic  relation between the welding current and the temperature measured by a radiation pyrometer. The objective of this low-order model is to design a model-based feedback controller and to investigate the consequences of applying feedback control of the process. Three different approaches for model reduction have been evaluated, namely the Krylov subspace method for moment    matching, balanced truncation and parametric system identification. The study provides a knowledge base for the selection of model order reduction methods when dealing with large-scale systems like finite element models of transient heat conduction, and it recommends parametric system identification. It renders sufficient approximations for controller design, no linearization of the finite element model is required, and there is no limit on degrees of freedom of the finite element model.

  • 564.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Modeling and simulation aspects of feedback control in gas tungsten arc welding: An experimental study2010Manuscript (preprint) (Other academic)
  • 565.
    Sikström, Fredrik
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Christiansson, Anna-Karin
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Lennartson, Bengt
    Chalmers University of Technology, Department of Signals and Systems.
    Modelling and Simulation for Feedback Control of Welding2007In: Proceeding (567) Modelling and Simulation (MS 2007): Montreal, CanadaMay 30 - June 1, 2007, ACTA Press , 2007, p. 131-136Conference paper (Refereed)
  • 566.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Role of fixture forces on distortion in gas tungsten arc welding: An experimental and modelling approach2011In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 225, no 1, p. 140-148Article in journal (Refereed)
    Abstract [en]

    Simulation and experiments show that the fixture clamping force has a significant influence on the structural integrity of a welded workpiece. This understanding is of great importance for the manufacture of aerospace components with tight tolerances in the specifications. The focus in the present study is on the temperature history during welding and residual deformation; its main contribution is a demonstrator designed for evaluation of the influence of fixture clamping forces and validation of the simulation results. The demonstrator concerns a simplified situation considering gas tungsten arc welding of a nickel-based metal plate fixed by a specially designed fixture, where one side of the plate was clamped with different levels of force. The temperature history was measured during the weld sequence and deformation measurements were performed after cooling and release of the workpiece from the fixture. The results from simulation and experimentation showed good agreement. The proposed strategy is industrially competitive and has shown that the looser the fixture clamps, the smaller the residual deformation. Furthermore, the study provides a knowledge base for selection of active fixture concepts in that the fixture clamping force can be determined in advance and possibly also be subject to force control.

  • 567.
    Sikström, Fredrik
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Christiansson, Anna-Karin
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Lennartson, Bengt
    Chalmers University of Technology, Department of Signals and Systems.
    Simulation for Design of Automated Welding2007In: EUROCON, 2007. The International Conference on "Computer as a Tool": Warsaw, Poland, 2007, IEEE Explore , 2007, p. 2263-2270Conference paper (Refereed)
    Abstract [en]

    This paper describes a promising approach where simulations were used in the design of real-time control for automated welding. A finite element method has been used for thermal modelling of gas tungsten arc welding on a simplified test object. Measurement data for model calibration and validation was acquired through thermal imaging during weld experiments on test objects of the alloy Fe-316. An optimisation scheme for inverse modelling was employed in the calibration of the distributed weld process model. Frequency weighted model reduction and parametric system identification were applied and evaluated to get a low order model of the single-input single-output dynamics between a simulated weld heat source (actuator) and a sensor. This low order model was then successfully used for controller design where the control signal was weld current and the measured output was a moving spot temperature. Finally, the closed-loop performance was evaluated by simulation of the weld process model showing improved temperature stability relative to open loop.

  • 568.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Ericson Öberg, Anna
    Volvo Construction Equipment, Arvika, Sweden.
    Prediction of penetration in one-sided fillet welds by in-process joint gap monitoring: an experimental study2017In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 61, no 3, p. 529-537Article in journal (Refereed)
    Abstract [en]

    The challenge to predict variations in penetration depth in one-sided fillet welds during robotized gas metal arc welding has been addressed by a pilot investigation of technical possibilities and limitations. The main cause for the variation in penetration depth is considered to be variation in joint gap size. Special attention has been paid in order to adopt the experimental conditions to conform to industrial welding conditions. The employed method uses in-process monitoring of joint gap size together with an empirical model relating penetration depth to gap size in order to predict this depth. The gap size estimates are based on image information from two cameras, one visual and one infrared. The results, that are evaluated off-line, confirm the development of a real-time method providing technical solutions that are industrially tractable. The results also pinpoint areas of further improvements towards increased robustness and reduced estimation uncertainties.

  • 569.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ericsson, Mikael
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Integration of finite element analysis and computer aided robotics for advanced programming of robotized welding2009In: ASM Proceedings of the International Conference: Trends in Welding Research / [ed] S.A. David, T. DebRoy, J.N. DuPont, T. Koseki, and H.B. Smartt, ASM International, 2009, p. 454-460Conference paper (Refereed)
    Abstract [en]

    This paper describes a promising approach where finite element analysis is combined with computer aided robotics in off-line programming of advanced robotized welding. Finite element analysis is used to find an optimized weld power signal based on weld trajectories obtained from computer aided robotic simulations. The weld power signal is calculated by applying feedback control in the finite element simulation. This optimization ensures a full penetration weld while the total specific thermal energy input is minimized in order to mitigate unwanted residual stress and distortion. The objective with this approach is to support the design of robotized welding and significantly reduce the number of costly trials in physical implementations. The relevance of this paper is a useful method for off-line optimization of robot trajectories and varying process parameters.

  • 570.
    Sikström, Fredrik
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Ericsson, Mikael
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science.
    3D-Scanning for Weld Distortion Measuring2006In: Instrumentation and Measurement Technology Conference, 2006. IMTC 2006. Proceedings of the IEEE, IEEE conference proceedings, 2006, p. 2132-2137Conference paper (Refereed)
    Abstract [en]

    Optical three dimensional scanning for weld distortion measurements have been performed for validation, inspection, general visualization and documentation of a robotized welding process. The planning, preparing and processing of the weld is done in a simulation-based concept where computer aided robotics software simulations are integrated with finite element analysis simulations with the objective to reduce global geometrical deformation during welding. The off-line programmed robot paths were used as an input for finite element calculations of temperature fields and distortion in the work piece. In order to validate the finite element model 3D-scannings have been performed before and after every single welding sequence. This paper describes a validation experiment with non-contact measurements of weld distortion and discusses limitations in optical 3D-scanning techniques used for this purpose

  • 571.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Heat input and temperatures in welding2013In: JOM-17 - International Conference on Joining Materials, JOM-Institute , 2013Conference paper (Refereed)
    Abstract [en]

    A key feature in welding is the energy supplied, in order to join the work pieces together. For all fusion welding methods, the supplied energy is so high that the work-piece joint surfaces are melted and fused together. The energy supplied is then transported away, mainly by conduction through the base materials. The temperature of the weld decreases and a solid joint is eventually formed. This may then undergo phase transformations and finally the weld joint reaches ambient temperature.

    The thermal history of a welded joint has a large effect on the microstructure and mechanical properties. Welding metallurgist therefore consider the cooling time t8/5 as crucial to understand the resulting properties of a joint in steel structures. The cooling time is influenced by several factors, like heat input, base material thickness, base material thermal properties, preheat an interpass temperatures etc. Regarding the heat input, the efficiency of the welding arc has for a long time been debated, i.e. how much of the arc energy really goes into the weld. Large efforts are being made to measure this very accurately.

    Another significant research field has been to measure or calculate the cooling time of welds, in particular t8/5. However, this cooling time is affected by the arc energy and by the arc efficiency.

    In a more macroscopic sense, it has been shown that the temperature of a welded structure can vary with the presence of for example internal heat sinks. Such variations may affect macroscopic properties like penetration. One way to ensure constant condition in terms of temperature could be to increase the heat input if the temperature decreases. However, how such variations affect for example the cooling rate has not been studied.The aim of the present paper is to report some experimental results regarding cooling rate in welded joints and put this into context of arc efficiency and temperature regulations and also discuss how the cooling rate may be affected in more production like welding situations.

  • 572.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Nilsen, Morgan
    University West, Department of Engineering Science, Division of Production Systems.
    Beam offset detection in laser stake welding of tee joints based on photodetector sensing2019In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 36, p. 64-71Article in journal (Refereed)
    Abstract [en]

    This paper presents an experimental study where a photodetector is used in a laser beam welding tool to monitor beam deviations (beam offsets) in stake welding of tee joints. The aim is to obtain an early detection of deviations from the joint centerline in this type of welding where the joint is not visible from the top side. The photodetector used is a GaP diode sensitive in the spectral range 150-550 nm corresponding to the spectral emissions form the plasma plume during keyhole welding. The photodetector signal has been evaluated by change point detection methods with respect to their detection performance. Both an off-line and an on-line method have been evaluated. The off-line method can be used to guide post weld inspection and the on-line method has the potential to enable on-line adaptive position control and/or the possibility to stop the process for repair. The results shows that the proposed method can be used as a go/no go system and to guide post weld inspection.

  • 573.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Nilsen, Morgan
    University West, Department of Engineering Science, Division of Automation Systems.
    Vision systems for in‐process monitoring of laser beam welding2015In: Proceedings of JOM 18 International conference on joining materials, Helsingör, Danmark, april 26-29, 2015, JOM-Institute , 2015, p. 1-8Conference paper (Refereed)
    Abstract [en]

    This paper addresses the issue of evaluating an optical vision system to be integrated with a 1μm laser beam welding tool for process monitoring. The boundary conditions for the system performance and system nature imposed by the needs in industrial production is highlighted. Initial welding experiments have been executed in order to understand the applicability of the vision system. The evaluation includes considerations on the required sensor bandwidth. The need for time synchronized data is emphasized and the use of numerical algorithms for enhancing the estimation and detection performanceof the system is discussed. The results shows a good potential for the system to give robust process information to be used in monitoring and control.

  • 574.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Runnemalm, Anna
    University West, Department of Engineering Science, Division of Production Systems.
    Broberg, Patrik
    University West, Department of Engineering Science, Division of Production Systems.
    Nilsen, Morgan
    University West, Department of Engineering Science, Division of Production Systems.
    Svenman, Edvard
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    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 (Other academic)
    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.

  • 575.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Production System.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production System.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production System.
    Analysis of Plunge and Dwell Parameters of Robotic FSW Using TWT Temperature Feedback Control2016In: Proceedings of 11th International Symposium on Friction Stir Welding, Cambridge, UK, 2016, p. 1-11Conference paper (Other academic)
    Abstract [en]

    Friction stir welding (FSW) and variants of the process have generated high interest in many industries due to its several advantages such as low distortion, superior mechanical properties over arc welding and the possibility of joining dissimilar materials. Increased complexity of industrial applications require a better control of the welding process in order to guarantee a consistent weld quality. This can be achieved by implementing feedback control based on sensor measurements. Previous studies have demonstrated a direct effect of weld temperature on the mechanical properties of FSW joints, [1], and therefore, temperature is chosen as primary process variable in this study.A new method for temperature measurement in FSW referred to as the Tool-WorkpieceThermocouple (TWT) method has recently been developed by De Backer. The TWT method is based on thermoelectric effect and allows accurate, fast and industrially suitable temperature monitoring during welding, without the need for thermocouples inside the tool [2].This paper presents an application of the TWT method for optimisation of the initial weld phases, plunge and dwell, operation in conventional FSW, which can also be applied to friction stir spot welding (FSSW). An analysis of the operation parameters by using feedback temperature control is presented aiming to better control of the initial weld phases through temperature feedback.

    The introduction of the TWT temperature sensor provides additional process information during welding. Fast data acquisition gives opportunity to differentiate different process phases: contact of probe tip with workpiece surface; plunge phase; dwell phase. This would be followed by tool retraction for FSSW or tool traverse phase for FSW.The effect of the plunge parameters on weld temperature and duration of each phase were studied for the purpose of optimising the process with respect to process (i) robustness, (ii)time, (iii) robot deflection and (iv) quality. By using temperature feedback, it is possible to control the plunge phase to reach a predefined weld temperature, avoiding overheating of the material, which is known to have a detrimental influence on mechanical properties. The work presented in this paper is an important step in the optimization of robotic FSSW and FSW.

  • 576.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Automation Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation Systems.
    Cooling rate effect on temperature controlled FSW process2015Conference paper (Refereed)
    Abstract [en]

    A continuous trend towards more demanding jointgeometries is imposed across various manufacturingindustries. During Friction Stir Welding (FSW) of suchcomplex geometries, the surrounding environment playsan important role on the final weld quality, especially inthermal aspects. In order to guarantee a consistent weldquality for different conditions, in-process weldingparameter adaptation is needed.This paper studies the effect of the cooling rate onmechanical properties for temperature controlled FSW byusing different backing bar materials. A new temperaturesensor solution, the Tool-Workpiece Thermocouple(TWT) method [1], was applied to measure thetemperature during welding. A FSW-robot equipped withtemperature and force feedback control was used, whererotation speed was varied to maintain a constant weldingtemperature. AA7075-T6 lap joints were performed withand without temperature control. The cooling rate duringwelding was acquired and macrographs and mechanicalproperties were evaluated for each weld. The rotationspeed offered a fast response promoting the heat inputnecessary to weld at the set temperature. Temperaturecontrolled welds presented a better behaviour undertensile loads. The results prove that temperature controlusing the TWT method is suitable to achieve higher jointquality and provides a fast setup of optimal parameters fordifferent environments.The work presented is an important step in the processoptimization through feedback control which willconsider not only the operational parameters of theprocess as such but also the resulting quality of the joint.

  • 577.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production Systems.
    Temperature measurements during friction stir welding2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 88, no 9-12, p. 2899-2908Article in journal (Refereed)
    Abstract [en]

    The increasing industrial demand for lighter, more complex and multi-material components supports the development of novel joining processes with increased automation and process control. Friction stir welding (FSW) is such a process and has seen a fast development in several industries.This welding technique gives the opportunity of automation and online feedback control, allowing automatic adaptation to environmental and geometrical variations of the component.Weld temperature is related to the weld quality and therefore proposed to be used for feedback control. For this purpose, accurate temperature measurements are required. This paper presents an overview of temperature measurement methods applied to the FSW process. Three methods were evaluated in this work: thermocouples embedded in the tool, thermocouples embedded in the workpiece and the tool-workpiece thermocouple(TWT) method. The results show that TWT is an accurate and fast method suitable for feedback control of FSW.

  • 578.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Automation Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation Systems.
    TWT method for temperature measurement during FSW process2015In: The 4th international Conference on scientific and technical advances on friction stir welding & processing, San Sebastian, Spain, 2015, p. 95-98Conference paper (Refereed)
    Abstract [en]

    Friction stir weld (FSW) has generated a high interest in many industry segments in the past 20 years. Along with new industrial challenges, more complex geometries and high quality demands, a better control of the welding process is required. New approaches using temperature controlled welding have been proposed and revealed good results. However, few temperature measurement methods exist which are accurate, fast and industrially suitable. A new and simple sensor solution, the Tool-Workpiece Thermocouple (TWT) method, based on the thermoelectric effect was recently developed.This paper presents a calibration solution for the TWT method where the TWT temperature is compared to calibrated thermocouples inside the tool. The correspondence between both methods is shown. Furthermore, a calibration strategy in different aluminium alloys is proposed, which is based on plunge iterations. This allows accurate temperature monitoring during welding, without the need for thermocouples inside the tool.

  • 579.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production Systems.
    Welding Temperature during FSW of 5 mm thickness AA6082-T62017In: 5th international conference on scientific and technical advances on friction stir welding & processing, Metz, France, 11-13 October 2017., 2017Conference paper (Other academic)
  • 580.
    Silveira, L. L.
    et al.
    Federal University of Technology - Parana, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR, Brazil.
    Pukasiewicz, A. G. M.
    Federal University of Technology - Parana, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR, Brazil.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zara, A. J.
    State University of Ponta Grossa, Ponta Grossa, PR, Brazil.
    Comparative Study of the Corrosion and Cavitation Resistance of HVOF and HVAF FeCrMnSiNi and FeCrMnSiB Coatings2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc , 2017, Vol. 2, p. 675-680Conference paper (Refereed)
    Abstract [en]

    Cavitation and corrosion on hydrodynamic components and systems reduces the operational efficiency. The use of wear resistant coatings have been studied as a solution to the problem of corrosion and cavitation in the industrial environment. Thermal spray processes are recognized as excellent technique to deposit coatings. The high velocity oxy-fuel process (HVOF) can produce high density and bond strength coatings. High velocity air-fuel process (HVAF) is an alternative process, shown to be superior regarding corrosion protection and production costs. HVAF can deposit coating with shorter dwell time and lower temperature, producing coating with lower oxide content This paper presents the use of HVOF and HVAF process to deposit FeCrMnSiNi and FeCrMnSiB coatings, studying the resistance against corrosion and cavitation in comparison to 316L HVOF coating. Microstructure was analyzed by XRD, microscopic means and mechanical testing. Cavitation and corrosion behavior of the coatings were also studied comparatively. HVAF coatings presented lower porosity and oxide levels, as well as higher hardness values, compared with the coatings deposited by HVOF process. The HVAF process presented better cavitation resistance than HVOF coatings. The FeCrMnSiNi HVAF coating had the best corrosion protection performance between the developed alloys. 

  • 581.
    Silveira, L. L.
    et al.
    UTFPR – Universidade Tecnológica Federal do Paraná, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR 84016-210, Brazil.
    Pukasiewicz, A. G. M.
    UTFPR – Universidade Tecnológica Federal do Paraná, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR 84016-210, Brazil.
    de Aguiar, D. J. M.
    UTFPR – Universidade Tecnológica Federal do Paraná, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR 84016-210, Brazil.
    Zara, A. J.
    UEPG – Universidade Estadual de Ponta Grossa, Ponta Grossa, PR 84010-330, Brazil.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Study of the corrosion and cavitation resistance of HVOF and HVAF FeCrMnSiNi and FeCrMnSiB coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 374, p. 910-922Article in journal (Refereed)
    Abstract [en]

    Cavitation and corrosion on hydrodynamic components and systems reduces the operational efficiency. The use of wear resistant coatings has been studied as a solution to the problem of corrosion and cavitation in industrial environments. The high velocity oxy-fuel process (HVOF) can produce coatings with high density and bond strength. High velocity air-fuel (HVAF) is an alternative process, which can deposit coatings with higher velocity and lower temperatures, compared to the HVOF process, resulting in lower oxide content. This paper analyzes the HVOF and HVAF processes to deposit FeCrMnSiNi and FeCrMnSiB coatings, comparing their cavitation and corrosion resistance. HVAF coatings presented lower porosity and oxide levels, as well as higher hardness values. The HVAF process presented better cavitation and corrosion resistance, due to lower porosity and oxide contents of the coatings. The amount of oxides and pores in the coatings was crucial in their corrosive behavior, by facilitating the penetration of the chloride ions through the pores, leading to a higher corrosion rate and pitting formation. © 2019 Elsevier B.V.

  • 582.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, SE-41296 Gothenburg, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Heat-Affected-Zone Liquation Cracking in Welded Cast Haynes® 282®2019In: Metals, ISSN 2075-4701, Vol. 10, no 1, article id 29Article in journal (Refereed)
    Abstract [en]

    Varestraint weldability testing and Gleeble thermomechanical simulation of the newly developed cast form of Haynes® 282® were performed to understand how heat-affected-zone (HAZ) liquation cracking is influenced by different preweld heat treatments. In contrast to common understanding, cracking susceptibility did not improve with a higher degree of homogenization achieved at a higher heat-treatment temperature. Heat treatments with a 4 h dwell time at 1120 °C and 1160 °C exhibited low cracking sensitivity, whereas by increasing the temperature to 1190 °C, the cracking was exacerbated. Nanosecond ion mass spectrometry analysis was done to characterize B segregation at grain boundaries that the 1190 °C heat treatment indicated to be liberated from the dissolution of C–B rich precipitates

  • 583.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Hot cracking in cast alloy 7182018In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 23, no 7, p. 568-574Article in journal (Refereed)
    Abstract [en]

    Hot cracking susceptibility of the Fe–Ni-based precipitation hardening cast superalloy Alloy 718 was studied by Varestraint weldability testing. The effect of two hot isostatic pressing (HIP) treatments commonly employed in the aerospace industry was investigated in reference to the as cast condition. It was found that the heat affected zone (HAZ) liquation cracking susceptibility increased for samples with pre-weld HIP treatments. The as cast condition disclosed the best response for liquation cracking followed by HIP-1120 (1120°C/4h (HIP) + 1050°C/1h and furnace cooling to 650°C/1h in vacuum + 950°C/1h) and HIP-1190 (1190°C/4h (HIP) + 870°C/10h and furnace cooling to 650°C/1h in vacuum + 950°C/1h). The amount of the secondary precipitates and base metal grain size was found to be important parameters influencing the cracking susceptibility. Regarding solidification cracking susceptibility, the three conditions appear to behave similarly. © 2018 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.

  • 584.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology, Gothenburg, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Review of Hot Cracking Phenomena in Austenitic Stainless Steels2016In: 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]

    Hot cracking is a phenomenon occurring during welding. Hot cracks that form in the fusion zone are named solidification cracking while cracking that takes place in the heat affected zone is referred to as liquation cracking. This paper reviews the hot cracking phenomena specifically of relevance to austenitic stainless steels. The currently existing main theories explaining solidification and liquation cracking are considered together with the influence of main parameters in relation to susceptibility towards hot cracking. Important factors are the base metal microstructure, primary solidification mode, solidification rate, distribution of delta ferrite, amount of nitrogen, level of impurities and minor elements.

  • 585.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Varestraint weldability testing of cast ATI® 718Plus™: a comparison to cast Alloy 7182019In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 2, p. 389-399Article in journal (Refereed)
    Abstract [en]

    Varestraint testing of the newly developed cast ATI® 718Plus™ after pseudo-HIP (hot isostatic pressing) heat treatments showed that the extent of solidification cracking was independent of the heat treatment condition. The susceptibility towards heat-affected zone (HAZ) liquation cracking was found to be related to the heat treatment dwell time rather than the temperature. The heat treatments at 1120 and 1190 °C for 24 h were the most susceptible to cracking. On the other hand, heat treatments at 1120, 1160 and 1190 °C for 4-h dwell time exhibited the least amount of cracking. The solidification cracking was found to be similar whereas the HAZ liquation cracking was lower for ATI® 718Plus™ after the heat treatment at 1120 and 1190 °C for 4-h dwell time in comparison to cast Alloy 718.

  • 586.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology,Department of Industrial and Materials Science, Gothenburg, Sweden.
    Fransson, William
    University West, Department of Engineering Science.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Brederholm, Anssi
    Aalto University School of Engineering, Helsinki, Finland.
    Hänninen, Hannu
    Aalto University School of Engineering, Helsinki, Finland.
    Varestraint Weldability Testing of ATI 718Plus®: Influence of Eta Phase2018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Eric Ott, Xingbo Liu, Joel Andersson, Zhongnan Bi, Kevin Bockenstedt, Ian Dempster, Jon Groh, Karl Heck, Paul Jablonski, Max Kaplan, Daisuke Nagahama, Chantal Sudbrack, Springer, 2018, p. 929-937Conference paper (Refereed)
    Abstract [en]

    This study investigates the effect of eta phase on hot cracking susceptibility of ATI 718Plus®. Two heat treatment conditions of 950 °C/1 h and 950 °C/15 h having different amounts of eta phase were tested by longitudinal Varestraint testing method. The heat treatment at 950 °C/15 h exhibited the highest amount of cracking. This was related to the higher amount of eta phase precipitation during the long dwell heat treatment which aided to extensive liquation during welding.

  • 587.
    Singh, Sukhdeep
    et al.
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Investigation on effect of welding parameters on solidification cracking of austenitic stainless steel 3142018In: Procedia Manufacturing, E-ISSN 2351-9789, p. 351-357Article in journal (Other academic)
    Abstract [en]

    This study investigates the solidification cracking susceptibility of the austenitic stainless steel 314. Longitudinal Varestraint testing was used with three different set of welding test parameters. Weld speed, current and voltage values were selected so that the same heat input resulted in all the test conditions. From the crack measurements it was seen that the test condition with the lowest current and welding speed value also produced the least amount of cracking with very good repeatability.

  • 588.
    Sivakumar, G.
    et al.
    Center for Engineered Coatings, International Advanced Research Center for Powder Metallurgy and New Materials, Hyderabad, India.
    Banerjee, S.
    Indian Institute of Technology Bombay, Department of Metallurgical Engineering and Materials Science, Mumbai, India.
    Raja, V. S.
    Indian Institute of Technology Bombay, Department of Metallurgical Engineering and Materials Science, Mumbai, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Hot corrosion behavior of plasma sprayed powder-solution precursor hybrid thermal barrier coatings2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 349, p. 452-461Article in journal (Refereed)
    Abstract [en]

    In recent times, plasma sprayed powder-solution precursor hybrid composite thermal barrier coatings have been developed to harness the dual benefits of both conventional atmospheric plasma spraying (APS) and solution precursor plasma spraying (SPPS) processes. In this study, hot corrosion behavior of plasma sprayed powder-solution precursor composite (PSP-SPC) YSZ TBCs in molten salt mixtures of 90 wt.% Na2SO4 + 5 wt.% V2O5 + 5 wt.% NaCl and 50 wt.% Na2SO4 + 50 wt.% V2O5 at 900 °C was investigated. The employed coating showed a bimodal microstructure comprising coarse splats derived from the powder feedstock as in the APS process and fine splats resulting from the solution precursor as typical of SPPS process. The PSP-SPC coatings showed a significantly higher resistance to spallation than APS, SPPS and EB-PVD coatings in both the salt environments. These coatings showed shorter life in vanadate environment compared to that of the chloride environments as the former promotes the formation of monoclinic ZrO2 and YVO4 phases more than the latter. © 2018

  • 589. Sivakumar, R.
    et al.
    Joshi, Shrikant V.
    Protective Coatings by Plasma Spraying: A Review1991In: Transactions of the Indian Ceramic Society, ISSN 0371-750X (Print), 2165-5456 (Online), Vol. 50, no 1, p. 1-14Article in journal (Refereed)
    Abstract [en]

    In recent years, the use of plasma-sprayed protective coatings has gained increasing acceptance for prolonging the service life of critical components exposed to aggressive environments during normal operation. This paper is aimed at providing an overview of the current state-of-the-art of the plasma coating technology. It includes a brief discussion of the various important aspects associated with the development of reliable protective coatings as well as their evaluation, and outlines some noteworthy advances made in the field of plasma spray materials and equipment in the past few years. The various factors influencing the coating quality are identified and the wide-ranging utility of plasma-sprayed coatings is also highlighted.

  • 590. Sjöberg, Göran
    et al.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjunnesson, Anders
    New Materials in the Design and Manufacturing of Hot Structures for Aircraft Engines: Allvac 718Plus2009In: XIX International Symposium on Air Breathing Engines 2009: ISABE 2009, Montreal, Canada, 7-11 September, 2009., Reston, VA: American Institute of Aeronautics and Astronautics, 2009, Vol. 3, p. 1406-1415Conference paper (Refereed)
  • 591.
    Skhabovskyi, Iaroslav
    et al.
    Universidade Federal de Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding Processes, Faculty of Mechanical Engineering, Uberlândia, Brazil.
    Batista, Natassia Lona
    Universidade Estadual Paulista (UNESP), Materials and Technology Department, School of Engineering, Guaratinguetá, Brazil.
    Damato, Cesar Augusto
    ALLTEC Materiais Compostos, São José dos Campos, Brazil.
    Reis, Ruham Pablo
    Universidade Federal de Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding Processes, Faculty of Mechanical Engineering, Uberlândia, Brazil.
    Botelho, Edson Cocchieri
    Universidade Estadual Paulista (UNESP), Materials and Technology Department, School of Engineering, Guaratinguetá, Brazil.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Welding Technology. Laprosolda – Center for Research and Development of Welding Processes, Faculty of Mechanical Engineering, Universidade Federal de Uberlândia (UFU), Uberlândia, Brazil.
    Appraisal of fiber-metal laminate panels reinforced with metal pins deposited by CMT welding2017In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 180, no Supplement C, p. 263-275Article in journal (Refereed)
  • 592.
    Sokolowski, Pawel
    et al.
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Musalek, Radek
    Inst Plasma Phys CAS, Dept Mat Engn, Vvi, Slovankou 3, Prague 18200, Czech Republi.
    Candidato, Rolando T. Jr.
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, France.
    Pawlowski, Lech
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Nait-Ali, Benoit
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Smith, David
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Thermophysical properties of YSZ and YCeSZ suspension plasma sprayed coatings having different microstructures2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 28-38Article in journal (Refereed)
    Abstract [en]

    The paper describes the ceramic top coats of Thermal Barrier Coatings (TBC) obtained by Suspension Plasma Spraying (SPS). The spray process realized with different plasma torches allowed obtaining coatings having different morphology, namely, columnar-like and two-zones microstructure. The microstructures influenced the thermal transport properties of TBC’s. The study analyses the thermophysical properties of yttria and yttria- with ceria- stabilized zirconia coatings, i.e. YSZ and YCeSZ, respectively. The spray processes were realized with the use of three different plasma spray torches: (i) SG-100; (ii) Axial III and (iii) hybrid WSP one. The deposition parameters were designed for each plasma torch separately. The microstructure of coatings was then analyzed using Optical and Scanning Electron Microscopy i.e. OM and SEM, respectively. The thermophysical properties of the coatings such as density, specific heat and thermal dilatation were measured using gas pycnometry, calorimetry and dilatometry methods respectively. The collected data were used, together with thermal diffusivity found with the use of laser flash method, to calculate the thermal conductivity of the deposits. The thermal conductivities of coatings were in a range from 0.63 to 0.99 [W/m.K] for YSZ samples and between 0.82 and 1.37 [W/m.K] in the case of YCeSZ coatings. Thermal transport properties were found to be influenced by the coatings’ porosity and their microstructure. Finally, the thermal conductivity values were successfully validated using response function method, which can be an alternative to complex FEM methods. (C) 2017 Elsevier B.V. All rights reserved.

  • 593.
    Sokolowski, Pawel
    et al.
    Wroclaw University of Technology, Faculty of Mechanical Engineering, ul. Lukasiewicza 5, Wroclaw, Poland.
    Mejias, Alberto
    Université Lillel, Laboratoire de Mécanique de Lille, LML UMR 8107, IUTA GMP, BP 90179, Villeneuve d'Ascq, France.
    Chicot, Didier
    Université Lillel, Laboratoire de Mécanique de Lille, LML UMR 8107, IUTA GMP, BP 90179, Villeneuve d'Ascq, France.
    Musalek, Radek
    Department of Materials Engineering, Institute of Plasma Physics, Za Slovankou 3, Prague, Czech Republic.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Pawlowski, Lech
    University of Limoges, Laboratory of SPCTS, UMR CNRS 7315, 12 rue Atlantis, Limoges, France.
    The evaluation of mechanical properties of suspension plasma sprayed zirconia coatings having various microstructures2016In: Proceedings of the International Thermal Spray Conference, ASM International, 2016, Vol. 1, p. 573-578Conference paper (Refereed)
    Abstract [en]

    The paper describes the investigations of mechanical properties of various zirconia coatings having different microstructure, phase content and chemical composition. The coatings were deposited using Suspension Plasma Spraying technology. The suspensions were formulated using three different powders: (i) ZrO2 + 8 wt.% Y2O3 (ii) ZrO2 + 14 wt.% of Y2O3 and (iii) ZrO2 + 24 wt.% of CeO2 + 2.5 wt.% of Y2O3. Moreover, three different plasma torches were to spray: (i) SG-100 of Praxair; (ii) Axial III of Mettech and (iii) hybrid Water-Stabilized Plasma torch of IPP Prague. The coatings had different microstructures: a columnar-like and a two-zone-microstructure. The analysis of mechanical properties was performed using instrumented indentation technique (NT) using a multi-cyclic loading to obtain the in-depth variation of the mechanical properties. The hardness (H) and Young’s modulus (E) of coatings were found out. The measurements were made on the surface of coatings. The influence of the coating morphology on their mechanical properties was researched and discussed.

  • 594.
    Sokolowski, Pawel
    et al.
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Musalek, Radek
    Inst Plasma Phys CAS, Vvi, Dept Mat Engn, Slovankou 3, Prague 18200, Czech Republic.
    Latka, Leszek
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Kozerski, Stefan
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Dietrich, Dagmar
    Tech Univ Chemnitz, Inst Mat Sci & Engn, D-09107 Chemnitz, Germany.
    Lampke, Thomas
    Tech Univ Chemnitz, Inst Mat Sci & Engn, D-09107 Chemnitz, Germany.
    Pawlowski, Lech
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, France.
    The microstructural studies of suspension plasma sprayed zirconia coatings with the use of high-energy plasma torches2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 250-261Article in journal (Refereed)
    Abstract [en]

    The presented studies are focused on the microstructure characterization of zirconia-based coatings deposited by two types of high-energy plasma torches: (i) Axial III; and, (ii) hybrid version of Water-Stabilized Plasma (WSP) torch. The suspensions were formulated using solid dispersed phase of: (i) zirconia stabilized with 14 wt of Y2O3 and (ii) zirconia stabilized with 24 wt% of CeO2 + 2.5 wt% of Y2O3 and continuous phase of water with ethanol. The spray process parameters were optimized for each plasma set-up individually. The in-flight observations (shadowgraphy) were performed to optimize the injection of the liquid feedstock into the plasma jet. Then the coating’s morphology and coating/substrate interface were characterized using conventional light microscopy and scanning electron microscopy (SEM). The results showed that through the change of deposition parameters various coatings microstructures could be obtained, in particular columnar and two-zones structures. The EDS/EDX and XRD studies showed that there was no significant change in chemical/phase composition of zirconia material before and after spraying. Electron backscatter diffraction (EBSD) method allowed to analyze the grain size in the coating microstructure as well as crystallographic orientation of individual grains. The results showed that coatings were characterized by submicrometric microstructure what corresponded to the size of powder particles used to formulate suspension. No texture was observed in the coatings microstructure. The surface topography analysis which was performed by confocal scanning laser microscopy (CSLM) and Shape From Shading (SFS) technique proved the great influence of suspension concentration on the coating structure. (C) 2017 Elsevier B.V. All rights reserved.

  • 595.
    Sreekanth, Suhas
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Ghassemali, Ehsan
    Jönköping University.
    Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 7182020In: Metals, E-ISSN 2075-4701, Vol. 10, no 1, p. 01-16, article id 96Article in journal (Refereed)
    Abstract [en]

    The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation.

  • 596.
    Steffenburg-Nordenström, Joachim
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Process chain simulation of forming, welding and heat treatment of Alloy 7182017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Manufacturing of aero engine components requires attention to residual stress and final shape of the product in order to meet high quality product standards.This sets very high demands on involved manufacturing steps to meet design requirements. Simulation of manufacturing processes can therefore be animportant tool to contribute to quality assurance.The focus in this work is on simulation of a manufacturing process chain comprising of sheet metal forming, welding and a stress relief heat treatment.Simulation of sheet metal forming can be used to design a forming tool design that accounts for the material behaviour, e.g. spring back, and avoid problems such as wrinkling, thinning and cracking. Moreover, the simulation can also show how the material is stretched and work hardened. The residual stresses after forming may be of local character or global depending on the shape that is formed. However, the heat affected zone due to welding is located near the weld.The weld also causes large residual stresses with the major component along the weld. It is found that the magnitude of the residual stresses after welding is affected by remaining stresses from the previous sheet metal forming. The final stress relieve treatment will relax these residual stresses caused by e.g. forming and welding. However, this causes additional deformations.The main focus of this study is on how a manufacturing process step affects the subsequent step when manufacturing a component of the nickel-based super alloy 718. The chosen route and geometry is a simplified leading edge of an exhaust case guide vane. The simulations were validated versus experiments. The computed deformations were compared with measurements after each manufacturing step. The overall agreement between experiments and measurement was good. However, not sufficiently accurate considering the required tolerance of the component. It was found from simulations that the residual stresses after each process affects the subsequent step. After a complete manufacturing process chain which ends with a stress relief heat treatment the residual stresses were not negligible. VIII Special experiments were performed for studying the stress relief in order to understand how the stresses evolve through the heat treatment cycle during relaxation. It was found that the stresses were reduced already during the beginning of the heating up sequence due to decreasing Young´s modulus and yield stress with increasing temperature. Relaxation due to creep starts when a certain temperature was reached which gave a permanent stress relief.

  • 597.
    Steffenburg-Nordenström, Joachim
    University West, Department of Engineering Science, Research Enviroment Production Technology West. GKN Aerospace Sweden.
    The evolution of residual stresses in a stress relief heat treatment of test specimen of alloy 7182016In: Mathematical Modelling of Weld Phenomena 11 / [ed] S. Sommitsch, N. Enzinger, P. Mayr, Graz, 2016, Vol. 11, p. 331-343Conference paper (Refereed)
    Abstract [en]

    Manufacturing of aero engine components requires attention to residual stress and final shape of the product in order to meet high quality product standards. This sets very high demands on involved manufacturing steps to meet design requirements. Simulations are used to assure the latter. This requires an appropriate model to account for stress relaxation. The study is part of a project where the aim is to simulate a chain of manufacturing steps e.g. forming, welding and heat treatment. The focus in this paper is on the stress relaxation during the heat treatment step. It is imperative to have relevant data for calibrating this part of a constitutive model.  A test procedure resembling the real conditions in the manufacturing chain is proposed. Tests were carried out on test specimens made of Alloy718 and used to calibrate a constitutive model. Comparisons between experimental and simulated results showed very good agreement.

  • 598.
    Steffenburg-Nordenström, Joachim
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. GKN Aerospace Sweden.
    Larsson, Mats
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Simulation of the influence of forming on residual stresses and deformations after welding and heat treatment in Alloy 7182014In: / [ed] E. Oñate, J. Oliver and A. Huerta, International Center for Numerical Methods in Engineering (CIMNE), 2014, p. 1657-1666Conference paper (Other academic)
    Abstract [en]

    Manufacturing of components in aero engines requires attention to residual stress and final shape of the product in order to meet high quality product standards. This sets very high demands on involved manufacturing steps. The manufacturing of a V-shaped leading edge of a vane is simulated. It is made of Alloy718, which is a nickel based heat resistant material commonly used in aerospace components. The manufacturing process chain consists of forming, welding and heat treatment. The results show that the remaining residual stresses after a manufacturing process chain are affected when the residual history from the formingprocess is considered. The residual stress decrease after heat treatment is about 55-65%. Moreover, the von Mises stress profile through thickness at the centre of the radius at the weld joint is about 25% higher when full forming history is considered.

  • 599.
    Steffenburg-Nordenström, Joachim
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. GKN Aerospace Sweden.
    Pérez Caro, Lluís
    IUC, Olofström, Sweden.
    Odenberger, Eva-Lis
    IUC, Olofström, Sweden.
    Oldenburg, Mats
    Luleå University of technology, Luleå, Sweden.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Comparison of forming, welding and heat treatment simulations in LS-DYNA and MSC Marc2016In: Proceedings of 10th International Conference on Trends in  Welding Research & 9th International Welding Symposium of Japan Welding, American Welding Society (AWS) & Japan Welding Society (JWS) , 2016, p. 660-663Conference paper (Refereed)
    Abstract [en]

    The manufacturing of components for aero engine structures from a flat sheet to the final shape usually requires several steps that may introduce residual stresses and shape distortions in the part. Depending on the magnitude, sign and distribution with respect to the stresses induced by the service load, the remaining stresses may affect the service life of a component, especially when submitted to cyclic loading. Nowadays, several types of software that have the ability to predict the residual stresses and the final shape of a component subjected to various process steps are available. However, literature shows a lack of comparison studies among different software tools for multi-step simulations of a manufacturing process. In this study, the manufacturing process chain of an aerospace component including forming, welding and heat treatment in the nickel-based superalloy 718 is modelled and simulated using the two finite element software codes LS-DYNA and MSC.Marc. The results from the displacement of the blank in the punch stroke direction, the equivalent plastic strain and the von Mises stress are compared between both FE codes. The displacement of the blank after forming is slightly higher in LS-DYNA compared to MSC.Marc, as well as the equivalent plastic strain and the von Mises stress values. This tendency is also observed after trimming and welding. It can also be noted that the distribution of both strains and stresses on the trimmed and welded parts varies between the two compared codes, presumably due to the choice of different solver options, explicit and implicit.

  • 600.
    Steffenburg-Nordenström, Joachim
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Simulation and validation of forming, edge milling, welding and heat treatment of an alloy 718 componentManuscript (preprint) (Other academic)
    Abstract [en]

    This paper describes finite element simulations of a manufacturing process chain consisting of forming, weld preparation by milling, laser welding and stress relief heat treatment of an alloy718 aero-engine part. The work also includes experimental validation with optical measurements of the part after each process step. Approximation and discretization errors were avoided by keeping the same mesh and constitutive model. The results show that the remaining stresses affect the subsequent manufacturing process step and therefore, simulation of the process chain is essential. The accuracy with respect to the geometry showed relatively good agreement between measurement and simulation.

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