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  • 1.
    Bartkowiak, T.
    et al.
    Poznan University of Technology, Poland.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF. Chalmers University of Technology, Sweden.
    Brown, C. A.
    Worcester Polytechnic Institute, USA.
    Establishing functional correlations between multiscale areal curvatures and coefficients of friction for machined surfaces2018In: Surface Topography: Metrology and Properties, ISSN 2051-672X, Vol. 6, no 3, article id 034002Article in journal (Refereed)
    Abstract [en]

    The objective of this research is to determine the strengths of correlation, and their variation with scale, between friction coefficients and topographic characterization parameters, calculated using statistical representations of multiscale areal curvatures. The surfaces are created by milling and manual polishing. Coefficients of friction were measured during bending under tension tests. Surfaces were measured with a white light interferometer. Curvature tensors were calculated using a normal based method adapted for multiscale analysis. Three different regions were analyzed from each of eight samples. Curvature tensor parameters: principal, mean, and Gaussian curvatures were calculated for scales between 0.78 and 47.08 μm. These statistical measures of the curvatures were regressed against the coefficient of friction. Three different analyses were performed, taking into account entire curvature distributions, only negative or positive values and curvatures of top heights. Strong correlations (R2 > 0.85 for many and as large as 0.96) were found for the standard deviations for all four curvature measures when entire distributions were considered. These results suggest that the frictional responses of surfaces could be related to the variance of their topographic curvatures. Average curvature parameters correlate strongly with coefficients of friction for negative values. Curvatures calculated from top regions present strong correlations for both mean and standard deviation of maximal, mean and Gaussian curvatures. This supports the use of multiscale curvature tensor methods for characterizing interactions between surface topography and tribological performance.

  • 2. Bartkowiak, T.
    et al.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Brown, C.A.
    Establishing functional correlations between areal curvature and coefficient of friction for machined surfaces2017Conference paper (Other academic)
  • 3.
    Berglund, Johan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Blateyron, François
    Digital Surf, France.
    Using SEM quad BSE images for roughness measurement – calibration of reconstructed surfaces2016Conference paper (Other academic)
  • 4.
    Berglund, Johan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF. Chalmers University of Technology, Sweden.
    Söderberg, Rikard
    Chalmers University of Technology, Sweden.
    Wärmefjord, Kristina
    Chalmers University of Technology, Sweden.
    Industrial needs and available techniques for geometry assurance for metal AM parts with small scale features and rough surfaces2018In: Procedia CIRP, Elsevier B.V. , 2018, p. 131-136Conference paper (Refereed)
    Abstract [en]

    From an industrial perspective this paper aims to explore the state of the art regarding GD&T for metal additive manufacturing, specifically regarding product definition and inspection. The available techniques for geometry assurance for parts with small scale features and rough surfaces are evaluated in terms of suitability for the task and readiness for industrial implementation. It is found that many of the remaining challenges seem to be related to processing of data rather than obtaining data. Current difficulties are related to issues such as calibration, surface determination and defining the most relevant parameters to tolerance and inspect.

  • 5.
    Berglund, Johan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Troell, Eva
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Surface Topography of Nitrided Steel Surfaces2017Conference paper (Other academic)
  • 6.
    Berglund, Johan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF. Chalmers University of Technology, Sweden.
    Troell, Eva
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Surface Topography of Nitrided Steel Surfaces2019In: J. Phys.: Conf. Ser.: Conference Series, Institute of Physics Publishing , 2019, Vol. 1183, no 1, article id 012005Conference paper (Refereed)
    Abstract [en]

    The effect of nitrocarburizing were investigated for two different steels, 42CrMo4 and 25CrMo4, with objective to evaluate the influence of initial surface topography on the resulting nitrocarburized surface with regard to surface topography and thickness of the compound layer. It was found that the nitrocarburizing process has an impact on the surface topography. The process creates a short-wave isotropic structure on the original surface and this is particularly evident for the smoother original surfaces. No significant effect on the compound layer thickness depending on the surface topography before heat treatment could be observed. © Published under licence by IOP Publishing Ltd.

  • 7.
    Brown, Christopher. A.
    et al.
    Worcester Polytechnic Institute, USA.
    Hansen, Hans N.
    DTU Technical University of Denmark, Denmark.
    Jiang, Xian J.
    University of Huddersfield, UK.
    Blateyron, Francoise
    Digital Surf, France.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF. Chalmers University of Technology, Sweden.
    Senin, Nicola
    University of Nottingham, UK; University of Perugia, Italy.
    Bartkowiak, Tomasz
    Poznan University of Technology, Poland.
    Dixon, Barnali
    University of South Florida, USA.
    Le Goïc, Gaetan
    Université de Bourgogne, France.
    Quinsat, Yann
    ENS Paris Saclay, France.
    Stemp, W. James
    Keene State College, USA.
    Thompson, Mary K.
    GE Additive, USA.
    Ungar, Peter S.
    University of Arkansas, USA.
    Zahouani, E. Hassan
    Ecole Nationale d’Ingénieurs de Saint-Etienne, France.
    Multiscale analyses and characterizations of surface topographies2018In: CIRP annals, ISSN 0007-8506, E-ISSN 1726-0604, Vol. 62, no 2, p. 839-862Article in journal (Refereed)
    Abstract [en]

    This work studies multiscale analyses and characterizations of surface topographies from the engineering and scientific literature with an emphasis on production engineering research and design. It highlights methods that provide strong correlations between topographies and performance or topographies and processes, and methods that can confidently discriminate topographies that were processed or that perform differently. These methods have commonalities in geometric characterizations at certain scales, which are observable with statistics and measurements. It also develops a semantic and theoretical framework and proposes a new system for organizing and designating multiscale analyses. Finally, future possibilities for multiscale analyses are discussed.

  • 8.
    Forsgren, Lilian
    et al.
    Chalmers University of Technology, Sweden.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Materials and Production, IVF, Tillverkningsprocesser. Chalmers University of Technology, Sweden.
    Thunberg, Johannes
    Chalmers University of Technology, Sweden.
    Rigdahl, Mikael
    Chalmers University of Technology, Sweden.
    Boldizar, Antal
    Chalmers University of Technology, Sweden.
    Injection Molding and Appearance of Cellulose-Reinforced Composites2019In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 60, no 1, p. 5-12Article in journal (Refereed)
    Abstract [en]

    Composite materials based on an ethylene-acrylic acid (EAA) copolymer and 20 wt% cellulose fibers were compounded by two runs in a twin-screw extruder. The composite material with cellulose fibers (CF) and a reference of unfilled EAA were injection molded into plaques using three different temperature profiles with end zone temperatures of 170°C, 200°C, and 230°C. The injection molded samples were then characterized in terms of their mechanical properties, thermal properties, appearance (color and gloss), and surface topography. The higher processing temperatures resulted in a clear discoloration of the composites, but there was no deterioration in the mechanical performance. The addition of cellulose typically gave a tensile modulus three times higher than that of the unfilled EAA, but the strength and strain at rupture were reduced when fibers were added. The processing temperature had no significant influence on the mechanical properties of the composites. Gloss measurements revealed negligible differences between the samples molded at the different melt temperatures but the surface smoothness was somewhat higher when the melt temperature was increased. In general, addition of the cellulose to the EAA reduced the gloss level and the surface smoothness.

  • 9.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Wretland, Anders
    GKN Aerospace Sweden AB, Sweden.
    Beno, Tomas
    University West, Sweden.
    Evaluation of surface integrity after high energy machining with EDM, laser beam machining and abrasive water jet machining of alloy 7182019In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, no 5-8, p. 1575-1591Article in journal (Refereed)
    Abstract [en]

    Development of future aero engine components based on new design strategies utilising topological optimisation and additive manufacturing has in the past years become a reality. This allows for designs that involve geometries of “free form” surfaces and material combinations that could be difficult to machine using conventional milling. Hence, alternative manufacturing routes using non-conventional high energy methods are interesting to explore. In this investigation, the three high energy machining methods abrasive water jet machining (AWJM), electrical discharge machining (EDM) and laser beam machining (LBM) have been compared in terms of surface integrity to the reference, a ball nosed end milled surface. The results showed great influence on the surface integrity from the different machining methods. It was concluded that AWJM resulted in the highest quality regarding surface integrity properties with compressive residual stresses in the surface region and a low surface roughness with texture from the abrasive erosion. Further, it was shown that EDM resulted in shallow tensile residual stresses in the surface and an isotropic surface texture with higher surface roughness. However, even though both methods could be considered as possible alternatives to conventional milling they require post processing. The reason is that the surfaces need to be cleaned from either abrasive medium from AWJM or recast layer from EDM. It was further concluded that LBM should not be considered as an alternative in this case due to the deep detrimental impact from the machining process. © 2018, The Author(s).

  • 10.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Rodri­guez Prieto, Juan Manuel
    Luleå University of Technology, Sweden.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Sveboda, Ales
    Luleå University of Technology, Sweden.
    Jonsén, Pär
    Luleå University of Technology, Sweden.
    Experimental and PFEM-simulations of residual stresses from turning tests of a cylindrical Ti-6Al-4V shaft2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 71, p. 144-149Article in journal (Refereed)
    Abstract [en]

    Alloy Ti-6Al-4V is a frequently used material in aero space applications due the high strength and low weight. This material is however often considered as a difficult to machine alloy due to several material properties such as the inherent characteristics of high hot hardness and strength which is causing an increased deformation of the cutting tool during machining. The thermal properties also cause a low thermal diffusion from locally high temperatures in the cutting zone that allows for reaction to the tool material resulting in increased tool wear. Predicting the behavior of machining of this alloy is therefore essential when selecting machining tools or machining strategies. If the surface integrity is predicted, the influence of different machining parameters could be studied using Particle Finite Element (PFEM)-simulations. In this investigation the influence from cutting speed and feed during turning on the residual stresses has been measured using x-ray diffraction and compared to PFEM-simulations. The results showed that cutting speed and feed have great impact on the residual stress state. The measured cutting force showed a strong correlation especially to the cutting feed. The microstructure, observed in SEM, showed highly deformed grains at the surface from the impact of the turning operation and the full width half maximum from the XDR measurements distinguish a clear impact from different cutting speed and feed which differed most for the higher feed rate. The experimental measurements of the residual stresses and the PFEM simulations did however not correlate. The surface stresses as well as the sign of the residuals stresses differed which might be due to the material model used and the assumption of using a Coulomb friction model that might not represent the cutting conditions in the investigated case. © 2018 Elsevier B.V. All rights reserved.

  • 11.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF, Tillverkningsprocesser. University West, Sweden.
    Steuwer, Axel
    Nelson Mandela Metropolitan University, South Africa.
    Stormvinter, Albin
    RISE - Research Institutes of Sweden, Materials and Production, IVF, Tillverkningsprocesser.
    Kristoffersen, Hans
    RISE - Research Institutes of Sweden, Materials and Production, IVF, Tillverkningsprocesser.
    Haakanen, Marja
    Stresstech OY, Finland.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Materials and Production, IVF, Tillverkningsprocesser.
    Residual stress state in an induction hardened steel bar determined by synchrotron- and neutron diffraction compared to results from lab-XRD2016In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 667, p. 199-207Article in journal (Refereed)
    Abstract [en]

    Induction hardening is a relatively rapid heat treatment method to increase mechanical properties of steel components. However, results from FE-simulation of the induction hardening process show that a tensile stress peak will build up in the transition zone in order to balance the high compressive stresses close to the surface. This tensile stress peak is located in the transition zone between the hardened zone and the core material. The main objective with this investigation has been to non-destructively validate the residual stress state throughout an induction hardened component. Thereby, allowing to experimentally confirming the existence and magnitude of the tensile stress peak arising from rapid heat treatment. For this purpose a cylindrical steel bar of grade C45 was induction hardened and characterised regarding the microstructure, hardness, hardening depth and residual stresses. This investigation shows that a combined measurement with synchrotron/neutron diffraction is well suited to non-destructively measure the strains through the steel bar of a diameter of 20 mm and thereby making it possible to calculate the residual stress profile. The result verified the high compressive stresses at the surface which rapidly changes to tensile stresses in the transition zone resulting in a large tensile stress peak. Measured stresses by conventional lab-XRD showed however that at depths below 1.5 mm the stresses were lower compared to the synchrotron and neutron data. This is believed to be an effect of stress relaxation from the layer removal. The FE-simulation predicts the depth of the tensile stress peak well but exaggerates the magnitude compared to the measured results by synchrotron/neutron measurements. This is an important knowledge when designing the component and the heat treatment process since this tensile stress peak will have great impact on the mechanical properties of the final component.

  • 12.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, IVF. University Wes, Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB, Sweden.
    Berglund, Johan
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, IVF.
    Grit Blasting for Removal of Recast Layer from EDM Process on Inconel 718 Shaft: An Evaluation of Surface Integrity2016In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 25, no 12, p. 5540-5550Article in journal (Refereed)
    Abstract [en]

    The heat generated during EDM melts the work material and thereby allows large amounts to be removed, but an unfavorable surface of a recast layer (RCL) will also be created. This layer has entirely different properties compared to the bulk. Hence, it is of great interest to efficiently remove this layer and to verify that it has been removed. The main objective of this work has been to study the efficiency of grit blasting for removal of RCL on an EDM aero space shaft. Additionally, x-ray fluorescence (XRF) has been evaluated as a nondestructive measurement to determine RCL presence. The results show that the grit-blasting processing parameters have strong influence on the ability to remove RCL and at the same time introduce beneficial compressive stresses even after short exposure time. Longer exposure will remove the RCL from the surface but also increase the risk that a larger amount of the blasting medium will get stuck into the surface. This investigation shows that a short exposure time in combination with a short grit-blasting nozzle distance is the most preferable process setting. It was further found that handheld XRF equipment can be used as a nondestructive measurement in order to evaluate the amount of RCL present on an EDM surface. This was realized by analyzing the residual elements from the EDM wire.

  • 13.
    Holmberg, Jonas
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes. University West, Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB, Sweden.
    Berglund, Johan
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Beno, Tomas
    University West, Sweden.
    A detailed investigation of residual stresses after milling Inconel 718 using typical production parameters for assessment of affected depth2020In: Materials Today Communications, ISSN 2352-4928, Vol. 24, article id 100958Article in journal (Refereed)
    Abstract [en]

    Production of superalloy gas turbine parts involves time consuming milling operations typically performed in a sequence from rough to finish milling. Rough milling using ceramic inserts allows high removal rates but causes severe sub-surface impact. A relatively large allowance is therefore left for subsequent cemented carbide milling. With increased knowledge of the affected depth it will be possible to reduce the machining allowance and increase efficiency of the manufacturing process. Milling Inconel 718 using typical production parameters has been investigated using new and worn ceramic and cemented carbide inserts. Residual stresses in a milled slot were measured by x-ray diffraction. Stresses were measured laterally across the slot and below the surface, to study the depth affected by milling. The most important result from this work is the development of a framework concerning how to evaluate the affected depth for a milling operation. The evaluation of a single milled slot shows great potential for determining the optimum allowance for machining. Our results show that the residual stresses are greatly affected by the ceramic and cemented carbide milling; both regarding depth as well as distribution across the milled slot. It has been shown that it is important to consider that the stresses across a milled slot are the highest in the center of the slot and gradually decrease toward the edges. Different inserts, ceramic and cemented carbide, and tool wear, alter how the stresses are distributed across the slot and the affected depth.

  • 14.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF. University West, Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB, Sweden.
    Berglund, Johan
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Beno, Tomas
    University West, Sweden.
    Surface integrity after post processing of EDM processed Inconel 718 shaft2018In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 95, no 5-8, p. 2325-2337Article in journal (Refereed)
    Abstract [en]

    Electrical discharge machining (EDM) is considered as an efficient alternative to conventional material removal concepts that allows for much higher material removal rates. However, EDM generates unwanted features such as re-cast layer (RCL), tensile residual stresses and a rough surface. In order to recover the surface integrity, different post processes has been compared: high-pressure water jet (HPWJ), grit blasting (GB) and shot peening (SP). Surface integrity has been evaluated regarding microstructure, residual stresses, chemical content and surface roughness. The results showed that a combination of two post processes is required in order to restore an EDM processed surface of discontinuous islands of RCL. HPWJ was superior for removing RCL closely followed by grit blasting. However, grit blasting showed embedded grit blasting abrasive into the surface. Regarding surface roughness, it was shown that both grit blasting and HPWJ caused a roughening of the surface topography while shot peening generates a comparably smoother surface. All three post processes showed compressive residual stresses in the surface where shot peening generated the highest amplitude and penetration depths. However, the microstructure close to the surface revealed that shot peening had generated cracks parallel to the surface. The results strongly state how important it is to evaluate the surface at each of the different subsequent process steps in order to avoid initiation of cracks. © 2017 The Author(s)

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