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  • 1.
    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).

  • 2.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF. University West, Sweden.
    Hammerberg, Peter
    Chalmers University of Technology, Sweden.
    Lundin, Per
    Schlumpf Scandinavia AB, Sweden.
    Olavison, Jari
    Volvo Group Trucks Operations, Sweden.
    Hardness depth assessment of induction hardened steel by a comparative approach using Barkhausen Noise and Ultrasonic signals2019In: Proceedings of ICBM13, 2019Conference paper (Other academic)
    Abstract [en]

    A major challenge in automotive industry when producing heat treated engine parts is achievement of necessary material properties for a given component to withstand loads during its use. Critical properties involve correct microstructure and hardening depth which is essential to verify from manufacturing.

    Today this is solely done by destructive testing where manufactured parts are sectioned to smaller pieces and the properties is verified relative the operational window of the process. For the case of camshafts this is necessary every time the production is reset from one type to another or other planned or un-planned interruptions. The verification process is very costly, since production stands still.

    The need for non-destructive alternatives is therefore obvious and prior investigations has shown great potential in both the Barkhausen noise (BN) and Ultrasonic testing (UT) methods. Recent research has also advanced the analysing methodology of the response signal for sub-surface microstructural characterization and case depth measurements. BN is well known of its sensitivity to microstructure and UT is also known to be effective for material characterization. One major difference between the two technologies is the sensitivity range (analysing depth) under the surface of the material to be characterized. Traditional BN is only effective within few tenths of millimetres from the surface while UT is sensitive to both surface and sub-surface characteristics of the material depending on the configuration.

    The major motive in this investigation has been to compare the two methods and to investigate if a combination of these methods could be used for assessment of the hardening depth of induction hardened steels for the depth interval 2-7 mm. This is a typical depth range when manufacturing induction hardened cam shafts within the heavy automotive industry.

    In the present investigation cylindrical steel specimens of grade C45 was induction hardened to generate different hardness depths. The heat treatment was performed in an induction hardening equipment by alternating the scanning speed and power. The produced specimens had hardness depth in the range 2-7 mm and was evaluated with by BN and UT measurements, independently, followed by destructive verification of the material properties.

    The results show a potential for both BN and UT to measure the hardening depth down to 4 mm. It was further shown that several BN parameters correlate with the hardening depth indicating that a combination of different parameters may be used for assessment using a triangulation approach.

  • 3.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lundin, Per
    Stresstech OY, Finland.
    Olavisson, Jari
    Volvo Powertrain AB, Sweden.
    Sevim, Solmaz
    Bodycote, Sweden.
    Non destructive testing of surface characteristics after nitrocarburizing of three different steel grades2017Conference paper (Other academic)
  • 4.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF. University West, Sweden.
    Palosaari, Mikko
    Stresstech OY, Finland.
    Hosseini, Seyed
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Larjosuo, Henri
    Stresstech OY, Finland.
    Andersson, Pär
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Round Robin Study on Residual Stresses Using X-RayDiffraction for Shot-Peened Tool Steel Specimens2018Conference paper (Refereed)
    Abstract [en]

    Residual stress measurements using x-ray diffraction is a well established methodused within the industrial and academic community to verify the performance of differentprocesses for metallic materials. The measurement gives an absolute value of the stress statewhich can be used to design and optimize the process route to induce beneficial compressiveresidual stresses and avoid detrimental tensile stresses. Investigating the uncertainty andaccuracy of the measurement system, operator and the material is therefore of high relevanceboth from an industrial and scientific point of view. Round robin testing is an important way toquantify the uncertainties that could affect the quality of the measured results and hence how aprocess is optimized and tuned. Such an investigation allows the operator to understand andreduce variations. Current round robin test includes results from five different laboratories usingcomparable equipments located in Sweden, Finland, Germany and United States. This workfocuses on five shot-peened tool steel specimens produced with identical process settings.Additionally, an investigation of the repeatability of the system, influence of the operator,variations within the specimen, and the long time stability of the specimens has been measured.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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)

  • 9.
    Jäger, Henrik
    et al.
    RISE, Swerea, KIMAB. University West, Sweden.
    Alagan, N. T.
    University West, Sweden.
    Holmberg, Jonas
    RISE, Swerea, IVF. University West, Sweden.
    Beno, T.
    University West, Sweden.
    Wretland, A.
    EDS Analysis of Flank Wear and Surface Integrity in Machining of Alloy 718 with Forced Coolant Application2016In: Procedia CIRP, Elsevier B.V. , 2016, p. 271-274Conference paper (Refereed)
    Abstract [en]

    There has been extensive research on forced coolant application, usually known as high pressure coolant, in machining heat resistant super alloys. This technology has shown to improve the tool life, chip segmentation, surface integrity and reduce the temperature in the cutting zone. A number of studies have been done on hydraulic parameters of the coolant. This study has been focused on residues on the flank face of the insert and residual stress on the workpiece surface generated by regular and modified cutting inserts. To identify any residual elements, analysis were done by energy dispersive X-ray spectrometer, EDS, on regular as well as modified inserts in combination with forced coolant application on both rake and flank face. The investigations have shown that the temperature gradient in the insert has changed between the regular and modified cutting inserts and that the tool wear and surface roughness is significantly affected by the modified cutting tool. © 2016 The Authors.

  • 10.
    Mahade, Satyapal
    et al.
    University West, Sweden.
    Ruelle, Celine
    ENSIL, France.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Holmberg, Jonas
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Björklund, Stefan
    University West, Sweden.
    Markocsan, Nicholaie
    University West, Sweden.
    Nylén, Per
    University West, Sweden.
    Understanding the effect of material composition and microstructural design on the erosion behavior of plasma sprayed thermal barrier coatings2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 488, p. 170-184Article in journal (Refereed)
    Abstract [en]

    In this work, three different TBC compositions comprising of yttria partially stabilized zirconia (8YSZ), yttria fully stabilized zirconia (48YSZ) and gadolinium zirconate (GZ) respectively, were processed by suspension plasma spray (SPS) to obtain columnar microstructured TBCs. Additionally, for comparison, lamellar microstructured, 7YSZ TBC was deposited by air plasma spray (APS) process. SEM analysis was carried out to investigate the microstructure and white light interferometry was used to evaluate the surface morphology of the as-sprayed TBCs. Porosity measurements were made using water intrusion and image analysis methods and it was observed that the SPS-YSZ and APS-YSZ TBCs showed higher porosity content than SPS-GZ and SPS-48YSZ. The as-sprayed TBC variations (APS-YSZ, SPS-YSZ, SPS-GZ, and SPS-48YSZ) were subjected to erosion test. Results indicate that the erosion resistance of APS-YSZ TBC was inferior to the SPS-YSZ, SPS-GZ and SPS-48YSZ TBCs respectively. Among the SPS processed TBCs, SPS-YSZ showed the highest erosion resistance whereas the SPS-48YSZ showed the lowest erosion resistance. SEM analysis of the eroded TBCs (cross section and surface morphology) was performed to gain further insights on their erosion behavior. Based on the erosion results and post erosion SEM analysis, erosion mechanisms for splat like microstructured APS TBC and columnar microstructured SPS TBCs were proposed. The findings from this work provide new insights on the erosion mechanisms of columnar microstructured TBCs and lamellar microstructured TBCs deposited by plasma spray.

  • 11.
    Suárez, A.
    et al.
    Tecnalia R&I, Spain.
    Veiga, F.
    Tecnalia R&I, Spain.
    Polvorosa, R.
    University of the Basque Country, Spain.
    Artaza, T.
    Tecnalia R&I, Spain.
    Holmberg, Jonas
    RISE - Research Institutes of Sweden, Materials and Production, IVF. University West, Sweden.
    de Lacalle, L. N. L.
    University of the Basque Country, Spain.
    Wretland, A.
    GKN Aerospace Engine Systems AB, Sweden.
    Surface integrity and fatigue of non-conventional machined Alloy 7182019In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 48, p. 44-50Article in journal (Refereed)
    Abstract [en]

    Alloy 718 is a high-strength, corrosion-resistant nickel chromium-based superalloy frequently used for applications, such as aerospace, marine, nuclear reactor and chemical industries, due to its outstanding inherent properties such as high strength and corrosion resistance at high temperatures together with good creep behaviour. Although, the use of conventional manufacturing processes is prevalent for their use on Alloy 718, alternative manufacturing technologies are gaining importance. This work compares the effects of alternative manufacturing processes, such as Abrasive water jet (AWJ), Wire Electrical Discharge Machining (WEDM) and ultrasound vibration assisted milling (UVAM) with conventional milling during the manufacture of Alloy 718 parts. Surface integrity, hardness, residual stress and fatigue strength obtained from these machining processes have been examined for cutting alloy 718. Results show that both residual stresses and surface roughness are correlated with fatigue strength. UVAM results shown an improvement on the surface integrity of the final workpiece. AWJ and WEDM show poorer results, further work on post-process technologies or process condition selection must be carry out to establish them as an alternative in Alloy 718 cutting operations.

  • 12.
    Wadman, Boel
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Ottosson, Peter
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Holmberg, Jonas
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Ingemarsson, Lars-Olof
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Sagström, Elisabeth
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Time-dependent residual stress and geometry analysis of UHSS deep drawn components,2013In: Proceedings of International Deep Drawing Research Group Conference, Zurich, Switzerland, June 2-5., 2013Conference paper (Other academic)
  • 13.
    Werke, Mats
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Wretland, Anders
    GKN Aerospace AB, Sweden.
    Ottosson, Peter
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Holmberg, Jonas
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Machens, Michael
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Semere, Daniel
    KTH Royal Institute of Technology, Sweden.
    Geometric distortion analysis using a combination of the contour method and machining simulation2018In: Procedia CIRP, 2018, p. 1481-1486Conference paper (Refereed)
    Abstract [en]

    During machining the material removal releases residual stresses introduced by previous process steps. This causes geometric machining distortions and thereby high rejection rates and costs. By simulating the process chain it is possible to predict this type of distortions. However, this requires advanced material models and accurate process- and material data for the individual processes. In order to simplify the modelling efforts a methodology that combines the contour method with machining simulation is proposed. The methodology is validated for an aerospace component using deep layer removal X-ray diffraction and CMM measurements. The methodology will improve possibilities to reduce machining distortions. © 2018 The Authors.

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