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  • 51.
    Ratanathavorn, Wallop
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Svetsteknologi.
    Dissimilar joining of aluminium to ultra-high strength steels by friction stir welding2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Multi-material structures are increasingly used in vehicle bodies to reduce weight of cars. The use of these lightweight structures is driven by requirements to improve fuel economy and reduce CO2 emissions. The automotive industry has replaced conventional steel components by lighter metals such as aluminium alloy. This is done together with cutting weight of structures using more advanced strength steels. However, sound joining is still difficult to achieve due to differences in chemical and thermal properties.

     

    This research aims to develop a new innovative welding technique for joining aluminium alloy to ultra-high strength steels. The technique is based on friction stir welding process while the non-consumable tool is made of an ordinary tool steel. Welding was done by penetrating the rotating tool from the aluminium side without penetrating into the steel surface. One grade of Al-Mg aluminium alloy was welded to ultra-high strength steels under lap joint configuration. Different types of steel surface coatings including uncoated, hot-dipped galvanised and electrogalvanised coating have been studied in order to investigate the influence of zinc on the joint properties. The correlation among welding parameters, microstructures, intermetallic formation and mechanical properties are demonstrated in this thesis.  Results have shown that friction stir welding can deliver fully strong joints between aluminium alloy and ultra-high strength steels. Two intermetallic phases, Al5Fe2 and Al13Fe4, were formed at the interface of Al to Fe regardless of surface coating conditions. The presence of zinc can improve joint strength especially at low heat input welding due to an increased atomic bonding at Al-Fe interface. The formation of intermetallic phases as well as their characteristics has been demonstrated in this thesis. The proposed welding mechanisms are given based on metallography investigations and related literature.

  • 52.
    Ratanathavorn, Wallop
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hybrid Joining of Aluminum to Thermoplastics with Friction Stir Welding2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Hybrid structures including aluminum-thermoplastic and aluminum-reinforced thermoplastic composite are increasingly important in the near future innovations due to its lightweight and high strength-to-weight ratio. A critical point for metal-polymer application is that sound joining of these materials is difficult to achieve owing to a large difference in surface energy and dissimilar structure between metal and polymer. In practice, two major joining methods for hybrid structures are mechanical joining and adhesive bonding. However, there are some drawbacks of these conventional methods such as stress concentration, long curing time and low reliability joints. A new novel metal-polymer hybrid joining is required to overcome these issues as well as manufacturing and cost perspectives.

    To this end, this work aims to develop a general methodology to apply friction stir welding techniques to join a wide range of thermoplastics with and without fibers to aluminum alloy sheets. The present work proposed an experimental study to attain insight knowledge on the influences of welding parameters on the quality of hybrid joints in term of the maximum tensile shear strength. This includes the role of tool geometries, welding methodology as well as material weldability in the investigation. The results showed that friction stir welding is a promising technique for joining of thermoplastic to aluminum. Microstructural observation showed that a good mixing between aluminum and thermoplastic as well as defect-free weldments were obtained. Tool geometries and welding speed are two factors that significantly contribute to the quality of friction stir welded hybrid joints. The results also demonstrated that weld fracture modes are associated with material mixing as well as interfacial bonding between aluminum and thermoplastic.

    An evaluation of the joint strength was benchmarked with the relevant literatures on hybrid joining. The results of proposed technique showed that the maximum tensile shear strength of friction stir welded joints were the same order of magnitude as the joints welded by laser welding.

  • 53.
    Ratanathavorn, Wallop
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Svetsteknologi.
    Melander, Arne
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Svetsteknologi.
    Influence of zinc on intermetallic compounds formed in friction stir welding of AA5754 aluminium alloy to galvanised ultra-high strength steel2017Inngår i: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, lap joints between AA5754 and DP1000 ultra-high strength steels were producedby friction stir welding. In order to investigate the roles of zinc on intermetallic phase formation and joint properties, steel substrates were used, two being galvanised coated and one uncoated. Joint performance has been evaluated in term of maximum tensile shear loading. The effects ofthe process parameter, translational speed; chemical compositions; and intermetallic phase formationon the mechanical properties have been investigated. The results show that joints witha galvanised layer exhibit higher strength as compared to the non-coated steel. A thicker galvanisedlayer promotes the presence of zinc in the aluminium matrix, resulting in better jointproperties. The level of zinc contents in the aluminium matrix depends on process temperature and material circulation characteristics. Two stable Al-rich intermetallic phases, Al5Fe2 and Al13Fe4, were detected at the interface regardless of the coating conditions.

  • 54.
    Repper, Elias
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Carsbring, Amanda
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Defect formation in laser welded steels after use of corrosion protection coating2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This bachelor thesis was made in collaboration with Scania. The objective was to find the cause for defects found in some rear axle welds. It was known axle material was coated with anti-corrosive oil.

    Oils were examined through ICP-AES, and then compared to the composition found on the surface of the steel samples. Elements found in the oils vastly differed from one another. One of the oils contains large amounts of aluminium while the other contains high levels of calcium. When samples surfaces were analysed using EDS, phases consisting of aluminium and calcium were observed.

    These results indicate that the wrong anti-corrosive had been used for the axle material which gave substandard welds. The oil used contained elements with a low vaporisation temperature, such as calcium. This causes instabilities in the keyhole, leading to collapse. Collapse of the keyhole facilitates the formation of defects.

  • 55. Speirs, Mathew
    et al.
    Dadbakhsh, Sasan
    KU Leuven, Belgium.
    Buls, S
    Kruth, JP
    Van Humbeeck, J
    Schrooten, J
    Luyten, Jan
    The effect of SLM parameters on geometrical characteristics of open porous NiTi scaffolds2013Inngår i: High Value Manufacturing: Advanced Research in Virtual and Rapid Prototyping - Proceedings of the 6th International Conference on Advanced Research and Rapid Prototyping, VR@P 2013, Leiria, Portugal: CRC Press , 2013, s. 309-314Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Selective Laser Melting (SLM) is a promising technique for the production of biometallic scaffolds for orthopaedic applications. To produce successful scaffolds, the laser parameters should be carefully selected in order to achieve open porosity especially when pores are <1000 μm. In this study, we investigate the effect of different laser parameters (capable to produce dense bulk NiTi samples) on production of scaffolds with open porosities of 1000 μm and varying strut thicknesses 100-300 μm. Two different sets of laser parameters were used: 40W laser power with 160 mm/s scanning velocity and 250W with 1000 mm/s, corresponding to low and high laser parameters respectively. Micro-CT scanning experiments were carried out to illustrate the limitations of laser parameters in production of open porous scaffolds. Volume fraction and closed porosity were assessed. It was found that a large CAD mismatch was observed in the building (XZ) direction and internal porosity appears within struts of the samples produced with high laser processing parameters. The residual particles on struts were also shown to increase as strut thickness increases.

  • 56.
    Stenarson, Fredrik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Tibblin, Fritjof
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Evaluation of phase relations in weld overlays of 316, 309MoL and SKWAM2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    AREVA NP Uddcomb AB wants to replace the material used for a specific valve seat used in boiling water reactors, BWR. Their solution is a weld overlay of different stainless steels composed of two buffer layers of the steel 309 MoL followed by two layers of the filler material SKWAM welded on type 316 stainless steel or carbon steel. The report focuses on the long term structural effects in the weld overlay due to the operating temperature in BWRs, in this case 270 °C. To investigate the thermodynamic stability in the weld overlay the computer software Thermo-Calc was used and a metallographic examination was carried out. The results from these procedures were compared and possible long term effects were discussed. Most likely spinodal decomposition is the most severe structural change that may appear in the material. At equilibrium conditions at the operating temperature ferrite is decomposed into Fe-rich and Cr-rich ferrite but since the kinetics is not included in the calculations it is not possible to determine the rate of decomposition.

  • 57.
    Strand, Henrik
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Apparatus for simulation of wear in heavy-duty oscillating journal bearings1999Inngår i: Proceedings OST Symposium on Machine DesignArtikkel i tidsskrift (Fagfellevurdert)
  • 58.
    Strand, Henrik
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Boundary condictions in finite element calculations utilizig conformal contact of cylindrical bodies2000Konferansepaper (Fagfellevurdert)
  • 59.
    Strand, Henrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Design, testing and analysis of journal bearings for construction equipment2005Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Grease-lubricated journal bearings present a common challenge for construction equipment manufacturers in the world. The common design methodology is based on empirical data and has worked very well historically because the market and governments have accepted that bearings in construction equipment need frequent lubrication and exchange of worn parts. Legal and market requirements will soon demand lower environmental impact and increased machine efficiency. These requirements call for better methods of designing grease lubricated journal bearings.

    The goal of the outlined work was to develop better design methods for grease lubricated journal-bearing design used in heavy-duty construction equipment machines, in order to prolong life and lubrication intervals.

    The research approach of the project can roughly be divided into three phases:

    1. Development of test apparatus and test methods for journal bearing studies.

    2. Bench tests of grease lubricated journal bearing design.

    3. Verification between bench tests and computer simulations.

    In the thesis the current state of the art in bearing design for construction equipment is discussed and summarized in the form of design guidelines. The suggested design steps are just a mean to get to the starting point of design. The simple guidelines do however serve a purpose when collected since most published bearing design guidelines are aimed at the bushing material or at continuously rotating bearings. The influence of housing, environment and load cases can not be ignored when designing a bearing. Long term field-testing and experience can not be replaced until better design criteria have been established.

    Paper A deals with the design of the bearing test apparatus that was built and evaluated. Comparisons between theoretical contact and contact elements in Finite Element program have been made and discussed in paper B. In paper C a replica technique for measuring wear of large field specimens was evaluated. A case study of bearing housing design was performed in paper D utilizing Finite Element program and then validated in paper E in the bearing test apparatus. The influence of grease groove design on bushing life was tested and evaluated in paper F. Wear simulation of a plain bushing has been performed with a Finite Element program and presented in paper G.

  • 60.
    Strand, Henrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Influence of grease groove design on busing wearArtikkel i tidsskrift (Fagfellevurdert)
  • 61.
    Strand, Henrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Influence of journal bearing housing stiffness on bushing wearArtikkel i tidsskrift (Fagfellevurdert)
  • 62.
    Strand, Henrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Journal bearing housing design2007Inngår i: TRIBOLOGY INTERNATIONAL, 2007, s. 665-671Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When designing journal bearing housings for construction equipment, one goal is to get an even pressure distribution over the length of the bushing. This is to avoid excessive wear due to contact pressure peaks.

    A housing that is considered good, does not allow the pin to deflect and keeps the stresses low in the weld. To do this it must be stiff and this will lead to high contact pressures on the edges of the bushing, which is not preferable since wear is highly dependent on the contact pressure level.

    If the distribution of the contact pressure could be smoothed out over the bushing, the material might be used more efficiently. The normal way to do this is to crown the bushing to allow for pin deflection. However this leads to reduced area in contact. Another method to avoid high pressures in the bearing is to optimize the bearing housing for optimum stiffness.

    This paper describes one way to optimize journal bearing housings in regard to the contact pressure in the tribo-contact. A statistical approach was applied to a parameterized finite element model with contact elements. Three parameters were analyzed at different loads; set ring thickness, set ring width and fillet weld size.

    The contact pressure distributions were evaluated in two different ways to a single value to meet the statistical demand of measurable result. The results show that the set ring thickness and width are the parameters that influence most the contact pressure distribution. To reduce the maximum contact pressure the set ring thickness should be kept small.

  • 63.
    Strand, Henrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Simulation of bushing wearArtikkel i tidsskrift (Fagfellevurdert)
  • 64.
    Strand, Henrik
    KTH, Tidigare Institutioner                               , Maskinkonstruktion.
    Wear measurement of plain journal bearing2002Konferansepaper (Fagfellevurdert)
  • 65. Strondl, A.
    et al.
    Khodaee, Alireza
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion. KTH, Centra, XPRES, Excellence in production research.
    Sundaram, M. V.
    Andersson, M.
    Melander, Arne
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion. KTH, Centra, XPRES, Excellence in production research. Swerea KIMAB, Sverige.
    Heikkilä, I.
    Miedzinski, A.
    Nyborg, L.
    Ahlfors, M.
    Innovative powder based manufacturing of high performance gears2016Inngår i: World PM 2016 Congress and Exhibition, European Powder Metallurgy Association (EPMA) , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    There are strong driving forces towards high-performance gear wheels which can handle higher engine outputs, or allow more compact designs of transmissions. Today the performance and life of conventionally manufactured gear wheels are limited by factors such as inhomogeneous microstructure and distribution of inclusions. Powder metallurgy (PM) can solve some of these problems but has so far had limitations caused by porosity. In this paper a cost effective way to eliminate porosity by HIP-ing without canister has been evaluated with encouraging results. Parameters such as powder particle size, lubricant and double pressing have been evaluated in the PM route in order to get a gas tight surface enabling effective post HIP-ing. So far double pressing has given promising results. Challenges such as open porosity, surface porosity and inclusions are addressed in the paper.

  • 66.
    Ståhlberg, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Thermoset polymers and coatings subjected to high compressive loads2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This study describes the mechanical response of thermoset polymers under high compressive loads. The study is divided into two parts. The first part focuses on the behaviour of a powder coating when used in a clamping force joint and how the properties vary when the chemical and physical structure of the coating is changed. The second part discusses the fundamental understanding of the behaviour of thermoset polymers with small thickness-to-width ratio subjected to compressive stresses, the aim being to develop mathematical material models for viscoelastic materials under high compressive loads.

    In the first part polyester powder coatings were used with variations in molecular weight, number of functional groups of the resin, amount and type of filler and thickness of the coating. The coatings were subjected to conventional tests for coatings and polymers and also to specially designed tests developed to study the behaviour of powder coatings in clamping force joints.

    The high compressive loads in a clamping force joint put high demands on the relaxation and creep resistance of the coating and the study shows the importance of crosslink density, filler content, and also coating thickness in order to achieve the desired mechanical properties of a coating.

    A high reactivity of the resin, facilitating a high crosslink density and hence a high Tg, is the most important property of the coating. A film with high crosslink density shows increase in relaxation time and in apparent yield strength under compression, and also an increase in relaxation modulus and storage modulus in tension at temperatures above Tg.

    Addition of fillers reduces the deformation during compression and tension, but also induces a lower strain at break and hence a more brittle coating. The reinforcing effect of the fillers is pronounced when increasing the crosslink density of the coating, especially in the compression tests. The effect is evident in compression even at low amounts of fillers, where the relaxation time and resistance to deformation are strongly increased. The combination of high crosslink density and addition of fillers is therefore desirable since fillers then can be used moderately in order to achieve a reinforcing effect in compression while minimising embrittlement.

    The study also showed that increased coating thickness will give rise to defects in the coating, especially voids and blisters due to evaporation of water formed during the curing of the polyester powder coating. These defects will give rise to stress concentrations and increased plastic deformations in the coating, impairing the properties of the clamping force joint.

    The results from relaxation tests in tension were used to create a micromechanical model. This model was used in finite element modelling to estimate the loss of clamping force in a screw joint and to correlate with the experimental results of the powder coatings.

    In the second part of the study a well-defined free radically cured vinyl ester resin was used and studied in six different geometries in order to determine the dependence of apparent mechanical properties on the particular size and shape of a sample when it is subjected to high compressive loads. Variation of the specimen thickness, boundary conditions and loading conditions reveals that the geometry of the sample has a significant effect on the mechanical performance of the polymer. The apparent modulus and the yield strength increase dramatically when the thickness-to-width ratio of the sample is reduced, whereas they decrease when the friction between the sample and the compression plate is reduced. The creep strain rate decreases when the thickness of the material is reduced and it decreases even more when the amount of material surrounding the compressed part of the sample is increased.

    Creep and strain recovery tests on large specimens were used to develop a mathematical model including non-linear viscoelastic and viscoplastic response of a thermoset vinyl ester. The model was used in FEM calculations where the experimental results were compared with the calculated results in order to model the trends of the material response when varying the sample geometry.

  • 67.
    Ståhlberg, Daniel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Properties of Powder Coatings in Load Carrying Construction2005Inngår i: JCT Research, ISSN 1547-0091, E-ISSN 2168-8028, Vol. 2, nr 6, s. 473-481Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study describes the mechanical behavior of powder coatings used under very high compressive loads in clamping force joints. Carboxyl functional polyester powder coatings cured with hydroxyl functional β- hydroxyalkylamides, with variations in coating thickness and amount and type of filler, have been studied. The coatings were subjected to conventional tests for coatings and polymers and also to specially designed tests developed to study the behavior of powder coatings in clamping force joints. The specially designed tests were used to study the coatings under compressive loads, and the relation between the results from these test methods and from conventional tests is discussed. The results show the importance of coating thickness in order to achieve the desired mechanical properties of a coating when used under high compressive loads. These loads put high demands on the stability of the coating, and the defects must be kept to a minimum. Increased thickness will give rise to more defects in the coating, especially voids and blisters due to the evaporation of water formed during the curing of the polyester powder coating. The surface roughness of the coating is also affected by the coating thickness, but the main influence originates from the type and amount of filler used. A rough surface will give rise to stress concentrations and increased plastic deformations in the coating, impairing the properties of the clamping force joint.

  • 68.
    Ståhlberg, Daniel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Junestam, Per
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Gamstedt, Kristofer
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Relaxation properties of particle filled coatings: Experimental study and modelling of a screw joint2006Inngår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 55, nr 2, s. 112-118Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study describes the mechanical behaviour of powder coatings used under very high compressive loads in clamping force joints. Carboxyl functional polyester powder coatings cured with hydroxyl functional P-hydroxyalkylamides with variations in amount of filler have been studied. The coatings were subjected to relaxation tests in tension and in compression. The tests in compression were performed in specially designed tests developed to study the behaviour of powder coatings under compressive loads in clamping force joints. The relaxation results for the matrix were used in a unit cell in micromechanical finite element (FE) model to predict the homogenised viscoelastic properties of the particle composite. These constitutive properties were subsequently used to evaluate the behaviour on a macromechanical scale in a screw joint. The model corresponds well with experimental data at ambient temperature. When increasing the temperature above the glass transition of the coating, however, the model predictions and experimental data differ. Experiments in compression show a much lower relaxation its compared to the FE model. The relaxation simulations of the coating under compressive loads from screw joints showed a significant sensitivity to the Poisson's ratio of the polymer matrix. As the Poisson's ratio approaches 0.5, the matrix becomes hydrostatically incompressible, which resulted in a negligible relaxation of the coating at the screw joint.

  • 69.
    Ståhlberg, Daniel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Marklund, Erik
    Nordin, Lars-Olof
    Varna, Janis
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Mechanical response of thermoset polymers under high compressive loads, 2: Modeling2005Inngår i: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 290, nr 11, s. 1073-1082Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A nonlinear viscoelastic material model was used to describe the experimental behaviour of thin vinyl ester specimens Subjected to compression in thickness direction. The stress-dependent material functions in the model were found in creep and strain recovery tests on thick cylindrical specimens. The elastic and creep response of thin thermoset polymer specimens subjected to compressive loads was simulated while varying the geometry of the test set samples. The calculated increase in the apparent elastic modulus and decrease of the creep-strain rate due to reduced thickness-to-width ratio is in a good qualitative correlation with experimental results for Corresponding geometries. The constraint due to friction and interaction with the material outside the loaded surface area were identified as the cause for high apparent stiffness, which converges with decreasing thickness to an asymptotic value dependent on the modulus and I Poisson's ratio of the material.

  • 70.
    Ståhlberg, Daniel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nordin, Lars-Olof
    Varna, Janis
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Mechanical response of thermoset polymers under high compressive loads, 12005Inngår i: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 290, s. 1063-1072Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present Study describes the mechanical response of thermoset polymers under high compressive loads. A well-defined free radically cured vinyl ester resin has been used and studied in six different geometries in order to determine the dependence of apparent mechanical properties on the particular size and shape of a sample. The mechanical response in compression has also been compared to the response in tensile tests. Variation of the film thickness, boundary conditions and loading conditions reveal that there is a significant effect on the mechanical performance (apparent properties) of the polymer. When the thickness-to-width ratio of the sample is reduced in a compression test, the friction between the sample and the compression plates proves to be I of great importance. The yield stress increases dramatically when the thickness of the sample is reduced, whereas it decreases when the friction between sample and the compression plate is reduced. The creep decreases when the thickness of the material is reduced and it decreases even more due to reaction of the material surrounding the compressed part of I! the sample. The described test conditions and observed I phenomena will be subject to simulation in Part 2 of this study.

  • 71.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Seizure mechanisms of wheel–rail contacts under lubricated conditions using a transient ball-on-disc test method2008Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, s. 867-874Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study focuses on the transition from mild to severe wear in the wheel and rail contact. Such a transition has been observed at increased loading (normal load, sliding velocity, or bulk temperature) which can be compared to a change from a wheel thread-rail head contact to a wheel flange-rail gauge contact. This transition was experimentally studied using a transient test method of ball-on-disc type at different sliding velocities, contact pressures, and lubricants. It can be seen in the results that different seizure mechanisms are active for different sliding velocities. Also the amount of applied lubricant clearly affects the transition to seizure.

  • 72.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olander, Lars
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Wear rate testing in relation to airborne particles generated in a wheel-rail contact2009Inngår i: Lubrication science, ISSN 0954-0075, Vol. 21, nr 4, s. 135-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study examines the relationship between generated airborne particles and wear rate in the wheel-rail contact. The wheel-rail contact is experimentally simulated by using pin-on-disc testing to determine the difference in wear rate between selected contact conditions.

    Wear is discussed both in tribological terms and by using the wear categories prevalent in the railway industry, namely, mild, severe and catastrophic wear. The discussion is based on wear depth, the coefficient of friction, topographical measurements and measurements of airborne particles generated in the contact.

    The tests were performed under selected loading conditions representative of different contact conditions in a real wheel-rail contact. The results indicate that wear rates vary with the contact conditions arising from different types of triggered wear transitions. This is emphasised by the number and size of the airborne particles generated.

  • 73.
    Sundh, Jon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Sundvall, Krister
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Seizure and wear rate testing of wheel–rail contacts under lubricated conditions using pin-on-disc methodology2008Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, s. 1425-1430Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An increased wear rate and a shift of wear mechanism in the wheel-rail contact has been observed in tight curves, mainly due to the change from an almost pure rolling contact to more of a sliding contact. The wheel flange-rail gauge contact is commonly known to experience the toughest conditions of the overall wheel-rail contact in terms of contact pressure and sliding velocity. The wheel flange-rail gauge contact is preferably lubricated to reduce the wear rate and to minimise the risk of transition to severe wear or seizure. The amount and type of lubrication are therefore important parameters if one is to control the wear rate. In this study, a flange contact is experimentally simulated using pin-on-disc testing, to determine the difference in wear rate among a selection of lubricants under different contact conditions. The selection of lubricants consisted of environmentally adapted oils, mineral oils, and greases containing different amounts of EP and AW additives.The results of the pin-on-disc testing indicate that both the amount and type of lubrication applied is decisive for the wear rate and active wear mechanism. Tests have also been performed to simulate either on-board or wayside lubrication, by applying the lubricant at different intervals. A general observation is that under starved lubrication conditions a transition to severe wear is initiated and the wear rate increases rapidly, i.e., all tests indicate that the contact between wheel and rail must be lubricated to avoid high wear rates.

  • 74. Tang, Wen
    et al.
    Policastro, Gina M.
    Hua, Geng
    University of Akron, United States .
    Guo, Kai
    Zhou, Jinjun
    Wesdemiotis, Chrys
    Doll, Gary L.
    Becker, Matthew L.
    Bioactive Surface Modification of Metal Oxides via Catechol-Bearing Modular Peptides: Multivalent-Binding, Surface Retention, and Peptide Bioactivity2014Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, nr 46, s. 16357-16367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of multivalent dendrons containing a bioactive osteogenic growth peptide (OGP) domain and surface-binding catechol domains were obtained through solid phase synthesis, and their binding affinity to hydroxyapatite, TiO2, ZrO2, CeO2, Fe3O4 and gold was characterized using a quartz crystal microbalance with dissipation (QCM-d). Using the distinct difference in binding affinity of the bioconjugate to the metal oxides, TiO2-coated glass slides were selectively patterned with bioactive peptides. Cell culture studies demonstrated the bioavailability of the OGP and that OGP remained on the surface for at least 2 weeks under in vitro cell culture conditions. Bone sialoprotein (BSP) and osteocalcein (OCN) markers were upregulated 3-fold and 60-fold, respectively, relative to controls at 21 days. Similarly, 3-fold more calcium was deposited using the OGP tethered dendron compared to TiO2. These catechol-bearing dendrons provide a fast and efficient method to functionalize a wide range of inorganic materials with bioactive peptides and have the potential to be used in coating orthopaedic implants and fixation devices.

  • 75. Thibblin, Anders
    et al.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    A test rig for evaluating thermal cyclic life and effectiveness of thermal barrier coatings inside exhaust manifolds2019Inngår i: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, nr AprilArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal Barrier Coatings (TBCs) may be used on the inner surfaces of exhaust manifolds in heavy-duty diesel engines to improve the fuel efficiency and prolong the life of the component. The coatings need to have a long thermal cyclic life and also be able to reduce the temperature in the substrate material. A lower temperature of the substrate material reduces the oxidation rate and has a positive influence on the thermo-mechanical fatigue life. A test rig for evaluating these properties for several different coatings simultaneously in the correct environment was developed and tested for two different TBCs and one oxidation-resistant coating. Exhausts were redirected from a diesel engine and led through a series of coated pipes. These pipes were thermally cycled by alternating the temperature of the exhausts. Initial damage in the form of cracks within the top coats of the TBCs was found after cycling 150 times between 50°C and 530°C. Temperature calculations showed that, besides evaluating the thermal cyclic life, the test method has the potential to provide a quick ranking of coating materials with respect to thermal insulation by measuring the temperature on the outer surface of the coated pipes. One of the major advantages of the presented test method compared to other methods described in the literature is that it ranks the thermal cyclic life and thermal properties of different coatings under realistic conditions in the correct environment. More cycles and higher temperatures are recommended for future tests, to accelerate the test, as well as evaluate whether the initial cracks in the TBCs will lead to spallation.

  • 76.
    Tolf, Erik
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Svetsteknologi.
    Challenges in Resistance Welding of Ultra High Strength Steels2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increasing the use of Ultra High Strength Steels (UHSS) in vehicle bodystructures is important for reducing weight and cutting CO2 emissions. This thesis investigates challenges in resistance welding that can be a barrier to implementing UHSS as a replacement for low strength steels in vehicle structures. Empirical research has been performed to offer new approaches for improved joint strength and to increase knowledge on cracking mechanisms in resistance projection welding and resistance spot welding of UHSS. By optimising the current build-up phase and peak current during the first milliseconds of weld time, it was shown that the strength could be improved by up to two-fold for projection welded joints. An approach to improve the ductility and strength of resistance spotwelds in UHSS using reduced cooling time was unsuccessful. The reduced cooling rate after weld metal solidification did not fully create the desired softened microstructure. The study on the surface cracking mechanism in resistance spot welded dual-phase UHSS showed that cracking is linked to the galvanization method. It is proposed that formation of aluminium oxide layers on the electrode tips increases the surface temperature and thereby increases the probability for liquid metal embrittlement and surface cracking.

  • 77. Tolf, Erik
    et al.
    Hedegård, Joakim
    Influence of Reduced Cooling Time on the Properties of Resistance Spot Welds2008Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 52, nr 3-4, s. 43-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reducing the cooling time in a resistance spot welding schedule offers two possible advantages. The first is decreased weld cycle time, which is of great importance in particular to car body assembly lines performing hundreds of millions of spot welds each year. Decreasing each resistance spot weld cycle time by a mere 0.1 s leads to substantial cost savings. The second advantage is the possibility to reduce the hardness in the weld metal and thereby improve fracture behaviour. Reducing the cooling time leads to reduced cooling rate of the weld metal and potentially a softer material. Two and three-sheet joint combinations of martensitic, dual phase, transformation induced plasticity (TRIP), complex phase and hardened boron steels were investigated in this study. The joints were evaluated by shear-, peel and cross-tension testing as well as metallographical examinations and hardness measurements. With knowledge of the materials weldability, and evaluation of the behaviour when welding with reduced cooling time, it was possible to develop optimised weld schedules and thereby increase productivity. It is recommended that the programming of the hold time in the power sources is modified in order to enable full flexibility in setting of the hold time /cooling time. This study showed that the cooling time could be reduced significantly without endangering the joint integrity.

  • 78. Tomkowski, Robert
    Holmberg, Jonas ()
    RISE.
    Jonsson, Stefan ()
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Hammersberg, Peter ()
    Chalmers.
    Kristoffersen, Hans ()
    RISE.
    Nerman, Peter ()
    Scania CV AB.
    Olavison, Jari ()
    Volvo AB.
    Archenti, Andreas ()
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Mätteknik och optik.
    The Barkhasuen Noise Measurements: Good Practice Guide2018 (oppl. 1)Bok (Fagfellevurdert)
    Abstract [en]

    The KTH Royal Institute of Technology (Stockholm, Sweden) as a project leader allowed strengthening collaboration between academic and industrial experts in the field of non-destructive testing (NDT), machining and metrology. This scientific consortium had found an efficient way for scientific collaboration, in which we conducted many experiments, meetings, and talks on the project’s research subject. This book is a result of all the mentioned activities and more. Many experts from both sides actively participated in the creation of this guide and are listed in the list of contributors.

    The authors hope that after reading this guide, BN measurements can be carried out more systematically, with higher accuracy, traceability and lower uncertainty. The authors do not aim to replace a whole raft of good textbooks, operator’s manuals, specifications, and standards (if they exist); rather, they want to present an overview of good practices and techniques. These recommendations are also a result of many discussions conducted by the project team members during the project’s duration.

    The book is divided into two parts. The first part of the book, “Measurement Good Practice Guide”, presents a comprehensive overview of the Barkhausen noise (BN) measurement method used to describe and analyze different features of ferromagnetic materials, such as residual stress level, hardening depth, among others. The primary focus is on mechanical parts for the automotive industry, in particular, the camshaft and crankshaft. The good practice guide is intended for those who need to make BN measurements but are not necessarily trained to use this method or are still not comfortable about measurement itself. By reading this guide, one can gain basic knowledge regarding good practices for making magnetic measurements with the BN method. Based on a few principles and tips from good practices, the reader will be able to create a Standard Operating Procedure (SOP) for their purpose. SOPs for BN are presented in the appendices.

    The second part of the book “Qualification and Certification of Personnel” presents requirements of the personal certification for Barkhausen testing and is aligned with applicable standards. The authors recommend performing internal and external certification of personnel to do achieve more conscious and reliable measurements.

    This book has been prepared by the scientific consortium under the research project FFI OFP4p – Non-Destructive Characterization Concepts for Production, 2015–2018 co-founded in 50% by VINNOVA, Sweden’s innovation agency. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.

  • 79.
    Tomkowski, Robert
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Jonsson, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Lundin, Per
    Stresstech Oy.
    Nerman, Peter
    Scania CV AB.
    Penetration depth investigation of Barkhausen noise signal for case-hardened components2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Non-destructive testing of layer properties in machine part loading, has greatly improved over the last 20 years. One of those NDT methods is Barkhausen Noise Analysis (BNA). The BNA-method is utilized to assess changes in the surface layer of ferromagnetic materials, especially for monitoring changes in hardness and residual stresses. The BNA-method works on the interaction between the external magnetic field and the ferromagnetic material. The reorganizations of the magnetic domains and the formation of an internal magnetic field are registered by the sensor. The magnitude of the registered signal and its parameters depends on many factors. Many of them are non-correlated, while others are strongly correlated. One can easily show that the set of factors affecting the Barkhausen signal has more than 200 components, including interactions between factors. Combination of all this factor results in material response for external magnetization. However, the effect of all factors can be changed by so called skin effect, where with the use of low frequency material is magnetized deeper than with higher frequency. Nevertheless, depth from which signal is registered, generated by material, does not exactly overlap magnetization depth. This so-called penetration depth is depended on both full material characteristics and magnetization parameters. Therefore, in this publication authors investigated real response of measured Barkhausen noise signal in relation to mentioned conditions.

  • 80.
    Wang, Wenqi
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hot working of ingots by increasingthe roll diameter during bar rolling2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In last ten years, the size range of dimensions program has increased and therefore the hot rolling process needs to be analysed and improved. The bar mill at Ovako Sweden AB in Hofors intends to increase the current roll diameter to improve the rolling capacity and to remove the existing bottleneck within the production flow. Therefore, this project is carried out to study the hot working of ingots within the current rolling setup, aiming to evaluate the subsequent change on ingot central deformation and porosity related to roller dimension. In this project, two plant trials are executed at Ovako Sweden AB and after the trials; analyses on ingot central deformation and central porosity are performed respectively with samples from the two trials. The results suggest that, after the first rolling stage, larger diameter rolls results in less pore defects but gives similar central deformation. Indicated from the results, the ingot is likely to have less central porosity but equal central deformation by increasing the roll diameter. After this project, we get a better perspective of the potential to boost the rolling capacity with a new larger roll and the subsequent quality benefits.

  • 81.
    Wanner, Bertil
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Archenti, Andreas
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Nicolescu, Cornel Mihai
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Hybrid machining: An industrial case-study comparing inconel718 reaming and drilling with abrasive waterjet technology2018Inngår i: Proceedings of 3rd International Conference on the Industry 4.0 Model for Advanced Manufacturing, Pleiades Publishing , 2018, nr 9783319895628, s. 109-114Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Abrasive waterjet technology is one of the fastest growing metal cutting technologies. When used in conjunction with conventional metal cutting methods, abrasive waterjet cutting can be both cost saving and environmentally favorable. This paper shows that when processing hard to cut alloys, abrasive waterjet will be an excellent hybrid alternative. Reaming and drilling have traditionally been used to produce turbine blisks. Reaming is a highly expensive method since it uses very large amounts of cutting tools. Especially when cutting hard materials such as Nickel alloys, tools have to be replaced after only a few minutes of usage. By applying abrasive waterjet cutting to part of the process, the cost for tooling can be almost entirely eliminated. It will also increase the return profit for revert material and greatly reduce environmental emissions. This is because reaming and drilling produce chips while large amounts of cutting fluids are being used. Abrasive waterjet cutting will produce one large metal chunk per cut and uses no cutting fluids. This paper presents a method to combine abrasive waterjet cutting with reaming and drilling.

  • 82.
    Wikström, Gabriel
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Återfjädring vid bockning av höghållfast stål2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 83.
    Wåhlin, Fredrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Direct-injected HCCI with diesel fuel2005Licentiatavhandling, monografi (Annet vitenskapelig)
  • 84. Yalchiner, Fikri Bashar
    et al.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Life Extension of Welded Structures Using HFMI Techniques - Potential Application to Offshore Structures2017Inngår i: 2nd International Conference on Structural Integrity, ICSI 2017 / [ed] Iacoviello, F Moreira, PMGP Tavares, PJS, Elsevier, 2017, Vol. 5, s. 377-384Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fatigue damage development in welded structures is a local phenomenon and if one need to achieve an extension of the life for the structure local post weld improvements need to be use in order to reduce/remove local features which contribute to the fatigue damage. In order to enhance the life time of load carrying welded structures without large amount of cost investments, e.g. redesign and replacement of existing structures, post weld improvement techniques need to be more applied. New High Frequency Mechanical Impact (HFMI) technologies have been developed in the last 10 years which enables cost-effective life extension and reparation of welded structures. The use improvement techniques for technical life enhancement upgrade and repair of welded structures within various industries, e.g. oil and gas, have been an accepted practice. HFMI treatment techniques are based on localized peening process of the welded joints and the devices are portable. The impacting results in a local cold plastic deformation which remove weld defects reduce stress concentration and induce compressive residual stresses which eventually will enhance the fatigue life of the welded structure. An overview of existing improvement techniques for welded structures is given followed by description of new technologies (HFMI). A brief description of the new international guideline and design recommendations within the International Institute of Welding (IIW) is given. Several validation studies on the fatigue performance of HFMI techniques are presented and onsite potential applications of the techniques for joints in fixed offshore structures are outlined.

  • 85. Yang, Shucai
    et al.
    Liu, Weiwei
    Ji, Wei
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion. Harbin University of Science and Technology, China.
    Liu, Xianli
    Zhu, Jie
    A novel method of experimental evaluation on BTA tool geometries2017Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 91, nr 9-12, s. 4253-4261Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Towards the problem of closed space of Boring and Trepanning Association (BTA) drill, this paper presents a novel experimental method to evaluate BTA tool geometries, and a turning-based test is conducted to simulate drilling. The three inserts of BTA drill are replaced by the three turning inserts, the rotation of BTA drill is transformed by workpiece rotation in turning, the feed of BTA drill changes into the feed of turning inserts, and the cutting area per BTA insert is simulated by the cutting depth in turning. To implement the approach, three angles, consisting of edge inclination, flank angle and edge declination, are organised by a three-factor and three-level Taguchi experiment for each BTA insert, e.g. outside insert, centre insert and middle insert. Cutting force, chip patterns and chip curl radius are observed and measured to evaluate the insert geometries.

  • 86.
    Yuan, Qilong
    et al.
    Foshan Univ, Sch Electromech Engn, Foshan, Peoples R China..
    Chen, I-Ming
    Nanyang Technol Univ, Sch Mech & Aerosp Engn, Singapore, Singapore..
    Lembono, Teguh Santoso
    Singapore Univ Technol & Design, Engn Prod Dev, Singapore, Singapore..
    Nelson Landén, Simon
    KTH, Skolan för industriell teknik och management (ITM).
    Malmgren, Victor
    KTH, Skolan för industriell teknik och management (ITM).
    Automatic robot taping system with compliant force control2018Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 94, nr 9-12, s. 4105-4113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In surface treatment processes like plasma spraying and spray painting of workpieces, protecting the uninvolved surface by applying masking tape is a common process. Due to the operation complexity for different geometries, such taping tasks depend on a lot of manual works, which is tedious and tiring. This paper introduces an automatic agile robotic system and the corresponding algorithm to do the surface taping. The automatic taping system consists of a 3D scanner for workpiece 3D model reconstruction, a taping end-effector which is mounted on a robot manipulator to handle the taping task, and a rotating platform that is used to hold the workpiece. The surface covering method and the taping path planning algorithms using the scanned model are introduced. With the implementation of the compliance mechanism, the force feedback and the tape-cutting mechanism, the system is able to tape flat, cylindrical, freeform, and grooved surfaces. Experiments conducted on taping an engine inner liner shows that the surface can be covered with uniform taping overlap and very little wrinkle. The proposed system is a useful taping package for industrial applications such as workpiece repairing and surface protection, where surface treatments are involved.

  • 87. Yuzvyuk, M. H.
    et al.
    Putrolaynen, V. V.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Processing of ultra-hard coatings based on AlMgB14 films2016Inngår i: 18th International Conference PhysicA.SPb26–29 October 2015, Saint Petersburg, Russian Federation, Institute of Physics Publishing (IOPP), 2016, Vol. 769, nr 1, artikkel-id 012039Konferansepaper (Fagfellevurdert)
    Abstract [en]

    First time AlMgB14 films were prepared in Ames Lab by pulsed laser deposition technique. In this work, RF magnetron sputtering from a single stoichiometric target was employed to fabricate hard AlMgB14 coatings on Si wafer and industrial items. Measurements of nanohardness and elastic Young's modulus were performed to determine reliable strength characteristics of samples. Smooth 3 μm thick AlMgB14 films with the RMS surface roughness to be less than 1 nm exhibit hardness of 34 GPa and modulus of elasticity of 230 GPa at 20 mN peak load.

  • 88.
    Zhu, Jinchao
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Khurshid, Mansoor
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Cargotec Sweden AB Bromma Conquip, Kronborgsgrand 23, S-16446 Kista, Sweden..
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Chalmers Univ Technol, Chalmersplatsen 4, S-41296 Gothenburg, Sweden..
    Accuracy of computational welding mechanics methods for estimation of angular distortion and residual stresses2019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 5, s. 1391-1405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study estimates the angular distortion and residual stresses due to welding using the following methodologies: thermo-elastic-plastic, inherent strain (local-global), and substructuring on two types of welded joints (T-type fillet weld and butt weld). The numerical results are compared with the experimental measurements and these methodologies are evaluated in terms of accuracy and computational time. In addition, the influence of welding sequence on distortion and transverse residual stresses has been studied numerically by implementing the thermo-elastic-plastic and inherent strain (local-global) methods on the T-type fillet weld. For the T-type fillet weld, the estimated angular distortion from these methods is much the same and in good agreement with the experimental measurements. For the butt weld, the angular distortion calculated by the inherent strain (local-global) method is largely underestimated. In order to gain a better understanding of where the underestimation of angular distortion in the inherent strain (local-global) method comes from, the study discusses the influence of block length and welding speed on angular distortion. It is found that for long weld length or slow welding speed, activating the plastic strain gradually by dividing the weld bead into an appropriate number of blocks can reduce the level of underestimation of angular distortion.

  • 89.
    Ånmark, Niclas
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Björk, Thomas
    Swerea KIMAB.
    Ganea, Anna
    Sandvik Coromant.
    Ölund, Patrik
    Ovako Hofors.
    Hogmark, Sture
    Uppsala Unniversitet.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    The effect of inclusion composition on tool wear in hard part turning using PCBN cutting tools2015Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 334, s. 13-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work reports on hard part turning of carburizing steels using a PCBN cutting tool in fine machining. Emphasis is on the link between composition of the inclusions in work material and wear mechanisms of the cutting tool. A Ca-treated machinability improved 20NiCrMo steel was included together with three other carburizing steels with different inclusion characteristics.

    Machining tests were conducted to examine cutting tool life and its balance between excessive flank wear or crater wear. The wear mechanisms were examined using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and a secondary electron (SE) detector.

    The longest tool life was obtained when cutting the Ca-treated steel. The improved machinability is linked to the deposition of complex (Mn,Ca)S and (Ca,Al)(O,S) protective slag layers that form on the rake face of the cutting tool during machining. Cutting in this steel also resulted in a typical ridge formation in the tool edge crater. Transfer of workpiece material to the rake face crater is characteristic in hard part turning of steel with high cleanliness. This is suggested to be related to the lack of the sulphides that lubricate conventional machinability treated steels, and that the crater wear of low-sulphur steel is more pronounced than for steels with higher sulphur content.

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