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  • 1.
    Andersson, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Budak, Nesrin
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Palmqvist, Niclas
    Distortions of overlap laser welded thin sheet mild steel beam structuresManuscript (preprint) (Other academic)
  • 2.
    Andersson, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    General regression model for prediction of spot weld sizes2011In: International Congress on Advances in Welding Science and Technology for Construction, Energy and Transportation Systems, 2011Conference paper (Other academic)
  • 3.
    Andersson, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Statistical Analysis of Variations in Resistance Spot Weld Results in Laboratory and Production EnvironmentManuscript (preprint) (Other academic)
  • 4.
    Andersson, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Statistical analysis of variations in resitance spot weld results in laboratory and productionIn: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936Article in journal (Other academic)
  • 5.
    Andersson, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Verification of the capability of resistance spot welding simulationManuscript (preprint) (Other academic)
  • 6.
    Andersson, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Verification of the Capability of Resistance Spot Welding Simulation for automotive process planningManuscript (preprint) (Other academic)
  • 7.
    Fahlkrans, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Scania CV, Stockholm, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Gårdstam, Johannes
    Swerea KIMAB, Stockholm, Sweden.
    Haglund, Sven
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Straightening of induction hardened shafts: influence on fatigue strength and residual stress2012In: HTM Journal of Heat Treatment and Materials, ISSN 1867-2493, Vol. 67, no 3, p. 179-187Article in journal (Refereed)
    Abstract [en]

    Straightening of distorted components after heat treatment is often a necessary operation. The straightening operation leads to local plasticization, which is affecting the residual stress state, the hardness, and ultimately the fatigue strength of the component. The present study evaluates the influence of a straightening operation on fatigue strength and on the residual stress state of induction hardened shafts of steel 42CrMo4. A simplified FEM model was formulated. The model showed that the residual stress state was asymmetric along the circumference of a straightened shaft. Fatigue testing was performed in three point bending and showed that the fatigue strength was reduced by up to some 20 % by heavy straightening. A fracture mechanics model for fatigue crack growth and arrest was developed. The model could be used to predict the fatigue strength of a straightened shaft provided that the residual stress state was known.

  • 8.
    Fahlkrans, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Scania CV, Stockholm, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Haglund, Sven
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Gas Quench Rate after Low Pressure Carburizing and its Influence on Fatigue Properties of Gears2013In: HTM - Journal of Heat Treatment and Materials, ISSN 1867-2493, Vol. 68, no 6, p. 239-245Article in journal (Refereed)
    Abstract [en]

    Process modifications of the gas quench sequence for low pressure carburized gears can increase the performance of up to 22 %, compared to direct gas quenching. Several test series were made with different interruptions of the gas quenching sequence, near the martensite start temperature Ms. The quench interruption resulted in an increase in magnitude of compressive residual stress which was attributed to temperature homogenization and rearrangement of local stresses. The increased fatigue strength was a result of the combination of enhancement of the compressive residual stress state, and of mechanical stabilization of austenite.

  • 9.
    Fahlkrans, Johan
    et al.
    Scania CV, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Johansson, Krister
    Scania CV, Stockholm, Sweden.
    Haglund, Sven
    Swerea KIMAB, Sweden.
    Hosseini, Seyed B.
    Swerea IVF, Stockholm, Sweden.
    Influence of tempering on contact fatigue2011In: International Journal of Microstructure and Materials Properties, ISSN 1741-8410, E-ISSN 1741-8429, Vol. 6, no 6, p. 465-478Article in journal (Refereed)
    Abstract [en]

    Most components are tempered after heat treatment operations such as case hardening or induction hardening. The common opinion is that the martensitic structure after heat treatment is too brittle and tempering is necessary to increase toughness.

    Tempering is an additional operation which leads to increased costs by energy, handling, and investments. Eliminating tempering from the heat treatment process leads to increased productivity, energy savings, and lowered environmental impact.

    Two carburised steels, Ovako 253A (?EN 22NiCrMo12-5F mod. A) and EN 20NiCrMo2 (SAE 8620, SS2506), were tested for contact fatigue resistance in a roller to roller rig. The tested samples were characterised with respect to amount of fatigue damage, residual stress, amount of retained austenite and hardness. The objective was to determine if tempering is always necessary after a heat treatment operation.

    The contact fatigue tests show that tempering results in lower contact fatigue resistance. Further, fatigue cracks were found to have initiated in different ways between tempered and untempered steel.

  • 10. Fahlström, Karl
    et al.
    Andersson, Oscar
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research.
    Karlsson, Leif
    Svensson, Lars-Erik
    Metallurgical effects and distortions in laser welding of thin sheet steels with variations in strength2017In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 22, no 7, p. 573-579Article in journal (Refereed)
    Abstract [en]

    Geometrical distortions occur while welding, but the understanding of how and why they occur and how to control them is limited. The relation between the weld width, weld metal volume, total energy input, width of hard zone and distortions when laser welding three different thin sheet steels with varying strength has therefore been studied. Weld metal volume and total energy input show a good correlation with distortion for one steel at a time. The best correlation with the when including all three steel grades was the width of the hard zone composed of weld metal and the martensitic area in the heat affected zone.

  • 11.
    Fahlström, Karl
    et al.
    Swerea KIMAB, Sweden.
    Andersson, Oscar
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering. KTH, Centres, XPRES, Excellence in production research. Volvo Cars, Sweden.
    Todal, Urban
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research.
    Minimization of distortions during Laser Welding of Ultra High Strength Steel2015In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 27, no S2, article id S29011Article in journal (Refereed)
    Abstract [en]

    Ultra high strength steels are frequently used within the automotive industry for several components. Welding of these components is traditionally done by resistance spot welding, but to get further productivity and increased strength, laser welding has been introduced in the past decades. Fusion welding is known to cause distortions due to built in stresses in the material. The distortions result in geometrical issues during assembly which become the origin of low joint quality due to gaps and misfits. U-beam structures of boron steel simulating B-pillars have been welded with laser along the flanges. Welding parameters and clamping have been varied to create different welding sequences and heat input generating a range of distortion levels. The distortions have been recorded dynamically with an optical measurement system during welding. In addition, final distortions have been measured by a digital Vernier caliper. The combined measurements give the possibility to evaluate development, occurrence, and magnitude of distortions with high accuracy. Furthermore, section cuts have been analyzed to assess joint geometry and metallurgy. The results show that final distortions appear in the range of 0–8 mm. Distortions occur mainly transversely and vertically along the profile. Variations in heat input show clear correlation with the magnitude of distortions and level of joint quality. A higher heat input in general generates a higher level of distortion with the same clamping conditions. Section cuts show that weld width and penetration are significantly affected by welding heat input. The present study identifies parameters which significantly influence the magnitude and distribution of distortions. Also, effective measures to minimize distortions and maintain or improve joint quality have been proposed. Finally, transient finite element (FE) simulations have been presented which show the behavior of the profiles during the welding and unclamping process.

  • 12.
    Fahlström, Karl
    et al.
    Swerea KIMAB.
    Andersson, Oscar
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering. KTH, Centres, XPRES, Excellence in production research. Volvo Cars Corporation.
    Todal, Urban
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB.
    Lars-Erik, Svensson
    Högskolan Väst.
    Leif, Karlsson
    Högskolan Väst.
    Distortion Analysis in laser Welding of Ultra High Strength Steel2014In: Proc 6th International Swedish Production symposium 2014, 2014Conference paper (Refereed)
    Abstract [en]

    Due to increased demands on reduced weight in automotive industries, the use of ultra high strength steels (UHSS) has increased. When laser welding UHSS ssheets, heating and cooling of the material will cause geometrical distortions and may cause low joint quality. 700 mm long U-beam structures of 1 mm thick boron steel simulating structural pillars in body-in-white constructions have been laser welded along the flanges with different welding speeds to investigate distortions and weld quality. The results show that final distortions appear in the range of 0-8 mm. FE simulation methods have also been presented which generally predict the distribution of welding distortions.

  • 13.
    Haglund, Sven
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Kristoffersen, Hans
    Swerea IVF.
    Simulation of residual stresses after straightening of induction hardened components2014In: HTM - Journal of Heat Treatment and Materials, ISSN 1867-2493, Vol. 69, no 3, p. 165-172Article in journal (Refereed)
    Abstract [en]

    Straightening is a manufacturing process where a component is bent, and plastically deformed, in order to reach a desired straightness. It is an unwanted but in many cases necessary process. For instance heat treatment operations such as carburizing and induction hardening may give distortions of magnitude that a straightening operation is required. The main disadvantage with straightening, apart from the extra processing step, is that it alters the residual stresses which decrease the fatigue strength of the component. In this paper, the straightening of a surface hardened shaft is simulated by FEM. The paper brings new insight into the complexity in the changes in residual stress that deviates far from the simplified views presented in literature. It will be shown that there are fundamental differences between a through hardened shaft and a surface hardened one as well as between shafts with shallow and deep surface hardening depths. The material studied is 42CrMo4 induction hardened by single shot. It is shown that the change in residual stresses is rather complex with decreased compressive residual stresses in a number of locations around the circumference while other locations have increased stresses. The amount of change in the residual stresses are largely governed by the required bending but by doing the straightening operation in an optimal way the negative effect can be reduced.

  • 14.
    Khodaee, Alireza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. SWEREA KIMAB, Sweden.
    Evaluation of effects of geometrical parameters on density distribution in compaction of PM gears2017In: Proceedings of the 20th International Esaform Conference on Material Forming: ESAFORM 2017, American Institute of Physics (AIP), 2017, Vol. 1896, article id 050006Conference paper (Refereed)
    Abstract [en]

    The usage of powder metallurgy (PM) for manufacturing of transmission components in automotive industries has been studied by many researchers. PM components have become of interest in recent years due to advancements in post processing possibilities such as hot isostatic pressing (HIP). Still in many of the forming process routes for making components from PM materials, the compaction of the powder into green component is the first step. Compaction is required to put the powder into the near net shape of the desired component and it causes a density gradient in the body of the green component. Basically the friction between powder particles and between the powder particles and die walls are the well-known roots for such density gradients in the compacted component. Looking at forming of PM gears, the gradient in density is one of the most important roots of problems in the processing of PM gears as well. That is because making a gear with full density and no pores will be very costly if large density gradients exist in the green component. The purpose of this study is to find the possible relations between the gear geometry and the density gradients in the green component after compaction in addition to the friction effects. For this purpose several gears should be tested. To reduce the research costs, the finite element (FE) method is used. First a FE model of the compaction process is developed and verified. To investigate the relations between the density gradients and the gear parameters such as addendum diameter (da) and the face width (b) several gear geometries have been studied. The compaction of selected gears is simulated using the FE model. The simulations results which are the distribution of density in the green component are evaluated and discussed and conclusion are made based on them.

  • 15.
    Khodaee, Alireza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Finite Element Analysis on the Friction Effects in the Gear Rolling Process2013In: NEWTECH 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Gear rolling as a manufacturing method for gear wheels has a number of advantages in comparison with traditional gear production methods which makes it an interesting topic for scientific research. The main benefits are reduced material consumption, fast cycle time of the process, improved strength of the product due to the alignment of the microstructure during cold forming and a good surface quality.

    There are several factors which can influence the process quality and accuracy of the geometry in the final state. One of the most important parameters is the friction between the tool and the blank during the forming process. Therefore it is of interest to study the effect of different friction models in finite element simulations to evaluate its effects on final gear wheel shape.

    In this paper the shear friction model is studied. Two friction factors will be studied in this case. Two dimensional FE calculations will be performed with the code DEFORM. The results of the FE simulations and the effect of friction factor on gear flank and tip geometry are presented. One example is presented of the effect on the so called “rabbit ear “at the gear tip.

  • 16.
    Khodaee, Alireza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Finite Element Simulation as a Tool to Evaluate Gear Quality after Gear Rolling2013In: Current State-Of-The-Art On Material Forming: Numerical And Experimental Approaches At Different Length-Scales, Pts 1-3, Trans Tech Publications Inc., 2013, Vol. 554-557, p. 300-306Conference paper (Refereed)
    Abstract [en]

    Gear rolling is a manufacturing technique for gears with many advantages like reducedmaterial consumption, reduced scrap generation, fast cycle times, good surface quality andimproved final properties of the gear wheels compared to conventional production technology basedon machining. In order to make use of all these advantages it is desired to reach the final shape ofthe gear wheel already after rolling. This means that post treatments like grinding should beavoided. This puts high requirements on the shape accuracy after gear rolling.In this paper it was studied if finite element simulation could be used to evaluate the shape accuracyafter gear rolling. The measurement of shape accuracy of gear wheels is specified in standards likeISO1328-1. The allowed deviations from nominal shape are often of the order of 10-30 μm for verygood qualities. So if such evaluation shall be possible from a finite element simulation the accuracymust be of the same order.In order to have sufficient accuracy of the finite element simulation 2D simulations were performedon a spur gear. The FE code DEFORM was utilized. The shape accuracy was evaluated for gearrolling of two cases. One case had gears with the module of 1 mm. The other case involved gearswith a significantly larger module of 4 mm. This was an interesting case since it is known that it ismore difficult to roll the gear with good accuracy in large modules.

  • 17.
    Khodaee, Alireza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Study of the effect of the reversal cycles in the gear rolling process by using finite element simulations2014In: ESAFORM 2014, 2014, p. 134-141Conference paper (Refereed)
    Abstract [en]

    The manufacturing of machine components with sustainable and innovative methods is an interesting topic for research. Gears are some components which have complexity in both design and production technology. Therefore applying innovative methods on gear manufacturing can be of interest to industry. One of the most promising production methods for gear wheels is Gear Rolling. The gear wheel is formed during a certain rolling process from a cylindrical blank into the final designed shape. The process of gear rolling with rotational gears is progressing by running several rolling cycles with one, or two dies in contact with a work-piece. A specified rotational speed and radial feed speed is applied to the dies in order to form the required geometry on the blank. In this paper, the authors have simulated the process with the finite element code, DEFORM 3D. Especially the effects of reversal cycles on final gear wheel geometry have been evaluated from the simulations. Different settings for the rotation direction of the dies have been used and the effects are evaluated with specific quality criteria.

  • 18.
    Lundin, Mathias
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Quality assurance for welding and quality levels for welds – Standards and requirements2013In: Proc 2nd Swedish Conference on design of welded structures, 2013Conference paper (Refereed)
  • 19.
    Melander, Arne
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Delic, Aldin
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Björkblad, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Juntunen, Pasi
    Samek, Ludovic
    Vadillo, Leire
    Finite element simulation of electro hydraulic forming2010In: International deep drawing research group (IDDRG) conference, Graz, Austria, 2010, p. 749-758Conference paper (Refereed)
  • 20.
    Melander, Arne
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Stenberg, Niclas
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Lundberg, M
    Björkblad, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Björkstam, D.
    Delic, Aldin
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Sheet metal forming of ultra high strength steels2009In: Proceedings of The International 3’rd Swedish Production Symposium, SPS’09 / [ed] B-G Rosén, Göteborg, 2009, p. 342-347Conference paper (Refereed)
  • 21.
    Melander, Arne
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Thoors, Håkan
    Swerea KIMAB.
    Stenberg, Niclas
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Ma, Ning
    RWTH Aachen.
    Spring back evaluation for high and ultra high strength sheet steels with the bending under tension machine2015In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 8, no 1, p. 137-144Article in journal (Refereed)
    Abstract [en]

    The Bending Under Tension (BUT) machine is used for evaluation of spring back in sheet metal forming. A strip is drawn over a rotating cylindrical die with different restraining forces. The strip is allowed to spring back after drawing and the curvature of the strip is measured. The loading sequence is typical to wall sections of pressed components, side wall curl, where the material has been bent, unbent and finally unloaded. The test was performed on four high and ultra high strength steels with tensile strengths in the range from 800 MPa to 1300 MPa. A clear separation of the data for the four steels was demonstrated. It was analysed to what extent the differences in spring back between the different steels was related to the differences in tensile strengths. A finite element simulation model was used to simulate the strip curvature after BUT testing. The material parameters of the model were fitted to monotonic uniaxial and equibiaxial tests and uniaxial cyclic tests. The model could describe the experimental data in a satisfactory way.

  • 22.
    Randelius, Mats
    et al.
    Swerea KIMAB, Sweden.
    Krantz, Therese
    Swerea KIMAB, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. Swerea KIMAB, Sweden.
    Experimental Testing and Computer Simulations of Ductile Fracture in Tool Steels2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 91-99Article in journal (Refereed)
    Abstract [en]

    Ductility was determined in experimental four-point bending tests of smooth specimens of tool steel. The tool steels had different contents of carbides and carbide sizes and with a hardness of approximately 60HRc. Two of the materials tested were produced powder metallurgically, one was spray formed and one was conventionally uphill ingot cast. Carbide size distribution analysis was performed on planar polished sections of each material. Correlation between carbide microstructure and ductility performance was obtained. The fracture mechanisms were investigated with fractography. A 3D FE-model was used to simulate the four-point bending tests and thereby analyse the matrix flow curve. Also the strain at failure was analysed for each material when simulations were performed based on experimental data. SEM-images of the materials carbide microstructure were used to create 2D FE-models. The models simulated crack initiation and propagation by removing elements in the steel matrix as the plastic strain reached a critical level. With three variants, simulations of crack initiation and propagation at carbides were investigated. That was carbides with no cohesion to matrix, carbides fixed to the matrix and carbides with internal cracks. Comparison of strains at failure for the 2D and the 3D FE-models showed good correlation.

  • 23.
    Randelius, Mats
    et al.
    Swerea Kimab, Sweden.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology. Swerea Kimab, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. Swerea Kimab, Sweden.
    Fatigue Strength of Conventionally Cast Tool Steels and its Dependence of Carbide Microstructure2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 83-90Article in journal (Refereed)
    Abstract [en]

    The axial fatigue strength at two million cycles was experimentally determined for two conventionally cast tool steels and successfully compared with results from a fatigue limit model. Specimens were tested both in the rolling and transverse direction and showed large differences in fatigue properties due to the segregated carbide microstructure. Rolling direction specimens experienced higher fatigue strength than the transverse direction specimens. This is due to smaller carbides present in the load affected cross section of the rolling direction fatigue test bars compared to the cross section of the transverse direction fatigue test bars. Fractographic analysis of failed specimens showed that large carbides had caused fatigue failure, which was also predicted by the model. Measured size distributions of carbides and inclusions were used as input data in the model. The probability that at least one particle will be present in the material volume having a size larger than the threshold value for crack propagation was calculated.

  • 24.
    Ratanathavorn, Wallop
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    A study of weld formation in friction stir welding of electrogalvanised steel to aluminium alloy in lap joint configurationIn: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774Article in journal (Refereed)
  • 25.
    Ratanathavorn, Wallop
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Dissimilar joining of aluminium to ultra-high strength steels by friction stir welding2017Doctoral thesis, comprehensive summary (Other academic)
    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.

  • 26.
    Ratanathavorn, Wallop
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    A study of friction stir welded joint between AA5754 and ultra-high strength steel in hot dip galvanized condition2014In: 10th Friction Stir Welding Symposium, Beijing, China, 2014, p. S2B-P5-Conference paper (Refereed)
  • 27.
    Ratanathavorn, Wallop
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Dissimilar joining between alumnium alloy AA6111 and thermoplastics using friction stir weldiing2015In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936Article in journal (Refereed)
  • 28.
    Ratanathavorn, Wallop
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Influence of zinc on intermetallic compounds formed in friction stir welding of AA5754 aluminium alloy to galvanised ultra-high strength steel2017In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936Article in journal (Refereed)
    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.

  • 29.
    Ratanathavorn, Wallop
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Joining of hybrid joints between thermoplastics and alumnium alloy by friction stir lap welding: a feasability study2014In: 10th Friction Stir Welding Symposioum, 2014, p. S6B-P4-Conference paper (Refereed)
  • 30.
    Rathanatavorn, Wallop
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Lindh-Ulmgren, Eva
    Swerea KIMAB.
    Åkermo, Malin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Burman, Magnus
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. mburman@kth.se.
    Hybrid joining of alumnium to thermoplastics with friction stir welding2012In: Proceedings Swedish production  Symposium 2012, 2012Conference paper (Refereed)
  • 31.
    Tolf, Erik
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Challenges in Resistance Welding of Ultra High Strength Steels2015Licentiate thesis, comprehensive summary (Other academic)
    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.

  • 32.
    Tolf, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Hedegård, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Surface breaking cracks in resistance spot welds ofdual-phase steels with electro and hot dip zinc coating2013In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 18, no 1, p. 25-31Article in journal (Refereed)
    Abstract [en]

    In normal production of resistance spot welded galvanised structures, it is difficult to completely avoid surface breaking cracks. Known key factors to cause cracking are zinc coating, electrode wear during subsequent welding and insufficient electrode cooling. In this report, an embrittlement mechanism was investigated that could be coupled to the galvanisation method for dual phase steels. With identical bulk material and weld parameters, the first 50 spot welds were crack free with electrogalvanised coating, while only 10 out of 50 were crack free with hot dip galvanised coating. Energy dispersive X-ray spectroscopy analysis of the worn electrode surfaces used for welding of the hot dip galvanised coating revealed areas of aluminium oxide. Since aluminium oxide is a very strong isolator, the electrical resistance will increase, which in turn is suggested to increase the surface temperature of the spot weld and thereby increase the probability for liquid metal embrittlement and surface cracks.

  • 33.
    Åslund, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Scania CV, Stockholm, Sweden.
    Melander, Arne
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Johansson, Krister
    Scania CV, Stockholm, Sweden.
    Haglund, Sven
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Welding Technology. KTH, Centres, XPRES, Excellence in production research. Swerea KIMAB, Stockholm, Sweden.
    Hosseini, Seyed B.
    Swerea IVF, Stockholm, Sweden.
    Influence of tempering on contact fatigue2009In: New challenges in heat treatment and surface engineering, conference in honour of Prof Božidar Liščić, Dubrovnik, Cavtat, Croatia 9-12 June 2009, 2009, p. 87-94Conference paper (Refereed)
    Abstract [en]

    Most components are tempered after heat treatment operations such as case hardening orinduction hardening. The common opinion is that the martensitic structure after heat treatmentis too brittle and tempering is necessary to increase toughness.

    Tempering is an additional operation which leads to increased costs by energy, handling,and investments. Eliminating tempering from the heat treatment process leads to increasedproductivity, energy savings, and lowered environmental impact.

    Two carburised steels, Ovako 253 and 20NiCrMo2 (AISI 8620, SS2506), were tested forcontact fatigue resistance in a roller to roller rig. The tested samples were characterised withrespect to amount of fatigue damage, residual stress, amount of retained austenite andhardness. The objective was to determine if tempering is always necessary after a heattreatment operation.

    The contact fatigue tests show that tempering results in lower contact fatigue resistance.

1 - 33 of 33
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