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  • 1.
    Adane, Tigist
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology. KTH.
    Towards a Generic Framework for the Performance Evaluation of Manufacturing Strategy: An Innovative Approach2018In: Towards a Generic Framework for the Performance Evaluation of Manufacturing Strategy: An Innovative Approach, Vol. 9, no 2, p. 131-156Article in journal (Refereed)
    Abstract [en]

    To be competitive in a manufacturing environment by providing optimal performance in terms of cost-effectiveness and swiftness of system changes, there is a need for flexible production systems based on a well-defined strategy. Companies are steadily looking for methodology to evaluate, improve and update the performance of manufacturing systems for processing operations. Implementation of an adequate strategy for these systems’ flexibility requires a deep understanding of the intricate interactions between the machining process parameters and the manufacturing system’s operational parameters. This paper proposes a framework/generic model for one of the most common metal cuttingoperations—the boring process of an engine block machining system. A system dynamics modelling approach is presented for modelling the structure of machining system parameters of the boring process, key performance parameters and their intrinsic relationships. The model is based on a case study performed in a company manufacturing engine blocks for heavy vehicles. The approach could allow for performance evaluation of an engine block manufacturing system condition. The presented model enables a basis for other similar processes and industries producing discrete parts.

  • 2.
    Adler, Jeanette
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Film Formation and Surface Tension Studies of Powder Coatings2005Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    In industrial use of paint systems a swift processing is crucial. Another very important issue is to improve the quality of the final coating. This report investigates the film formation process of powder coatings, specially the spreading of individual powder particles. The obtained results can be used to understand and control the film formation process. In this way the desired levelling can be achieved and thus the desired gloss or other surface characteristics that may be required. This means that the method could be used when evaluating different polymer and additive combinations that could be used to change film formation behaviour or curing time for powder coating systems to suit various substrates. It makes it possible to avoid and minimize different surface defects as orange peel or cratering in the powder coated film.

    We used a reflection optical microscope to better understand the film formation process and especially the spreading of a powder melt on surfaces with various surface energies. The obtained data were: the particle diameter, the area, area ratio and the contact angle of the powder particle as a function of time and temperature. This information can be used to derive the surface tension of any powder melt.

    In this report we evaluate the dependencies of temperature, heat rate and surface energy for powder coatings on different substrates. The method provides information that can be used to optimize the film formation of a specific powder coating/substrate combination. This method can be used to evaluate the powder spreading and levelling on different substrates from a surface tension point of view.

    We found, as expected, that the powder flows out on a hydrophilic surface and is inhibited by a hydrophobic. The increase of the area ratio on a hydrophilic surface was about five times as the initial area coverage and on a hydrophobic surface only two times the initial area coverage. The contact angle between the melted powder particle on the different surface types could be calculated. The melt surface tension could be calculated since three substrates surfaces with various surface energies were used. The melt surface tension was found to be about 18.5 mN/m.

  • 3.
    Aldén, Rickard
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Metallurgical investigation in weldability of Aluminium Silicon coated boron steel with different coating thickness.2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Hot-pressed aluminium and silicon coated boron steel is used in the car industry where high tensile strength is of great importance, such as in the safety cage of a car where deformation has to be kept to a minimum in case of a collision. After hot-pressing the AlSi-boron steel shows excellent properties with high tensile strength, minimal spring back and also shows good protection against corrosion. A thickness of the AlSi coating of 150 [g/m2] for AlSi coated boron steel is typically used by the car industry today. However the coating thickness would be desirable to be minimized to 80 [g/m2]. Welding of this boron steel with 80 [g/m2]have shown difficulties; and it’s not clear why this occurs.

    In this report the metallurgical properties of the different coating layers will be investigated, simulations with Thermocalc module Dictra will be used, SEM/EDS will be used to characterize phases in coating layers and correlate to weldability. Resistance spot welding tests will also be performed where the welding parameters of pre-pulse, pulse time, time in between pulses and current will be varied to achieve desirable weld plug diameter without expulsion. Hardness testing in form of micro Vickers will executed. The Materials used will be USIBOR® 1500, AS80 with four different annealing times and one sample of AS150.

  • 4.
    Alipour, Yousef
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Machining of CoCr28Mo62011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The machining process of Cobait-Chromium medical ailoys become a veryessential topic for research due to widening range of application. They aregeneraily used because of their high wear resistance, low corrosioncharacteristics and high fatigue strength. This project describes an investigationof chip formation during the machining of Cobalt-Chromium-Molybdenum highcarbon alloy. A quick stop device has been employed to investigate mechanismof chip formation through analyzing of shear zone and shear plane. Thicknessmeasurement of segments, surface conditions after finishing, lowest valley andhighest peak with three different cutting tool inserts were studied as weil.Moreover cutting force measurement at different cutting speeds, feeds and radialnoses were performed. Microstructure and hardness of work material before andafter machining has been studied. Tool life of inserts was evaluated bymeasuring flank wear.

    The consequences obtained from the study illuminated:

    1. For the constant cutting speed and nose radius flank wear increased whenthe feed increased.
    2. For the constant feed and nose radius, increase in the cutting speedlowered flank and crater wear.
    3. Cutting force increased with the increase in feed.
    4. Increase in cutting speed to 40 m/min raised cutting force. However afterthat cutting force decreased.
    5. Insert CNMG 120408-MF1 TS2000 with cutting data v~=70 m/min, ap= 3mm and f=0.1 mm seemed fit the best in base of lower flank and craterwear, almost lower cutting force and smoother finish roughness.
  • 5.
    Al-Saadi, Munir
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Microstructures and mechanical properties: Forged vs rolled bar in Sanmac 22052016In: Stainless Steel World, ISSN 1383-7184, Vol. 28, no July/August, p. 45-48Article in journal (Refereed)
  • 6.
    Al-Saadi, Munir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Sandberg, Fredrik
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Microstructure characterisation in alloy 8252018Conference paper (Refereed)
  • 7.
    Al-Saadi, Munir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Sandberg, Fredrik
    Comparative Study of Microstructures Evolution of Columnar and Equiaxed Grain Structurs in Alloy 825 after Hot Compression2018In: 3rd InternationalConference on Ingot Casting, Rolling and Forging, ICRF2018, in Stockholm, 16-19October, 2018, article id 114Conference paper (Refereed)
  • 8.
    Araya, Juan Manuel
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Economics and Management (Div.).
    Value Stream Mapping Adapted to High-Mix, Low-Volume Manufacturing Environments2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This research work proposes a new methodology for implementing Value Stream Mapping, in processes that feature a High-Mix, Low-Volume product base.   The opportunity for adapting the methodology singularly for these types of environments was identified because implementing Value Stream Mapping as proposed in Learning to See features several drawbacks when implemented in High-Mix, Low-Volume.  Although Value Stream Mapping has been proven to enhance many types of processes, its advantages are shrunk if they are implemented in High-Mix, Low-Volume processes.  

    High-Mix, Low-Volume processes are types of processes in which a high variety of finished goods are produced in relatively low amounts.  The high variety of finished goods causes several complications for the implementation of flow.  The difficulties that prevent the flow are the following:

    • The variance in the products: With hundreds, or sometimes thousands of possible finished goods, the number of products causes a non-repetitive process.
    • The variance in the routings:  All of the products that are produced can have completely different process routings, or order of stations it has to visit.  This makes the application of production lines quite difficult.
    • The variance in the cycle times for each process.  Each of the different products can have completely different capacity requirements at a specific machine, which limits the predictability of the process.

     

    This purpose of the thesis is to gather the best practices for controlling and improving High-Mix, Low-Volume processes and merge them with some innovative ideas to create an inclusive Value Stream Mapping methodology which is better fitted with the types of complications in High-Mix, Low-Volume environments.  In parallel, the methodology is tested with the company: Boston Scientific, in their Ureteral Stents manufacturing process.   The real-life experimentation will allow for the fine-tuning of the methodology, in order to truly create impact in the process.

     

     

     

     

  • 9. Arvidsson, M.
    et al.
    Ringstad, L.
    Skedung, L.
    Duvefelt, Kenneth
    KTH, School of Industrial Engineering and Management (ITM).
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Feeling fine - the effect of topography and friction on perceived roughness and slipperiness2017In: Biotribology, ISSN 2352-5738, Vol. 11, p. 92-101Article in journal (Refereed)
    Abstract [en]

    (1) Background. To design materials with specific haptic qualities, it is important to understand both the contribution of physical attributes from the surfaces of the materials and the perceptions that are involved in the haptic interaction. (2) Methods. A series of 16 wrinkled surfaces consisting of two similar materials of different elastic modulus and 8 different wrinkle wavelengths were characterized in terms of surface roughness and tactile friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using free magnitude estimation. Friction experiments were performed both by participants and by a trained experimenter with higher control. (3) Results and discussion. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 μm and roughness above 100 μm. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent. The friction is related to contact area between finger and material. Somewhat surprising was that the material with the higher elastic modulus was perceived as more slippery. A concluding finding was that the flat (high friction) reference surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction components.

  • 10.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Khurshid, Mansoor
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Cargotec Sweden AB.
    Ultimate Strength Capacity of Welded Joints in High Strength Steels2017In: 2nd International Conference on Structural Integrity, ICSI 2017 / [ed] Iacoviello, F Moreira, PMGP Tavares, PJS, Elsevier, 2017, Vol. 5, p. 1401-1408Conference paper (Refereed)
    Abstract [en]

    High strength steels are nowadays used in a wide range of weight lifting applications, e.g. spreaders and cranes, where there is a demand on lightweight design of these structures with increased structural performance where the welds become more sensitive to failure. This study focuses on investigating the influence of the mismatch in the yield strength of the weld filler material and the welds penetration depth on the ultimate strength capacity and failure modes of butt and fillet welded high strength steels of yield strength in the range of 350 960 MPa. The load carrying capacities of these mentioned joints are evaluated with experiments and compared with the estimations by finite element analysis (FEA), and design rules in Eurocode 3 and American Welding Society Code AWS D1.1. Fully penetrated joint with under-matched filler material is more ductile and the ultimate strength capacity of base plate can be achieved. It is observed that joints with under-matched filler material are more sensitive to penetration ratio. This influence is more pronounced in joints in S960 steel welded with under-matched filler material. It is also found that the design rules in Eurocode3 (valid for design of welded joints in steels of grade up to S700) can be extended to designing of welds in S960 steels using correlation factor of one.

  • 11.
    Bergsåker, B. Henric M.
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Zhou, Yushan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Possnert, G.
    Likonen, J.
    Pettersson, J.
    Koivuranta, S.
    Widdowson, A. M.
    Deep deuterium retention and Be/W mixing at tungsten coated surfaces in the JET divertor2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014061Article in journal (Refereed)
    Abstract [en]

    Surface samples from a full poloidal set of divertor tiles exposed in JET through operations 2010-2012 with ITER-like wall have been investigated using SEM, SIMS, ICP-AES analysis and micro beam nuclear reaction analysis (μ-NRA). Deposition of Be and retention of D is microscopically inhomogeneous. With careful overlaying of μ-NRA elemental maps with SEM images, it is possible to separate surface roughness effects from depth profiles at microscopically flat surface regions, without pits. With (3He, p) μ-NRA at 3-5 MeV beam energy the accessible depth for D analysis in W is about 9 μm, sufficient to access the W/Mo and Mo/W interfaces in the coatings and beyond, while for Be in W it is about 6 μm. In these conditions, at all plasma wetted surfaces, D was found throughout the whole accessible depth at concentrations in the range 0.2-0.7 at% in W. Deuterium was found to be preferentially trapped at the W/Mo and Mo/W interfaces. Comparison is made with SIMS profiling, which also shows significant D trapping at the W/Mo interface. Mixing of Be and W occurs mainly in deposited layers.

  • 12.
    Bhatti, Ayjwat Awais
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Computational weld mechanics: Towards simplified and cost effective FE simulations2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is the demand of the world’s ever increasing energy crisis to reduce fuel consumption wherever possible. One way of meeting this demand is by reducing the weight of a structure by replacing thick plates of low strength steel with thin plates of high strength steel in the structure. Fusion welding process is extensively used in the manufacturing industry, however, despite many advantages different problems such as weld defects, residual stresses and permanent distortions are associated with this process.

    Finite element (FE) method has proved itself as an alternative and acceptable tool for prediction of welding residual stresses and distortions. However, the highly nonlinear and transient nature of the welding process makes the FE simulation computationally intensive and complex. Thus, simplified and efficient welding simulations are required so that they can be applied to industrial scale problems.

    In this research work an alternative FE simulation approach for the assessment of welding residual stresses, called rapid dumping is developed. This approach proved to be efficient and predicted the residual stress with acceptable accuracy for different small scale welded joints. This approach was further implemented on a large scale welded structures along with other available approaches. It was found that the computational time involved in the welding simulations for large structures using rapid dumping approach can be reduced but at the cost of accuracy of the results.

    Furthermore, influence of thermo-mechanical material properties of different steel grades (S355-S960) on welding residual stresses and angular distortion in T-fillet joints is investigated. It is observed that for assessment of residual stresses, except yield stress, all of the thermo-mechanical properties can be considered as constant. For the prediction of angular distortions with acceptable accuracy, heat capacity, yield stress and thermal expansion should be employed as temperature dependent in the welding simulations.

    Finally, the influence of two different LTT (Low Transformation Temperature) weld filler material on residual stress state and fatigue strength was investigated. It was observed that a reduction in tensile residual stresses at the weld toe of the joint was observed. Furthermore, at higher R-ratio no significant increase in the fatigue strength was observed . However, at low R-ratio significant  increase in fatigue strength was observed.

  • 13. Cui, Y.
    et al.
    Liu, Y.
    Wang, Xi Vincent
    KTH, Centres, XPRES, Excellence in production research. KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Production Systems.
    Ding, W.
    Liu, Q.
    Research on measurement of cutting area temperature and its prediction model2018In: International Journal of Manufacturing Research, ISSN 1750-0591, Vol. 13, no 3, p. 209-226Article in journal (Refereed)
    Abstract [en]

    In this paper, the temperature measuring tool based on NiCr/NiSi thin film thermocouple is developed. 6,061 aluminium alloys is selected as the experiment object. Based on the cutting area temperature result during field test, the central composite design is utilised, which contains the parameters of cutting speed, feed rate and cutting depth. Regarding each parameter, three levels are selected and then the second-order regression equation between cutting area temperature and three cutting parameters is established. The data of experimental measurement corresponds well with the mathematical prediction, which confirms that the experimental and mathematical methods are valid in the research on cutting area temperature.

  • 14.
    Danielsson, Carl-Ola
    KTH, Superseded Departments, Mechanics.
    Continuous electropermutation using ion-exchange textile2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Increased levels of nitrate in ground water has made many wells unsuitable as sources for drinking water. In this thesis an ion-exchange assisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. A new ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an continuous electropermutation cell. The ion-exchange textile have a high permeability and provides faster ion-exchange kinetics compared to ion-exchange resins. The sheet shaped structure of the textile makes it easy to incorporate into the cell. A report on the development of a new electro-membrane module, capable of incorporating an ion-exchange textile spacer, is presented. A theoretical study of the flow field through the electro-membrane module was performed using two different 2-D models. The calculated flow distributions provided by different proposed module designs were compared and a prototype module was produced. The flow field obtained with the prototype cell was visualised in a experimental cell with a transparent plexiglass cover. A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are presented and volume averaged to give macro-homogeneous equations. The model equations are analysed and relevant simplifications are motivated and introduced. The dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment. An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained

  • 15. 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.

  • 16.
    Fu, Qilin
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology. Plasmatrix Materials AB.
    High dynamic stiffness nano-structured composites for vibration control: A Study of applications in joint interfaces and machining systems2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vibration control requires high dynamic stiffness in mechanical structures for a reliable performance under extreme conditions. Dynamic stiffness composes the parameters of stiffness (K) and damping (η) that are usually in a trade-off relationship. This thesis study aims to break the trade-off relationship.

    After identifying the underlying mechanism of damping in composite materials and joint interfaces, this thesis studies the deposition technique and physical characteristics of nano-structured HDS (high dynamic stiffness) composite thick-layer coatings. The HDS composite were created by enlarging the internal grain boundary surface area through reduced grain size in nano scale (≤ 40 nm). The deposition process utilizes a PECVD (Plasma Enhanced Chemical Vapour Deposition) method combined with the HiPIMS (High Power Impulse Magnetron Sputtering) technology. The HDS composite exhibited significantly higher surface hardness and higher elastic modulus compared to Poly(methyl methacrylate) (PMMA), yet similar damping property. The HDS composites successfully realized vibration control of cutting tools while applied in their clamping interfaces.

    Compression preload at essential joint interfaces was found to play a major role in stability of cutting processes and a method was provided for characterizing joint interface properties directly on assembled structures. The detailed analysis of a build-up structure showed that the vibrational mode energy is shifted by varying the joint interface’s compression preload. In a build-up structure, the location shift of vibration mode’s strain energy affects the dynamic responses together with the stiffness and damping properties of joint interfaces.

    The thesis demonstrates that it is possible to achieve high stiffness and high damping simultaneously in materials and structures. Analysis of the vibrational strain energy distribution was found essential for the success of vibration control.

  • 17.
    Gkotsis, P.
    et al.
    Cranfield University, UK.
    Leighton, G.
    Cranfield University, UK.
    Bhattacharyya, D.
    Cranfield University, UK.
    Wright, R.V
    Cranfield University, UK.
    Zhu, M.
    Cranfield University, UK.
    Kirby, P.B.
    Cranfield University, UK.
    Saharil, Farizah
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Göran, Stemme
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Crystal growth template removal: application to stress reduction in PZT microstructures2007In: Proc. International Symposium on Integrated Ferroelectrics 2007, 2007Conference paper (Refereed)
  • 18. Gu, H.
    et al.
    Wang, C.
    Gong, S.
    Mei, Y.
    Li, H.
    Ma, Weimin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Investigation on contact angle measurement methods and wettability transition of porous surfaces2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 292, p. 72-77Article in journal (Refereed)
    Abstract [en]

    Various solid surfaces (e.g., smooth titanium surface, smooth aluminum surface, polished copper surfaces, polished silver surfaces and porous copper surfaces) were prepared to quantify the reliability of half-angle algorithm and axisymmetric drop shape analysis (ADSA) algorithm for calculating contact angles. Besides, the effects of surface conditions on contact angle values were also investigated. The experimental results of 10 repeated tests for each surface show that both algorithms have good accuracy for an acute contact angle, while the ADSA algorithm is better than the half-angle algorithm for an obtuse contact angle. Furthermore, with the decrease of surface roughness, the contact angle increases but the standard deviation of contact angles by 10 repeated tests decreases. In addition, the porous layer on copper surface by electrochemical deposition shows a super hydrophilic property, but it could change to be super hydrophobic after exposed in ambient air for 24 h. Interestingly, the surface wettability reverses to be super hydrophilic again after it is immersed in water, and the inorganic contamination is the reason of formal change from the super hydrophilic status to the super hydrophobic status.

  • 19.
    Gürdür, Didem
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Vulgarakis Feljan, Aneta
    Ericsson Research, Sweden.
    El-khoury, Jad
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Mohalik, Swarup Kumar
    Ericsson Research, India.
    Badrinath, Ramamurthy
    Ericsson Research, India.
    Mujumdar, Anusha Pradeep
    Ericsson Research, India.
    Fersman, Elena
    Ericsson Research, Sweden.
    Knowledge Representation of Cyber-physical Systems for Monitoring Purpose2018In: 51st CIRP Conference on Manufacturing Systems, Elsevier, 2018, Vol. 72, p. 468-473Conference paper (Refereed)
    Abstract [en]

    Automated warehouses, as a form of cyber-physical systems (CPSs), require several components to work collaboratively to address the common business objectives of complex logistics systems. During the collaborative operations, a number of key performance indicators (KPI) can be monitored to understand the proficiency of the warehouse and control the operations and decisions. It is possible to drive and monitor these KPIs by looking at both the state of the warehouse components and the operations carried out by them. Therefore, it is necessary to represent this knowledge in an explicit and formally-specified data model and provide automated methods to derive the KPIs from the representation. In this paper, we implement a minimalistic data model for a subset of warehouse resources using linked data in order to monitor a few KPIs, namely sustainability, safety and performance. The applicability of the approach and the data model is illustrated through a use case. We demonstrate that it is possible to develop minimalistic data models through Open Services for Lifecycle Collaboration (OSLC) resource shapes which enables compatibility with the declarative and procedural knowledge of automated warehouse agents specified in Planning Domain Definition Language (PDDL).

  • 20.
    Hedberg, Yolanda S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Metal release from stainless steel in biological environments: A review2016In: Biointerphases, ISSN 1934-8630, E-ISSN 1559-4106, Vol. 11, no 1, article id 018901Article, review/survey (Refereed)
    Abstract [en]

    Due to its beneficial corrosion resistance, stainless steel is widely used in, e.g., biomedical applications, as surfaces in food contact, and for products intended to come into skin contact. Low levels of metals can be released from the stainless steel surface into solution, even for these highly corrosion resistant alloys. This needs to be considered in risk assessment and management. This review aims to compile the different metal release mechanisms that are relevant for stainless steel when used in different biological settings. These mechanisms include corrosion-induced metal release, dissolution of the surface oxide, friction-induced metal release, and their combinations. The influence of important physicochemical surface properties, different organic species and proteins in solution, and of biofilm formation on corrosion-induced metal release is discussed. Chemical and electrochemical dissolution mechanisms of the surface oxides of stainless steel are presented with a focus on protonation, complexation/ligand-induced dissolution, and reductive dissolution by applying a perspective on surface adsorption of complexing or reducing ligands and proteins. The influence of alloy composition, microstructure, route of manufacture, and surface finish on the metal release process is furthermore discussed as well as the chemical speciation of released metals. Typical metal release patterns are summarized.

  • 21. Herzog, Gerd
    et al.
    Benecke, Gunthard
    Buffet, Adeline
    Heidmann, Berit
    Perlich, Jan
    Risch, Johannes F.H.
    Santoro, Gonzalo
    Schwartzkopf, Matthias
    Yu, Shun
    Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85c, D-22607 Hamburg, Germany.
    Wurth, Wilfried
    Roth, Stephan V.
    In-situ GISAXS investigation of polystyrene nanoparticle spray deposition onto a silicon substrate2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 36, p. 11260-11266Article in journal (Refereed)
    Abstract [en]

    We investigated the spray deposition and subsequent self-assembly during drying of a polystyrene nanoparticle dispersion with in situ grazing incidence small-angle X-ray scattering at high time resolution. During the fast deposition of the dispersion and the subsequent evaporation of the solvent, different transient stages of nanoparticle assembly can be identified. In the first stage, the solvent starts to evaporate without ordering of the nanoparticles. During the second stage, large-scale structures imposed by the breakup of the liquid film are observable. In this stage, the solvent evaporates further and nanoparticle ordering starts. In the late third drying stage, the nanoparticles self-assemble into the final layer structure.

  • 22.
    Heydari, Golrokh
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tyrode, Eric
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Stenroos, Christian
    Koivuluoto, Heli
    Tuominen, Mikko
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ultralow ice adhesion on hydrophilic and molecularly smooth mica surfacesManuscript (preprint) (Other academic)
    Abstract [en]

    Despite much research on designing surfaces for combating icing, no permanent solution has been achievedusing solid materials. Inspired by the slippery surface of ice, attributed to the presence of a quasi-liquid layeracting as a natural lubricant, we hypothesize that flat hydrophilic surfaces with a hydration layer remaining inthe liquid-like state at the solid-ice interface could result in low ice adhesion. Utilizing temperature-controlledice adhesion measurements on the molecularly smooth basal plane of muscovite mica, we observed the lowestreported ice adhesion on solid surfaces down to temperatures of -35 ºC. The ice adhesion is dramatically higheron flat hydrophilic silica surfaces. We discuss these findings in terms of what is known about mica-water andmica-ice interactions.

  • 23.
    Heydari, Golrokh
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tyrode, Eric
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Visnevskij, Ceslav
    Makuska, Ricardas
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Temperature-Dependent Deicing Properties of ElectrostaticallyAnchored Branched Brush Layers of Poly(ethylene oxide)2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 17, p. 4194-4202Article in journal (Refereed)
    Abstract [en]

    The hydration water of hydrophilic polymersfreezes at subzero temperatures. The adsorption of suchpolymers will result in a hydrophilic surface layer that stronglybinds water. Provided this interfacial hydration water remainsliquidlike at subzero temperatures, its presence could possiblyreduce ice adhesion, in particular, if the liquidlike layer isthicker than or comparable to the surface roughness. Toexplore this idea, a diblock copolymer, having one branchedbottle-brush block of poly(ethylene oxide) and one linear cationic block, was electrostatically anchored on flat silica surfaces. Theshear ice adhesion strength on such polymer-coated surfaces was investigated down to −25 °C using a homebuilt device. Inaddition, the temperature dependence of the ice adhesion on surfaces coated with only the cationic block, only the branchedbottle-brush block, and with linear poly(ethylene oxide) was investigated. Significant ice adhesion reduction, in particular, attemperatures above −15 °C, was observed on silica surfaces coated with the electrostatically anchored diblock copolymer.Differential scanning calorimetry measurements on bulk polymer solutions demonstrate different thermal transitions of waterinteracting with branched and linear poly(ethylene oxide) (with hydration water melting points of about −18 and −10 °C,respectively). This difference is consistent with the low shear ice adhesion strength measured on surfaces carrying branchedbottle-brush structured poly(ethylene oxide) at −10 °C, whereas no significant adhesion reduction was obtained with linearpoly(ethylene oxide) at this temperature. We propose a lubrication effect of the hydration water bound to the branched bottlebrushstructured poly(ethylene oxide), which, in the bulk, does not freeze until −18 °C.

  • 24.
    Häggström, Daniel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Björklund, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Evaluation of synchronizer loading parameters and their ability to predict failure2018In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 9, p. 1093-1104Article in journal (Refereed)
    Abstract [en]

    Molybdenum coated gearbox synchronizers are tested in a mu-comp test rig under varying loading conditions until failure. Four different parameters used to describe the thermomechanical load are evaluated just before failure to compare their ability to predict failure. The parameters evaluated are the synchronized kinetic energy, the synchronization power, and the focal as well as the average surface temperature increase. The focal surface temperature increase as well as the average surface temperature increase is found to predict failure with relatively good accuracy. It is shown that there exists a threshold which divides the synchronizer into either a very long or a very short service life. Additionally, a method to determine the average surface temperature in the gearbox management system is proposed.

  • 25.
    Ji, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering. Harbin University of Science and Technology, China.
    Liu, X.
    Wang, Lihui
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Production Systems. Harbin University of Science and Technology, Harbin, China.
    Meng, Y.
    Wu, X.
    A study on geometry modelling of a ball-end mill with chamfered cutting edge2015In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 19, p. 205-211, article id 279Article in journal (Refereed)
    Abstract [en]

    This paper presents a geometry modelling approach to cross-section parameters of chamfered cutting edge on a ball-end mill of solid carbide (BEMSC). Both the cutting edge curve and the CR (chamfer in rake face) face models are derived. Based on the CR face model, a new method for CR face grinding path generation is proposed. By determining the relationship between the length and the angle parameters of the CR face equation, its grinding path can be derived. After solving the rake face equation using this method, its grinding path as well as the grinding paths of the LF (land on flank face) face and the second flank face can also be computed. The geometry model has been validated through a series of numerical simulations.

  • 26.
    Kaufmann, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Czumanski, Thomas
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Manufacturing process adaptation for integrated cost/weight optimisation of aircraft structures2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 2, p. 162-166(5)Article in journal (Refereed)
    Abstract [en]

    A methodology is developed that enables cost-efficient design of composite aircraft structures. In earlier work, a cost/weight optimisation framework was presented. This framework is here enhanced by a module that minimises the manufacturing cost in each iteration by adaptation of manufacturing parameters. The proposed framework is modular and applicable to a variety of parts and geometries. Commercially available software is used in all steps of theoptimisation. The framework extension is added to an existing cost/weight optimisation implementation and tested on an airliner centre wing box rear spar. Three optimisation runs are performed, and a low cost, an intermediate and a low weight design solution are found. The difference between the two extreme solutions is 4.4% in manufacturing cost and 9.7% in weight. Based on these optimisation trials, the effect of the introduced parameter adaptation module is analysed.

  • 27.
    Kohrs, Johnny
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Modell för planhetsstyrning i mångvalsarsverk2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Reversible cluster mills equipped with actuators for flatness control are used when cold rolling high-grade steel strip. In order to meet high customer demands in terms of flatness, it is important to maintain an effective flatness control during the rolling process. Examples of flatness errors affecting the quality of the strip are long edge, long center, quarter buckles and herringbone. The objective of this thesis was to evaluate the flatness control and devising a flatness model for shifting of tapered first intermediate rolls in the 20-high cluster mill KV77 at Sandvik Materials Technology in Sandviken. The flatness actuators in the mill are shifting of tapered first intermediate rolls, tilting of the upper cluster of rolls and backup roll bending due to saddle displacement. The project has involved both practical trials in the rolling mill and theoretical attempts with the calculation software Cluster. The flatness model was developed based on a regression analysis of process data from the mill.

    Conclusions concerning the flatness actuators effect on strip flatness could be drawn based on trial results. Backup roll bending alters the flatness of the strip with up to 20 I-units at the edges and 10 I-units at the center. Backup roll bending appears to be an inefficient flatness actuator in terms of reducing quarter buckles. Tilting of the upper cluster of rolls alters the flatness of the strip near the edges with 60 I-units and shifting of tapered first intermediate rolls alters the flatness of the strip near the edges with 100 I-units. Reducing long edges resulted in a long center and vice versa. The flatness model that was developed is able to predict a suitable shifting of tapered first intermediate rolls using rolling force, strip width, yield stress, front tension and back tension. The flatness model explained 78 % of the variation in shifting of tapered first intermediate rolls with a standard deviation of about 6 mm.

  • 28.
    Larberg, Ylva
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Åkermo, Malin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    On the interply friction of different generations of unidirectional prepreg materials2008In: Proceedings of 13th European Conference on Composite Materials (ECCM 13), 2008Conference paper (Refereed)
    Abstract [en]

    With the aim of reducing cost of prepreg composite components, manufacturing methods are developed and refined. An automatic tape laying machine can shorten the process cycle by stacking prepreg flat and thereafter allow for forming into desired shapes. Forming of stacked prepreg requires knowledge about the uncured properties of prepreg, such as viscosity of the matrix, intra- and interply deformation properties. This study focuses on the interply friction, i.e. the friction at the prepreg-prepreg interface, and how this affects the forming. The conclusions presented here show that the difference between prepreg material systems is significant. Further, it is concluded that the prepreg-prepreg friction is governed by a combination of Coulomb and hydrodynamic friction, where different mechanical phenomena dominate depending on the test conditions.

  • 29.
    Larberg, Ylva
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Åkermo, Malin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Norrby, Monica
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    On the in-plane deformability of cross-plied unidirectional prepreg2011In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, no 8, p. 929-939Article in journal (Refereed)
    Abstract [en]

    The work presented herein aims to characterise the in-plane properties of cross-plied unidirectional prepreg using the bias extension method. The study is focusing on carbon fibre/epoxy material systems and testing is performed at elevated temperatures to enhance formability. Using digital image correlation (DIC), the specimen deformation and fibre rotation is captured during tests. The study shows that the cross-plied unidirectional material deforms at different characteristic length scales as deformation continues: first seemingly continuous and later in form of bands. Further, the different type of prepreg materials investigated behaves differently; for one type the pin-jointed net theory fit well, enabling simple estimation of resulting fibre angle, while for another not. Different loading speed, temperatures and layup methods are investigated in order to pin-point its influence on the deformability.

  • 30.
    Liu, Jiewei
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Do-Quang, Minh
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Thermohydrodynamics of boiling in binary compressible fluids2015In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 92, no 4, article id 043017Article in journal (Refereed)
    Abstract [en]

    We numerically study the thermohydrodynamics of boiling for a CO2 + ethanol mixture on lyophilic and lyophobic surfaces in both closed and open systems, based on a diffuse interface model for a two-component system. The corresponding wetting boundary conditions for an isothermal system are proposed and verified in this paper. New phenomena due to the addition of another component, mainly the preferential evaporation of the more volatile component, are observed. In the open system and the closed system, the physical process shows very different characteristics. In the open system, except for the movement of the contact line, the qualitative features are rather similar for lyophobic and lyophilic surfaces. In the closed system, the vortices that are observed on a lyophobic surface are not seen on a lyophilic surface. More sophisticated wetting boundary conditions for nonisothermal, two-component systems might need to be further developed, taking into account the variations of density, temperature, and surface tension near the wall, while numerical results show that the boundary conditions proposed here also work well even in boiling, where the temperature is nonuniform.

  • 31.
    Liu, Xian-Li
    et al.
    Harbin Univ Sci & Technol, Harbin 150080, Heilongjiang, Peoples R China..
    Shi, Jin-Kui
    Harbin Univ Sci & Technol, Harbin 150080, Heilongjiang, Peoples R China..
    Ji, Wei
    Harbin Univ Sci & Technol, Harbin 150080, Heilongjiang, Peoples R China.;KTH Royal Inst Technol, S-10044 Stockholm, Sweden..
    Wang, Lihui
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Production Systems.
    Experimental Evaluation on Grinding Texture on Flank Face in Chamfer Milling of Stainless Steel2018In: CHINESE JOURNAL OF MECHANICAL ENGINEERING, ISSN 1000-9345, Vol. 31, no 1, article id UNSP 71Article in journal (Refereed)
    Abstract [en]

    The surface quality of chamfer milling of stainless steel is closed related to the products of 3C (Computer, Communication and Consumer electronics), where a cutter is a major part to achieve that. Targeting a high-quality cutter, an experimental evaluation is carried out on the influence of grinding texture of cutter flank face on surface quality. The mathematic models of chamfer cutter are established, and they are validated by a numerical simulation. Also the grinding data are generated by the models and tested by a grinding simulation for safety reasons. Then, a set of chamfer cutting tools are machined in a five-axis CNC grinding machine, and consist of five angles between the cutting edge and the grinding texture on the 1st flank faces, i.e., 0A degrees, 15A degrees, 30A degrees, 45A degrees and 60A degrees. Furthermore, the machined cutting tools are tested in a series of milling experiments of chamfer hole of stainless steel, where cutting forces and surface morphologies are measured and observed. The results show that the best state of both surface quality and cutting force is archived by the tool with 45A degrees grinding texture, which can provide a support for manufacturing of cutting tool used in chamfer milling.

  • 32.
    Lousada, Claudio Miguel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Soroka, Inna L.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Yagodzinskyy, Y.
    Tarakina, N. V.
    Todoshchenko, O.
    Hänninen, H.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gamma radiation induces hydrogen absorption by copper in water2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 24234Article in journal (Refereed)
    Abstract [en]

    One of the most intricate issues of nuclear power is the long-term safety of repositories for radioactive waste. These repositories can have an impact on future generations for a period of time orders of magnitude longer than any known civilization. Several countries have considered copper as an outer corrosion barrier for canisters containing spent nuclear fuel. Among the many processes that must be considered in the safety assessments, radiation induced processes constitute a key-component. Here we show that copper metal immersed in water uptakes considerable amounts of hydrogen when exposed to γ-radiation. Additionally we show that the amount of hydrogen absorbed by copper depends on the total dose of radiation. At a dose of 69 kGy the uptake of hydrogen by metallic copper is 7 orders of magnitude higher than when the absorption is driven by H2(g) at a pressure of 1 atm in a non-irradiated dry system. Moreover, irradiation of copper in water causes corrosion of the metal and the formation of a variety of surface cavities, nanoparticle deposits, and islands of needle-shaped crystals. Hence, radiation enhanced uptake of hydrogen by spent nuclear fuel encapsulating materials should be taken into account in the safety assessments of nuclear waste repositories.

  • 33.
    Lousada, Cláudio M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Fernandes, Ricardo M. F.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Tarakina, Nadezda V.
    Soroka, Inna L.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Synthesis of copper hydride (CuH) from CuCO3·Cu(OH)2 – a path to electrically conductive thin films of Cu2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 20, p. 6533-6543Article in journal (Refereed)
    Abstract [en]

    The most common synthesis methods for copper hydride (CuH) employ hard ligands that lead to the formation of considerable amounts of metallic Cu as side-product. Here we explore a synthesis method for CuH(s) through the reaction of CuCO3 center dot Cu(OH)(2)(s) with hypophosphorous acid (H3PO2) in solution, via the formation of the intermediate Cu(H2PO2)(2)(aq) complex. The reaction products were characterized with XRD, FTIR and SEM at different reaction times, and the kinetics of the transformation of Cu(H2PO2)(2)(aq) to CuH(s) were followed with NMR and are discussed. We show that our synthesis method provides a simple way for obtaining large amounts of CuH(s) even when the synthesis is performed in air. Compared to the classic Wurtz method, where CuSO4 is used as an initial source of Cu2+, our synthesis produces CuH particles with less metallic Cu side-product. We attribute this to the fact that our reaction medium is free from the hard SO42- ligand that can disproportionate Cu(I). We discuss a mechanism for the reaction based on the known reactivity of the reagents and intermediates involved. We explored the possibility of using CuH(s) for making electrically conductive films. Tests that employed water-dispersed CuH particles show that this compound can be reduced with H3PO2 leading to electrically conductive thin films of Cu. These films were made on regular office paper and were found to be Ohmic conductors even after several weeks of exposure to ambient conditions. The fact that the synthesis reported here produces large amounts of CuH particles in aqueous media, with very little impurities, and the fact that these can then be converted to a stable electrically conductive film can open up new applications for CuH such as for printing electrically conductive films or manufacturing surface coatings.

  • 34.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi. Zhengzhou Univ, Sch Mat Sci & Engn, Peoples R China.
    Sun, Yufu
    Yang, Yong
    Non-Vacuum Sintering Process of WC/W2C Reinforced Ni-Based Coating on Steel2016In: Metals and Materials International, ISSN 1598-9623, E-ISSN 2005-4149, Vol. 22, no 2, p. 311-318Article in journal (Refereed)
    Abstract [en]

    Ni-based composite coatings containing varied contents of tungsten carbides on low carbon steel were fabricated. Effects of sintering temperature and tungsten carbides contents on the surface, interface, microstructure and wear resistance of the coatings were investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Vickers microhardness tester, bulk hardness tester and pin-on-disc tribometer. The results indicated that with appropriate sintering temperature (1230 degrees C), smooth coating surfaces can be achieved. Favorable interfaces about 200 mu m can be got that both the chemical composition and property of the interfacial region showed gradual transitions from the substrates to the coatings. Microstructure of the coatings consists of tungsten carbides and M7C3/M23C6 in the matrix. With excessive sintering temperature, tungsten carbides tend to dissolve. Ni-based coatings containing tungsten carbides showed much higher level of bulk hardness and wear resistance than ISO Fe360A and ASTM 1566 steels. With increasing contents of tungsten carbides from 25% to 40%, bulk hardness of Ni-based coatings gradually increased. Ni-based coating with 35% tungsten carbides performed the best wear resistance.

  • 35. Maalouf, Maher
    et al.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Failure strength prediction of aluminum spot-welded joints using kernel ridge regression2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 91, no 9-12, p. 3717-3725Article in journal (Refereed)
    Abstract [en]

    The current paper presents an alternative method for failure strength prediction of spot-welded joints in aluminum, based on nonlinear regression analysis, namely, the kernel ridge regression method. Welding parameters such as electrode force, welding current, and welding time are studied in the experimental investigation to measure their effects on the nugget size and failure strength of the resistance spot welds. Coupons are manufactured and tensile tested and the results show that the welding current and time have the largest effect on the nugget size and the failure strength. The results of this study are compared to those of the least squares method and they indicate that the truncated-regularized kernel ridge regression algorithm significantly improves the coefficient of determination and reduces the mean squared error.

  • 36.
    Mahdavi Shahri, Meysam
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Fatigue Assessment of Friction Stir Welded Joints in Aluminium Profiles2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Friction stir welding (FSW) is a low heat input solid state welding technology. It is often used for fabrication of aluminium alloys in transportation applications including railway, shipbuilding, bridge structures and automotive components. In these applications the material is frequently subject to varying load conditions and fatigue failure is a critical issue. In most cases standard codes and fatigue guidelines for aluminium welded joints address only welded structures with conventional welding methods but not those with FSW procedure. In the scope of this thesis fatigue life assessment of friction stir welded components was performed using theoretical approaches along with finite element method (FEM). The further aim of this study was to generate a basis for standardization of fatigue assessment of friction stir welded joints.

    Friction stir welded hollow aluminium panels of alloy 6005A are investigated. The panels are used for train wall sides, train floors, deck and bridges. Each panel is made of several profiles that are joined with the friction stir welding method. Fatigue bending tests were performed for profiles in these panels. Fatigue cracks and failure appeared at notches in the profiles. With FEM simulations critical positions for crack initiation and failure were identified. The method of critical distance was used to analyse and estimate the fatigue life. It was shown that the failure location and fatigue limit could be predicted for both base metal and weld location. Choice of welding procedure (clamping condition) can significantly influence the fatigue life. It was shown that for some panels the critical distance method was not able to explain the failure in the weld. In this case fracture mechanics together with residual stress analysis were used successfully to predict the failure.

    Assuming homogeneous material properties throughout the weld and the base material, FEM analysis for T and overlap joints as well can provide a reasonable fatigue prediction. This suggests that the same assumption can be extended to complex components for failure analysis of the friction stir welded joints when using the critical distance method.

    Fatigue assessment of friction stir welded joints was also performed using standard codes Eurocode 9 and IIW. Fatigue curves of traditional fusion welded joints were used. The results are in reasonable agreement with experimental data and FEM predictions.

  • 37.
    Mahdavi Shahri, Meysam
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Osikowicz, Wojciech
    Sapa Technology.
    Critical distance method to estimate the fatigue life time of friction stirwelded profiles2012In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 37, p. 60-68Article in journal (Refereed)
    Abstract [en]

    The fatigue failure of friction stir (FS) welded aluminium panels of alloy 6005A has been analysed. Thesepanels are produced with two main joint geometries: namely half overlap and hourglass. Presence ofcrack like notches (interface between the welded work pieces) and blunt notches (corners and bendsin the base metal) have been studied with finite element method (FEM) stress analysis combined withthe critical distance method. It was shown that the failure location and fatigue limit could be predictedfor three of the four types of profiles considered. Choice of the welding procedure (clamping condition),however, can significantly influence the fatigue life and prediction accuracy. When different welding procedurewas used the weld failure was not reproduced by model and failure location was not predictedcorrectly. In this case fracture mechanics approach along with residual stress analysis has been used toanalyse the failure. It is also shown that local plastic deformation on the crack tip is induced by clampingresulting in tensile residual stresses at the crack tip. Taking stress intensity factor of the residual stressinto account, the position of the failure can be explained

  • 38.
    Mahdavi Shahri, Meysam
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Sandstöm, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Fatigue Strength of Friction Stir WeldedAluminium Profile for Train Car Application2008Conference paper (Refereed)
    Abstract [en]

    Friction stir welded aluminium alloys are used for many applications in transportation. In theseapplications the material is frequently subject to varying load conditions, making fatigue failure acritical issue. In the scope of this paper, the fatigue performance of friction stir welded profiles ofAl-alloy 6005A has been investigated. A profile that is used for railway car wall side panels waschosen. The profiles were joined together with the friction stir welding method at both sides ofthe profile. 3-point fatigue bending tests were performed for the profiles. Stress ranges givingfailure after 105 to 106 cycles with the stress ratio R=0.1 were used.With FEM simulations critical positions for crack initiation and failure were identified in the parentmetal. These positions were all at narrow radii in the profiles. In fact, the fatigue failures alwaysoccurred at these positions. The maximum stress varied somewhat between the positions. Inspite of this, the cracking and failure took place at six different positions indicating that the profilehad a balanced design.The maximum von Mises stress at the failure positions as determined with FEM was about 50%higher than the corresponding uniaxial fatigue data for the same number of cycles. Thissuggests that the cracks initiate at places with high stresses but propagate into areas with lowerstresses.The FSW joint was a lap-butt joint with a sharp notch (interface between the work pieces) next tothe weld nugget. Since both sides of the profile were welded, such sharp notches appeared onboth sides. In most profiles cracks initiated and propagated form the notch where the centre loadwas placed. However, failure never took place there, i.e. complete fracture was not observed.The direction in which the cracks propagated was perpendicular to the plane of the profiles andperpendicular to the maximum stress direction. On the opposite side to the load position nocracking was observed

  • 39.
    Mittal, Nitesh
    et al.
    Indian Institute of Technology, India.
    Deva, Dinesh
    Kumar, Rudra
    Sharma, Ashutosh
    Exceptionally robust and conductive superhydrophobic free-standing films of mesoporous carbon nanocapsule/polymer composite for multifunctional applications2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 93, no 8, p. 492-501Article in journal (Refereed)
    Abstract [en]

    A novel mesoporous carbon nanocapsule (MCC)/polyvinylidene fluoride (PVDF) polymer composite based free-standing film with multifunctional properties is fabricated by a facile solution approach that is appropriate for dip coating, brush-on and spray applications. The MCC/PVDF composite film exhibits superhydrophobic properties with a water contact angle of approximately 160° and a sliding angle of 5°. The films have a high thermal stability (up to 350 °C in oxidative atmosphere) and are also electrically conductive (tunable from ∼10−3 S m−1 to 10−2 S m−1). The superhydrophobicity is retained even in highly corrosive acidic and basic conditions (pH 1.29–13.54, concentrated HNO3 exposure and ammonium hydroxide solution), as well in a wide humidity range (35–83%). The mesoporous carbon containers (∼100 nm–1 μm size) also provide an interesting platform for encapsulating a variety of functional nanomaterials and activate release, thereby adding to the multi-functionality of the superhydrophobic conductive films of exceptional environmental stability, mechanical strength (∼0.1 GPa) and flexibility.

  • 40.
    Morin, Claes
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Utredning av risker och begränsningar vid användning av gasmetallbågsvetsning vid montage2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis work has evaluated the risks of getting lack of fusion during gas metal arc welding of single-bevel prepared T-joints. The work has been done at DEKRA Industrial AB that is specialized in certification, testing and inspection. The reason for this work is an earlier case where ultrasound testing indicated lack of fusion and lack of penetration was located in the major part of the weld joints in a construction. Those weld joints had been gas metal arc welded and had a single-bevel preparation.

    A literature study was done on the subject of weld arc theory and the cause of lack of fusion. Then four samples were welded trying to imitate the earlier case, two with a wide joint preparation and two with a narrow preparation. The samples were subjected to ultrasound testing and macroscopic analysis to evaluate the existence of lack of fusion and other defects.

    The literature study shows that lack of fusion appear as soon the weld arc miss the base material and the molten weld consumable solidify on unmelted material. One of the causes is a wrong pistol angle which will make the weld arc miss one of the joint walls. Also, another important parameter is the electrode stick-out. A too long stick-out generates a too cold process or a too large puddle of melted metal depending if the welding parameters are adjusted to compensate the stick-out. When welding with a single-bevel joint, there is a heightened risk of getting the described problems because of the bad accessibility.

    The results from the welding were that the narrow prepared joints were hard to weld with and get proper quality, with lack of penetration and lack of fusion. The conclusion from the welding and testing is that the risk of getting lack of fusion is high while welding narrow single-bevel prepared Tjoints.

  • 41.
    Natale, Lorenzo
    KTH, School of Chemical Science and Engineering (CHE).
    Optimization of liquid flow rate distribution in etching modules through numerical simulationsand experiments2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to simulate the liquid flow rate distribution in the etching modules and find the optimal setup in order to achieve a distribution as homogenous as possible. The commercial software Matlab 2015a has been employed for all the numerical simulations. The optimization has been carried out varying several parameters, i.e. spray cross sections of the nozzles, the oscillation parameters, the rotating angle of the nozzles within etching module 1 and the nozzle arrangement inside the modules. Furthermore, the optimization has been carried out separately along the two directions of the modules. The results achieved computationally have been validated via experimental procedures. During this study a specific experimental setup has been developed in order to be able to compare experimental and computational results. The validation process has shown that the computational method matches the experimental results to a good extent. The experimental liquid distribution in etching module 2 widely matches the simulations to a quantitative extent, while the one in etching module 1 provides the same qualitative but different quantitative results.

  • 42.
    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)
  • 43.
    Ratanathavorn, Wallop
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Development and evaluation of hybrid joining for metals to polymers using friction stir welding2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Combinations of different materials are increasingly used in the modern engineering structures. The driving forces of this trend are rising fuel costs, global warming, customer demands and strict emission standards. Engineers and industries are forced to improve fuel economy and cut emissions by introducing newly design engines and lightweighting of structural components. The use of lightweight materials in the structures has proved successful to solve these problems in many industries especially automobile and aerospace. However, industry still lacks knowledge how to manufacture components from polymeric materials in combination with metals where significant differences exist in properties.

    This thesis aims to demonstrate and generate the methodology and guidelines for hybrid joining of aluminium alloys to thermoplastics using friction stir welding. The developed technique was identified, optimized and evaluated from experimental data, metallography and mechanical characterization. The success of the technique is assessed by benchmarking with recent literatures.

    In this work, lap joints between aluminium alloys (AA5754, AA6111) and thermoplastics (PP, PPS) were produced by the friction stir welding technique. The specimens were joined with the friction stir welding tools under as-received conditions. Metallic chips were generated and merged with the molten thermoplastic to form a joint under the influence of the rotating and translating tool. The effects of process parameters such as rotational speed, translational speed and distance to backing were analyzed and discussed. The investigation found joint strength was dominated by mechanical interlocking between the stir zone and the aluminium sheet. The results also show that the joint strength is of the same order of magnitude as for other alternative joining techniques in the literature.

  • 44.
    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.

  • 45.
    Ratanathavorn, Wallop
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hybrid Joining of Aluminum to Thermoplastics with Friction Stir Welding2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 46.
    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.

  • 47.
    Repper, Elias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Carsbring, Amanda
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Defect formation in laser welded steels after use of corrosion protection coating2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

  • 48.
    Stenarson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tibblin, Fritjof
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Evaluation of phase relations in weld overlays of 316, 309MoL and SKWAM2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

  • 49.
    Strand, Henrik
    KTH, Superseded Departments, Machine Design.
    Apparatus for simulation of wear in heavy-duty oscillating journal bearings1999In: Proceedings OST Symposium on Machine DesignArticle in journal (Refereed)
  • 50.
    Strand, Henrik
    KTH, Superseded Departments, Machine Design.
    Boundary condictions in finite element calculations utilizig conformal contact of cylindrical bodies2000Conference paper (Refereed)
12 1 - 50 of 77
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