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  • 301.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shape verification aimed for manufacturing process control2011Inngår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 49, nr 3, s. 403-409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 µm. Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.

  • 302.
    Beronius, Alfred
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    An internal combustion engine intake system and its acoustic properties.2015Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Mufflers are a common measure for attenuation of noise in ducts, such as an intake system of an automotive vehicle. To compare different mufflers against each other it is vital to determine the acoustic properties of the system. There exist several approaches to determine the properties of muffler configurations, either analytical, numerical or by conducting measurements. Transmission loss predicts the properties of a muffler independent of source and termination and is a favorable choice when comparing different sets of muffler configurations against each other. Two methods, the decomposition method and the transfer matrix method are the two common approaches when evaluating the transmission loss of a muffler. In this thesis analytical, numerical and experimental approaches were applied to an expansion chamber and an internal intake system. The results were compared concluding that there was a great agreement between the numerical and analytical approach. The result from experimental measurements on the other hand deviated from the other two, indicating a dysfunctional test rig. The microphone spacing and microphone location was determined as the cause for the erroneous results. Further improvements of the test rig are needed to reassure a functional test setup. Only then can more complex analysis of mufflers, e.g. with an underlying mean flow, be utilized.

  • 303. Bertoni, Alessandro
    et al.
    Bertoni, Marco
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Isaksson, Ola
    Value visualization in Product Service Systems preliminary design2013Inngår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 53, s. 103-117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Emerging from a study in the European aerospace industry, this paper identifies a gap in the way value-related information is communicated to designers of hardware in the preliminary stages of Product Service System (PSS) design. To fit this gap a Lifecycle Value Representation Approach, named LiVReA, that uses color-coded 3D CAD models to enable value information to be translated into visual features, is presented. Such approach aims at enhancing designers' awareness of the value contribution of an early design concept on the overall PSS offer by complementing requirements-based information with criteria reflecting the fulfillment of customers and system value. The paper details the development of the approach, its underlying rationale, the results of preliminary validation activities and the potential for industrial application in the light of the currently available PSS representation tools

  • 304.
    Bertoni, Alessandro
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Bertoni, Marco
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Johansson, Christian
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Analysing the effects of value drivers and knowledge maturity in preliminary design decision-making.2015Inngår i: ICED 15, VOL 10: DESIGN INFORMATION AND KNOWLEDGE MANAGEMENT, Design Society , 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents the results of a three-days experiment to test the use of informationfrom a value assessment model and from a knowledge maturity scale in decisionmakingin preliminary design. A visual analogue scale was used to collect individualinformation from designers through questionnaires. Bivariate statistical analysis wasapplied to study the correlations between both the use of value drivers and knowledgematurity and the designers' awareness of the design problem to be addressed. Resultsshow that value drivers and knowledge maturity information increase the decisionmakers’ awareness of (1) the different perceptions of design team members about theneeds to be satisfied and (2) the technical solution to be developed in the productconcept under consideration.

  • 305.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Bertoni, Alessandro
    Broeze, Henk
    Dubourg, Gilles
    Sundhurst, Clive
    Using 3D CAD models for value visualization: an approach with SIEMENS NX HD3D Visual Reporting2014Inngår i: Computer-Aided Design and Applications, ISSN 1686-4360, Vol. 11, nr 3, s. 284-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent literature in Systems Engineering has suggested the use of “value” to drive decision-making activities during preliminary design, in particular when choosing technologies and components for a complex system. However, to correctly evaluate design trade-offs, a visual link has to be established between the results of the value model and a product shape/geometry. This paper proposes the use of color-coded 3D CAD models to support the visualization of value analysis results in a Stage-Gate® process. The approach has been developed and exemplified within a case study related to the design of an aero-engine component, and has been demonstrated using SIEMENS NX HD3D Visual Reporting. The results of verification activities conducted in a laboratory setting show that the use of color-coded 3D CAD models increases the decision makers’ awareness of value-related information in a Stage-Gate process.

  • 306.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Bertoni, Alessandro
    Isaksson, Ola
    Amnell, Henrik
    Johansson, Christian
    Value-oriented concept selection in aero-engine sub-systems design: the EVOKE approach2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Value Driven Design methodologies extend the Requirements Management and Systems Engineering processes to reduce time and costs needed to identify the right solution direction to be pursued in detailed design. Emerging from the findings of an EU FP7 research project, the paper describes an approach, named EVOKE, that uses value as a basis for preliminary concept selection in the design of system components. EVOKE takes as input a list of value dimensions and drivers communicated by the system integrators, together with information about the high-level engineering characteristics of a candidate design, to enable early stage value analysis to be executed the by sub-system manufacturers. The approach and its technological enablers are described in detail through the use of a case study related to the design of new intermediate compressor case for turbofan engines.

  • 307.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Bertoni, Alessandro
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Johansson, Christian
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Knowledge Enabled Engineering2015Inngår i: International Workshop of Advanced Manufacturing and Automation, Trans Tech Publications Inc., 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The development of complex product-service combinations challenges the existing practices for engineering knowledge management. The objective of the paper is to highlight how such practices need to change to meet the engineers’ demand for knowledge when developing “functions” instead of merely hardware. It further proposes Knowledge Enabled Engineering (KEE) as an umbrella term that collects engineering knowledge management methods and tools inspired by the second wave of knowledge management, and that are aimed to meet needs of today’s modern knowledge workers in engineering organizations. The current state of readiness of these approaches is eventually described together with results from verification and validation activities.

  • 308.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Eres, Hakki
    Scanlan, Jim
    Co-creation in complex supply chains: the benefits of a Value driven Design approach2014Inngår i: Product Development in the Socio-sphere: Game Changing Paradigms for 21st Century Breakthrough Product Development and Innovation / [ed] Schaefer, Dirk, Switzerland: Springer International Publishing , 2014Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In the last decade, as the manufacturing companies have reconsidered the overall concept of goods production, their focus shifted from developing ‘products’ to ‘solutions’. In complex supply chains, the combination of products and services that maximize customers’ and stakeholders’ value can be identified only if manufacturers improve their ability to co-create, establishing more interactive relationships with end users, clients and sub-contractors. Methodologies for Value Driven Design (VDD) are emerging as enablers for cross-functional and cross-organizational knowledge sharing, reinforcing early stages design iterations to emphasize the maturation of the requirements across supply chain levels. This chapter highlights the uptake of VDD in a traditionally protective domain, such as the aerospace sector. It describes methods and tools for value assessment, and points toward the most relevant initiatives in this domain. Eventually, it discusses areas of further research to promote the effective use of the VDD methodology while designing complex engineering systems.

  • 309.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Hallstedt, Sophie
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för strategisk hållbar utveckling.
    Isaksson, Ola
    Value assessment of sustainability hotspots in conceptual design: an aerospace study.2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Nowadays, when designing structural aero-engine components, the engineering team does not only deal with aerodynamics and structural mechanics criteria. Rather, it needs to make more informed decisions based on the value and sustainability contribution of a design concept. This paper proposes a novel approach that combines qualitative sustainability assessment techniques, which are Environmental Impact Assessment (EIA) and Strategic Sustainability Assessment (SSA), with Net Present Value (NPV) analysis to facilitate early stage decision-making in design. A case study, related to the development of a new high-temperature aero-engine component, illustrates how EIA and SSA identify sustainability hotspots for a new product technology, and how NPV is used to assess alternative solution strategies within the hotspot. Within the studied case, the milling process was identified as a sustainability hotspot, therefore two process options - Electro-Chemical Milling (ECM) and Mechanical Milling (MM) - where benchmarked by calculating their NPV in alternative future scenarios, featuring different market and regulatory assumptions. The approach and its constituting models have been preliminarily verified with designers and process owners in co-located industrial workshops.

  • 310. Bertoni, Marco
    et al.
    Johansson, Christian
    Larsson, Tobias
    Methods and Tools for Knowledge Sharing in Product Development2011Inngår i: Innovation in Product Design: From CAD to Virtual Prototyping / [ed] Bordegoni, Monica; Rizzi, Caterina, New York: Springer , 2011, s. 37-53Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The emerging industrial business partnerships, which feature cross-functional and cross-company development efforts, raise the barrier for the establishment of effective knowledge sharing practices in the larger organization. This chapter aims to highlight the role of knowledge as a key enabler for effective engineering activities in the light of such emerging enterprise collaboration models. Knowledge Enabled Engineering (KEE) is presented as an approach to enhance the extended organization’s capability to establish effective collaboration among its parts, in spite of different organizational structures, technologies or processes. KEE is analysed in its constituent parts, highlighting areas, methods and tools that are particularly interesting for leveraging companies’ knowledge sharing capabilities.

  • 311. Bertoni, Marco
    et al.
    Larsson, Andreas
    Ericson, Åsa
    Chirumalla, Koteshwar
    Larsson, Tobias
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Isaksson, Ola
    Randall, Dave
    The rise of social product development2012Inngår i: International Journal of Networking and Virtual Organisations, ISSN 1470-9503, Vol. 11, nr 2, s. 188-207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the paper is to discuss the rising potential of social software to increase the knowledge management capabilities of virtual product development teams. It presents six fundamental transitions, elaborated from the empirical findings, which justify the rise of a more bottom-up, social creation and sharing of engineering knowledge in the virtual organisation. The study suggests that traditional engineering knowledge management approaches alone are not sufficient to support development activities in the virtual organisation, and that such teams display an increasing demand for social, comparatively lightweight and remixable platforms for bottom-up, social creation and sharing of knowledge.

  • 312.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Quan, Chenggen
    National University of Singapore.
    Tay, Cho Jui
    National University of Singapore.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Simultaneous measurement of translation and tilt using digital speckle photography2010Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 49, nr 18, s. 3573-3579Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Michelson-type digital speckle photographic system has been proposed in which one light beam produces a Fourier transform and another beam produces an image at a recording plane, without interfering between themselves. Because the optical Fourier transform is insensitive to translation and the imaging technique is insensitive to tilt, the proposed system is able to simultaneously and independently determine both surface tilt and translation by two separate recordings, one before and another after the surface motion, without the need to obtain solutions for simultaneous equations. Experimental results are presented to verify the theoretical analysis.

  • 313.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Tay, C.J.
    National University of Singapore.
    Quan, C.
    National University of Singapore.
    Niu, H.
    National University of Singapore.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Two wavelength simultaneous DSPI and DSP for 3D displacement field measurements2011Inngår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, nr 10-11, s. 2437-2440Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel optical system is proposed that implements digital speckle pattern interferometry (DSPI) and digital speckle photography (DSP) simultaneously using two wavelength illumination of an object for simultaneous measurement of all three components of the displacement vector field. A collimated red light illuminates both the object and a reference surface in a DSPI configuration which is sensitive to out-of-plane displacement field while a blue light illuminates the object in a DSP configuration which is sensitive to in-plane displacement fields. A color 3-CCD camera records the red and blue lights individually through its red and blue channels, respectively. Two reference images and one image in the deformed state of the object are required for quantitative measurement. Experimental results are presented to validate the system.

  • 314.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsmo, S.P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Consideration of X-ray microtomography to quantitatively determine the size distribution of bubble cavities in iron ore pellets2013Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, s. 312-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray microtomography data of iron ore green pellets of approx. 12 mm in diameter were recorded using a commercial instrument. The reconstructed volume after thresholding represented a unique dataset consisting of a three-dimensional distribution of equiaxed objects corresponding to bubble cavities. This dataset was used to successfully validate a stereological method to determine the size distribution of spherical objects dispersed in a volume. This was achieved by investigating only a few cross-sectional images of this volume and measuring the profiles left by these objects in the cross-sectional images. Excellent agreement was observed between the size distribution of the bubble cavities obtained by directly classifying their size in the reconstructed volume and that estimated by applying the aforementioned stereological method to eight cross-sectional images of the reconstructed volume. Subsequently, we discuss the possibility of calibrating X-ray tomography data quantitatively using the size distribution of the bubble cavities as a figure of merit and the results obtained by applying the stereological method to SEM images as reference data. This was justified by considering the validity of the stereological method demonstrated by tomography, the accurate thresholding made possible by back-scattered electron imaging and the solid reproducibility of the results obtained by SEM. Using different threshold values for binarization of the X-ray microtomography data and comparing the results to those obtained by SEM, we found that X-ray microtomography can be used after proper calibration against SEM data to measure the total porosity of the bubble cavities but can only provide a rough estimate of the median diameter because of the limited resolution achieved in this study.

  • 315.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Alfredsson, K. Svante
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Carlberger, Thomas
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Adhesive Tapes; Cohesive Laws for a Soft Layer2014Inngår i: Procedia Materials Science, ISSN 2211-8128, Vol. 3, s. 1389-1393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For adhesive tapes, the strain before fracture often exceeds 500%. Although the maximum stresses are quite modest the high strains to fracture result in impressive fracture energy. Due to hydrostatic stress the fracture process often starts by nucleation of microscopic cracks inside the layer. The final crack path is usually close to one of the adherends.

    Repeated experiments are performed both with DCB-specimens and butt-joints. The used adhesive tape is an acrylic foam tape with a thickness of 1.1 mm and a width of 19 mm. The geometry of the specimen is adapted to the properties of the soft layer. For the DCB-specimen this implies that the length of the specimen is about 1 m. The evaluated cohesive laws from the DCB- specimens give a fracture energy of 2 kN/m and a maximum stress about 0.5 MPa. For the butt-joints, the evaluated cohesive law corresponds well to the results from the DCB-experiments. However, the strain to fracture is slightly smaller. The stress in these specimens is distributed over a larger area and a nucleated crack rapidly crosses the load bearing area and fails the joint prematurely. For both kinds of experiments the evaluated cohesive laws show a small linear part. After this part there is an almost linear strain-hardening phase until fracture.

  • 316.
    Biel, Anders
    et al.
    Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Cohesive zone modelling of nucleation, growth and coalesce of cavities2017Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 204, nr 2, s. 159-174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The stress-deformation relation i.e. cohesive law representing the fracture process in an almost incompressible adhesive tape is measured using the double cantilever beam specimen. As in many ductile materials, the fracture process of the tape involves nucleation, growth and coalesce of cavities. This process is studied carefully by exploiting the transparency of the used materials and the inherent stability of the specimen configuration. Utilising the path independence of the J -integral, the cohesive law is measured. The law is compared to the results of butt-joint tests. The law contains two stress peaks—the first is associated with nucleation of cavities at a stress level conforming to predictions of void nucleation in rubber elasticity. The second stress peak is associated with fracture of stretched walls between fully-grown cavities. After this second peak, a macroscopic crack is formed. The tape suffers at this stage an engineering strain of about 800%. A numerical analysis with the determined cohesive law recreates the global specimen behaviour.

  • 317.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Strength and toughness in shear of constrained layers2018Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 138, s. 50-63Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Confined layers may fracture in shear. This occurs, for example in adhesive joints and composite materials. A common mechanism for shear fracture is the formation of shear hackles associated with an expansion of the layer. This makes shear toughness and strength depend on the constraint of the expansion. By constraining the expansion using external loading in experiments, the expansion is reduced but not totally inhibited. The experiments are evaluated using the path independent properties of the J-integral. It is shown that the shear toughness increases for the more constrained case. Thus, from a strength analysis perspective, ignoring the expansion leads to a conservative estimate of the fracture properties. Extrapolation of the evaluated properties to totally inhibited expansions gives the traction separation relation and the fracture toughness for a layer in simple shear.

  • 318.
    Biju, Dona
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära.
    A parametric study of oil-jet lubrication in gear wheels2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A parametric study of oil-jet lubrication in gear wheels is conducted using Computational Fluid Dynamics (CFD) to study the effect of the different design parameters on the cooling performance in a gearbox. Flow in oil jet lubrication is found to be complex with the formation of oil ligaments and droplets. Various hole radii of 1.5, 2 and 2.5 mm along with five oil velocities is analyzed and it is found that at lower volumetric rates, velocity has more effect on the cooling and at higher volumetric rates, hole size has more effect on the cooling. At higher velocities, the heat transfer is much greater than the actual heat production in the gear wheel, hence these velocity ratios are considered less suitable for jet lubrication. At low velocity ratios of below 2, the oil doesn’t fully impinge the gear bottom land and the sides leading to low cooling. Based on the cooling, impingement length and amount of oil lost to the casing surface, 2 mm hole with a velocity ratio of 2.225 is selected for a successful oil jet lubrication. Varying the inlet position in X, Y and Z directions (horizontal, vertical and lateral respectively) is found to have no improvement on the cooling. Making the oil jet hit the gear wheel surface at an angle is found to increase the cooling. Analysis with the use of a pipe to supply oil was conducted with circular and square inlet and it was found that the heat transfer decreases in both cases due to the splitting of oil jet caused by the combination of the effects of high pressure from the pipe and vorticity in the air field. A method has been developed for two gear analysis using overset meshes which can be used for further studies of jet lubrication in multi-gear systems. Single inlet is found to be better for cooling two gear wheels as it would require a reduced volumetric flow rate compared to double inlets. Oil system requirements for jet lubrication was studied and it was concluded that larger pumps have to be used to provide the high volumetric rates and highly pressurized oil required. On comparing the experimental losses from dip lubrication and the analytical losses for jet lubrication, dip lubrication is found to have lesser loses and more suitable for this case. Good quality lubrication would reduce the fuel consumption and also increase the longevity of gearboxes and hence more research into analyzing alternate lubrication systems can be carried out using the results from this thesis.

  • 319.
    Bilen Oytun, Peksel
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Advanced Model of Acoustic Trim; Effect on NTF Accuracy2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 320. Birgersson, F.
    et al.
    Finnveden, Svante
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    A spectral super element for modelling of plate vibration. Part 2: turbulence excitation2005Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 287, nr 02-jan, s. 315-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the accompanying paper, the suitability of a spectral super element to predict the response to point force excitation, was demonstrated. This paper expands the element formulation to also include distributed forces, which is useful when studying distributed excitation. First the sensitivity function, i.e. the structural response to a travelling pressure wave, is found. This sensitivity function and a wavenumber frequency description of the wall pressure are then used to predict the response of a turbulence excited panel in a numerically efficient way. The predictions were validated by a conventional finite element method and also compared to measurements.

  • 321. Birgersson, F.
    et al.
    Finnveden, Svante
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Nilsson, C. M.
    A spectral super element for modelling of plate vibration. Part 1: general theory2005Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 287, nr 02-jan, s. 297-314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamic response of vibrating structures is studied with a proposed merger of the standard finite element method with the more computationally efficient spectral finite element method. First a plate structure is modelled with a newly developed spectral super element. Then this element is coupled to other parts that can have a more complex geometry and are modelled entirely with conventional finite elements. Some numerical examples are given to illustrate and validate the developed method and studies of numerical stability are also presented. In an accompanying paper the predicted and measured response of a turbulence excited aircraft panel are compared.

  • 322.
    Birgersson, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Ferguson, Neil S
    Application of the spectral finite element method to turbulent boundary layer induced vibrations of plates2003Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 259, s. 873-891Artikkel i tidsskrift (Fagfellevurdert)
  • 323.
    Bissal, Ara
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Salinas, Ener
    Magnusson, Jesper
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Engdahl, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    On the Design of a Linear Composite Magnetic Damper2015Inngår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 51, nr 11, artikkel-id 8003305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-voltage direct current (HVdc) breakers are the key components in the realization of multiterminal HVdc grids. In the presence of fault current, these breakers should be able to deliver impulsive forces to swiftly open the metallic contacts. After the acceleration phase, the moving armature should be decelerated using controllable forces to avoid plastically deforming fragile components integrated in the system. In this paper, finite-element method-based simulation models, complimented with small-scale and large-scale experimental prototypes, were utilized to benchmark different damping topologies. It was found that a Halbach-based configuration can deliver a damping force that is almost two and a half times larger than its sequel. Its sequel, composed of vertically stacked oppositely oriented magnets, is easier to assemble and is also capable of generating a considerable damping force. Finally, it has been shown that both these schemes, inserted in a composite tube, have a potential to be used as dampers in HVdc breakers.

  • 324. Bjerkén, Christina
    et al.
    Kao-Walter, Sharon
    Ståhle, Per
    Fracture Mechanisms of a Thin Elastic Plastic Laminate2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centre cracked panel test geometry is used. Each of the layers forming the laminate is also tested separately. The result is compared with the measured fracture strength of the individual layers. It is observed that the load carrying capacity increases dramatically for the laminate. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at small nominal strain. The toughness compares well with the accumulated toughness of all involved layers. Possible fracture of the interface between the layers is discussed.

  • 325.
    Bjurhager, Ingela
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Gamstedt, E. KristoferUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Predicting creep rate in archeological wood from theVasa ship – a first appraoch2012Konferanseproceedings (Fagfellevurdert)
  • 326.
    Bjurhager, Ingela
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Gamstedt, Kristofer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Keunecke, Daniel
    Niemz, Peter
    Berglund, Lars A.
    Mechanical performance of yew (Taxus baccata L.) from a longbow perspective2013Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, nr 7, s. 763-770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Yew (Taxus baccata L.) longbow was the preferred weapon in the Middle Ages until the emergence of guns. In this study, the tensile, compression, and bending properties of yew were investigated. The advantage of yew over the other species in the study was also confirmed by a simple beam model. The superior toughness of yew has the effect that a yew longbow has a higher range compared with bows made from other species. Unexpectedly, the mechanical performance of a bow made from yew is influenced by the juvenile-to-mature wood ratio rather than by the heartwood-to-sapwood ratio. A yew bow is predicted to have maximized performance at a juvenile wood content of 30-50%, and located at the concave side (the compressive side facing the bowyer). Here, the stiffness and yield stress in compression should be as high as possible.

  • 327.
    Bjurhager, Ingela
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Vorobyev, AlexeyUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.van Dijk, NicoUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.Gamstedt, E. KristoferUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.Ahlgren, AndersOlofsson, Magnus
    Investigation of time-dependent deformation of wood from the warship Vasa2013Konferanseproceedings (Fagfellevurdert)
  • 328.
    Blanchard, Pierre
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Residual stresses and indentation.2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The correlatioin between residual stresses and the global properties from an indentation test, i.e. hardness and size of the contact area, has been studied frequently in recent years. The investigations presented have been based on experimental, theoretical and numerical methods and as a result, the basic features of the problem are fairly well understood in the case of residual equi-biaxial surface stresses. The more general case, when the principal surface stresses are not necessarily equi-biaxial, has received nuch less attention and it is therefore the aim of the present study to remedy this shortcoming. In doing so, qualitative results are of immediate interest in this initial study but possible ways of quantitative descriptions are also discussed for future purposes. The present analysis is based on numerical methods and in particular the finite element method (FEM) is relied upon. Classical Mises elastoplastic material behavior is assumed throughout the investigation.

  • 329.
    Blanco, Blas
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Development of new techniques for the numerical modelling of railway track dynamics. Application to rolling noise assessment2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The numerical modelling is widely employed for the prediction of the railway track dynamic behaviour, which is of utmost importance for the characterisation of the undesired medium-high frequency phenomena, such as corrugation, wheel-out-of-roundness and noise emission. This study is devoted to the improvement of railway track numerical modelling, the efficient resolution of the problem in the time domain and the assessment of rolling noise for different approaches of the track modelling.

    Regarding the enhancement of the railway track numerical modelling, two main core ideas have led the development of this task. On the one hand, the rail modelling, and on the other hand, the characterisation of the finite length nature of track supports. The proposals of this work include two basic premises, accuracy and computational efficiency.

    Firstly, the study makes use of Timoshenko beam theory for the numerical description of the rail. However, the conventional Timoshenko finite element involves drawbacks for the description of the rail dynamic behaviour and the calculation of the wheel-rail interaction in the time domain. These problems are addressed by improving the finite element formulation, which is based on the description of its local displacements.

    Secondly, the versatility of numerical methods is exploited to develop a distributed model of support. It substitutes the usual concentrated model, which entails overestimation of the periodicity effects and disruption of the wheel-rail interaction in the time domain.

    Thirdly, the advantages of the formulation of numerical models in the frequency domain are explored focusing on the ability to fairly describe the sleeper dynamics, the enhancement of the model boundaries and the realistic modelling of the track components dissipative behaviour. Moreover, the frequency domain response can be used to obtain the wheel-rail interaction in the time domain efficiently, by means of the moving Green's function.

    Lastly, this work deals with the assessment of rolling noise, in which particular emphasis is made on the influence of track dynamics in the noise prediction. At this regard, a methodology is proposed to account for the track periodicity, load speed and finite length of supports.

  • 330.
    Blanco, Blas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. University of Navarra, Spain.
    Alonso, A.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Gil-Negrete, N.
    Gimenez, J. G.
    Distributed support modelling for vertical track dynamic analysis2018Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 56, nr 4, s. 529-552Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The finite length nature of rail-pad supports is characterised by a Timoshenko beam element formulation over an elastic foundation, giving rise to the distributed support element. The new element is integrated into a vertical track model, which is solved in frequency and time domain. The developed formulation is obtained by solving the governing equations of a Timoshenko beam for this particular case. The interaction between sleeper and rail via the elastic connection is considered in an analytical, compact and efficient way. The modelling technique results in realistic amplitudes of the pinned-pinned' vibration mode and, additionally, it leads to a smooth evolution of the contact force temporal response and to reduced amplitudes of the rail vertical oscillation, as compared to the results from concentrated support models. Simulations are performed for both parametric and sinusoidal roughness excitation. The model of support proposed here is compared with a previous finite length model developed by other authors, coming to the conclusion that the proposed model gives accurate results at a reduced computational cost.

  • 331.
    Blom, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    A non-linear constitutive audio frequency magneto-sensitive rubber model including amplitude, frequency and magnetic field dependence.2011Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 330, nr 5, s. 947-954Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel constitutive model of magneto-sensitive rubber in the audible frequency range is presented. Characteristics inherent to magneto-sensitive rubber within this dynamic regime are defined: magnetic sensitivity, amplitude dependence, elasticity and viscoelasticity. Prior to creating the model assumptions based on experimental observations concerning these components are formulated. The first observation is that not only does the rubber display a strong amplitude dependence even for small strains, but also the magnetic sensitivity is strongly amplitude dependent. The second and third are, respectively, that the elastic component is magneto-sensitive, whereas the viscoelastic dependence on magnetic induction appears to be small. Thus, the model is developed from these assumptions and parameters are optimized with respect to experimental values for one case and subsequently validated for others; a very good agreement is obtained.

  • 332.
    Blom, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Amplitude and frequency dependence of magneto-sensitive rubber in a wide frequency range2005Inngår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 24, nr 5, s. 656-662Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two new aspects of the dynamic behaviour in the audible frequency range of magneto-sensitive (MS) rubber are highlighted: the existence of an amplitude dependence of the shear modulus - referred to as the Fletcher-Gent effect - for even small displacements, and the appearance of large MS effects. In order to illustrate these two features, results are presented of measurements performed in the audible frequency range on two different kinds of rubber: silicone and natural rubber with a respective iron particle volume concentration of 33%. The particles used are of irregular shape and randomly distributed within the rubber. An external magnetic field of 0-0.8 T is applied. Both kinds of rubber are found to be strongly amplitude dependent and, furthermore, displaying large responses to externally applied magnetic fields - a maximum of 115%. Also included are graphs of measurements on silicone and natural rubber devoid of iron particles. Those results support the conclusion that introducing iron particles in the rubber gives rise to a strong, non-negligible, amplitude dependence in the entire frequency range.

  • 333.
    Blom, Peter
    et al.
    KTH, Tidigare Institutioner, Farkostteknik.
    Kari, Leif
    KTH, Tidigare Institutioner, Farkostteknik.
    Magneto-rheological rubber isolators in the audible frequency range2004Inngår i: Nordic Vibration Research, 2004Konferansepaper (Annet vitenskapelig)
  • 334.
    Blom, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Magneto-sensitive rubber in the audible frequency range2005Inngår i: CONSTITUTIVE MODELS FOR RUBBER IV / [ed] Per-Erik Austrell, Leif Kari, London: Taylor & Francis, 2005Konferansepaper (Fagfellevurdert)
  • 335.
    Blom, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Smart audio frequency energy flow control by magneto-sensitive rubber isolators2008Inngår i: Smart materials and structures (Print), ISSN 0964-1726, E-ISSN 1361-665X, Vol. 17, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A magneto-sensitive rubber isolator inserted between a source and an infinite plate is modelled in the audible frequency range, and the energy flow into the plate with the rubber subjected to a magnetic field applied perpendicular to the axial displacement is calculated. Subsequently the result is compared to the corresponding energy flow for zero magnetic induction; upon the application of an external magnetic field the rubber becomes stiffer, thus shifting the internal resonances of the isolator. This is a fast and reversible process enabling adaption of the isolator to rapidly changing audio frequency conditions by simply turning on and off a magnetic field. In the application example considered, the energy flow into the plate at the first internal dynamic peak stiffness frequency is reduced by approximately 7 dB-a large difference in a sound and vibration context-by inducing magnetic saturation of the rubber.

  • 336.
    Blom, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    The frequency, amplitude and magnetic field dependent torsional stiffness of a magneto-sensitive rubber bushing2011Inngår i: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 60, nr 1, s. 54-58Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dynamic torsional stiffness model of a magneto-sensitive circular annular rubber bushing is presented where influences of frequency, amplitude and magnetic field dependence are included. This is achieved by employing a newly developed non-linear magneto-sensitive audio frequency constitutive equation in an engineering formula for the torsional stiffness of a rubber bushing. The engineering stiffness formula predicts the frequency and amplitude dependent stiffness in a simple way, based on geometric dimensions and the shear modulus. The shear modulus is provided by the rubber model. The results from these calculations predict and clearly display the possibility of controlling over a large frequency range, through the application of a magnetic field, the magneto-sensitive rubber bushing stiffness.

  • 337.
    Blomberg, C
    KTH.
    Aspects of fluctuations in non-linear biological systems - Motion in bistable potentials and selection equations2004Inngår i: SIMPLICITY BEHIND COMPLEXITY / [ed] Klonowski, W, LENGERICH: PABST SCIENCE PUBLISHERS , 2004, Vol. 3, s. 25-60Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two rather different topics are discussed with one common factor: they are driven by irregular influences. The first part considers the stochastic transition between potential minima over a maximum (barrier), and is treated as a Brownian motion description of reaction rates. We also discuss the related problem of "stochastic resonance", in which a small oscillating force synchronises transitions. In both these cases, the emphasis is on the formalism, and the relations between the two problems are stressed. The other type of problem considers growth and competition equations of macromolecules, relevant for early molecular evolution on the path to the first life. Selection rates are simple and straightforward as long as competition essentially concerns limited resources. The situation gets more complex, when molecules are considered co-operative, e.g. they can catalyse growth processes. This corresponds to the hypercycle concept of Eigen, and is also a scenario for a RNA world. Components that use the support from other components may thrive, but can lead to the extermination of an entire system as the supporters may decline in the competition. As in the first part, the emphasis is on the formalism. We also take up probability aspects and problems that appear together with small probabilities and possibilities of exponential growth. Finally, the possibility of saving the co-operativity by spatial structures are discussed.

  • 338.
    Blomfors, Mattias
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB, Betong & Berg.
    Zandi, Kamyab
    RISE., SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB, Betong & Berg.
    Lundgren, Karin
    Larsson, Oskar
    Honfi, Daniel
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Engineering Assessment Method for Anchorage in Corroded Reinforced Concrete2016Inngår i: IABSE Congress Stockholm, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment. Report, IABSE c/o ETH Hönggerberg , 2016, s. 2109-2116Konferansepaper (Fagfellevurdert)
    Abstract [en]

    There is an increasing need for reliable methods to assess load-carrying capacity and remaining service life of existing infrastructure. Several previous research projects have resulted in a verified, simple 1D model for assessment of anchorage in corroded reinforced concrete structures. Previous verification has involved both experiments and detailed 3D NLFE analyses. To further develop the 1D model it needs to be extended to comprise more practical situations. In order to facilitate an efficient extension procedure in the future, the size of 3D NLFE model that is required to capture the bond behaviour between corroded reinforcement and concrete is investigated. Beam-end models and models of sub-sections were studied, and the results in terms of bond stress and crack pattern were compared. Preliminary results indicate good agreement for some situations; however for some cases a section model seems to overestimate the capacity.

  • 339.
    Bodin, Olle
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Simulations of compressible flows associatedwith internal combustion engines2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Vehicles with internal combustion (IC) engines fueled by hydrocarbon compoundshave been used for more than 100 years for ground transportation.During these years and in particular the last decade, the environmental aspectsof IC engines have become a major political and research topic. Followingthis interest, the emissions of pollutants such as NOx, CO2 and unburnedhydrocarbons (UHC) from IC engines have been reduced considerably.Yet, there is still a clear need and possibility to improve engine efficiencywhile further reducing emissions of pollutants. The maximum efficiency ofIC engines used in passenger cars is no more than 40% and considerably lessthan that under part load conditions. One way to improve engine efficiencyis to utilize the energy of the exhaust gases to turbocharge the engine. Whileturbocharging is by no means a new concept, its design and integration intothe gas exchange system has been of low priority in the power train designprocess. One expects that the rapidly increasing interest in efficient passengercar engines would mean that the use of turbo technology will become morewidespread.The flow in the IC-engine intake manifold determines the flow in the cylinderprior and during the combustion. Similarly, the flow in the exhaust manifolddetermines the flow into the turbine, and thereby the efficiency of theturbocharging system.In order to reduce NOx emissions, exhaust gas recirculation (EGR) is used.As this process transport exhaust gases into the cylinder, its efficiency is dependenton the gas exchange system in general. The losses in the gas exchangesystem are also an issue related to engine efficiency. These aspects have beenaddressed up to now rather superficially. One has been interested in globalaspects (e.g. pressure drop, turbine efficiency) under steady state conditions.In this thesis, the flow in the exhaust port and close to the valve as wellas in the exhaust manifold is studied. Since the flow in the port can be transonic,we study first the numerical modeling of such a flow in a more simplegeometry, namely a bump placed in a wind tunnel. Large-Eddy Simulationsof internal transonic flow have been carried out. The results show that transonicflow in general is very sensitive to small disturbances in the boundaryconditions. Flow in the wind tunnel case is always highly unsteady in the transonicflow regime with self excited shock oscillations and associated with that 

    also unsteady boundary-layer separation. The interaction between separationzone and shock dynamics was carried out by one-, and two-point correlationsas well as dynamic mode decomposition (DMD). A clear connection betweenseparation bubble dynamics and shock oscillation was found. To investigatesensitivity to periodic disturbances the outlet pressure in the wind tunnel casewas varied periodically at rather low amplitude. These low amplitude oscillationscaused hysteretic behavior in the mean shock position and appearance ofshocks of widely different patterns.The study of a model exhaust port shows that at realistic pressure ratios,the flow is transonic in the exhaust port. Furthermore, two pairs of vortexstructures are created downstream of the valve plate by the wake behind thevalve stem and by inertial forces and the pressure gradient in the port. Thesestructures dissipate rather quickly. The impact of these structures and thechoking effect caused by the shock on realistic IC engine performance remainsto be studied in the future.The flow in a heavy-duty exhaust manifold was studied under steady andengine-like boundary conditions. At all conditions, significantly unsteady flowis generated in the manifold and at the inlets to the turbine and EGR cooler.The inflow to the turbine is dominated by a combination of the blow-downpulse coming from one cylinder, and the scavenging pulse from another at thefiring frequency.

  • 340. Boer, C.R.
    et al.
    Gudmundson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Rebelo, N
    Comparison of elasto-plastic FEM, rigid-plastic FEM and experiments for cylinder upsetting1982Konferansepaper (Fagfellevurdert)
  • 341.
    Boere, S.W.
    et al.
    Department of Mechanical Engineering, Eindhoven University of Technology.
    Lopez Arteaga, Ines
    Department of Mechanical Engineering, Eindhoven University of Technology.
    Kuijpers, A.H.W.M.
    Department of Mechanical Engineering, Eindhoven University of Technology.
    Nijmeijer, H.
    Department of Mechanical Engineering, Eindhoven University of Technology.
    Prediction of road texture influence on rolling resistance and tire/road noise2009Inngår i: Proceedings of Euronoise 2009, 2009Konferansepaper (Annet vitenskapelig)
  • 342. Bogey, Christophe
    et al.
    Gojon, Romain
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Feedback loop and upwind-propagating waves in ideally expanded supersonic impinging round jets2017Inngår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 823, s. 562-591Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aeroacoustic feedback loop establishing in a supersonic round jet impinging on a flat plate normally has been investigated by combining compressible large-eddy simulations and modelling of that loop. At the exit of a straight pipe nozzle of radius r(0), the jet is ideally expanded, and has a Mach number of 1.5 and a Reynolds number of 6 x 10(4). Four distances between the nozzle exit and the flat plate, equal to 6r(0), 8r(0), 10r(0) and 12r(0), have been considered. In this way, the variations of the convection velocity of the shear-layer turbulent structures according to the nozzle-to-plate distance are shown. In the spectra obtained inside and outside of the flow near the nozzle, several tones emerge at Strouhal numbers in agreement with measurements in the literature. At these frequencies, by applying Fourier decomposition to the pressure fields, hydrodynamic-acoustic standing waves containing a whole number of cells between the nozzle and the plate and axisymmetric or helical jet oscillations are found. The tone frequencies and the mode numbers inferred from the standing-wave patterns are in line with the classical feedback-loop model, in which the loop is closed by acoustic waves outside the jet. The axisymmetric or helical nature of the jet oscillations at the tone frequencies is also consistent with a wave analysis using a jet vortex-sheet model, providing the allowable frequency ranges for the upstream-propagating acoustic wave modes of the jet. In particular, the tones are located on the part of the dispersion relations of the modes where these waves have phase and group velocities close to the ambient speed of sound. Based on the observation of the pressure fields and on frequency-wavenumber spectra on the jet axis and in the shear layers, such waves are identified inside the present jets, for the first time to the best of our knowledge, for a supersonic jet flow. This study thus suggests that the feedback loop in ideally expanded impinging jets is completed by these waves.

  • 343. Bolinder, T.
    et al.
    Faleskog, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Evaluation of the influence of residual stresses on ductile fracture2015Inngår i: Journal of Pressure Vessel Technology-Transactions of the ASME, ISSN 0094-9930, E-ISSN 1528-8978, Vol. 137, nr 6, artikkel-id 061408Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the significance of residual stresses on ductile fracture is investigated by a set of experiments that are analyzed by finite element simulations. The treatment of residual stresses as expressed in fracture assessment procedures such as R6 is believed to be very conservative for ductile materials, when fracture occurs at high primary loads. Earlier numerical studies have reinforced this belief. This is supported in the current study. Tests on notched 3PB specimens with and without residual stresses were conducted on two ferritic steels. The residual stresses were introduced by applying a compressive preload on notched specimens. The tests were designed to achieve crack initiation at load levels around the plastic limit load. The crack growth in the tests was measured by a compliance method and by color marking of the crack surface. The crack tip driving force J was evaluated numerically for specimens with and without residual stresses. The experimental results show that the residual stresses clearly contribute to J at low primary loads. However, this contribution diminishes as the primary loads increase. The experimental results were also compared with results evaluated using the R6 procedure. These comparisons revealed overly high conservatism in R6 for cases with residual stresses compared to the ones for cases without residual stresses where less conservatism was evident.

  • 344. Bolinder, T.
    et al.
    Sattari-Far, I.
    Faleskog, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Evaluation of the influence of residual stresses on ductile fracture2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this work the significance of residual stresses for ductile fracture was investigated. The treatment of residual stresses as expressed in fracture assessment procedures such as the R6 method is believed to be very conservative for ductile materials, when fracture occurs at high primary loads. Earlier numerical studies have reinforced this belief. Tests on notched 3PB specimens with and without residual stresses were conducted on two ferritic steels. The residual stresses were introduced by applying a compressive pre-load on notched specimens. The tests were designed to achieve crack initiation at load levels around the limit load. The crack growth in the tests was measured by a compliance method and by colour marking of the crack surface. The crack-tip driving force J was evaluated numerically for specimens with and without residual stresses. The experimental results show that the residual stresses clearly contribute to J at low primary loads. However, this contribution diminishes as the primary loads increase. The experimental results were also compared with results evaluated using the R6 procedure. These comparisons revealed an overly high conservativeness in R6 for cases with residual stresses compared to the conservativeness for cases without residual stresses.

  • 345.
    Bolmsjö, Gunnar
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för maskinteknik (MT).
    Ferreira Magalhaes, Ana Catarina
    University West.
    Cederqvist, Lars
    SKB AB, Oskarshamn, Sweden.
    De Backer, Jeroen
    University West.
    Robotic Friction Stir Welding of complex geometry and mixed materials2018Inngår i: ISR 2018: 50th International Symposium on Robotics June, 20-21, 2018, Messe München, Munich, Germany, VDE Verlag GmbH, 2018, s. 35-41Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Friction stir welding (FSW) is a solid state process for joining materials which has demonstrated advantages compares with other methods which include joining of mixed materials, hard to weld alloys and consistent and high quality. This paper presents a study of robotic FSW initiated by Volvo Skoevde plant to join an insert workpiece of extruded aluminium with a cylinder block of aluminium casting. A three-stage procedure was decided to determine the feasibility to apply robotic FSW. The stages included study of welding the mixed materials, weld along the complex joint line with holes and channels close to the joint, and finally welding the cylinder block. The results based on preliminary analysis indicate that the final tests were successful and the process is feasible for the challenging case study. However, further studies are recommended in order to identify the operating parameters window, tool design, and control of the process in order to optimize productivity and quality.

  • 346.
    Boqvist, Emil
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Investigation of a swing check valve using CFD2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master’s thesis is made to increase the understanding of the dynamic characteristics of a typical large swing check valve used in a system that transports pressurized water to a reactor tank.3D FSI-simulations are performed for a number of transients in order to study the dynamic characteristics their dependence of the deceleration rate. The purpose is to find information about the dynamics that could be used in a future improvement of a 1D-model.Steady state simulations are performed for angles in the whole spectrum. Seven transient FSI-simulations with different constantly decelerating flows from 630 kg/s2 (6.7 m/s2) to 40 320 kg/s2 (430 m/s2) have been performed. The pressure on the disc caused by the hydraulic torque is integrated and the corresponding torque contribution, together with the weight torque, is used in the second law of motion to calculate the movement of the disc throughout the transients.Steady state simulations yield the pressure drop over the valve, which could be compared with field measurements in order to validate the CFD-simulations. Comparison of the pressure distribution on the disc for the steady state and transient simulations shows the importance of taking the disc angular velocity into account when modelling in 1D. Correlations between the angle, angular velocity, torque and mass flow are obtained from the transient FSI-simulations. Torque coefficients according to (Li & Liou, Vol. 125) are also brought out from the simulated transients, but in order to create a model in line with this approach further simulations have to be performed. A prediction of the pressure rise that occurs when a swing check valve closes in backward flow according to the Joukowsky equation is brought out and gives an idea of the loadings that the system has to be able to handle.

  • 347. Borg, K I
    et al.
    Soderholm, Lars
    KTH, Tidigare Institutioner, Mekanik.
    Essen, Hanno
    KTH, Tidigare Institutioner, Mekanik.
    Response to "Comment on 'Force on a spinning sphere moving in a rarefied gas' and 'On the inverse Magnus effect in free molecular flow'" [Phys. Fluids 16, 3832 (2004)]2004Inngår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 16, nr 10, s. 3833-3833Artikkel i tidsskrift (Annet vitenskapelig)
  • 348.
    Borhani Khomami, Arghavan
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Separate analysis of Small Pipes in Piping Analysis.2015Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A piping system generally consists of primary system, large pipes, and secondary system, small pipes [1]. The primary system can be analysed separately without considering the secondary system. However, the opposite is not true because the primary system affects the movement of the secondary system. The aim of this study is to investigate the possibility of analysing the small pipes separately, which is called for sub-modelling, and then if the sub-modelling is possible, generate and validate a method which makes this sub-modelling possible.

    The response spectrum method [2] is used for analysing the structure. A ground acceleration spectra in three directions is applied at the primary structure, a new floor response spectra is then generated with the results from the analysis of the primary structure [3]. The calculated floor response spectra is applied at the secondary structure. The results from this analysis is compared to the results from applying the ground acceleration at the total structure. Two different ground accelerations are applied on two different models. A separation would be allowed if the results of the secondary structure are more than 90% of the results of the whole structure in all parts of the secondary structure in all studied cases. The results after separation reach more than 100% of the results from the analysis of the whole structure, called for conservative results, in three cases but not all the cases. The separation will be allowed in those three cases where the results reach 90% of the results taken from the whole structure, but not in that case where results does not reach 90%.

  • 349.
    Borodulina, Svetlana
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Kulachenko, Artem
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Tjahjanto, Denny
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Constitutive modeling of a paper fiber in cyclic loading applications2015Inngår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 110, s. 227-240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The tensile response of dense fiber-based materials like paper or paperboard is mainly dependent of the properties of the fibers, which store most of the elastic energy. In this paper, we investigate the influence of geometrical and material parameters on the mechanical response of the pulp fibers used in paper manufacturing. We developed a three-dimensional finite element model of the fiber, which accounts for microfibril orientation of cellulose fibril, and the presence of lignin in the secondary cell wall. The results showed that the change in the microfibril orientation upon axial straining is mainly a geometrical effect, and is independent of the material properties of the fiber, as long as the deformations are elastic. Plastic strain accelerates the change in microfibril orientation and thus makes it material-dependent. The results also showed that the elastic modulus of the fiber has a non-linear dependency on microfibril angle, with elastic modulus being more sensitive to the change of microfibril angle around small initial values of microfibril angles. Based on numerical results acquired from a 3D fiber model supported by available experimental evidence, we propose an anisotropic-kinematic hardening plasticity model for a fiber within a beam framework. The proposed fiber model is capable of reproducing the main features of the cyclic tensile response of a pulp fiber, such as stiffening due to changing microfibril angle. The constitutive model of the fiber was implemented in a finite-element model of the fiber network. By using the fiber network model, we estimated the level of strain that fiber segments accumulate before the typical failure strain of the entire network is reached.

  • 350.
    Borodulina, Svetlana
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Motamedian, Hamid Reza
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Kulachenko, Artem
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Effect of fiber and bond strength variations on the tensile stiffness and strength of fiber networks2018Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 154, s. 19-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As fiber and bond characterization tools become more sophisticated, the information from the fiber scale becomes richer. This information is used for benchmarking of different types of fibers by the paper and packaging industries. In this work, we have addressed a question about the effect of variability in the fiber and fiber bond properties on the average stiffness and strength of fiber networks. We used a fiber scale numerical model and reconstruction algorithm to address this question. The approach was verified using the experimental sheets having fiber data acquired by a fiber morphology analyzer and corrected by microtomographic analysis of fibers in these sheets. We concluded, among other things, that it is sufficient to account for the average bond strength value with an acceptable number of samples to describe dry network strength, as long as the bond strength distribution remains symmetric. We also found that using the length-weighted average for fiber shape factor and fiber length data neglects the important contribution from the distribution in these properties on the mechanical properties of the sheets.

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