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  • 1.
    Abelen, Aisha
    et al.
    Eindhoven Univ Technol, Netherlands.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Modelling of rate-dependent inelasticity and damage in semi-crystalline polymers using an Eulerian framework2023In: International Journal of Engineering Science, ISSN 0020-7225, E-ISSN 1879-2197, Vol. 193, article id 103945Article in journal (Refereed)
    Abstract [en]

    The present paper concerns the mechanical response of semi-crystalline polymers during cyclic loading, and it includes both modelling and experimental testing. The model is Eulerian in the sense that it is independent of measures of total deformation and plastic/inelastic deformations. It is able to account for such essential phenomena as strain-rate dependence, work hardening, and damage. The model was applied to uniaxial tension tests performed on high-density polyethylene (HDPE), which is a semi-crystalline polymer widely used in the industry. Two types of tests were conducted: monotonic tests, and loading-unloading tests. The model was able to reproduce the experimental results very well. The proposed model was also implemented as a UMAT in Abaqus, including an analytic tangent. The UMAT was used for simulating two 3D geometries. The implementation seems to be robust, and no convergence problems were observed.

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  • 2.
    Abrahamsen, Rune
    et al.
    Moelven Limtre, Norway.
    Bjertnæs, Magne A.
    Sweco, Norway.
    Bouillot, Jacques
    Eiffage, France.
    Brank, Boštjan
    University of Ljubljana, Slovenia.
    Crocetti, Roberto
    Moelven SE, Sweden.
    Flamand, Olivier
    CSTB, France.
    Garains, Fabien
    Arbonis, France.
    Gavrić, Igor
    InnoRenew, Slovenia.
    Hahusseau, Ludwig
    Eiffage, France.
    Jalil, Alan
    CSTB, France.
    Johansson, Marie
    RISE, Sweden.
    Johansson, Thomas
    Moelven, Sweden.
    Ao, Wai Kei
    Uni Exeter, UK.
    Kurent, Blaž
    University of Ljubljana, Slovenia.
    Landel, Pierre
    Linnaeus University, Faculty of Technology, Department of Building Technology. Rise, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Malo, Kjell
    NTNU, Norway.
    Manthey, Manuel
    CSTB, France.
    Nåvik, Petter
    Sweco, Norway.
    Pavic, Alex
    Uni Exeter, UK.
    Perez, Fernando
    Smith&Wallwork, Switzerland.
    Rönnquist, Anders
    NTNU, Norway.
    Šušteršič, Iztok
    InnoRenew, Slovenia.
    Tulebekova, Saule
    NTNU, Norway.
    Dynamic response of tall timber buildings under service load: results from the dynattb research program2023In: World Conference on Timber Engineering 2023 (WCTE 2023): Timber for a Livable Future, 19-22 june, 2023,Oslo, Norway / [ed] Nyrud, A. Q. and Malo, K. A. et al., Curran Associates, Inc., 2023, p. 2907-2914Conference paper (Refereed)
    Abstract [en]

    Wind-induced dynamic excitation is a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway, i.e. vibration serviceability problem. Although some TTBs have been instrumented and measured to estimate their key dynamic properties (eigenfrequencies, mode shapes and damping), no systematic evaluation of dynamic performance pertinent to wind loading had been performed for the new and evolving construction technologies used in TTBs. The DynaTTB project, funded by the ForestValue research program, mixed on site measurements on existing buildings excited by mass inertia shakers (forced vibration) and/or the wind loads (ambient vibration), for identification of the structural system, with laboratory identification of building elements mechanical features, coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and provide key elements to finite element models. This paper presents an overview of the results of the project and the proposed Guidelines for design of TTBs in relation to their dynamic properties.

  • 3.
    Abu-Ragheef, Basil
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Polymer Aging Mechanics: An investigation on a Thermoset Polymer used in the Exterior Structure of a Heavy-duty Vehicle2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The use of plastic materials in the design of vehicle components is primarily driven by the need for vehicle weight and cost reduction. Additionally, these materials give design engineers freedom in creating appealing exterior designs. However, creating self-carrying exterior structures with polymers must fulfill long-term strength, creep and fatigue life requirements. Thus, the polymer polyDicyclopentadiene (pDCPD) has been chosen for this purpose. Its aging mechanics need to be understood by the design engineers to make the right decisions. This thesis has carried out mechanical tests such as uniaxial tensile testing, fatigue, and creep testing. Digital image correlation (DIC) system has been used to capture strain data from tensile tests. In the final analysis, DIC measurements proved more accurate than extensometer data retrieved from the testing machine. The rise in temperature has been captured using thermal imaging. Several degradation processes have been explored including physical aging, thermo-oxidation, photo-oxidation, chemical- and bio- degradations. Test results showed significant changes in mechanical properties after 17 years of aging. Additionally, severe thermal degradation has been observed in one of the tested panels of pDCPD. Temperature can rise to significant levels during cyclic loading at high stresses, which could have an impact on physical aging effects. Viscoelastic behavior has been explored and changes in dynamic and creep properties have been observed. The investigation also reviled that different defects caused by flawed manufacturing also can affect the material severely as one case has proved in this research.

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  • 4.
    Albertsson, Robin
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Hermansson, Joakim
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    LNG träningsmanual för M/T Bit Viking2013Independent thesis Basic level (university diploma), 10 HE creditsStudent thesis
    Abstract [sv]

    Denna uppsats är gjord på uppdrag av Tarbit Shipping som år 2011 konverterade sin tankbåt M/T Bit Viking från konventionell drift på tjockolja till LNG (Liquefied Natural Gas).Uppdraget som gavs var att upprätta en tränings manual till fartyget då det är ett krav från IMO (International Maritime Organization). Manualen skrevs i 3 st huvuddelar Kategori A, B och C. Kategori A är till för att manskap ombord ska få en kännedom om gasen och säkerhet runt den, Kategori B är skriven till däcksbefäl där det krävs en större kännedom om gasen och Kategori C är till för maskinbefäl. Manualen finns nu ombord på fartyget och på rederi kontoret för utbildning av nypåmönstrad personal och fortlöpande utbildning av ordinarie personal. Manualen är ett resultat på tolkning av IMO´s IGF kod (ANNEX11. RESOLUTION MSC.285(86)) där det står riktlinjer för säkerheten ombord på fartyg med maskiner som drivs på naturgas.

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    Slutrapport LNG träningsmanual
  • 5.
    Alm, Christoffer
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Mehari, Amanuel
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Utveckling av hanteringsmaskin för IKEA-påsar2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Det här examensarbete handlar om att ta fram en ny maskin, en hanteringsmaskin, till TEXO Application i Älmhult. Syftet med maskinen är att den ska vika IKEAs kundpåsar, hanteringsmaskinen ska användas på samtliga IKEA varuhus världen över. Utvecklingen av hanteringsmaskinen går från enkla skisser av flera koncept till val av koncept och utveckling en denna till en fullständig ritning som det sedan byggs en prototyp utfrån. Effektiviseringen bland samtliga varuhus beräknas att öka då denna lösning ger de anställda mer tid till annat arbete.

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    Utveckling av hanteringsmaskin för IKEA-påsar
  • 6.
    Al-Najjar, Basim
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    A method and an apparatus for predicting the condition of amachine or a component of the machine2016Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention relates to a methodand an apparatus for predicting the condition of a machine or a component of the machine based on measurements of a condition monitoring parameter. The apparatus comprising a data storage for storing a moving window including measurement values of the condition monitoring parameter, a monitoring module configured to determine whena measurement value exceeds a potential failure level at which damage of the machine or component is considered initiated, and to determine the point in time (tP) when the monitoring parameter exceeded the potential failure level, a data cleaning module configured to discarda new measurement value if it is smaller than the latest stored measurement value inthe moving window, to determine an expected value for the measurement based on a defined pattern for the condition monitoring parameter, which pattern reflects an expected behavior of the monitoring parameter after damage has been initiated, and the time elapsed since the point in time the monitoring parameter exceeded the potential failure level, and to discard the new measurement value if it deviates too much from the expected value, and to store not discarded measurement values in the moving window, and a prediction module configured to predict the level of the condition monitoring parameter at a future point in time based on the measurement

  • 7.
    Al-Najjar, Basim
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    A universal coupling for transferring rotary movements between an inputshaft and an output shaft2016Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention relates to a universal coupling for transferring rotary movements between an input shaft and an output shaft (when the angel between the shafts can be about 90 degree), wherein each of the shafts are arranged to rotate about a longitudinal axis of the shaft, the coupling comprising: an input joint member and output joint member movably coupled to each, and the input joint member  is fixedly connected to the input shaft and the output joint member is fixedly connected to the output shaft.  Each of the input and output joint members comprises at least one annular part having a cross section and defining a central aperture, the annular part of the input joint member passes through the aperture of the annular part of the output joint member, and the annular part of the output joint member passes through the aperture of the annular part of the input joint member, and the area of each the central apertures is larger than the cross section area of each of the annular parts and two spaced apart contact points are formed between the annular parts of the input and output joint members.

  • 8.
    Alnimairi, Ibrahim
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Arrabi, Salim
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Experimental acceleration Measurements and Finite Elements Modeling2021Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Heavy crushing machines under their production shifts, creates various levels of vibration, noise and dynamic forces which can be transferred to other parts of the industrial unit. Such kind of factors applies continuous forces on machine parts which can cause gradual fatigue, creep and eventually failure of machine.

    In this thesis work we are studying Jaw crusher machine from Sandvik company, since the company has a high focus on safety and quality, this thesis is aiming to estimate the dynamic foundation loads that are transmitted to substructure of the jaw crusher.

    The thesis is based on estimating power spectral density transmissibility matrix-single value decomposition (PSDTM-SVD), between jaw crusher foot (CRF), side wall (SW) and substructure (SS) in x, y, z positions to identify model parameters including damped eigenfrequencies and mode shapes.

    This research has concluded that it is possible to estimate the transmitted load force by finding the relation between displacement transmissibility and force transmissibility by employing (PSDTM-SVD) method. In fact (PSDTM-SVD) is a sufficient method to estimate the damped eigenfrequencies and mode shapes during operation. 

    Nevertheless, it is majorly important to have good coherence between measured data, in this case data that have been conducted in Y direction had a good coherence of 0.9.

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  • 9.
    Bhatia, Abhikaran
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Dynamic Analysis of a Window connected via the Click-In System2022Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is often needed to predict the behavior of structures. With the helpof an FE model, it is possible to see the motion of the structure. Inthis, Master thesis work time domain analyses were carried out on afinite element model representing a window attached by click-ins. Theaim was to establish an FE model which gives a good correlation withtest data. The finite element modelling was carried out in MSC Apex.MSC Nastran was utilised to analyze the FEA model and the resultwas post-processed in Simxpert. Different vibrational tests were made. A crane was used to exciteand support the wall together with the window and the responseswere recorded with tri-axial accelerometers. During the thesis, it wasfound that the FE model requires more work and accurate boundaryconditions to provide better resemblance with the test data.The results deviate from the measured. This opens future possibilities tocarry on the project.

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  • 10.
    Bolmsjö, Gunnar
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Ferreira Magalhaes, Ana Catarina
    University West, Sweden.
    Cederqvist, Lars
    SKB AB Oskarshamn, Sweden.
    De Backer, Jeroen
    University West, Sweden.
    Robotic Friction Stir Welding of complex geometry and mixed materials2018In: ISR 2018: 50th International Symposium on Robotics June, 20-21, 2018, Messe München, Munich, Germany, VDE Verlag GmbH, 2018, p. 35-41Conference paper (Refereed)
    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.

  • 11.
    Brandt, Anders
    et al.
    University of Southern Denmark, Denmark.
    Linderholt, Andreas
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    A Periodogram-Based Method for Removing Harmonics in Operational Modal Analysis2012In: International Conference on Noise and Vibration Engineering 2012 (ISMA 2012): Proceedings of a meeting held 17-19 September 2012, Leuven, Belgium. Including USD 2012 / [ed] P. Sas, S. Jonckheere & D. Moens, Leuven: Katholieke Universiteit Leuven, Department of Mechanical Engineering , 2012, p. 2625-2634Conference paper (Refereed)
    Abstract [en]

    In many cases where operational modal analysis is of interest, harmonic components are disturbing the estimation of modal parameters. Sometimes the harmonics can be included in the parameter estimation process and subsequently removed (because the damping values become unrealistically low). However, this is difficult if a natural frequency is very close to, or coincides with, a harmonic. In this paper we investigate a recently proposed method for removing harmonics when estimating spectral densities for operational modal analysis. The method is essentially based on removing the harmonics in a periodogram, prior to estimating the spectral density by smoothing the same periodogram. This makes it a very time efficient method, as the harmonic removal is integrated into the spectral analysis process. To produce data for testing the method, a finite element dynamic model representing a wind turbine was created. The MATLAB-based finite element code CALFEM was used to achieve a flexible description of the tower. An aerodynamic force representation excited the rotating structure. An unbalance in one of the blades was introduced to produce a harmonic at the rotation speed of the turbine. To validate the efficiency of the harmonic removal, modal parameters were estimated using simulated data prior to, and after, removing the harmonics. The results show that the harmonic removal with the proposed method is efficient.

  • 12.
    Chen, Yousheng
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    Experimental Validation of a Nonlinear Model Calibration Method Based on Multiharmonic Frequency Responses2017In: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423, Vol. 12, no 4, article id 041014Article in journal (Refereed)
    Abstract [en]

    Correlation and calibration using test data are natural ingredients in the process of validating computational models. Model calibration for the important subclass of nonlinear systems which consists of structures dominated by linear behavior with the presence of local nonlinear effects is studied in this work. The experimental validation of a nonlinear model calibration method is conducted using a replica of the École Centrale de Lyon (ECL) nonlinear benchmark test setup. The calibration method is based on the selection of uncertain model parameters and the data that form the calibration metric together with an efficient optimization routine. The parameterization is chosen so that the expected covariances of the parameter estimates are made small. To obtain informative data, the excitation force is designed to be multisinusoidal and the resulting steady-state multiharmonic frequency response data are measured. To shorten the optimization time, plausible starting seed candidates are selected using the Latin hypercube sampling method. The candidate parameter set giving the smallest deviation to the test data is used as a starting point for an iterative search for a calibration solution. The model calibration is conducted by minimizing the deviations between the measured steady-state multiharmonic frequency response data and the analytical counterparts that are calculated using the multiharmonic balance method. The resulting calibrated model's output corresponds well with the measured responses.

  • 13.
    Chen, Yousheng
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Nasrabadi, Vahid
    Chalmers University of Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    Informative Data for Model Calibration of Locally Nonlinear Structures Based on Multi-Harmonic Frequency Responses2016In: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423, Vol. 11, no 5, article id 051023Article in journal (Refereed)
    Abstract [en]

    In industry, linear FE-models commonly serve as baseline models to represent the global structural dynamics behavior. However, available test data may show evidence of significant nonlinear dynamic characteristics. In such a case, the baseline linear model may be insufficient to represent the dynamics of the structure. The causes of the nonlinear characteristics may be local in nature and the remaining parts of the structure may be satisfactorily represented by linear descriptions. Although the baseline model can then serve as a good foundation, the physical phenomena needed to substantially increase the model's capability of representing the real structure are most likely not modelled in it. Therefore, a set of candidate nonlinear property parameters to control the nonlinear effects have to be added and subjected to calibration to form a credible model. The selection of the calibration parameters and the choice of data for a calibration metric form a coupled problem. An over-parameterized model for calibration may result in parameter value estimates that do not survive a validation test. The parameterization is coupled to the test data and should be chosen so that the expected co-variances of the chosen parameter's estimates are made small. Accurate test data, suitable for calibration, is often obtained from sinusoidal testing. Because a pure mono-sinusoidal excitation is difficult to achieve during a test of a nonlinear structure, the excitation is here designed to contain sub and super harmonics besides the fundamental harmonic. The steady-state responses at the side frequencies are shown to contain valuable information for the calibration process that can improve the accuracy of the parameter estimates. The nonlinear steady-state solutions can be found efficiently using the multi-harmonic balance method. In this paper, synthetic test data from a model of a nonlinear benchmark structure are used for illustration. The model calibration and an associated K-fold cross-validation are based on the Levenberg-Marquardt and the undamped Gauss-Newton algorithm, respectively. Starting seed candidates for calibration are found by the Latin hypercube sampling method. The realization that gives the smallest deviation to test data is selected as a starting point for the iterative search for a calibration solution. The calibration result shows good agreement with the true parameter setting, and the K-fold cross validation result shows that the variance of the estimated parameters shrinks when adding sub and super harmonics to the nonlinear frequency response functions.

  • 14. Claesson, Ingvar
    et al.
    Håkansson, Lars
    Lagö, Thomas
    Zimmergren, Rolf
    Hällerstedt, Göran
    Device and a method for preventing or reducing vibrations in a cutting tool2007Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    An arrangement for reducing vibrations in a tool holder (4) with a cutting tool (3) and has a vibration sensor on the tool holder (4) that is connected to a guide unit (11). The tool holder (4) has further two piezo-electric actuators 14 and 15.

    Under the influence of the vibration sensor (9), the guide unit (11) provides an electric alternating current that is actively guided over time so that the actuators movably affect the tool holder (4) to reduce the vibrations in this. To also be able to dampen transients in the tool holder (4) this is movably connected with a passive dampening arrangement that is independent of the guide unit (11) and that is based on the principle of a springing (8) suspended mass (7). The invention also relates to a method for reducing vibrations. The vibrations in the tool holder are sensed and a corresponding signal is provided to a guide unit that over time provides actively guided signals to the actuators. The tool holder is also passively influenced by a dampening arrangement that is independent of the guide unit.

  • 15. Claesson, Ingvar
    et al.
    Lagö, Thomas
    Håkansson, Lars
    Method and a device for vibration control2004Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A device for vibration control in a machine for internal turning uses a cutting tool supported by a tool holder, and has a control unit, a vibration sensor connectible to the control unit, and an actuator connectible to the control unit. The actuator has an active element, which converts an A.C. voltage supplied by the control unit to the actuator into dimensional changes. The active element is adapted to be embedded in the body of the tool holder, and is adapted to be embedded in such a manner that the dimensional changes impart bending to the body of the tool holder. A method for vibration control in internal turning and a tool holder for internal turning are provided.

  • 16. Claesson, Ingvar
    et al.
    Lagö, Thomas
    Håkansson, Lars
    Method and device for controlling a turning operation2005Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A device increases the surface smoothness of a turned surface. The device comprising a control system with a control unit and an actuator connectible to the control unit and connectible with a tool holder. The actuator in adapted to impart a vibrating motion in the lateral direction to the tool holder. A method will also increase the surface smoothness of a turned surface, comprising the step of controlling the vibrations of the tool holder during turning. The method also comprises the step of imparting a vibrating motion in the lateral direction to the tool holder. Moreover, a turning lathe and a turning tool holder which like the device are designed to generate vibrating motion in the lateral direction.

  • 17. Claesson, Ingvar
    et al.
    Lagö, Thomas
    Håkansson, Lars
    Method and device for vibration control2008Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A device and method for vibration control in a machine for cutting, said machine comprising a cutting tool supported by a tool holder. The device comprises a control unit and converting means which are connectible to the control unit and comprise a vibration sensor and an actuator. The actuator comprises an active element which converts an A.C. voltage supplied by the control unit to the actuator into dimensional changes. Said active element is adapted to be embedded in the body of the tool holder and in such manner that said dimensional changes impart bending to the body of the tool holder.

  • 18.
    Croitoru, Cristian
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Rydersten, Mikael
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Koppling för kraftuttag: En stelkroppsdynamisk simulering av ett kopplingsförlopp.2023Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Studien handlar om utveckling av ett flexibelt klokopplingssystem tillsammans med SwePart Transmissioner AB. Principen bygger på att en hylsa med utvändiga splines belastas i inkopplingsförloppet. Hylsan skapar en axiell rörelse som sedan absorberas av fjädrar vilket utgör flexibiliteten i klokopplingen. Studien besvarar frågorna om vilka samband som finns mellan olika faktorer i systemet och hur dessa påverkar dimensioneringen samt vilka modifieringar som måste göras för att uppfylla funktionskraven. Författarna har gjort ett flertal simuleringar på inkopplingsförloppet med programmet MSC Adams för att generera data som krävs för att kunna dimensionera systemet. Resultatet av varje simuleringsförsök utgörs av plottar med storheter som vridmoment, fjäderkraft och förskjutningar. En analys är sedan gjord för att finna den bästa dimensioneringen av ett antal kandidater av kopplingen samt flera olika förslag på idéer för vidare studier. Det finns flera olika samband mellan de uppsatta faktorerna och en dimensionering rekommenderas.

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  • 19.
    Dhafer, Yasir
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Utveckling och dimensionering av ett fäste till en mobil tvättanläggning2017Independent thesis Basic level (professional degree), 180 HE creditsStudent thesis
    Abstract [sv]

    Professionella tvättmaskiner ger upphov till dynamiska krafter som uppstår vid centrifugering. När dessa maskiner används på en släpvagn kan dessa stora krafter skada underlaget. För att undvika skador på släpvagnens underlag så är det viktigt att fördela och dämpa dessa krafter. Genom att konstruera ett fäste som innehåller något dämpningselement kan man dämpa och fördela dessa krafter. På uppdrag av Linneuniversitetet i Växjö och med samlad information från företaget Electorlux Wascator i Ljungby genomfördes detta arbete. Arbetets syfte är att få fram en fungerande produkt som säkerställer användningen av tvättmaskiner på en släpvagn utan att underlaget tar skada. Med hjälp av produktutvecklingsprocessen utvecklades ett fäste som har som en uppgift att fördela de stora krafterna som uppstår vid centrifugering. Fästet består av två balkar, varje balk består av två L-profiler som är ihopkopplade med en fackverkskonstruktion. Fästet är gjort av aluminium som har beteckningen SS6082 T6. Fyra stycken gummidämpare valdes för att sitta under varje infästningspunkt från tvättmaskinen till fästet.

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  • 20.
    Dugic, Izudin
    et al.
    Jönköping University.
    Diószegi, Attila
    Jönköping University.
    Svensson, Ingvar L.
    Jönköping University.
    Metal Expansion Penetration on Concave Casting Surfaces of Grey Cast Iron Cylinder Heads2006Report (Other academic)
    Abstract [en]

    Cylinder heads have an extremely complex shape with large areas of concave casting surfaces. The concave casting surfaces are often associated with metal expansion penetration problems or other surface defects, e. g. surface shrinkage. The defects cause high production costs due to component rejection and increased fettling time. This report presents an investigation of the microstructure in grey cast iron close to the sand-metal interface affected by metal penetration in a complex shaped casting. The dominant penetration defect observed in the cylinder heads was expansion penetration. Even pre-solidification penetration and sand crack defects were observed. The microstructure found in the non penetrated areas is typical for solidification of grey iron cast in sand moulds.

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  • 21.
    Dugic, Izudin
    et al.
    Jönköping University.
    Svensson, Ingvar L
    Jönköping University.
    An investigation of the effect of five different inoculants on the metal expansion penetration in grey cast iron1999Report (Other academic)
    Abstract [en]

    The production of quality castings requires the casting surface to be clean and free from defects. In some grey cast iron components which are cast in sand moulds, the metal sometimes penetrates into the mould, producing difficulties in cleaning the components. The defect causes very high costs due to component rejection and increased fettling in the casting industry. Most of the grey iron foundries around the world have problems with metal penetration on applicable components. In this work the problem of metal penetration has been studied using a commercial casting component. Eight castings were mounted on the pattern plate and five different inoculants were investigated. The experiments show that the inoculation of grey cast iron will influence the metal penetration in areas with late solidification times and where the melt is in contact with the sand mould. In all experiments 0.14 % inoculant was added in the pouring ladle. The experiments show that the best results to reduce metal penetration have been obtained when using the inoculant which contained silicon, aluminium and zirconium. Using this inoculant, the average penetration area was only about 20 % of what was found using the worst inoculant. However, this inoculant also gave rise to a large tendency to formation sinks.The experiments also show two main classes of eutectic cell size. One class nucleated at the beginning of the eutectic solidification and one at the end of the solidification. Two other inoculants, both containing Al and Si have about the same base composition. From the measurements of penetration areas, one can draw the conclusion that the inoculant with the smallest grain size gives nuclei with the shortest lifetime. The coarser grains give a longer dissolution time and this promotes the survival of the nuclei. At the end of solidification, a larger amount of graphite will precipitate at higher temperatures if new nuclei can be activated. If the hot spot is located close to the metal surface, the metal will expand into the mould; resulting in metal expansion penetration. The worst cases of metal penetration have been obtained using an inoculant containing titanium. A large number of small eutectic cells and high volume of the small cells were observed, which leads to severe penetration.

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  • 22.
    Dugic, Izudin
    et al.
    Jönköping University.
    Svensson, Ingvar L
    Jönköping University.
    The effect of inoculant amount and casting temperature on metal expansion penetration in grey cast iron1999Report (Other academic)
    Abstract [en]

    The composition of the inoculant, containing different elements, as well as inoculant amount have been shown to play an important role in solidification of cast iron. Three different inoculant amounts and different pouring temperatures were used on a commercial casting. From the results of the ocular inspection of the castings, the eutectic cell size and distribution measurements, it can be concluded that nucleation of the eutectic cells plays an important role in formation of the expansion penetration. The castings show two different types of surface defects; namely, bulb and metal expansion penetration. The mechanisms of bulb and formation metal expansion penetration seems to be related. The influence of the melt casting temperatures showed the following results; by using a lower temperature the degree of metal penetration was reduced but the bulb formation is unchanged. This is applies to experiments using 0.15 % and 0.30 % inoculant. The amount of inoculant added shows a clear effect on the degree of metal penetration. The expansion penetration disappeared at 0.05 % addition at the two highest pouring temperatures although at the lowest temperature some penetration did occur. The low temperature did not show any tendency to form white solidification in this casting components. The pouring temperature seems to have a large influence in combination with high additions of inoculants. A low pouring temperature seems to increase the formation of bulbs caused by excess material at solidification. 2 The mechanism of bulb formation is proposed to depend on formation of a thin solidified layer when the metal has filled the mould. The shell is thin, and a later expansion of the metal, during solidification pushes the shell outward and forms a bulb, instead of bursting and metal penetration of the sand mould.

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  • 23.
    Elrakayby, H.
    et al.
    University of Strathclyde, UK.
    Gonzalez, D.
    University of Strathclyde, UK.
    Gomez-Gallegos, Ares Argelia
    University of Strathclyde, UK.
    Mandal, P.
    University of Strathclyde, UK.
    Zuelli, N.
    University of Strathclyde, UK.
    A study on modelling the superplastic behaviour of Ti54M alloy2020In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 306, p. 9-14Article in journal (Refereed)
    Abstract [en]

    Superplastic forming is a cost-effective process for manufacturing complex-shaped titanium parts. TIMETAL ® 54M (Ti54M) is a titanium alloy that has been commercially available since 2003, however studies on modelling its superplastic behaviour are scarce in the literature. Finite element modelling can be used to enable the manufacturing of complex-shaped parts economically as the number of experimental trials can be reduced. This paper illustrates the implementation of a microstructural-based model to predict the superplastic behaviour of Ti54M alloy during forming at elevated temperature. The parameters of the material model are derived in this work for the Ti54M alloy. A Matlab script has been developed for the calculation and calibration of the material model parameters based on material experimental data. The material model was implemented into the finite element commercial software Abaqus by means of a user-defined subroutine. The finite element calculations take into account also grain size evolution. Finally, a pressure profile was numerically calculated for forming a non-commercial part via superplastic forming targeting optimal conditions for the material.

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  • 24.
    Eng Stensson, Alexander
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Olsson, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Optimering av en planetväxel genom användning av ett aktivt balanseringssystem2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Arbetets syfte är att undersöka hur en planetväxel kan optimeras med avseende på kostnad och momentöverföringskapacitet då det konceptuella balanseringssystemet skapat av Swepart Transmission AB appliceras på en planetväxel. Arbetet undersöker även huruvida höghållfasta stål kan användas för att optimera en planetväxel ytterligare. Planetväxlarna i detta arbete genererades i programvaran KISSsoft och 3D-modeller av dessa planetväxlar skapades i SolidWorks. Olika tillverkningsfel introducerades i en planetväxel och dess inverkan på lastfördelningen mellan planethjulen samt balanseringsystemets förmåga att reducera dessa fel undersöktes med hjälp av programvaran MSC Adams. Resultatet från undersökningarna i MSC Adams användes sedan för att optimera planetväxlarna. För planetväxlarna utfördes slutligen en mass- och kostnadsjämförelse för att undersöka hur konkurrenskraftig en planetväxel med Sweparts balanseringssystemet är jämfört med dagens konventionella planetväxlar.

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    Optimering av en planetväxel genom användning av ett aktivt balanseringssystem
  • 25.
    Eriksson, Hampus
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Chen, Fang
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Omkonstruktion av komponenter i en desinfektionsdiskmaskin med syfte att reducera monteringstiden2015Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Fokus i detta arbete ligger i att konstruera om vissa delar av produkten för lättare och snabbare montering. Huvudproblemen som upptäcks i detta arbete handlar om skymd sikten vid monteringen samt bristande utrymme för installation av komponenter. Arbetet börjar med att formulera undersökningsproblemet och sedan presenteras olika vetenskapliga metoder, relevanta teorier samt genomförandet av arbetet. Nulägesbeskrivning, nulägesanalys samt förbättringsförslag till problemen utförs i genomförandet. På grund av att ingen egen tillverkning sker på företaget har författarna valt att utföra beräkningar istället för att verifiera att lösningarna till problem håller. Resultatet i detta arbete blir att antalet delar och skruvar har minskats samt att sikten och tillgängligheten vid insättning av komponenter har förbättrats, vilket kommer att minska monteringstiden till en viss del.

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  • 26.
    Ghachi, Ratiba F.
    et al.
    Qatar University, Qatar.
    Alnahhal, Wael I.
    Qatar University, Qatar.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Renno, Jamil
    Qatar University, Qatar.
    Tahidul Haque, A. B. M.
    SUNY Buffalo, USA.
    Shim, Jongmin
    SUNY Buffalo, USA.
    Aref, Amjad
    SUNY Buffalo, USA.
    Optimization of Viscoelastic Metamaterials for Vibration Attenuation Properties2020In: International Journal of Applied Mechanics, ISSN 1758-8251, E-ISSN 1758-826X, Vol. 12, no 10, article id 2050116Article in journal (Refereed)
    Abstract [en]

    Metamaterials (MMs) are composites that are artificially engineered to have unconventional mechanical properties that stem from their microstructural geometry rather than from their chemical composition. Several studies have shown the effectiveness of viscoelastic MMs in vibration attenuation due to their inherent vibration dissipation properties and the Bragg scattering effect. This study presents a multiobjective optimization based on genetic algorithms (GA) that aims to find a viscoelastic MM crystal with the highest vibration attenuation in a chosen low-frequency range. A multiobjective optimization allows considering the attenuation due to the MM inertia versus the Bragg scattering effect resulting from the periodicity of the MM. The investigated parameters that influence wave transmission in a one-dimensional (1D) MM crystal included the lattice constant, the number of cells and the layers' thickness. Experimental testing and finite element analysis were used to support the optimization procedure. An electrodynamic shaker was used to measure the vibration transmission of the three control specimens and the optimal specimen in the frequency range 1-1200 Hz. The test results demonstrated that the optimized specimen provides better vibration attenuation than the control specimens by both having a band-gap starting at a lower frequency and having less transmission at its passband.

  • 27.
    Holmquist, Adam
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Emanuelsson, Oscar
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Feasibilitetsstudie fartygsframdrift med ångjetstråle: En förstudie om de fysikaliska och tekniska möjligheterna att framdriva fartyg med ångjetstråle2018Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A future alternative propulsion method of ships could be a steam jet that is expanded via an ejector. The purpose of the study was to conduct an experiment on two different types of outlet nozzles on the diffuser of the ejector. This was carried out to find which design that is suitable for this propulsion method and what propulsion force that was possible to achieve. The result of the study was then thought to be used as a basis for further studies of steam jet propulsion through an ejector, to possibly increase the energy efficiency in comparison with today's propulsion methods. The result shows that a circular jet provides maximum propulsion force despite a lower inlet pressure and a water temperature at 70 °C in comparison with a flat jet at higher inlet pressures and equal temperature. The experiment gave no measurable propulsion force when expanding wet steam at a pressure of 3 MPa and a temperature at 150 °C.

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    Feasibilitetsstudie fartygsframdrift med ångjetstråle
  • 28. Håkansson, Lars
    et al.
    Olsson, Sven
    Claesson, Ingvar
    Anordning för styrning av vibrationer i en maskin förskärande bearbetning2004Patent (Other (popular science, discussion, etc.))
  • 29.
    Izadi, Alireza
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Damir, Isa
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Javaid, M. Yasar
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Experimental Study of Cabin and Engine Mounts and Their Effects on Cabin Noise Pressure2011Independent thesis Advanced level (degree of Master (One Year)), 60 credits / 90 HE creditsStudent thesis
    Abstract [en]

    This project investigates engine and cabin mounts of articulated haulers. Experimental study of engine and

    cabin mounts identifies the structural behaviour of the complicated metal-net elastomeric mounts to isolate

    driver from noise and vibration transfer. In order to achieve the expected results, the loss factor and dynamic

    stiffness of engine mount is studied to provide fundamental information of the energy dissipation.

    A simple experimental method is presented in this project to evaluate the frequency dependent rubber mount

    stiffness and damping characteristics by utilizing the measured complex frequency response function from low

    frequency. The study shows the transition of the rubber mount stiffness from static to dynamic values. Using the

    experimentally estimated values of the rubber mount stiffness and damping, the dynamic response of the tested

    spring-mass system using a metal-net rubber mount as the elastic element can be accurately reproduced.

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    Volvo Construction Equipment
  • 30.
    Josefson, Lennart
    et al.
    Chalmers University of Technology.
    Lindström, Per
    Chalmers University of Technology.
    Molin, Mats
    Forsmarks Kraftgrupp.
    2D and 3D Simulation of the IIW Round Robin Benchmark2010Report (Other academic)
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    IIW_2010_XIII-2325
  • 31.
    Kodakadath Premachandran, Rammohan
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Håkansson, Lars
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Methodology for 3D simulation and analisys of a combination of axial impact and rotation of a DTH drilling system2023In: 29th International Congress of Sound and Vibration, 2023Conference paper (Other academic)
    Abstract [en]

    There is an increasing need for an effective monitoring strategy for the performance and condition of Down The Hole drilling. To achieve that, it is important to gain knowledge in the physics involved in Down The Hole drilling processes.A logical way to gain such understanding is to develop simulation models that are capable to represent the process. That requires physical understanding and thus, it is an iterative process. To capture the physics, it is essential to couple the axial impact, and the subsequent axial motion, with the rotation of the drill. The indentation into the rock due to impact and the subsequent resistance against rotation will couple the rotation to the axial motion and vice versa. The scenario is complicated due to the non-linear nature in the contacts and the varying stiffness of the rock.This paper presents a methodology that can be used to couple the axial and rotational motions of the DTH drills and explores the pros and cons of such a 3D simulation model.Keywords: DTH, 3D simulation, Condition monitoring

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  • 32.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco Rock Drills AB, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Håkansson, Lars
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Gothberg, Mattias
    Atlas Copco Rock Drills AB, Sweden.
    An initial investigation of the correlation between a number of drilling related quantities measured during down the hole drilling2017In: Proceedings of the 24th International Congress on Sound and Vibration, Curran Associates, Inc., 2017Conference paper (Other academic)
    Abstract [en]

    Optimizing the performance for down the hole (DTH) drills is becoming increasingly important. This is due to that the industry is becoming highly competitive and therefore there is an ever-increasing demand for improving the efficiency of the drilling process. To do this, it is important to have a robust monitoring system in place that should be based on in-depth knowledge of the underlying physics of the drilling system and process. Such a system will assist drillers in improving the perfor-mance e.g. by providing recommendations concerning the settings of the drilling. To understand the performance of the system, it is very important to understand the information that can be extracted from different drilling related quantities. In this work, information obtained from the pressure signals from the feed/holdback line, impact pressure line and rotation line together with vibration signals measured with the aid of accelerometers mounted at specific locations on the drill rig are discussed. For instance, spectral properties of these quantities for good and bad drilling cases are investigated. The results indicate correlations, to some extent, between the spectral properties and the quality of the drilling.

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  • 33.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco Rock Drills AB, Sweden.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Håkansson, Lars
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Gothberg, Mattias
    Atlas Copco Rock Drills AB, Sweden.
    Numerical 1D and 3D models representing a DTH drilling system: A comparison of accuracy and computational speed2018In: 25th International Congress on Sound and Vibration 2018 (ICSV 25): Hiroshima Calling. Proceedings of a meeting held 8-12 July 2018, Hiroshima, Japan, Auburn, AL: International Institute of Acoustics & Vibration , 2018, Vol. 1, p. 394-401Conference paper (Refereed)
    Abstract [en]

    The drilling industry is steadily moving towards automation. To have a better control over the drilling operation and to optimize the drilling performance, it is necessary to have a good understanding of the physics involved in the process. A good simulation model of the drilling process/system would be of great value in assisting this and in enabling the development of strategies to optimize it. A representative simulation model can provide insights into various phenomena that appear during drilling for different drilling conditions. Such a model is also likely to be of assistance in preparing various measurements. Issues such as choosing the type of sensors, their positions and which quantities to measure are supported by a model. A well calibrated model in combination with information extracted from measured data are hence likely to assist in selecting control strategies for optimized drilling performance. In this paper we present a MATLAB based 1D simulation model of a Down The Hole (DTH) drill and compare it with an existing 1D model in terms of computational speed and accuracy. The emphasis is to make a 3D model of a DTH system that is computationally efficient and accurate.

  • 34.
    Kovacikova, Janka
    et al.
    Slovak University of Technology in Bratislava, Slovakia.
    Ivankova, Olga
    Slovak University of Technology in Bratislava, Slovakia.
    Drobny, Dusan
    Samsung electonics, Slovakia.
    An Influence of a Shape of a Flaw on a Value of Stress on Beams2016In: Applied Mechanics and Materials, ISSN 1660-9336, E-ISSN 1662-7482, Vol. 837, p. 230-233Article in journal (Refereed)
    Abstract [en]

    The main topic of this paper is finite element analysis of 4-point loaded glulam beams which contain different types of flaws. There were modeled four types of beams. First type was the beam without a flaw, second was the beam with a central crack in the middle of span located at the bottom edge of the beam, third model of beams contained also the central crack but this crack was located 20 mm above the edge and the last model contained a hole in the middle of the span as simulation of a knot. These models were performed and analyzed in ANSYS. Task was considered as two dimensional. There were compared values of stress in different types of beam's models.

  • 35.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    An Eulerian formulation of orthotropic elasticity and inelasticity2023In: International Conference on Plasticity, Damage, and Fracture, January 3-9, 2023: Barcelo Bavaro Punta Cana, Dominican Republic, 2023Conference paper (Refereed)
  • 36.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    An Eulerian Plasticity Model Applied for Prediction of Residual Stresses in Thermal Problems2020In: 3rd International Conference on Recent Innovations in Engineering (ICRIE) 2020, 9-10 September, 2020, Duhok, Iraq, 2020Conference paper (Refereed)
  • 37.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    An Eulerian Plasticity Model Applied to Simulation of Welding2019In: International Conference on Plasticity, Damage and Fracture, 2019Conference paper (Refereed)
  • 38.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Modelling of orthotropic elasticity and inelasticity of injection-moulded low-density polyethylene using an Eulerian model2022In: 11th European Solid Mechanics Conference4 - 8 July 2022, Galway, Ireland, 2022Conference paper (Refereed)
  • 39.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Numerical study of influence of thermal recovery on the residual stress state after melting and solidification2021In: 25th International Congress of Theoretical and Applied Mechanics – Book of Abstracts / [ed] A. Corigliano, IUTAM , 2021Conference paper (Refereed)
  • 40.
    Kroon, Martin
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Prediction of Residual Stress States Using an Eulerian Plasticity Model2021In: 16th US National Congress on Computational Mechanics, July 25-29, 2021, 2021Conference paper (Refereed)
  • 41.
    Kroon, Martin
    et al.
    Royal Institute of Technology.
    Faleskog, Jonas
    Royal Institute of Technology.
    Öberg, Hans
    Royal Institute of Technology.
    A probabilistic model for cleavage fracture with a length scale: parameter estimation and predictions of growing crack experiments2008In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, no 8, p. 2398-2417Article in journal (Refereed)
    Abstract [en]

    A probabilistic model for the cumulative probability of failure by cleavage fracture was applied to experimental results where cleavage fracture was preceded by ductile crack growth. The model, introduced by Kroon and Faleskog [Kroon M, Faleskog J. A probabilistic model for cleavage fracture with a length scale – influence of material parameters and constraint. Int J Fract 2002;118:99–118], includes a non-local stress with an associated material related length scale, and it also includes a strain measure to account for the number of nucleated cleavage initiation sites. The experiments were performed on single edge cracked bend test specimens with three different crack lengths at the temperature 85 °C, which is in the upper transition region for the steel in question. The ductile rupture process is modelled using the cell model for nonlinear fracture mechanics. The original cleavage fracture model had to be modified in order to account for the substantial number of cleavage initiators being consumed by the ductile process. With this modification, the model was able to accurately capture the experimental failure probability distribution.

  • 42.
    Kroon, Martin
    et al.
    Royal Institute of Technology.
    Faleskog, Jonas
    Royal Institute of Technology.
    Öberg, Hans
    Royal Institute of Technology.
    A probabilistic model for cleavage fracture with a length scale: parameter estimation and predictions of stationary crack experiments2004In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 71, no 1, p. 57-79Article in journal (Refereed)
    Abstract [en]

    This study presents a large experimental investigation in the transition temperature region on a modified A508 steel. Tests were carried out on single-edge-notch-bend specimens with three different crack depth over specimen width ratios to capture the strong constraint effect on fracture toughness. Three test temperatures were considered, covering a range of 85 °C. All specimens failed by cleavage fracture prior to ductile tearing. A recently proposed probabilistic model for the cumulative failure by cleavage was applied to the comprehensive sets of experimental data. This modified weakest link model incorporates a length scale, which together with a threshold stress reduce the scatter in predicted toughness distributions as well as introduces a fracture toughness threshold value. Model parameters were estimated by a robust procedure, which is crucial in applications of probabilistic models to real structures. The conformity between predicted and experimental toughness distributions, respectively, were notable at all the test temperatures.

  • 43.
    Kroon, Martin
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Lindström, Per
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Rubin, M. B:
    Technion, Israel.
    Prediction of welding residual stresses using an Eulerian plasticity model2022In: Proceedings M2D2022 - 9th International Conference on Mechanics and Materials in Design, Funchal/Portugal 26-30 June 2022 / [ed] J.F. Silva Gomes and S.A. Meguid, 2022, p. 167-168, article id 18249Conference paper (Refereed)
    Abstract [en]

    Solidification processes play an important role in several industrial processes, such as weldingand additive manufacturing, and the resulting residual stress state is often critical for thestructural integrity of the material. A thermomechanical model was developed for the analysisand prediction of such solidification processes. The approach is based on a model proposed byRubin (Int. J. Eng. Sci. 25, 1175-1191, 1987). This plasticity model was formulated for finitestrains using an Eulerian evolution equation for a unimodular elastic distortional deformationtensor. This evolution equation automatically ensures thermodynamic consistency andpreservation of isochoric inelastic deformations. A 2D problem in the form of a butt weld jointwas analyzed. The main outcome from the analyses were the residual stress distributions. Theresults are compared to experimental data from the literature.

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  • 44.
    Kroon, Martin
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Rubin, M. B.
    Technion, Israel.
    An Eulerian model for orthotropic elasticity and inelasticity applied to injection-moulded low-density polyethylene2022In: Mechanics of materials, ISSN 0167-6636, E-ISSN 1872-7743, Vol. 167, article id 104239Article in journal (Refereed)
    Abstract [en]

    Anisotropic elasticity and inelasticity is of relevance in many practical applications. The Eulerian formulation for anisotropic elastic and inelastic response based on microstructural vectors is used here to model an injection-moulded low-density polyethylene. In contrast with Lagrangian models of inelasticity, the Eulerian formulation is insensitive to arbitrariness of the reference and intermediate configurations as well as to measures of total and inelastic deformations. A specific strain-space-type anisotropic yield function is proposed that depends on anisotropic measures of elastic deformation and anisotropic hardening variables. Use is also made of a rate-independent model with a smooth elastic-inelastic transition. The material parameters were calibrated to reproduce uniaxial test data for loading in three directions in the moulding plane. In addition, a strongly objective numerical implementation is presented and used to simulate stretching of a plate with a circular hole. In contrast with metals, this polyethylene experiences elastic deformations of about 10%. Although the inelastic spin rate could not be determined by the available test data, simulations of loadings in different material directions yield observable influences of inelastic spin rate.

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    Fulltext
  • 45.
    Larsson, Andreas
    Chalmers.
    Localization of Finite Element Model Errors: Error Criteria and Identifiability1999Licentiate thesis, monograph (Other academic)
  • 46.
    Larsson, Andreas
    et al.
    Chalmers University of Technology.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    A Comparison of Finite Element Model Error Localization Methods1999In: 1999 IMAC XVII - 17th International Modal Analysis Conference, Orlando, Florida, 1999, p. 929-935Conference paper (Refereed)
    Abstract [en]

    The aim of this study is to compare a new and some existing finite element model error localization methods. The methods are applied to two problems. First, fundamental properties of the error localization methods are studied on a simple sprung mass  system.  In  the second  problem  a  three-bay  frame structure is studied. Here the analytical results of a finite element analysis is taken as substitute for measured data. The model differences between this model and a perturbed model are then found by use of error localization methods.

    When data from a known finite element model take place as substitute for test data, the cause of the differences between the data sets are known. A so-called consistent para- meterization, i.e. a parameterization of the quantities known to be in error, is then possible. The error localization method are  compared for both consistent and inconsistent parameterization.

    A pre-error localization is made. It is based on the finite element model’s properties. Candidate model parameters, possibly in error, for which the experimental data are not informative,  are  rejected.  Non-identifiable  parameters  are also rejected. Quantification of data information richness and identifiability with newly developed index numbers support the pre-error localization.

    Four error localization methods are compared. Two of these are developed by Lallement and Piranda. These are the so- called Balancing of Eigenvalue Equation and Best Subspace Methods. The third is developed by Link and Santiago and is the Substructure Energy Function Method. A new localization method, using gradient and Hessian information of the error criterion function, constitute the fourth method.

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    A COMPARISION OF FINITE ELEMENT MODEL ERROR LOCALIZATION METHODS.pdf
  • 47.
    Larsson, Andreas
    et al.
    Chalmers University of Technology.
    Abrahamsson, Thomas
    Chalmers.
    On the Parameter Identifiability and Test Data Informativeness in Finite Element Model Error Localization2000In: Proceedings of IMAC XVIII, San Antonio, TX, 2000, p. 1520-1527Conference paper (Refereed)
    Abstract [en]

    Two fundamental questions that arise in finite ele- ment model updating and error localization prob- lems are addressed. These are whether available test data are informative enough with respect to the quantification of possible model errors and whether sufficient identifiability of such errors is at hand for a given test data set. We advocate the use of informativeness and identifiability based indices in a preparatory process to increase the likelihood of a successful error localization. Based on model properties, such informativeness and identifiability indices may be used in the pre-test planning for the determination of frequency, time and spatial resolution to be used in a vibratory test.

     

    First, the test data informativeness with respect to model parameters which might be in error is quan- tified. Here a dual assumption is made such that if model parameter perturbations could be detected by data from the planned test, then the test data could be used to detect such perturbations, i.e. the test is informative. A Data Information Richness (DIR) index has been developed to assess the level od Data Informativeness with respect to model parameters. Secondly, the identifiability of the model parame- ters are studied. The dynamic properties of a struc- ture, as recorded by a measurement system, may under certain conditions change similarly by changing one parameter or a set of other parame

    ters. Should that be the case, there is no identifi- ability and before a meaningful error localization may take place, either complementary test data have to be added or a re-parameterization of the model has to be made. To assess the identifiability, identifiability based criteria are further developed, based on earlier work by the authors. A newly developed orthogonality/co-linearity index ocI assist in the re-parameterization of systems with low identifiability.

     

    The methods of preparatory error localisation are applied to a six-degree-of-freedom system in a numerical example in which the analytical results of a finite element analysis are taken as substitute for measured data.

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    On the Parameter Identifiability and Test Data Informativeness in Finite Element Model Error Localization.pdf
  • 48.
    Levin, Erik
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Andersson, Daniel
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Utveckling av bakluckan på Volvos ramstyrda dumper2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Målet med detta arbete var från början att ta fram 2-3 olika koncept som hindrar dumperns baklucka från att studsa och skapa onödigt buller. En produktutvecklingsprocess anpassades för projektet och användes för att systematiskt genomföra arbetet. Under arbetets gång gjordes valet att uppdatera målet till att ta fram en fullskalig prototyp och testa denna på en dumper. Resultatet blev en robust och ekonomisk produkt som hindrar bakluckan från att studsa och sänker dumperns bullernivå avsevärt.

    Download full text (pdf)
    fulltext
  • 49.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials.
    An Experimental Substructure Test Object: Components Cut Out From A Steel Structure2021In: Dynamic Substructures, volume 4: Proceedings of the 38th IMAC, A Conference and Exposition on Structural Dynamics 2020 / [ed] Linderholt A., Allen M..S., Mayes R.L., D'Ambrogio W, Springer, 2021, Vol. 4, p. 149-156Conference paper (Other academic)
    Abstract [en]

    Substructuring is the topic of the Society of Experimental Mechanics’ Technical Division on Dynamic Substructures. During a number of the most recent IMAC conferences, a lot of studies of coupling and de-coupling of substructures have been presented. In addition, frequency response-, modal- and state-space based techniques for coupling of components represented by numerical or experimental models have been developed. In many such studies, the dynamics of the numerically coupled structures are compared with test data stemming from measurements of the physically assembled counterparts.

    An embedded issue when assembling components is the interfacing between the substructures, introducing dry friction in the form of micro slip and varying contact areas. These introduced sources of deviation between the numerically formed assembly and its real world counterpart blend with sources, of deviation, such that test data being incomplete, biased or having random errors.

    Here, the initial test object is manufactured as a one piece solid structure. After that, the structure will be cut to form two substructures. Finally, the substructures will be assembled again. Vibrational tests will be made on the solid structure, the substructures as well as on the assembly. The aim is to compare vibrational data and differences in dynamical properties; especially damping, eigenfrequencies and linearity between the solid structures, the numerically formed assembled and the physical re-assembled structure are studied. The purpose of the study is to isolate the causes of possibly deviations by removing the issues stemming from unknown interfaces. Here, the structure together with synthetic modes are presented.

  • 50.
    Linderholt, Andreas
    Chalmers University of Technology.
    Localization of Finite Element Model Errors: Error Criteria and Identifiability1999Licentiate thesis, monograph (Other academic)
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