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  • 1.
    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.

  • 2.
    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.

  • 3.
    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

  • 4.
    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.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8. 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.

  • 9. 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.

  • 10. 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.

  • 11. 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.

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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.

  • 18.
    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.

  • 19. Håkansson, Lars
    et al.
    Olsson, Sven
    Claesson, Ingvar
    Anordning för styrning av vibrationer i en maskin förskärande bearbetning2004Patent (Other (popular science, discussion, etc.))
  • 20.
    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.

  • 21.
    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)
  • 22.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco Rock Drills AB.
    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.
    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.

  • 23.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco Rock Drills AB.
    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.
    Numerical 1D and 3D models representing a DTH drilling system: A comparison of accuracy and computational speed2018In: Proceedings of the 25th International Congress on Sound and Vibration, The International Institute of Acoustics and Vibration , 2018 / [ed] The International Institute of Acoustics and Vibration , 2018., International Institute of Acoustics and Vibration (IIAV) , 2018Conference 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.

  • 24.
    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.

  • 25.
    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.

  • 26.
    Larsson, Andreas
    Chalmers.
    Localization of Finite Element Model Errors: Error Criteria and Identifiability1999Licentiate thesis, monograph (Other academic)
  • 27.
    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.

  • 28.
    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.

  • 29.
    Linderholt, Andreas
    Chalmers University of Technology.
    Localization of Finite Element Model Errors: Error Criteria and Identifiability1999Licentiate thesis, monograph (Other academic)
  • 30.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Model Calibration of an A600 Wind Turbine Blade2013In: Proceedings of the International Modal Analysis Conference (IMAC XXXI), Orange County, CA, 2013Conference paper (Refereed)
  • 31.
    Linderholt, Andreas
    Chalmers tekniska högskola.
    Test Design for Finite Element Model Updating: Identifiable Parameters and Informative Test Data2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is important to predict structural phenomena, such as noise and fatigue, stemming from vibra- tions. To do this, reliable structural dynamic models are needed. To be useful the models have to compare well with reality in the validation against test data; if not, the models should be mod- ified. The thesis research is in the field of computational model updating, which is, more often than not, the updating of uncertain parameters of a finite element model to better correlate to test data. This is a specialization that started to grow in the 1970s, and since then much research has been done. The work presented here concerns the design of tests for model updating, which is one of several model updating sub-tasks.

     For a test to be useful for model updating, the test data set must be such that the model param- eters are sufficiently well identifiable. The dynamic properties of a structure to be compared with test data may under certain conditions change similarly when one parameter or a set of other parameters is changed. When this happens, there is lack of identifiability and, before a meaningful model updating can take place, either complementary test data have to be added or a re-parameterization of the model must be made. An index was developed, the Orthogonality- Co-linearity Index (OCI), that helps to find the best way to reduce the number of parameters when there is low identifiability. For the model updating, test data also need to be informative with respect to the parameters to be tuned. The data informativeness depends on the test design, i.e. the choice of stimuli and the placement of the actuators and sensors. A data informativeness index that supports the design of an informative test is proposed. Procedures were also worked out to make the test design robust with respect to parameter uncertainties. The study is limited to linear and time-invariant systems.

  • 32.
    Linderholt, Andreas
    et al.
    Chalmers University of Technology, Sweden.
    Abrahamsson, Thomas
    Chalmers University of Technology, Sweden.
    A Comparison of Finite Element Model ErrorLocalization Methods1999In: International Modal Analysis Conference (IMAC) XVII, Orlando, Florida, 1999., 1999, p. 929-935Conference paper (Other academic)
    Abstract [en]

    The aim of this study is to compare a new and some existing finite elementmodel error localization methods. The methods are applied to two problems. First,fundamental properties of the error localization methodsare studied on asimple sprung mass system. Inthe second problem a three-bay frame structure is studied.Here the analytical results of a finite element analysisis taken as substitute for measured  data. The model differences between  thismodel 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-calledconsistent para­ meterization, i.e. a parameterization of the quantities known to be in error, is then possible. The error localization methods are compared for both consistent and inconsistent parameterization. A pre-error  localization  is  made. It is based  on  the  finiteelement model's properties. Candidatemodel 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.

  • 33.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Abrahamsson, Thomas
    Chalmers.
    Finding Local Non-Linearities Using Error Localization from Model Updating Theory: Proceedings of the 30th IMAC, A Conference on Structural Dynamics, 20122012In: Topic in Nonlinear Dynamics: Vol. 3 / [ed] D. Adams, G. Kerschen, A. Carrella, New York: Springer, 2012, p. 323-334Chapter in book (Refereed)
    Abstract [en]

    Within the aerospace industry, linear finite element models are traditionally used to describe the global structural dynamics of an aircraft. Ground vibration test data serve to facilitate the validation of models which are then used to characterize the aeroelastic behavior of the aircraft and to predict the responses due to dynamic loads. Thus, it is vital that the models contain the essential dynamics of the aircraft. Observed nonlinearities are judged to be local in nature whereas the main part of the structure behaves linearly under normal loading. In this work we focus on the identification of nonlinear effects and do that based on model updating theory. That includes methods for error localization with proper selection of candidate error parameters. The nonlinearities are treated as local modeling errors not considered in the linear system model. The error localization behavior is studied using synthetic test data from a simple system, known as the ECL Benchmark, with known nonlinear properties.

  • 34.
    Linderholt, Andreas
    et al.
    Chalmers University of Technology, Sweden.
    Abrahamsson, Thomas
    Chalmers University of Technology, Sweden.
    On the Parameter Identifiability and Test Data Informativeness in Finite Element Model Error Localization2000In: Proceedings of IMAC XVIII - 18th International Modal Analysis Conference, 2000, p. 1520-1527Conference paper (Other academic)
    Abstract [en]

    Two fundamental questions that arise in finite ele­ment 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 of data informativeness with respect to model parameters. Secondly, the identifiability of the model parame­ ters are studied. The dynamic properties of a struc­  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.

  • 35.
    Linderholt, Andreas
    et al.
    Chalmers University of Technology.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    On the Requirements of Physical Parameters to be used in Model Updating2001In: Proceedings of International Conference on Structural System Identification, Kassel, Germany, 2001Conference paper (Refereed)
    Abstract [en]

    A fundamental question that arises in finite element model updating and error localization problems is which requirements that have to be fulfilled by the physical parameters to be used in the procedures.

     

    One requirement is that the test data are informative with respect to the chosen parameters. That implies that a change of a certain parameter should give a detectable change in the model’s dynamic behaviour. Another requirement is that the chosen parameters should be identifiable. The dynamic properties of a structure, as recorded by a measurement system, may under certain conditions change similarly by changing one parameter or a set of other parameters. Should that be the case, there is no identifiability.

     

    This article shows that parameters of which test data have low informativeness and parame- ters that are lacking identifiability, are of no use for error localization or model updating and should therefore not be used for these purposes. Thus, 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.

     

    Before an error localization is to be carried out a preparatory error localization, using only data from an FE-analysis, is justified. The purpose of such preparatory work is both to decide which parameters to use to quantify model errors and to design the tests for the error localiza- tion in order to meet the parameter requirements.

  • 36.
    Linderholt, Andreas
    et al.
    Chalmers University.
    Abrahamsson, Thomas
    Chalmers University.
    Parameter Identifiability in Finite Element Model Error Localization1999In: Svenska Mekanikdagarna, Stockholm, 1999Conference paper (Refereed)
  • 37.
    Linderholt, Andreas
    et al.
    Chalmers University.
    Abrahamsson, Thomas
    Chalmers.
    Parameter Requirements in Model Updating2001In: Nordic Vibration Research, Stockholm, 2001Conference paper (Refereed)
  • 38.
    Linderholt, Andreas
    et al.
    Chalmers tekniska högskola, Sweden.
    Abrahamsson, Thomas
    Chalmers tekniska högskola, Sweden.
    Test Data Informativeness Assessment for Finite Element Model Updating2002Report (Other academic)
    Abstract [en]

    Before a computational model updating or an error localization is to be carried out, a prepara­ tory error localization using only analytical data is justified. The purpose of such preparation should be to select the parameters for quantifying model errors and also to design optimal tests for determining the correct parameter setting. For a successful error localization, it is required that the test data should be informative with respect to the parameters chosen. The demand for test data informativeness limits the experiment with regard to the spatial resolution of sensors, bandwidth of excitation, signal-to-noise ratios, etc. On the other hand, for a given test condition and test data, the omnipresent noise may make parameter estimates useless because of estima­ tion covariances that are too large. This is often caused by over parameterized models; these should be identified by the preparatory error localization and remedied by are-parameterization before model updating take place.

     

    The aim of this study is to quantify data informativeness with respect to physical parameters that are used in error localization and model updating. The data informativeness  is shown to relate to the Fisher information matrix. Deterministic finite-element related state-space models in combination with stochastic noise models are used for evaluating data informativeness.  A nu­ merical study utilizing a finite-element model validated by test data from a scanning laser vi­ brometer is used to substantiate the theory.

  • 39.
    Linderholt, Andreas
    et al.
    Chalmers University of Technology.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    Test Data Informativeness Assessment for Finite Element Model Updating2003In: Proceedings of IMAC XXI, Orlando, Florida, 2003Conference paper (Refereed)
    Abstract [en]

    In advance of a computational model updating or an er- ror localization, it can be advantageous to make a pre- paratory error localization using a nominal analytical model. The purpose is then to select parameters for quantifying model errors and also to design effective tests for determining the best parameter setting. For suc- cessful error localization, the test data must be informa- tive with respect to the model parameters chosen. For dynamic  computational  models,  the  demand  for  test data informativeness puts limitations on the experiment with regard to spatial resolution of sensors, bandwidth of excitation, signal-to-noise ratios, etc.

     

    Solving a full test design optimization problem is a huge task, sometimes impossible in practice, due to its com- binatorial nature. The number of possible sensor/actua- tor  placement  combinations  grows  rapidly  as  the number of sensor and actuator candidates increases. For industrial sized problems, finding a sub-optimal solu- tion may be a more realistic target.

     

    The aim of this study is to quantify data informative- ness, shown to relate to the Fisher information matrix, with respect to physical parameters that are used in error localization and model updating. Deterministic finite- element models in combination with stochastic noise models are used for evaluating data informativeness, and a procedure for test design optimization with re- spect to this is devised.

  • 40.
    Linderholt, Andreas
    et al.
    Chalmers University.
    Abrahamsson, Thomas
    Chalmers.
    Test Design aiming at Informative Test Data with Respect to Model Parameters2002In: Proceedings of The International Conference on Structural Dynamics Modelling, 2002Conference paper (Refereed)
  • 41.
    Linderholt, Andreas
    et al.
    Chalmers University of Technology.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    Hoang, Nam
    Structural Engineering Program, School of Civil Engineering, Asian Institute of Technology.
    Information in Data Used for Finite Element Model Updating: Theory and Experiment2001In: Proceedings of SEM Annual Conference on Experimental Mechanics, Portland, Oregon, 2001Conference paper (Refereed)
    Abstract [en]

    To discriminate bad parameter settings from good, in finite element modelling, experimental data is usually required. Such experimental data should be informative with respect to the parameters in ques- tion. The demand for informativeness put require- ments on the experiment with regards to spatial resolution of sensors, bandwidth of shaker excita- tion, ambient noise levels, etc. In this paper, in- formativeness is studied by means of the Fisher information matrix and parameter accuracy is relat- ed to the adjoint statistical Cramer-Rao lower bound. The evaluation of information content in data used for model updating is discussed. Deter- ministic state-space models and stochastic noise models are used for informativeness evaluation. A numerical study together with Scanning laser vi- brometer measurements, on a system with well known mass perturbations, are used to substantiate the theory.

  • 42.
    Linderholt, Andreas
    et al.
    Chalmers University of Technology.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    Hoang, Nam
    Structural Engineering Program, School of Civil Engineering, Asian Institute of Technology.
    Informative Data for Model Parameter Updating2001In: Proceedings of IMAC XIX, Orlando, Florida, 2001, p. 581-586Conference paper (Refereed)
    Abstract [en]

    Before an error localization is to be carried out a preparatory error localization, using only data from an FE-analysis, is justified. The purpose of such preparatory work is both to decide what parameters to use to quantify model errors and to design opti- mal tests for the error localization. A reasonable re- quirement on the parameterization is that the test data are informative with respect to the parameters. That implies that a change of a certain parameter should give a detectable change in the model’s dy- namic behaviour.

     

    The aim of this study is to examine data informa- tivity with respect to physical parameters, used in error localization and model updating. The data in- formativity is here quantified by the use of the Fisher information matrix. It is shown that the in- formativity depends on both excitation and meas- urements. It is reasonable to believe that parameters of which test data have low informativ- ity, are of no use for error localization and should not be used for model updating purposes. Such pa- rameters should be excluded from the parameters set or the test aimed for its determination should be re-designed.

  • 43.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Abrahamsson, Thomas
    Chalmers University of Technology.
    Johansson, Anders
    Chalmers University of Technology.
    Mahdiabadi, Morteza Karamooz
    Technical University of Munich, Germany.
    Rixen, Daniel
    Technical University of Munich, Germany.
    The Dynamic Behavior of Three Sets of the Ampair 600 Wind Turbine2016In: Proceedings of the International Modal Analysis Conference (IMAC XXXIV), 2016 / [ed] Society of Experimental Mechanics, SEM Society of Experimental Mechanics , 2016Conference paper (Other academic)
    Abstract [en]

    A modified version of the Ampair 600 wind turbine was defined by the SEM substructuring focus group to be a benchmark for use in the pursuit of developing methods for high precision experimental substructuring. Today, seven such, intended to be identical, systems have been assembled at test laboratories within Europe and the USA. This paper reports the experimentally found dynamic behavior of five out of the seven systems. The aim of the study is to provide high fidelity data to support future component synthesis and model validation activities. Comparisons are made by evaluating deviations of measured frequency response functions and identified structural eigenfrequencies together with the correlation between eigenvector estimates. The testing is made in two parts. First, partly assembled systems, not including the rotors or the blades, are tested. This constitutes one possible and logical subsystem splitting that is likely to appear in future substructure synthesis efforts. In the second part, the fully assembled benchmark systems are tested. The test procedure, the test setup, the obtained test data and test data statistics are presented.

  • 44.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Abrahamsson, Thomas
    Chalmers, Sweden.
    Johansson, Anders
    Chalmers, Sweden.
    Steinepreis, Daniel
    University of Stuttgart, Germany.
    Reuss, Pascal
    University of Stuttgart, Germany.
    A Comparison of the Dynamic Behavior of Three Sets of the Ampair 600 Wind Turbine2015In: Dynamics of Coupled Structures: Proceedings of the 33rd IMAC, A Conference and Exposition on Structural Dynamics, 2015 / [ed] Matt Allen, Randall L. Mayes, Daniel J. Rixen, Springer Publishing Company, 2015, Vol. 4, p. 99-110Conference paper (Other academic)
    Abstract [en]

    The Ampair 600  wind turbine assembly has been modified to suit as a benchmark structure in the pursuit of finding best practices for experimental substructure coupling of structural dynamic systems. Seven such systems have been assembled in test laboratories in Europe and in the USA. We scrutinize the dynamic behavior of the total assembly of three of those by vibration testing and compare the test outcome from seemingly identical assemblies. The aim is to support future component synthesis activities with high fidelity data and support future model validation. Comparisons are made by evaluating deviations of measured frequency response functions, the differences of identified structural eigenfrequencies and the correlation between eigenvector estimates. The testing is made in two parts. First, a partly assembled system, not including the hub and blades, is tested. This constitutes one possible and logical subsystem splitting that is likely to appear in future substructure synthesis efforts. In the second part, the full system assembly is tested. The test procedure, the test setup, the obtained test data and test data statistics are presented.

  • 45.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Chen, Yousheng
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Orlowitz, Esben
    University of Southern Denmark, Denmark.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    A study of the coupling between test data accuracy and life prediction2014In: Proceedings of ISMA2014 including USD2014: 26th International Conference on Noise and Vibration Engineering and 5th International Conference on Uncertainty in Structural Dynamics, 15-17 September 2014, Leuven, Belgium / [ed] P. Sas, H. Denayer & D. Moens, Leuven: Katholieke Universiteit Leuven, Department of Mechanical Engineering , 2014, p. 415-428Conference paper (Other academic)
    Abstract [en]

    Computational models are regularly used to predict responses and the life of structures. Often, the computational models are validated by use of data stemming from vibration testing. However, the damping values are almost always taken from test alone and hence cannot be validated. Experimentally obtained damping values are well known to have relatively high uncertainties. In the present paper we investigate how life time predictions are affected by modal damping uncertainties by simulating responses due to random loads. The simulations are based on experimental modal analysis results of a structure consisting of two steel plates which are joined by bolts, tested under several different experimental support conditions. The results illustrate the importance of careful consideration of experimental test setups, as these can strongly affect the obtained damping estimates. This, in turn, can lead to large differences in predicted life time.

  • 46.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Olsson, Jörgen
    RISE Research Institutes of Sweden AB.
    A simulation based study of low frequency transient sound radiation from floors: a concrete vs. a hybrid floor2017In: Proceedings of the 24th International Congress on Sound and Vibration, Curran Associates, Inc., 2017Conference paper (Other academic)
    Abstract [en]

    Timber is a renewable and human friendly construction material and thereby a potential solution toachieve life cycle sustainable buildings. However, it is clear that impact sound and vibrations withinthe low frequency range still are challenges for wooden joist floors. Another challenge is the,mostly, larger building heights of wooden or hybrid floors compared to the heights of concretefloors. Using timber as the structural joist floor material could imply fewer stories due to maximumallowed building heights, which renders in less income in a building project. Accurate simulationsof impact sound may decrease the need for prototypes; thus saving money and time in the timberbuilding industry. Here, a hybrid joist floor consisting of wood, sand and steel is compared to aconcrete floor in terms of radiated impact sound into a rectangular cavity. The hybrid floor is designedsuch that its mass distribution and global stiffness are close to the same properties of theconcrete floor. Finite element models are used for simulations of the radiated transient sound inducedby impact forces having the characteristics of human walking. The simulations indicate thatsimilar surface mass and bending stiffness of a floor intersection give similar impact sound transmissionproperties around the first bending mode, while it is not necessary so at higher frequencies.Keywords: timber buildings, impact sound, simulation

  • 47.
    Linderholt, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Scheel, Maren
    Chalmers University of Technology, Sweden.
    Johansson, Anders
    Chalmers University of Technology, Sweden.
    Effects of Interface Loading in Dynamic Substructuring2015In: ICoEV 2015: International Conference on Engineering Vibration, (ICoEV) 2015 Ljubljana, 7-10 September, 2015 / [ed] Miha Boltezar, Ljubjana: University of Ljubljana , 2015Conference paper (Other academic)
    Abstract [en]

    Over the last few IMAC conferences, the SEM substructuring focus group’s benchmark; the Ampair A600 wind turbine, has been thoroughly studied, at substructure as well as system levels but also by implementation of different substructuring techniques for assembling experimental and/or analytical component models.

    Within the focus group, work dedicated to appropriate interfacing between substructures has furthermore been an area of increased interest. This is notable through the use of the transmission simulator method. This paper draws on that paradigm in studying the end effects on assembled structures of using nominally identical substructure models derived from experimental setups with different levels of mass loading at the interface. Specifically, experimental models for an A600 blade and bracket system attached to dummy masses of different sizes are coupled to an analytical model of the hub. The results are compared to analytical results of the full system.

  • 48.
    Lindström, Per
    et al.
    Chalmers University of Technology.
    Faraji, Maneli
    Chalmers University of Technology.
    Review and Selection of a Finite Element Simulation Platform For Academic and Industrial Analyses of In-Service Welding Operations2004In: Proceedings of OMAE’04 23rd International Conference on Offshore Mechanics and Arctic Engineering, June 20-25, 2004, Vancouver, British Columbia, Canada, ASME Press, 2004, Vol. 2, p. 801-806, article id 51246Conference paper (Refereed)
    Abstract [en]

    In order find a general platform/environment forsimulation of in-service welding operations, a review andanalysis of non-linear Finite Element Analysis, FEA, programshave been performed. Free and commercial softwares havebeen considered and the programs that have been reviewed andevaluated are ABAQUS, CALCULIX, CODE-ASTER, MARCand SYSWELD. Different platforms, i.e. workstation configurationswith the associated Operative System, OS, has alsobeen investigated to find an optimised simulation platformsolution. To facilitate the selection of a suitable simulationplatform, the performance and durability of ABAQUS has beenevaluated by means of an in-service weld simulation.The residual weld hoop stresses of the weld simulationhave been compared with the results of girth weld experimentsfrom bibliographic sources. To enhance the evaluation processas well as gain experiences of measuring residual weld stresses,two (2) girth welds with measurement of the weld hoop stresseshave been carried out. The maximum solving performance ofABAQUS was obtained by means of a tailor-made workstation,configured with the OS Slackware Linux 9.1 and a speciallycompiled Linux kernel.The findings of the research will be utilized on selection ofa FEA-simulation platform that will be used for the purpose ofscientific research and industrial development in the field of inservicewelding operations.

  • 49.
    Lindström, Per
    et al.
    University West ; DNV GL Materials Laboratory, Norway.
    Jonsson, Anders
    DYNAmore Nordic AB .
    Jernberg, Anders
    DYNAmore Nordic AB .
    Östby, Erling
    DNV GL Materials Laboratory, Norway.
    Non-linear fracture mechanics in LS-DYNA and LS-PrePost2015In: European LS-DYNA Conference 2015: Conference Papers, Würzburg: DYNAmore GmbH , 2015Conference paper (Other academic)
    Abstract [en]

    Fracture mechanics provides an engineering framework for assessing the consequences of defects instructures. In linear elastic fracture mechanics (LEFM), stress intensity factors KI, KII and KIII are usedfor characterizing the stress singularity at the crack tip, which arises from the theory of linear elasticity.Crack growth is assumed to occur when KI exceeds the fracture toughness KC. LEFM can be usefulfor brittle materials, or when the size of the plastic zone is small compared to global dimensions. In non-linear fracture mechanics (EPFM), an energy based criterion is used for assessing the risk forcrack growth: if the energy release rate at the crack tip exceeds what is required for creating newsurfaces in the material, crack growth will occur. Under certain assumptions the energy release rate atthe crack tip can be calculated by a path independent integral, the so-called J-integral. In modernFE-based fracture mechanics applied to practical design, the structure under consideration ismodelled, including cracks at specific locations, and the J-integral values are computed and used asdesign criteria. From a numerics viewpoint, the J-integral has many appealing properties: it can beevaluated from the far-field solution, which reduces numerical errors that may arise close to the cracktip, and the expected path-independence can to some extent be used as a quick check on solutionvalidity.Evaluation of the J-integral from LS-DYNA simulation results has been implemented as a postprocessingtool in LS-PrePost, including consistent treatment of residual stresses. The implementationcovers both 2D (plane stress / plane strain) and 3D applications, using the virtual crack-tip extension(VCE) method. The tool is accessible both via the LS-PrePost GUI and via command file interface.

  • 50.
    Lindström, Per
    et al.
    DNV Materials Laboratory ; Chalmers University of Technology.
    Josefson, Lennart
    Chalmers University of Technology.
    2D, Axisymmetric and 3D Finite Element Analysis Assessment of the IIW RSDP Round Robin Initiative, Phase 1 and Phase 22012Report (Other academic)
    Abstract [en]

    A further assessment of the IIW numerical and experimental test RSDP Round Robin Initiative, Phase 1 and Phase 2 is presented. Focus is on the weld process specification, and the importance ofuse of as realistic as possible weld process parameters in the weld simulations. Considerable interpretation is often required of the weld designer and of the FE modeller when simulatinga weld process. The paper demonstrates, on the IIW RSDP round Robin benchmarks, that with interpretation and judgement, Computational Welding Mechanics using a variety of models and approaches is possible. Difficulties in interpretation could be substantially reduced through the use of industrial methods of specification, weld process specifications (WPS). For this reason, the authors recommend that all benchmarks follow the standards and definitions used in internationally recognised industrial standards. For the Phase 1 benchmark three-pass butt welded pipe case, which was a designed case for weld simulations, rotationally symmetric and fully 3D results are presented for temperatures, deformations and stresses. These results are compared with IIW benchmark results, and differences caused by weld process parameters and material modelling (for the mechanical analysis) are discussed.For the Phase 2 benchmark two pass butt welded coupon plate case, experimental results are available. The incomplete documentation from the weld experiment compared to realistic WPS is discussed. 3D thermal results coupled with generalised plane strain 2D results for temperatures, deformations and stresses using correct WPS and realistic material data are presented and compared with IIW benchmark results. SFor both Benchmarks the LS-Dyna FE software was used, with a major modification being a modified Goldak heat source model.

12 1 - 50 of 58
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