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  • 3251. Wall, Johan
    Simulation-Driven Design of Complex Mechanical and Mechatronic Systems2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Effective and efficient product development is critical to business success on the increasingly competitive global market, and simulation has proven to support this in many sectors. The aim of this thesis is to study how properties of complex mechanical and mechatronic systems can be more efficiently and systematically predicted, described, assessed and improved in product development. The purpose is to elaborate an approach that can, rather than only verifying solutions that are already decided upon, support dialogues with customers, stimulate creation of new concepts and provide guidance towards more optimised designs, especially in early development stages. This is here termed simulation-driven design. To be useful for this, product models and simulation and optimisation procedures must be efficient, that is, they must accurately answer posed questions and point towards better solutions while consuming an acceptable amount of time and other resources. In this thesis a coordinated approach to create such efficient decision support is elaborated. This is done by action research through two industrial case studies; an automobile exhaust system representing a complex mechanical system and a water jet cutting machine representing a mechatronic system. The general knowledge gained from these case studies should be a good base for coming implementation of this approach as an inherent working routine in companies developing complex mechanical and mechatronic products. A specific result is a validated virtual model of the exhaust system, which facilitates fast structural dynamics simulation of customer proposed design layouts. It is also shown that the non-linear flexible joint between the manifold and the rest of the exhaust system makes the system behaviour complex. This has resulted in an additional general research question, namely how systems that are linear, except for small but significant non-linear parts, can be simulated in an efficient way. Another specific result is a validated real-time virtual machine concept for simulation of the water jet cutting machine, which facilitates early-stage design optimisation. As the mechanics and the control system are considered simultaneously, interaction effects can be utilised. An introductory optimisation study shows a significant potential for improved manufacturing accuracy and a more light-weight design. This potential would not likely have been found through a conventional sequential design approach. The results of this thesis indicate that there is a great potential for improved product development performance in small and medium-sized companies. By incorporating modern simulation support these companies can improve their competitiveness as well as contribute to improved resource efficiency of society at large. In doing so, it is important to find a good balance between model fidelity, validity and cost for achieving a relevant decision support. The coordinated approach to simulation-driven design elaborated in this thesis is a promising and systematic way of finding this balance.

  • 3252. Wall, Johan
    et al.
    Englund, Thomas
    Ahlin, Kjell
    Broman, Göran
    Influence of a bellows-type flexible joint on exhaust system dynamics2004Inngår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 218, nr 12, s. 1473-1478Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Most modern cars have a bellows-type flexible joint between the manifold and the catalytic converter to allow for thermal expansion and to decouple large engine movements and vibrations from the rest of the exhaust system. To obtain better understanding of the influence of this joint, the dynamic response of a typical exhaust system is studied when excited via different joint configurations. Measurements show the great order of reduction of vibration transmission to the exhaust system that a bellows joint, with and without an inside liner, gives in comparison with a stiff joint. For the combined bellows and liner joint vibration transmission is however higher than for the bellows alone. Together with some other aspects this makes the choice of including a liner in the exhaust system application complex. For a system in general the possibility of tuning the friction limit of the liner, to minimise overall vibrations through friction based damping, depends on how close to ideal the excitation source is and its location. Anyhow, the combined bellows and liner joint makes the exhaust system behaviour significantly non-linear, whereas the system behaviour proves to be essentially linear when the bellows has no liner, which imply that the liner needs to be included in theoretical models when present in the real system.

  • 3253. Wall, Johan
    et al.
    Englund, Thomas
    Ahlin, Kjell
    Broman, Göran
    Modelling of multi-ply bellows flexible joints of variable mean radius2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Bellows flexible joints are included in automobile exhaust systems to allow for engine movements and thermal expansion and to reduce vibration transmission. Generally the joint consists of a flexible bellows, an inside liner and an outside braid. In this work the bellows is considered. A straightforward way to model the bellows is to use shell finite elements. Due to the convoluted geometry of the bellows that procedure requires however a high number of elements, meaning that the bellows model would constitute a large part of the model of the exhaust system. For more effective dynamics simulations a beam finite element representation of the bellows has been presented in a prior work. This modelling procedure was implemented in the commercial software I-DEAS and was verified against experimental results available in the literature for single-ply bellows of constant mean radius. This paper suggests adjustments by which this procedure can be extended to model also multi-ply bellows of variable mean radius. Experimental investigations of a double-ply bellows having decreasing mean radius towards its ends are included for verification. The agreement between theoretical and experimental results is very good, implying that the suggested extension of the modelling procedure is valid. It is also shown that the procedure can easily be implemented into other commercial software (in this case ABAQUS). The experimental investigation reveals an intriguing resonance frequency shift at small excitation force levels. Although considered to be of minor significance for the present application of the bellows, a hypothetic qualitative explanation to the observed phenomenon is given.

  • 3254. Wall, Johan
    et al.
    Englund, Thomas
    Berghuvud, Ansel
    Identification and Modelling of Structural Dynamics Characteristics of a Water Jet Cutting Machine2004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dynamic characteristics of a water jet cutting machine, to be used in a virtual machine implemented in an analysis tool for engineering design, are derived. Machine users need for more cost effective production put demands on faster cutting. Faster cutting results in higher dynamic loads. As a consequence, problems with unwanted vibrations that decrease cutting precision may occur. Prediction of such potential problems is facilitated by an analysis tool for evaluation of suggested design solutions early in the product development process. The present work contributes to ongoing development of such an analysis tool for design engineers. An iterative approach including both theoretical and experimental analysis is applied in order to derive a structural dynamics model of the studied machine. A complex dynamic behaviour of the machine is found. High correlation between results obtained from theoretical and experimental modal analysis implies that the developed model can be used with confidence in future studies of the machine’s total system behaviour.

  • 3255. Wallin, Johanna
    et al.
    Chirumalla, Koteshwar
    Thompson, Anthony
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Developing PSS Concepts from Traditional Product Sales Situation: The Use of Business Model Canvas2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In recent years there has been growing interest in utilizing a product-service system (PSS) approach when developing products and services in order to arrive at a business model focused on selling function or availability instead of physi-cal products. However, the complex nature of PSS development has left many manufacturers still struggling to arrive at PSS concepts out of their traditional product sales situation in early design phases. The purpose of this paper is to propose an approach using the Business Model Canvas which could help manufacturers in the transition towards PSS development by articulating key business elements in developing and analyzing PSS concepts evolving from their traditional product sales situation. The paper presents preliminary findings from the aerospace industry and discusses the evolution of key business elements for PSS concepts from traditional product sales situation using the Business Model Canvas. Finally, the potential benefits of using the Business Model Canvas in a PSS context are discussed.

  • 3256.
    Wang, Cong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Numerical Assessment of a Novel Ventilation Strategy for Operating Rooms in Comparison with Turbulent Mixing and Laminar Air Flow2018Inngår i: Proceedings of The 15th Conference of the International Society of Indoor Air Quality & Climate (ISIAQ). July 22-27, 2018; Philadelphia, PA, USA, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Infectious airborne particles can cause surgical site infections (SSIs). SSIs cause substantially increased morbidity and mortality as well as patients’ sufferings. A well-functioning ventila-tion system in an operating room (OR) plays an essential role in the prevention of SSIs. In this study, we applied Computational Fluid Dynamics (CFD) to evaluate the performance of a novel OR ventilation strategy – temperature controlled airflow (TAF) against two widely used OR ventilation systems: laminar airflow (LAF) and turbulent mixing airflow (TMA). The performance was measured in terms of airborne bacteria concentration. Simulation results confirmed the superiority of LAF and TAF to TMA in providing high air cleanliness and also showed that TAF can serve as an efficient alternative to LAF.

  • 3257.
    Wang, Cong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Holmberg, Sture
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Application of open-source CFD software to the indoor airflow simulation2017Inngår i: In: Proceedings of 38th AIVC - 6th TightVent & 4th Venticool Conference, 2017. September 13-14 2017; University Of Nottingham, Nottingham  – UK, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of open-source CFD has been growing in both industry and academia. Open-source CFD saves users a considerable license cost and provides users with full transparency of implementation and maximum freedom of customization. However, it is often necessary to assess the performance of an open-source code before applying it to the practical use. This study applies one of the most popular open-source CFD codes – OpenFOAM to theindoor airflow and heat transfer prediction. The performance of OpenFOAM is evaluated and validated against awell-documented benchmark test. Various OpenFOAM built-in turbulent viscosity models are attempted withinthe framework of Reynolds Averaged Navier-Stokes Simulation (RANS) approach and the simulation results arecompared to the experimental data. Among all models, the 𝑘 − 𝜔 𝑆𝑆𝑇 model has shown the best overall performance, whereas the standard 𝑘 − 𝜀 model is the most robust one despite its deficiencies. The results of this study demonstrate the capability of OpenFOAM in the field of indoor air simulation and promote users confidence in using OpenFOAM in their research work.

  • 3258.
    Wang, Cong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Holmberg, Sture
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Influence of the shape of surgical lamps on the airflow and particle distribution in operating rooms2018Inngår i: Proceedings of Roomvent & Ventilation 2018. June 02-05, 2018; Espoo, Finland, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Operating room ventilation plays a significant role in reducing bacteria carrying particles concentration and preventing post-operative infections. The ventilation airflow may be disturbed by objects and heat loads and their effectiveness in reducing bacteria concentration can be compromised. Surgical lamps are one of the major disturbances in an operating room. This study numerically investigated the influence of lamp shapes on airflow patterns and dispersion of airborne bacteria.

    Two different shapes of lamps were studied: a closed-shape and an open-shape lamp. The simulation was performed based on the physical configuration of two operating rooms ventilated respectively by laminar airflow and temperature controlled airflow. Results show that the closed-shape lamp severely obstructs the airflow and results in high bacteria concentration in the laminar airflow, whereas the open-shape lamp has a negligible impact on the particle dispersion. The temperature controlled airflow is less sensitive to obstructions and maintains a clean surgical site with both types of lamps.

  • 3259.
    Wang, Da
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Servin, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mickelsson, Kjell-Ove
    Outlet design optimization based on large-scale nonsmooth DEM simulation2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    We consider the application of a nonsmooth discrete element method (NDEM) [1-3] to geometricdesign optimization of a balling drum outlet used in production of iron ore pellets. The geometricdesign optimization problem is based on the need for spatially and temporally homogeneous flow ofpellets from the balling drum onto a wide belt conveyor feeding a roller sieve. Homogeneous pelletflow makes sieving most efficient and facilitates good control in the hardening furnace. The model ofthe pellet material and balling drum are specified in a NDEM framework. The simulation andanalysis procedure is described. A material flow profile in terms of design parameters is computedfrom simulation data and used for solving the design optimization problem. The solution is comparedwith different designs used in a real production plants. It is demonstrated that the method can clearlydistinguish between the original and improved design in that plant. The uncertainty in the optimaldesign parameters is discussed and put in relation to the assumptions and approximations behind the particular NDEM that is used. Proposal for how to improve and validate the material and ballingdrum model is given.

    The particular NDEM is described in more detail in an accompanying paper [4] where the method isalso contrasted to the more conventional smooth discrete element method (DEM) [5]. The nonsmoothapproach allows for time integration using time-steps much larger than the characteristic elasticresponse time. Given an efficient solver and that the system and application justifies the nonsmoothapproximation a considerable speed-up can be achieved, though it should be recognized that this issignificantly problem dependent. The current paper includes analysis of the computational efficiencyof the NDEM approach to the particular case of balling drum outlet flow analysis with a given errortolerance. Time estimates of a corresponding smooth DEM approach is provided for comparison.

  • 3260.
    Wang, Fei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Properties of multilayered and multicomponent nitride alloys from first principles2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is a theoretical exploration of properties of multilayered and multicomponent nitride alloys, in particular their mixing thermodynamics and elastic behaviors. Systematic investigation of properties of a large class of materials, such as the multicomponent nitride solid solutions, is in line with the modern approach of high-throughput search of novel materials. In this thesis we benchmark and utilize simple but efficient methodological frameworks in predicting mixing thermodynamics, Young’s moduli distribution of multilayer alloys and the linear thermal expansion of quaternary nitride solid solutions.

    We demonstrate by accurate ab-initio calculations that Ti1−xAlxN solid solution is stabilized by interfacial effects if it is coherently sandwiched between TiN layers along (001). For TiN/AlN and ZrN/AlN multilayers we show higher thermodynamic stability with semicoherent interfaces than with isostructural coherent ones.

    Accurate 0 Kelvin elastic constants of cubic TixXyAl1xyN (X=Zr, Hf, Nb, V, Ta) solid solutions and their multilayers are derived and an analytic comparison of strengths and ductility are presented to reveal the potential of these materials in hard coating applications. The Young’s moduli variation of the bulk materials has provided a reliable descriptor to screen the Young’s moduli of coherent multilayers.

    The Debye model is used to reveal the high-temperature thermodynamics and spinodal decomposition of TixNbyAl1−x−yN. We show that though the effect of vibration is large on the mixing Gibbs free energy the local spinoal decomposition tendencies are not altered. A quasi-harmonic Debye model is benchmarked against results of molecular dynamics simulations in predicting the thermal expansion coefficients of TixXyAl1xyN (X=Zr, Hf, Nb, V, Ta).  

  • 3261.
    Wang, Ruoli
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Biomechanical consequences of gait impairment at the ankle and foot: Injury, malalignment, and co-contraction2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The human foot contributes significantly to the function of the whole lower extremity during standing and locomotion. Nevertheless, the foot and ankle often suffer injuries and are affected by many musculoskeletal and neurological pathologies. The overall aim of this thesis was to evaluate gait parameters and muscle function change due to foot and ankle injury, malalignment and co-contraction. Using 3D gait analysis, analytical analyses and computational simulations, biomechanical consequences of gait impairment at the ankle and foot were explored in ablebodied persons and in patient groups with disorders affecting walking.

    We have characterized gait patterns of subjects with ankle fractures with a modified multi-segment foot model. The inter-segmental foot kinematics were determined during gait in 18 subjects one year after surgically-treated ankle fractures. Gait data were compared to an age- and gender-matched control group and the correlations between functional ankle score and gait parameters were determined. It was observed that even with fairly good clinical results, restricted range of motion and malalignment at and around the injured area were found in the injured limb.

    Moment-angle relationship (dynamic joint stiffness) - the relationship between changes in joint moment and changes in joint angle - is useful for demonstrating interaction of kinematics and kinetics during gait. Ankle dynamic joint stiffness during the stance phase of gait was analyzed and decomposed into three components in thirty able-bodied children, eight children with juvenile idiopathic arthritis and eight children with idiopathic toe-walking. Compared to controls, the component associated with changes of ground reaction moment was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two subcomponents of this component which are based on magnitudes and rates of change of the ground reaction force and of its moment arm. And differences between the two patient groups and controls were most evident and interpretable here.

    Computational simulations using 3D musculoskeltal models can be powerful in investigating movement mechanisms, which are not otherwise possible or ethical to measure experimentally. We have quantified the effect of subtalar malalignment on the potential dynamic function of the main ankle dorsiflexors and plantarflexors: the gastrocnemius, soleus and tibialis anterior. Induced acceleration analysis was used to compute muscle-induced joint angular and body center of mass accelerations. A three-dimensional subject-specific linkage model was configured by gait data and driven by 1 Newton of individual muscle force. The excessive subtalar inversion or eversion was modified by offsetting up to ±20˚ from the normal subtalar angle while other configurations remain unaltered. We confirmed that in normal gait, muscles generally acted as their anatomical definitions, and that muscles can create motion in many joints, even those not spanned by the muscles. Excessive subtalar eversion was found to enlarge the plantarflexors’ and tibialis anterior’s function.

    In order to ascertain the reliability of muscle function computed from simulations, we have also performed a parametric study on eight healthy adults to evaluate how sensitive the muscle-induced joints’ accelerations are to the parameters of rigid foot-ground contact model. We quantified accelerations induced by the gastrocnemius, soleus and tibialis anterior on the lower limb joints. Two types of models, a ‘fixed joint’ model with three fixed joints under the foot and a ‘moving joint’ model with one joint located along the moving center of pressure were evaluated. The influences of different foot-ground contact joint constraints and locations of center of pressure were also investigated. Our findings indicate that both joint locations and prescribed degrees-of-freedom of models affect the predicted potential muscle function, wherein the joint locations are most influential. The pronounced influences can be observed in the non-sagittal plane.

    Excessive muscle co-contraction is a cause of inefficient or abnormal movement in some neuromuscular pathologies. We have identified the necessary compensation strategies to overcome excessive antagonistic muscle cocontraction at the ankle joint and retain a normal walking pattern. Muscle-actuated simulation of normal walking and induced acceleration analysis were performed to quantify compensatory mechanisms of the primary ankle and knee muscles in the presence of normal, medium and high levels of co-contraction of two antagonistic pairs (gastrocnemiustibialis anterior and soleus-tibialis anterior). The study showed that if the co-contraction level increases, the nearby synergistic muscles can contribute most to compensation in the gastrocnemius-tibialis anterior pair. In contrast, with the soleus-tibialis anterior co-contraction, the sartorius and hamstrings can provide important compensatory roles in knee accelerations.

    This dissertation documented a broad range of gait mechanisms and muscle functions in the foot and ankle area employing both experiments and computational simulations. The strategies and mechanisms in which altered gait and muscles activation are used to compensate for impairment can be regarded as references for evaluation of future patients and for dynamic muscle functions during gait.

  • 3262.
    Wang, Ruoli
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Broström, Eva
    Women's and Children's Health, Karolinska Institutet.
    Esbjörnsson, Anna-Clara
    Women's and Children's Health, Karolinska Institutet.
    Gutierrez-Farewik, Elena
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Analytical decomposition can help to interpret ankle joint moment-angle relationship2012Inngår i: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 22, nr 4, s. 566-574Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Moment-angle relationship (dynamic joint stiffness) - the relationship between changes in joint moment and changes in joint angle - is useful for demonstrating interaction of kinematics and kinetics during gait. However, the individual contributors of dynamic joint stiffness are not well studied and understood, which has thus far limited its clinical application. In this study, ankle dynamic joint stiffness was analyzed and decomposed into three components in thirty able-bodied children during the stance phase of the gait. To verify the accuracy of the decomposition, the sum of decomposed components was compared to stiffness computed from experimental data, and good to very good agreement was found. Component 1, the term associated with changes in ground reaction force moment, was the dominant contribution to ankle dynamic joint stiffness. Retrospective data from eight children with juvenile idiopathic arthritis and idiopathic toe-walking was examined to explore the potential utility of analytical decomposition in pathological gait. Compared to controls, component 1 was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two sub-components of component 1 which are based on magnitudes and rates of change of the ground reaction force and of its moment arm, and differences between the two patient groups and controls were most evident and interpretable here. Findings of the current study indicate that analytical decomposition can help identify the individual contributors to joint stiffness and clarify the sources of differences in patient groups.

  • 3263.
    Wang, Ruoli
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Gutierrez-Farewik, Elena
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    A parametric study of the rigid foot-ground contact model: effects on induced angular accelerations of the lower limb joints in the stance-phaseManuskript (preprint) (Annet vitenskapelig)
  • 3264.
    Wang, Ruoli
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Gutierrez-Farewik, Elena
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Compensatory strategies in response to excessive muscle co-contraction at the ankle joint during walkingManuskript (preprint) (Annet vitenskapelig)
  • 3265.
    Wang, T.C.
    et al.
    LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing.
    Ståhle, Per
    Luleå tekniska universitet.
    Stress state in front of a crack perpendicular to bimaterial interface1998Inngår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 59, nr 4, s. 471-485Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a dislocation simulation approach, the basic equation for a crack perpendicular to a bimaterial interface is formulated in this paper. A novel expansion method is proposed for solving the problem. The complete solution for the problem, including the T stress ahead of the crack tip and the stress intensity factors are presented. The stress field characteristics are analyzed in detail. It is found that ahead of the crack tip and near the interface the normal stress, perpendicular to the crack plane, σx, is characterized by the K fields and the normal stress σy is dominated by the K field plus T stress in the region of 0 < r/b < 0.4 for 6/ao≤0.1, where b is the distance from the crack tip to the interface

  • 3266.
    Wang, Yuli
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Yang, M. -G
    Gao, B.
    Dynamics of ultra-high speed liquid jets in still gas2013Inngår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, ISSN 0253-231X, Vol. 34, nr 9, s. 1654-1658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Instability of free liquid jets is an important fundamental problem rising from multiple engineering fields such as material processing, energy production, etc. Ultra-high speed condition brings new difficulties to stability research. This work demonstrates flow patterns of ultra-high speed liquid jet (UHSLJ) and points out the potential challenges in relevant investigation, from a turbulence point of view. A PDA measurement of flow velocity and droplet size on a cross-section of UHSLJ is present. Flow physics involved in the jet is discussed together with the limitation of this measurement. It is found that the velocity profile on the measured section obeys 1/7 power law. Concentration of droplets has an inverse gradient (from outer region of a jet pointing to the inner region) in the breakup section. Flow properties hold an axisymmetric distribution in the atomization section while this section itself has an evident two-layer (core-outer) structure. The length scales (size of drop) that be resolved by the present experiment is estimated to be only 0.1% of the entire scales.

  • 3267.
    Was, Loïc
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Mechanical Engineering for Electronics.2012Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Schlumberger drilling tools are exposed to very hard loading conditions (shocks, vibrations,

    thermal cycling) while performing a job. As these tools are full of electronics, issues can quickly come

    from electronics failure. Mechanisms of failure occurring in electronics are very complex but can be

    predicted in some cases.

    The first part of the thesis describes in which context mechanical engineering applied to

    electronics is used in Schlumberger. The different kinds of failure which will be investigated in the

    report are presented in this part.

    The second part deals with fatigue models used in electronics. From classical methods used in

    mechanical engineering to calculate a material fatigue life, fatigue models are adapted and

    formulated for special applications.

    The third part investigates the issue of capacitor flex-cracking which occurs when boards do not

    remain flat during loadings (shocks or thermal cycling). Root causes of this mechanism of failure are

    investigated in this part to find key points where improvements have to be made to avoid failure.

    The fourth part presents a common failure which deals with Plated Through Holes (PTHs) issues.

    A simple model of investigations is established.

    The fifth part deals with fatigue life of leadless components (resistors) under thermal cycling.

    Even if the failure is revealed during shock tests, the damage is mostly created during the thermal

    cycles applied on the board prior to shock. The effect of the size of the component is discussed in this

    part.

    The last part deals with modal analysis on a given board in order to be able to reduce the impact

    and the damage of shocks applied on this board. Simulation and experimental modal analysis are

    compared in order to see the influence of certain parameters on the natural frequencies of the

    board.

  • 3268. Weddfelt, K.
    et al.
    Saadati, Mahdi
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Larsson, Per-Lennart
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    On the load capacity and fracture mechanism of hard rocks at indentation loading2017Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 100, s. 170-176Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The load capacity of selected hard rocks subjected to circular flat punch indentation is investigated. The compacted zone underneath the indenter is assumed to be limited and only responsible for the load transition to the rest of the material. Therefore, the theory of elasticity is used to define the stress state in a semi-infinite medium loaded by a flat punch indenter. The final load capacity is related to the formation of a sub-surface median crack that initiates due to tensile hoop (circumferential) stresses. Therefore the final failure should occur at a force level in which the hoop stress is greater than the tensile strength of the rock. Since the tensile stress is distributed over a volume of material, tensile crack failure can occur at different locations with tensile hoop stress depending on where the most critical flaw is located. Therefore, the initiation of the median crack that should be responsible for the final load capacity is treated as a probabilistic phenomenon. This process is described by Weibull theory which will be used as a failure criterion. It is assumed here that the opening of median crack triggers a final violent rupture, therefore the assumption in Weibull theory, that the final failure occurs as soon as a macroscopic fracture initiates from a microcrack is fulfilled. The effective volume is calculated for a semiinfinite medium loaded by a flat punch indenter. The material properties of Bohus granite obtained from three point bending tests are used as reference values in describing the Weibull size effect. The experimental results for the stamp load capacity of three selected hard rocks are taken from the literature. They are considered similar rocks to the reference material in this paper, which is Bohus granite. The model describes the observed load capacity with a very good accuracy for all three rocks. It is likely that the presently proposed methodology is applicable for other types of semi-brittle materials and indenter shapes.

  • 3269.
    Wei, Liang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Elsinga, Gerrit E.
    Brethouwer, Geert
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Turbulens. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Schlatter, Philipp
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Johansson, Arne V.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Turbulens. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Universality and scaling phenomenology of small-scale turbulence in wall-bounded flows2014Inngår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 26, nr 3, s. 035107-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Reynolds number scaling of flow topology in the eigenframe of the strain-rate tensor is investigated for wall-bounded flows, which is motivated by earlier works showing that such topologies appear to be qualitatively universal across turbulent flows. The databases used in the current study are from direct numerical simulations (DNS) of fully developed turbulent channel flow (TCF) up to friction Reynolds number Re-tau approximate to 1500, and a spatially developing, zero-pressure-gradient turbulent boundary layer (TBL) up to Re-theta approximate to 4300 (Re-tau approximate to 1400). It is found that for TCF and TBL at different Reynolds numbers, the averaged flow patterns in the local strain-rate eigenframe appear the same consisting of a pair of co-rotating vortices embedded in a finite-size shear layer. It is found that the core of the shear layer associated with the intense vorticity region scales on the Kolmogorov length scale, while the overall height of the shear layer and the distance between the vortices scale well with the Taylor micro scale. Moreover, the Taylor micro scale collapses the height of the shear layer in the direction of the vorticity stretching. The outer region of the averaged flow patterns approximately scales with the macro scale, which indicates that the flow patterns outside of the shear layer mainly are determined by large scales. The strength of the shear layer in terms of the peak tangential velocity appears to scale with a mixture of the Kolmogorov velocity and root-mean-square of the streamwise velocity scaling. A quantitative universality in the reported shear layers is observed across both wall-bounded flows for locations above the buffer region.

  • 3270.
    Wei, Liang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Turbulens.
    Pollard, Andrew
    Queens Univ, Kingston, ON, Canada.
    Direct numerical simulation of low Mach number turbulent wall bounded flow with favourable and adverse pressure gradients2012Inngår i: Journal of turbulence, ISSN 1468-5248, E-ISSN 1468-5248, Vol. 13, nr 5, s. 1-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Direct numerical simulation (DNS) of turbulent isothermal-wall bounded flow subjected to favourable and adverse pressure gradient (FPG, APG) at low Mach number is investigated. The FPG/APG is obtained by imposing a concave/convex curvature on the top wall of a plane channel. The flows on the bottom and top walls are a tripped turbulent and laminar boundary layers, respectively. It is observed that the flow reaches equilibrium in the FPG region and the first and second order statistics are strongly influenced by the pressure gradients. For FPG/APG regions very near the bottom plane wall, the correlations between the streamwise pressure gradient and the spanwise vorticity flux and between the spanwise pressure gradient and the streamwise vorticity flux in the wall-normal direction are high on the wall and quickly drops to a negligible value within the viscous sublayer. Related flow physics and linkage to energy balance transport is discussed.

  • 3271.
    Weiber, Ingrid
    et al.
    Blekinge Tekniska Högskola, Fakulteten för hälsovetenskaper, Institutionen för hälsa.
    Tengland, Per-Anders
    Berglund, Johan
    Blekinge Tekniska Högskola, Fakulteten för hälsovetenskaper, Institutionen för hälsa.
    Eklund, Mona
    Social and Healthcare Professionals' Experiences of Giving Support to Families Where the Mother Has an Intellectual Disability: Focus on Children2014Inngår i: Journal of Policy and Practice in Intellectual Disabilities, ISSN 1741-1122 , Vol. 11, nr 4, s. 293-301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Families where the mother has an intellectual disability need support to counteract possible detrimental life circumstances for the children involved. The aim of this study was to describe social and healthcare professionals' experiences of providing support for families with maternal intellectual disability and specifically focused on if and how they believed the support practices benefited the children. Seven focus group interviews were performed with 29 professional informants. The transcripts were analyzed with qualitative content analysis. Three themes were identified: support practices, pedagogical strategies when supporting families with maternal intellectual disability, and maintaining the child perspective. The support practices mainly dealt with parenting skills, which were addressed by a variety of teaching methods and practices, while the children were at risk of not being seen or heard.

  • 3272.
    Weihong, Yang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Do-Quang, Minh
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Amberg, Gustav
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Impact of viscoelastic droplets2017Inngår i: Journal of Non-Newtonian Fluid Mechanics, ISSN 0377-0257, E-ISSN 1873-2631, Vol. 243, s. 38-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We conduct numerical experiments on viscoelastic droplets hitting a flat solid surface. The results present time-resolved non-Newtonian stresses acting in the droplet. Comparing with the simulation of the impact of a Newtonian droplet, the effects of viscoelasticity on droplet behaviors such as splashing, the maximum spreading diameter and deformation are analyzed. With detailed information on the contact line region, we demonstrate how the contact line behaves according to the transition of the fluid property from elasticity dominated to shear-thinning dominated when a droplet expands and contracts on the substrate. The propose of this work is to discuss whether and how the elasticity in an impinging droplet takes effect.

  • 3273.
    Welander, Simon
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Serviceförbättringar av GTC-200MSS2013Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Som ett sista arbete på högskoleingenjörsutbildningen i maskinteknik på Umeå universitet så har jag sett över servicevänligheten på ett reservkraftsaggregat. Attacus Power AB har stått som värd för detta arbete och även tillhandahållit arbetsplats under utförandet.

    Ett reservkraftsaggregat är ofta en dieseldriven motor kopplad till en generator som alstrar ström. Denna ström kan sedan användas för att driva sjukhus eller liknande vid ett eventuellt strömavbrott.

    Modellen som skulle ses över heter GTC-200MSS och den är en extra tyst modell avsedd för platser som filminspelningar och liknande där ljudnivån är en viktig faktor.

    Det jag skulle utföra var att försöka hitta en lösning där motor och generator, med så litet ingrepp som möjligt, kunde tas ut för underhåll.

    Arbetet började med att olika lösningsförslag togs fram. Allt från att vicka av hela höljet, till en ny utformning av modellen. Efter att alla förslag presenterats och gåtts igenom med inblandade på företaget, så beslutades att en lösning där en truck eller liknande med hjälp av sina gafflar kunna lyfta ut motor och generator var den bästa lösningen.

    För att göra det enkelt för de som skulle utföra ingreppet så gjordes en enkel manual.

    En modell togs fram där truckens gafflar legat till grund för utförandet samt dess belastningsfall. Genom att lägga till en enkel dropplåt under motor och generator ökas trivsamheten för de som ska arbeta med maskinen efter ett par år då maskinen blir lättare att hålla ren.

    För att inte bygga för mycket på höjden beslutades att göra dörren så stor som det gick och sedan även sänka dörren så att den nedre dörrkarmen inte skulle bli ett hinder för gafflarna.

    En FEM-analys gjordes för att se om konstruktionen skulle klara av de olika belastningsfallen. Det visade sig att så inte var fallet utan en förstärkning var ett måste.

    Elskåpet placerades om för att inte vara i vägen för den högre generatorplaceringen. Detta var inte optimalt då installationen kommer försvåras eftersom väggen som den nu ska fästas på installeras sist med höljet.

    Om denna rapport skulle göras om, så skulle större vikt läggas på att se om generatordörren kunnat användas som en lösning. Detta skulle medföra fördelar som att elskåpet inte skulle behöva flyttas samt att tyngdpunkt av generatorn och motorn skulle hamna närmare trucken vid ett lyft.

  • 3274.
    Wennhall, Thomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Provmiljö för mekaniskt hjärta: Konstruktion av mätutrustning2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Företaget Real Heart i Västerås håller på att utveckla ett mekaniskt hjärta.Företaget har som slutmål att det skall kunna vara ett alternativ tillhjärttransplantation. När en sådan produkt utvecklas finns det en

    forskningsprocess som är viktig att följa. Real heart har under 10 år skapat nio prototyper och det är nu dags att verifiera att den nionde prototypen är redo för prekliniska tester. För att göra detta behöver det mekaniska hjärtat utsättas för

    liknande förhållanden som i en människokropp och relevanta parametrar som det tryck och flöde som det mekaniska hjärtat kommer ge upphov till i aortan i kroppen skall mätas. I denna studie har en sådan provmiljö utvecklats. För att

    åstadkomma detta har en designprocess använts vilken resulterade i en provmiljö där tryck kan mätas med hjälp av två olika metoder och flöde kan mätas med en metod. Provmiljön ger i ett och samma system värden från dessa

    metoder. När provmiljön var färdig utvärderades den genom att göra ett test med det mekaniska hjärtat, detta test följde en experimentell metod.

    Testet resulterade i värden som var lovande, mätvärdena hade dock lite för stor spridning och förbättringsförslag på detta och annat formulerades.

  • 3275.
    Wentzel, Henrik
    Scania AB, Sweden.
    Modal control in reliability testing of truck components2013Inngår i: Proceedings 11th Biennial International Conference on Vibration Problems (ICOVP-2013) / [ed] Z. Dimitrovová, J.R. de Almeida, R. Gonçalves, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Reliability testing of components is an important part of the development process for heavy trucks. Components such as cabins, fuel tanks and mudguards are tested as subsys-tems, e.g. without the complete vehicle, in test rigs. Reference signals of sensors are obtained through measurements on the complete vehicle in service conditions. The test rig is designed and controlled so as to reproduce the reference signals. It is generally held that a good corre-lation between the reference signals and the corresponding test signals indicate that the test reproduces the damaging process of the service conditions. Due to the differences between the test setup and the complete vehicle it is not possible to perfectly reproduce neither the ser-vice conditions nor the reference signals. It is proposed to use a modal filter to estimate the modal displacements, and to control the test rig so as to reproduce the estimated modal dis-placements. The modal filter has been applied to an industrial test of a truck cabin.

  • 3276.
    Wentzel, Henrik
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Skruvförband: fasad hylsa2009Patent (Annet (populærvitenskap, debatt, mm))
  • 3277.
    Wentzel, Henrik
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Stag för upphängning av skärm2008Patent (Annet (populærvitenskap, debatt, mm))
  • 3278.
    Wentzel, Henrik
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Sätt och anordning för vibrationsdämpning i skruvförband2005Patent (Annet (populærvitenskap, debatt, mm))
  • 3279. Werme, Fredrik
    Energiförluster orsakade av uppriktningsfel och obalanser i roterande maskiner2017Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    This bachelor's thesis is the final step in earning a degree in mechanical engineering by Karlstad University, the faculty of health, science and technology. Constituents of the thesis are Maskin och Laserteknik AB, Gothenburg and Bilfinger Industrial Service AS located in Porsgrunn.

    The study objective has been to describe the correlation between loss of energy and amplitudes of vibration in a drive train due to faulty settings. The area of interest was vibrations caused by misalignment and imbalance only. More specifically the change of apparent power to an AC motor when introduced to different settings, was measured and calculated.

    Initially measurements of supplied current to the AC motor that turns the drive train was measured while coupling and balancing settings were ideal, according to recommendations from Prüftechnik and ISO 1940-1:2003. Vibrational spectrums were also collected for different components of the drive train. This was accomplished using a multimeter and equipment used industrially for shaft alignment and balancing of rotating machinery.

    Incorrect settings were thereafter applied to the power train, resulting in various misalignments between the coupling halves. Data was recorded and analyzed with said equipment, for each individual setting.

    The faulty settings that were included was mass unbalance applied to the rotor, vertical angular misalignment and vertical offset between the coupling halves. 

    The results showed that increased unbalance applied to the rotor decreased the supplied current to the AC motor and therefore the apparent power. There was no pattern in the change of apparent power supplied to the AC motor when introduced to large angular misalignment between the coupling halves, nor was there for large vertical offsets. The conclusion was such that there was a correlation between vertical amplitudes of vibration and/or reactional forces in the bearings in the pillow block and apparent power supplied to the AC motor of the power train. In the case of vertical angular misalignment and vertical offset, there were no observed relations between the settings and change of apparent power.

  • 3280.
    Werner, Elin
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    Materialanalys & optimering av hydrauliska högtryckskopplingar med hjälp av simuleringar2018Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Optimering av prestanda görs på FEM ½” koppling på Parker Hannifin AB med hjälp av finita element analyser (FEA). De kritiska komponenterna som är styrningen, kulhållaren och nippelhuset är i fokus. En noggrannare materialanalys genomförs för att få mer verklighetbaserande materialdata på kopplingen. 

    Hela nippelhuset antas härdas efter varit i kontakt med företaget som utför härdningen på komponenten. För att få mer information om materialdata utförs statiska trycktester på en koppling. De uppmätta töjningarna från testerna jämförs med töjningarna i simuleringarna. Sträckgränsen och hårdnadskoefficienten på styrningen och kulhållaren kan justeras något från testerna men resultatet har flera osäkerheter. 

    Antalet kulor i kopplingen mellan 15 och 12 kulor undersöks efter önskemål från företaget. Analyser om hur en härdning påverkar styrningen görs samt hur nippelhuset påverkas av en ythärdning i form av sätthärdning.

    Vid härdning av styrningen uppkom de minsta deformationerna och spänningarna. Kulhållaren visade tydligt på mindre deformationer och spänningar om antalet kulor minskas från 15 till 12 kulor i kopplingen. För att minska kulintrycket på nippelhuset rekommenderas att ythärda komponenten med en 27 % hårdare yta än den nuvarande. På grund av uppskattade värden på materialdata på ythärdningen behöver mer information införskaffas. Detta för att kunna avgöra vilken tjocklek på ytans härdning som krävs för 12 kulor i kopplingen.

  • 3281.
    Westerling, Lars
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Lundberg, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik.
    Stresses in a long cylindrical conductor moving axially through a pair of electrode plates under stationary conditions2013Inngår i: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 80, nr 2, s. 021013-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a conductor carrying electric current, the Lorentz force gives rise to mechanical stresses. Here, we study a long elastic cylindrical conductor that moves axially with constant velocity through two electrode plates. The aims are to explore how the stresses in the conductor depend on the velocity in the stationary case of constant current and to assess the validity of the analytic method used. The diffusion equation for the magnetic flux density is solved by use of Fourier transform, and the current density is determined. The stresses, due to the Lorentz force, are found by use of an analytic method combining the solutions of a quasi-static radial problem of plane deformation and a dynamic axial problem of uniaxial stress. They are also determined through FE analysis. Radial field profiles between the plates indicate a velocity skin effect signifying that the current and the magnetic field are concentrated near the cylindrical surface up-stream and are more uniformly distributed downstream. The radial and hoop stresses are compressive, while the axial stress is tensile. The von Mises effective stress increases towards the symmetry axis, in the downstream direction, and with velocity. There are circumstances under which a large current can produce an effective stress in a copper conductor of the order of the yield stress without causing a significant temperature rise. The stresses obtained with the two methods agree well, even relatively near the electrode plates. The analytical method should be useful in similar cases as well as for the provision of test cases for more general simulation tools.

  • 3282.
    Westman, Eva-Lis
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pederson, Robert
    Luleå tekniska universitet.
    Wikman, Bengt
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical and microstructural evaluation of elevated temperature compression tests on Ti-6AI-4V2004Inngår i: Ti-2003 : science and technology: proceedings of the 10. World Conference on Titanium, held at the CCH-Congress Center Hamburg, Germany, 13 - 18 July 2003 / [ed] Gerd Lütjering, Weinheim: John Wiley & Sons, 2004Konferansepaper (Fagfellevurdert)
  • 3283.
    Westman, Jonas
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Nyberg, Mattias
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Environment-Centric Contracts for the Design of Cyber Physical Systems2014Rapport (Annet vitenskapelig)
    Abstract [en]

    A contract splits the responsibilities between a component and its environment into a guarantee that expresses an intended property under the responsibility of the component, given that the environment fulfills the assumptions. Although current contract theories are limited to express contracts over interfaces of components, specifications that are not limited to interfaces are used in practice and are needed in order to properly express safety requirements. A framework is therefore presented, generalizing current contract theory to environment-centric contracts - contracts that are not limited to the interface of components. The framework includes revised definitions of properties of contracts, as well as theorems that specifies exact conditions for when the properties hold. Furthermore, constraints are introduced, limiting the ports over which an environment-centric contract is expressed where the constraints constitute necessary conditions for the guarantee of the contract to hold in an architecture.

  • 3284.
    Westman, Jonas
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Nyberg, Mattias
    Törngren, Martin
    Structuring Safety Requirements in ISO 26262 using Contract Theory2013Rapport (Annet vitenskapelig)
    Abstract [en]

    ISO 26262 - ''Road vehicles-Functional Safety'' is a standard for the automotive industry, administered in an attempt to prevent potential accidents due to systematic and random failures in the Electrical/Electronic-system. ISO 26262 is based on the principle of relying on safety requirements as the main source of information to enforce correctness of design. We show that the contract theory from the SPEEDS FP6 project provides a suitable foundation to structure safety requirements in ISO 26262. Contracts provide the necessary support to separate the responsibilities between a system and its environment by explicitly imposing requirements on the environment as assumptions, in order to guarantee the safety requirements. We show this by characterizing two levels of safety requirements with contracts for an industrial system where we also show how contract theory supports the verification of consistency and completeness of safety requirements.

  • 3285.
    Weyrauch, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    The Paperboard Testing-Machine: Development Process2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The design of a paperboard testing machine, developed in order to analyse the mechanical behaviour of paperboard during the combined of out-of-plane shear and compressive loading as in the deepdrawing process, is presented. The methodology to design a paperboard testing machine is discussed and the most appropriate concepts are compared and evaluated. The design process is presented in detail, and some pilot tests are performed to give an overview about the functionality of the manufactured prototype.

  • 3286.
    Widlund, Ola
    et al.
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    Snygg, Henrik
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    Johnson, Erland
    RISE - Research Institutes of Sweden, Säkerhet och transport, Safety.
    Load classification of scaffolding systems: Using numerical modelling to show compliance with regulatory requirements2017Inngår i: Proceedings of NAFEMS World Congress 2017, Stockholm 11-14 June 2017, Stockholm, Sweden., 2017Konferansepaper (Fagfellevurdert)
  • 3287.
    Wiklund, Daniel
    et al.
    Swerea IVF, Box 104, Mölndal, SE-431 22, Sweden.
    Larsson, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Phenomenological friction model in deep drawing of aluminum sheet metals2018Inngår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 418, nr 1, s. 1-8, artikkel-id 012097Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Friction is an important parameter in sheet metal forming since it influences the flow of material in the process. Consequently, it is also an important parameter in the design process of new stamping dies when numerical simulations are utilized. Today, the most commonly used friction model in forming simulations is Coulomb’s friction which is a strong simplification of the tribological system conditions and a contributory cause of discrepancy between simulation and physical experiments. There are micromechanical models available but with an inherent complexity that results in limited transparency for users. The objective in this study was to design a phenomenological friction model with a natural level of complexity when Coulomb’s friction is inadequate. The local friction model considers implicit properties of tool and sheet surface topography, lubricant viscosity, sheet metal hardness and strain, and process parameters such as sliding speed and contact pressure. The model was calibrated in a Bending-Under-Tension test (BUT) and the performance was evaluated in a cross shaped geometry (X-die). The results show a significant improvement of the simulation precision and provide the user a transparent tribological system. © Published under licence by IOP Publishing Ltd.

  • 3288.
    Wiklund, U.
    et al.
    Department and Division of Materials Science, Uppsala University.
    Gunnars, Jens
    Luleå tekniska universitet.
    Högmark, S
    Department and Division of Materials Science, Uppsala University.
    Influence of residual stresses on fracture and delamination of thin hard coatings1999Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 232, nr 2, s. 262-269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The risk of fracture and delamination of residually stressed coating system is examined. Stress concentrations are generated at the interface of coated systems where the substrate deviates from being perfectly smooth, flat and infinitely large. Using finite element calculations, such stresses induced at pores, edges or scratches are analysed for a number of representative coatings/substrate systems. The effect of the interface topography, coating thickness and elastic mismatch on the interfacial stresses are investigated. Generally, thin coatings compared to the interface topography are less sensitive to residual stress induced failure. At a critical coating thickness, normal stress across the interface of a magnitude comparable to that of the residual stress level is induced, which may initiate coating delamination. The interface stress state becomes independent of the coating thickness if the coating is thicker than about three times the amplitude of the interface roughness. The interface stress scales approximately linearly with the maximum inclination of the surface profile. It is demonstrated experimentally that the high residual stress in ceramic coatings may cause local coating fracture and delamination at, e.g., the tip of an edge or at rough substrate when the coating is thick relative to the edge radius or the surface topography, respectively.

  • 3289. Wikman, Bengt
    Friction modelling in numerical simulation of iron powder die pressing1997Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 3290. Wikman, Bengt
    Inverse modelling for determination of constitutive parameters: a literature review1999Rapport (Annet vitenskapelig)
    Abstract [en]

    This literature review concerns concepts, ideas and methods for the theoretical framework behind the development of an inverse modelling system. The intention is to give a survey of some available literature on topics related to inverse modelling for determination of constitutive parameters and to put the individual aspects into context.

  • 3291. Wikman, Bengt
    Modelling and simulation of powder pressing with consideration of friction1999Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Finite element modelling and simulation of the powder pressing process can be used in the rational development of powder metallurgy (PM) components. Many of the nonlinear finite element (FE) codes available today can be used for powder pressing simulations. The critical features of such simulations include almost every aspect of nonlinear FE analysis. This may be material behaviour, large deformation and contact boundary conditions, as well as the temperature and density dependence of the process. It is thus important to use appropriate models which capture the event of pressing and make the analysis worthwhile. The objective of the research presented in the present thesis has been to tighten the connection between models of powder pressing and pressing reality. There are mainly two reasons for this action: to increase the predictive capability of the pressing simulations and to reach further understanding of the PM forming process. The sliding friction contact between the powder and the tool is known to prevent homogeneous densification in the die pressing of metal powders. It is also known that the coefficient of friction in the contact varies considerably during pressing. A friction model with a nonconstant friction coefficient has been developed in this research. The model has been fitted to data from friction experiments. The final density distribution and press forces have been shown to be depentend on the choisce of friction model. The influence of a continuously varying initial density distribution on the numericalsimulations has also been investigated. The final density distribution shows a significant dependence on the starting conditions. A modification has been made to the DiMaggio-Sandler cap model which takes into account density dependence in describing the cohesive strength of powder materials. As friction models have been included in the analyses, it has also been of interest to effectively calibrate the models. Here, the friction coefficient has been estimated by combining an experiment with modelling of the experiment. Two methods for assessment of friction are presented, an optimization approach and an analytical approach. The experimental data have been taken from the single-action cold pressing of a cylinder-shaped component. A procedure to estimate friction also in low density regime is presented. In modelling the hot isostatic pressing (HIP) of powder materials, different deformation mechanisms are active during the consolidation process. The early stage of consolidation is dominated by granular behaviour. In order to account for these early granular deformation mechanisms in the numerical analyses, a combined elasto-plastic and elasto-viscoplastic material model has been developed and tested. Analysis with the combined material model shows improved characterization of the initial deformations compared with results from using the elasto-viscoplastic model only.

  • 3292. Wikman, Bengt
    et al.
    Bergman, Greger
    Luleå tekniska universitet.
    INVSYS - an Inverse Modelling System: user manual2000Rapport (Annet vitenskapelig)
    Abstract [en]

    INVSYS is a tailor-made programming system for the analysis of inverse problems. The origin of the present code springs from the need to test and evaluate modelling techniques in the context of inverse analysis. The program is based on a modified sequential simplex optimisation algorithm (subplex). How to use the system is described and exemplified in this manual.

  • 3293. Wikman, Bengt
    et al.
    Bergman, Greger
    Gestamp Hardtech AB.
    Oldenburg, Mats
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Estimation of constitutive parameters for powder pressing by inverse modelling2006Inngår i: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 31, nr 5, s. 400-409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Powder metallurgy processes are used in many material technologies for manufacturing of a wide range of industrial parts. Products such as components for cars, cemented carbides and high-speed steels for mechanical cutting, magnets and soft magnetic materials, bearings and refractory metals are made from powder. These parts are manufactured by powder die pressing followed by sintering of the resulting green body in a furnace. Traditionally, experience-based methods have been used to design and adapt the processing variables for optimal performance. Cost savings can be made if the tool design can be based on reliable predictive numerical simulations of the powder compaction process. Computer modelling could aid process and design engineers in selecting and optimizing the best pressing route for many industrial components. The aim of the present work has been to develop an efficient way to determine the necessary constitutive model parameters of the numerical models by means of inverse modelling. An experiment for establishing input data to the inverse problem has been designed and validated. The objective function is formed based on the discrepancy in force-displacement data between the numerical model prediction and the experiment. Minimization of the objective function with respect to the material parameters is performed using an in-house optimization software shell which is built on a modified Nelder-Mead simplex method also known as the subplex method. The completed analyses show that the proposed approach can readily be used to determine material parameters.

  • 3294. Wikman, Bengt
    et al.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Design of the container for hot isostatic pressing of a diesel engine piston top2003Inngår i: P / M Science & Technology Briefs, ISSN 1527-2478, Vol. 5, nr 1, s. 10-14Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Numerical simulations of the hot isostatic pressing (HIP) process for manufacturing of a piston top have been used to achieve near net shape in this work. The shape of the container is optimised by repeated simulations of the manufacturing process. The application is a piston top for a large diesel engine. The aim is to contribute to the development of an integrated computer based tool for the design and manufacture of hot isostatically pressed products. The computer aided concurrent engineering (CACE) system which is integrated using a relational database includes the solid modeller of a computer aided design system, codes for non-linear finite element analysis (FEA), and data from a coordinate measuring system (CMM). Predictions of near net shape geometry obtained numerically are in tolerable agreement with experimental measurements. The model is based on an associated flow rule and linear isotropic hardening is assumed, the material properties correspond to AISI 304 steel.

  • 3295. Wikman, Bengt
    et al.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Inverse modelling of powder compaction: the influence of material and friction behaviour interaction2000Inngår i: Proceedings of 2000 Powder Metallurgy World Congress : November 12 - 16, 2000, Kyoto International Conference Hall, Japan: organized by Japan Society of Powder and Powder Metallurgy, Japan Powder Metallurgy Association / [ed] Koji Kosuge; Hiroshi Nagai, Tokyo: Japan Society of Powder and Powder Metallurgy , 2000Konferansepaper (Fagfellevurdert)
  • 3296. Wikman, Bengt
    et al.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Modelling of powder-wall friction for simulation of iron powder pressing1997Inngår i: Proceedings of the International workshop on modelling of metal powder forming processes, 1997Konferansepaper (Fagfellevurdert)
  • 3297. Wikman, Bengt
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Modelling methods in pressing simulations of metal powder components1998Inngår i: Simulation of materials processing : theory, methods and applications: international conference on numerical methods in industrial forming processes, NUMIFORM '98 / [ed] J. Huétink; F.P.T. Baaijens, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1998, s. 397-402Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The process of pressing metal powder to net shape with subsequent sintering is very important for the automotive industry and similar industries with production of metal components in large quantities. The development of products and tools for the pressing of the products is a very time consuming and costly process. It is of great importance for the industry to be able to predict the result of the pressing operation with respect to the powder flow and final density distribution. With this knowledge the time and cost for product development, tool manufacturing and tool testing can be significantly reduced. In this work a set of methods used for analyses of the pressing process are presented. The methods used are based on an explicit finite element formulation with arbitrary Lagrangian Eulerian formulation. The material model used is a cap-plasticity model. The contact constraint are imposed with a method based on explicit integration of the contact interface equations in order to determine the contact forces. The contact algorithm includes a non-linear friction model with parameters based on experimental observations. An analysis of a pressed component is presented and compared with experimental results.

  • 3298. Wikman, Bengt
    et al.
    Reyre, M.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Three dimentional finite element analysis of powder compaction2002Inngår i: Process modeling in powder metallurgy & particulate materials: proceedings of the 2002 International Conference on Process Modeling in Powder Metallurgy & Particulate Materials, [held October 28 - 29, 2002, Newport Beach, California] / [ed] Alan Lawley, Princeton, NJ: Metal powder industries federation , 2002, s. 115-122Konferansepaper (Fagfellevurdert)
  • 3299. Wikman, Bengt
    et al.
    Solimannezhad, N.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Wall friction coefficient estimation through modelling of powder die pressing experiment2000Inngår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, nr 2, s. 132-138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Forming of PM components through powder pressing is a process, which is influenced by the friction between the powder and the tool walls. For good performance of the pressing process it is of great interest to understand and estimate the effects of powder-wall friction. However, quantification of the friction coefficient between the powder and the tool is a delicate task. Local contact conditions, such as contact stress, must be measured or otherwise estimated in order to evaluate the coefficient of friction. Here, the friction coefficient is estimated by combining an experiment with modelling of the experiment. Two methods for assessment of friction are presented, an optimization approach using finite element analyses and an analytical approach. Experimental data are taken from the single action cold pressing of a cylinder shaped component.

  • 3300. Wikman, Bengt
    et al.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A combined material model for numerical simulation of hot isostatic pressing2000Inngår i: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 189, nr 3, s. 901-913Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In modelling of hot isostatic pressing (HIP) of powder materials the constitutive model should be able to describe different deformation mechanisms during the consolidation process. In the early stage, the consolidation is dominated by granular behaviour. As temperature and pressure increase in the powder the deformation can be described by a viscoplastic model. Experimental observations show substantial time-independent deformation in the early stage. At this stage of the densification process, pores in the powder are still interconnected. This cannot be described properly by a viscoplastic model. The inconsistency between the deformation mechanisms can be treated by a combined elasto-plastic and elasto-viscoplastic model. Here a granular plasticity model is combined with a viscoplastic model. In previous works the viscoplastic model, power-law breakdown, has been used to describe the entire deformation process. The combined model is implemented into an in-house finite deformation code for the solution of coupled thermomechanical problems. The simulation of a hot isostatic pressing test with dilatometer is performed in order to compare calculated results with the experimental measurement. The results from previously performed analysis carried out with a viscoplastic model only are also compared. Analysis with the combined material model shows good agreement with the experiment for the whole densification process.

63646566676869 3251 - 3300 of 3456
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