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  • 1.
    Andersson, Erika
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies.
    De fem enkla maskinernas integrerande i den fria leken inom förskolans arena: En studie baserad på barns undersökande av enkel teknik i den fria leken.2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of the study is to demonstrate how children apply simple technology in preschool through “The Big Five”. Observations and "Interview on the move" are the method choices that answer the purpose and questions of the study. Observations and interviews have been conducted in the preschool outdoor environment during a morning and are based on the children's free play where the aim is to start from the children's perspective and reflections. The situations that have been chosen for the study are based on the children's curiosity and demonstrated interests. The result of the study shows that two of “The Big Five” are applied by the children in the preschool outdoor environment and free play. This is demonstrated by their use of the leaning plane and the wheel from “The Big Five”. It shows by their use of tools such as exploration, part of the game and through concepts. This is done through a sociocultural perspective where different factors influence children's learning.

  • 2.
    Bagheri, R.
    et al.
    University of Zanjan, Iran.
    Ayatollahi, M.
    University of Zanjan, Iran.
    Mousavi, Mahmoud
    Aalto University, Finland.
    Analysis of cracked piezoelectric layer with imperfect non-homogeneous orthotropic coating2015In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 93, p. 93-101Article in journal (Refereed)
    Abstract [en]

    Abstract The fracture problem for a medium composed of a cracked piezoelectric strip with functionally graded orthotropic coating is studied. The layer is subjected to anti-plane mechanical and in-plane electrical loading. In this paper, we first address, the problem of a screw dislocation located in a substrate which is imperfectly bonded to the coating. Then, in order to model the cracked piezoelectric layer, by means of the dislocation solution, we construct integral equations for the layer, in which the unknown variables are dislocation densities. These unknowns are determined through satisfaction of the boundary conditions on the crack faces. By use of the dislocation densities, the field intensity factors are determined. Several examples are presented to demonstrate the applicability of the proposed solution. ", keywords = Piezoelectric strip; Functionally graded layer; Imperfect bonding; Multiple cracks; Stress intensity factors, isbn = 0020-7403, doi=https://doi.org/10.1016/j.ijmecsci.2014.11.025

  • 3.
    Bagheri, R.
    et al.
    University of Zanjan, Iran.
    Ayatollahi, M.
    University of Zanjan, Iran.
    Mousavi, Mahmoud
    Aalto University, Finland.
    Analytical solution of multiple moving cracks in functionally graded piezoelectric strip2015In: Applied mathematics and mechanics, ISSN 0253-4827, E-ISSN 1573-2754, Vol. 36, no 6, p. 777-792Article in journal (Refereed)
    Abstract [en]

    The dynamic behaviors of several moving cracks in a functionally graded piezoelectric (FGP) strip subjected to anti-plane mechanical loading and in-plane electrical loading are investigated. For the first time, the distributed dislocation technique is used to construct the integral equations for FGP materials, in which the unknown variables are the dislocation densities. With the dislocation densities, the field intensity factors are determined. Moreover, the effects of the speed of the crack propagation on the field intensity factors are studied. Several examples are solved, and the numerical results for the stress intensity factor and the electric displacement intensity factor are presented graphically finally.

  • 4.
    Borregales, Manuel
    et al.
    University of Bergen, Norway..
    Radu, Florin A.
    University of Bergen, Norway..
    Kumar, Kundan
    University of Bergen, Norway.
    Nordbotten, Jan M.
    University of Bergen, Norway.; Princeton University, USA..
    Robust iterative schemes for non-linear poromechanics2018In: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499, Vol. 22, no 4, p. 1021-1038Article in journal (Refereed)
    Abstract [en]

    We consider a non-linear extension of Biot's model for poromechanics, wherein both the fluid flow and mechanical deformation are allowed to be non-linear. Specifically, we study the case when the volumetric stress and the fluid density are non-linear functions satisfying certain assumptions. We perform an implicit discretization in time (backward Euler) and propose two iterative schemes for solving the non-linear problems appearing within each time step: a splitting algorithm extending the undrained split and fixed stress methods to non-linear problems, and a monolithic L-scheme. The convergence of both schemes are shown rigorously. Illustrative numerical examples are presented to confirm the applicability of the schemes and validate the theoretical results.

  • 5.
    Carlson, Philip
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics, Science, Mathematics and Engineering Education Research.
    Konstruktions- och Materialförbättring hos Superkritiska Ventiler2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 6.
    Dugalic, Adnan
    Karlstad University.
    NG stand mechanical interface analysis for vehicle integrated RBS 70 NG2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    RBS 70 was introduced 1978 in Sweden and developed to be counter threats on the battlefield. This weapon is efficient against both conventional and small targets. Main components of the system are stand, sight and missile in container. RBS 70 NG with three legs is named as MANPADS configuration and has requirements for the natural frequency in launching direction to 4-6 Hz when placing it to a concrete ground.This Master Thesis has focus on vehicle integrate system, which requires legs to be removed from the MANPADS configuration and put it on a platform placed on a vehicle. For the vehicle integrated system 3.5 Hz will be acceptable as the lowest natural frequency. Four different concepts were purposed and evaluated for the mechanical interface between RBS 70 NG system and weapon platform: Existing platform with fix interface between RBS 70 NG system and platform where the thickness of the roof plate is 5 mm (named as reference model). Modified platform with thick plate (thickness of 30 mm) and fix interface between RBS 70 NG system and platform. Existing platform with damped interface between RBS 70 NG system and platform where the thickness of the roof plate is 5 mm. Modified platform with thick plate (thickness of 30 mm) and damped interface between RBS 70 NG system and platform.The final concept should meet the main requirements of SMU (Stabilized Mirror Unit) and simultaneously keep natural frequency for RBS 70 NG system within requirements.A theoretical evaluation of the longitudinal stiffness for the dampers has been calculated in the report and inputted as the value of the dampers in ANSYS R18.1. Modal analysis and harmonic response analysis was performed for all proposed concepts.Magnification ratio calculation for a system without dampers will illustrate that the upcoming amplitude for the 5 mm plate will amplified more than 30 mm plate at coherent frequencies.By studying the results it illustrates that a plate with thickness of 30 mm helps to minimize the disturbance in elevation direction but not in azimuth direction. To minimize the disturbance in all directions concepts with dampers will be a satisfied solution.

  • 7.
    Eriksson, Daniel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Grasping of Non-Rigid Objects: Relation Between Physical Properties and Subjective Experiences2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 8.
    Eriksson, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Undersökning av svetsegenskaper för svetsning med rörtråd kontra homogen tråd2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Welding is a common method for joining of metal or plastic construction parts. This report describes several different weld methods in general terms. The report focuses on the GMAW method, specifically MAG welding.

    A case study has also been performed for the company Wenmec. The task received from the company was to compare the mechanical properties of joints welded with the tube electrode called Nittetsu SM-3A and joints welded with the homogenous electrode called ESAB Aristorod 12.63. Both types of weld joint were welded with the MAG method with an Argon based shielding gas with 18% CO2. The final task of this study is to compare the cost of these electrodes and then help Wenmec to decide which electrode that is the most cost effective.

    Tensile testing, impact testing and fatigue testing were performed on the weld joint samples. The hardnesses, microstructures, failure zones and chemical composition were examined with optical microscopy and SEM.

    The weld time, the amount of consumed electrode and the weld energy was measured during welding. These properties were similar and the differences between the different joints could be ignored.

    Both weld joint types showed similar microstructures and hardnesses. The microstructure was ferrite with carbides or perlite at the grain boundaries. Some silicon oxides were found in the grains.

    The yield strength, ultimate tensile strength and cycles to fatigue failure were similar in the two joint types, but the Aristorod weld joint showed higher impact strength and elongation at break.

    The chemical composition showed that the SM-3A electrode was a metal cored electrode with some additions of deoxidizing elements and a Copper coating. The Aristorod 12.63 electrode also showed the presence of deoxidizing elements and likely had a Titanium based coating. The sheet metal used as the work pieces are called Ruukki Laser 355 MC and is steel with low Carbon content, some Manganese and some impurities.

    The SM-3A electrode was costlier than the 12.63 electrode. This work concluded that the 12.63 electrode was a better alternative for Wenmec due to the lower cost, higher impact strength and higher elongation at break

  • 9.
    Fariborz, Shahriar
    Amirkabir University, Iran.
    Free vibration of a rod undergoing finite strain2012In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 382, no 1Article in journal (Refereed)
    Abstract [en]

    The finite strain longitudinal free vibration of a rod is studied. Utilizing second Piola-Kirchhoff stress and Green strain tensors, the equation of motion is written in terms of displacement in reference configuration. Three different types of homogenous boundary conditions may be considered for the rod, leading to three nonlinear eigenvalue problems. The series solutions with three terms satisfying the boundary conditions are utilized and the relationships between amplitudes of vibration are obtained by means of the Galerkin method. The backbone curves are drawn and the internal resonance between different modes of vibration is analyzed.

  • 10.
    Fernandes, Ralston
    et al.
    Texas A&M University at Qatar.
    Mousavi, Mahmoud
    Aalto University, Finland.
    El-Borgi, Sami
    University of Carthage, Tunisia.
    Free and forced vibration nonlinear analysis of a microbeam using finite strain and velocity gradients theory2016In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 227, no 9, p. 2657-2670Article in journal (Refereed)
    Abstract [en]

    A nonlinear finite strain and velocity gradient framework is formulated for the Euler-€Bernoulli beam theory. This formulation includes finite strain and the strain gradient within the strain energy generalization as well as velocity and its gradient within the kinetic energy generalization. Consequently, static and kinetic internal length scales are developed to capture size effects. The governing equation with initial and boundary conditions is obtained using the variational approach. Free and forced vibration of a simply supported nanobeam is studied for different values of static and kinetic length scales using the method of multiple scales.

  • 11.
    Gustafsson, Filip
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Wet clutch load modeling for powershift transmission bench tests.2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis a model is developed for calculating the loads on the wetclutches in apowershift transmission. This thesis was done at Volvo CE in Eskilstuna and is focusedon their 4-speed countershaft transmissions. The goal of the project is to be able tocalculate the loads automatically during the transmission tests and thus acquire increasedknowledge about what occurs during operation.The model was developed by first generating a number of concepts and then evalu-ating them to decide which one should be developed further. The chosen concept wasthen developed further and implemented into the test equipment as a calculation script.The chosen loads to model were the energy absorbed in each clutch, the coefficient offriction (COF) and the slip distance. The COF was later found to give too unreliableresults to be used in any other way than as a benchmark for how well the model wasconfigured and to see any large changes in COF.The model was validated by calculating the energy absorbed in a HTE-200 seriestransmission and comparing it to a reference calculation model. It was seen that theresults from the new model are very close to the reference result. The energy lostcalculated by the new model will be equal to 94 % of the energy lost calculated by thereference model, but only when measuring the inertia phase. The energy lost is equalto 135 % when the torque phase is included. The increasing difference is believed tobe because of an error in the reference model that means it does not cover the torquephase.

  • 12.
    Ingmarsson, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Mekanisk arm för att assistera vid lindning på trumma2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a part of a manufacturing process to produce a kind of steel strip there is a need to guide two strips of steel to the correct position on a revolving drum. It is imperative for the following step in the process that the positioning of the strips are precise. The guidance of the steel strips is currently done by hand. 

    The mechanical replacement for the guidance is supposed to operate unattended once the winding process has begun. The aim is that one operator, instead of two as it is done today, will set up the whole machine including the mechanical replacement and then let the winding of the drum be uninterrupted until it is finished. It is important that the winding goes without interruption to reduce the risk of injuries as well as increase productivity. 

    During the thesis work a thorough pre-study was done, mainly by communicating with the operators of the winding machine since there was almost no available literature. The pre-study led to a complete specification of the mechanical replacement as well as a few ideas for concepts. Since several of the concepts were dependent on one another, a chain of concept selections were performed to get the best complete concept possible. The complete concept provided the foundation for the layout construction created in Computer Aided Design (CAD).

    The new construction is mounted so that it can move in the horizontal plane in order to fulfill the requirements of the production. The guidance is made possible using three separate wheels that are adjustable in two directions. The adjustments to the wheels are made possible by the use of electrically controlled cross sliding tables, that also improve ergonomics for the operator. The most important of the wheels is the 'groove' wheel. The main function of the groove wheel is to guide the underside of both strips to the correct position on the drum, it is placed in the groove of the drum hence the name groove wheel.

    The final construction meet all the demands from the initial specification and about half of the optional requirements. Further development of the construction require the FEM analysis to be confirmed and it would also be preferable to produce some sort of prototype to prove the concept of the groove wheel. The prototype is highly important since the groove wheel has a vital role in the product.

  • 13.
    Janebrink, Niklas
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Construction of tilt table with high loads: A construction with complete hydraulic system2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    At Uddeholm AB, they today use two overhead cranes with chains to move and tilt steel sheets for visual inspection of surface defects. The tilting is done to give the operator a better view of these defects using reflection of light. The problem with this approach is that it is combined with danger of life with hanging load, in case a chain breaks. Therefore Uddeholm AB would like to develop a tilt table that can be mounted on their lift table they use today.

    To solve this problem, 5 concepts was developed using a product development process. The chosen concept was further developed into a product that met the defined load case to tilt the sheets, weighing up to 20 tonnes, 55 degrees. The design that was selected use two points of rotation and is driven by three hydraulic cylinders.

    The structure has been calculated by hand and with the structural mechanics software Ansys. To tilt the table a complete hydraulic system was developed and dimensioned. The hydraulic system has been calculated by hand and simulated by a computer program called Hopsan developed at Linköping University. 

  • 14.
    Jernberg, Hannes
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Utökade tillämpningsmöjligheter för turbinlösning i våtpartiet hos tissuemaskiner: Konceptförslag som möjliggör tillämpning av turbinlösning för maskiner vars banbredd är bredare än 2,9 meter2014Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    AbstractThis thesis is the final part of the Innovation and Design Engineering Programme (180 ECTS credits)at the Faculty of Health, Nature and Engineering Science at Karlstad University. The extent of thisthesis is 22.5 ECTS credits and has been performed independently by Hannes Jernberg during thespring of 2013. Metso Paper Karlstad AB is the task maker of this project, and Arvid Johansson is thecompany Representative. Metso Paper Karlstad AB is one of the world leading developer andmanufacturer of tissue paper machines.In the current situation, the company has developed and patented a power management systembased on a Cross Flow Turbine. The current construction is limited to a paper width of 2.9 meters.The company wants to take advantage of all the opportunities provided by the patents, to develop aturbine solution paper machine with a paper width that is wider than 5.5 meters, and give the abilityto manufacture paper for lower energy consumption which is an important part of the production asit is very energy intensive.Problems arise with the increasing length of the turbine, ultimately resulting in that the deflectionbecomes too big and that the momentums, due to the increased torque the turbine blades breaks.By applying the design process, this work has resulted in a number of potential solutions to theproblem. Sketches, LEGO and engineering methodologies have contributed to the good result.The recommended solution generated by this project is to place two regular sized turbines by 2.9meters. The first turbine is placed in its optimal position at the Driver side of the turbine, themomentum provided by the water is leaded by a shaft towards the engine side of the machine. Thesecond turbine is placed directly under the first shaft. This allows the second turbine take care of therest of the water and energy.

  • 15.
    Jonsson, Emil
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Konstruktion av lyftverktyg: Lyftverktyg till L-stöd för enklare hantering2019Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The company Falcken Forshaga are manufacturing lifting tools for the steel, paper and concrete industry. The company wants a lifting tool for L-supports which they want to be able to sell to the concrete industry. The reason for this is that todays ways of lifting and rotation of the supports are done by slings which are time consuming to use because the process is done in multiple steps. The reason why the supports are rotated is because they are casted lying down and are transported standing up which means that the supports needs to be lifted and then rotated. The purpose of this project is to simplify the process between casting and transport as well as learn to work on a project at a company. The goal of the work is to design a lifting tool which follows the requirements set by Falcken for the lifting tool and so it can gain CE-mark in the future. To design a lifting tool the product development process was used as it best fits this project. The work started with status analysis to be able to study the steps which occur in the process today from casting to transport. This is today made possible in three steps lift, rotation and movement to make it ready for transportation. A project plan was developed where the project was divided into different parts with goals to always have something to work against which brings the work forward. A risk analysis over the project was constructed at the beginning to analyze potential risks with the aim to minimize them. The biggest risk that was analyzed was that the project will become delayed, to counter this the project plan needs to be up to date as well as to get help if in need. The next step in the process is to list all the specifications and requests from Falcken and summarize them to be able to generate concepts. A second risk analysis was made to analyze the potential risks with or around the lifting tool during lift where the biggest risks is those who involve people getting injured and are the most important to minimize. To generate the concepts the 6-3-5-method was used and resulted in five different concepts which was analyzed further and filtered through an elimination matrix where the best concept was selected. The concept that was chosen and was designed in Autodesk Inventor was a support arm lift which locks in the sides of the L-support and has beams which run along the sides of the support and in underneath the lower edge of the support with plates. The tool is designed to lift in front of the center of gravity of the support which means that when the support is lifted the whole thing will rotate by itself which means that the steps from casting to transport will be done in one step instead of three. To ensure the strength of the construction it is calculated against safety factor of three as well as it is controlled with a FEM-analyze in Creo parametric 5 and inventor 2019 on details with are too complicated to calculate by hand. The tool which was designed meets all the requirement that was set but to achieve a tool which is sellable and is CE-marked more risks must be analyzed according to SS-EN ISO 12100:2010 and its life span has to be calculated via fatigue calculations as well as it must be manufactured and tested.

  • 16.
    Jonsson, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Uppstagning av grenrör för Volkswagen rallycrossmotor2013Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This report is an examination conducted by Per Jonsson, a student at the University of Karlstad. The examination includes 22.5 credits and it’s a compulsory part in the Bachelor of Science in mechanical Engineering topic.

    The company Trollspeed, manufactures high-performance racing engines used by racing teams at the elite level. Big turbochargers and related equipment are assembled together with custom built exhaust manifolds to achieve maximum power output. Together, these parts contribute to a high mass and have to be braced up.     Today’s bracing solotion lead to inevitable tension effects within the manifold that makes cracking occur. This work is about developing a new bracing solution that can handle higher tensions.   The project is divided into two parts. The first part covers the development of a measurement tool for analyzing motion and force effects within the manifold. The development of the gauge resulted in a measurement scale with pointers for the visualization of movements and mounted load cells for analyzing the impact force. This gauge is the basis for the project's second part that covers finding a solution for a new bracing of the manifold.      The selection of strut is based on the measurement results that shows analyzes of motion and force effects. The brace resulted in a M6 turnbuckle.     The installation of this strut is an important element to improve the quality of the manifold. The engine has to be warmed up at least five times before mounting the strut and the manifold weight must be pretensioned using a turnbuckle with ¾ turns turning at that.

  • 17.
    Kindberg, Elin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Monteringslösning för sänglyftsystem: Ett produktutvecklingsprojekt för framtagning av en anpassningsbar infästning av sänglyft samt tillbehörshjälpmedel på befintlig säng2013Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    During the spring semester 2013, the project “Mounting solution for bed lift system“ has  been performed in the course Bachelor’s thesis for degree of Bachelor of Science in Innovation and Design Engineering (MSGC12) at Karlstad’s University. The project was performed in cooperation with ComfortSystem Scandinavia AB, a company that develops and markets products in the area of beds for health care. The aim of the project was to find a new mounting solution for a bed lift system. The product is an adjustable lift that can be applied to an ordinary bed by installing mounting brackets.  The purpose of the project was to develop a mounting solution that would be applicable to a wider range of bed types.  In addition, the solution would also allow an improved applicability of the accessories comprising Comfort System’s assortment, that previously only been applied on health care beds. The company ambition of mounting bed lift and accessories to regular beds is to reach a broader segment of customers, thus increasing the sales.

     

    This project follows the methodology recommended for the product development process. The process is iterative and characterizes problem solving and user customization, and includes life cycle perspective of developing a new product.  The starting-point of the project was to identify customers’ requirements. Interviews were made with four different target groups comprising, technicians, ordinators, caregivers and patients (users). The study about the user was supplemented with analysis in ergonomics, semantics and the environmental impact of products.  Creative methods were used to find solutions. Accordingly, the solutions were evaluated through the assessment of systematic matrixes for decisions, and reconciliations with the employer.

     

    The final selection of the concept consist a gadget for attachment, and a frame for accessories.  The concept is a flexible modular solution that can be used with or without the possibility of mounting accessories. Due to the possible variations of height and width, the module is adapted to fit a broader range of beds. The frame for accessories can be added to the product afterward. The solution is customized, thus it allows for the opportunity to secure different facilities to the bed. With the new solution, the assembly has become both easier and more understandable to implement, because the fact that accessories nowadays can be fixed by a new secure mounting method with measured spaced for accessories. In addition, the solution provides the user with more freedom in designing the bed in the way that fits their personal environment. The new solution for mounting have fewer steps for assembly than previous solution, the ergonomic for technicians who install the product has also been improved. 

     

    To reach a final product, an evaluation and testing of the proposed concept required, thus a prototype must be made. When the project has been completed, the progress and results of the project are to be handed over to the employer at Comfort System.

  • 18.
    Korsunsky, Alexander M.
    et al.
    University of Oxford, UK .
    Guénolé, Julien
    FAU, Germany.
    Salvati, Enrico
    University of Oxford, UK .
    Sui, Tan
    University of Oxford, UK .
    Mousavi, Mahmoud
    University of Oxford, UK & Aalto University, Finland.
    Prakash, Arun
    FAU, Germany.
    Bitzek, Erik
    FAU, Germany.
    Quantifying eigenstrain distributions induced by focused ion beam damage in silicon2016In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, p. 47-49Article in journal (Refereed)
    Abstract [en]

    Abstract Eigenstrain offers a versatile generic framework for the description of inelastic deformation that acts as the source of residual stresses. Focused ion beam (FIB) milling used for nanoscale machining is accompanied by target material modification by ion beam damage having residual stress consequences that can be described in terms of eigenstrain. Due to the lack of direct means of experimental determination of residual stress or eigenstrain at the nanoscale we adopt a hybrid approach that consists of eigenstrain abstraction from molecular dynamics simulation, its application within a finite element simulation of a flexible silicon cantilever, and satisfactory comparison of the prediction with experimental observation. Directions for further enquiry are briefly discussed. ", keywords = Focused ion beam milling; Molecular dynamics; Eigenstrain; Residual stress, isbn = 0167-577X, doi=https://doi.org/10.1016/j.matlet.2016.08.111

  • 19.
    Larsson, Marcus
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Transportör: Lokal logistik2012Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This report is the result of a project work carried out at Karlstad University in conjunctionwith the local consulting firm Camatec where most of the work has been performed.The work can be classified as a classic engineering work with supportive theories andcalculations which in this context is relevant.The engineering project has focused on developing new standards for a conveyor that is usedin the Värmland paper industry where large rolls of paper are produced. A conveyor can takeits appearance in many different forms but in this thesis it has been an exemplary look and ithas also become modulatable with a central section, a drive end and a turning end.The construction work has been build under CAD programs such as Pro Engineer, drawingshave been created and costings have been analyzed. Strength calculations have been made andcooperation from several different companies have erected to explore different solutions andideas for a modern and sustainable conveyor.

  • 20.
    Lie Gustavsson, Victor
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Konstruktion av infästning till dysa2014Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The goal of this thesis is to design an attachment between a duct and a pod. A pod is what could be compared to an outboard engine for larger vessels. The pod is placed on the outside of the ship’s hull and can rotate 360 ̊. A duct is a large steel ring that can be placed around the propeller on the pod to increasethe propulsion force of the ship in lower velocities. The thesis is written for Rolls Royce AB in Kristinehamn.The demanded requirements of the design are: it must be easy to adapt to different sizes and shapes of pod houses, the duct must be able to bemounted and dismounted from the pod.The result from this thesis is that anupper and a lower attachment weredesigned. The upper attachment consists of two parallel steel plates which arebolted together with a screw plate that is welded to the pod house.The lower attachment is basically a wing with a streamlined profile which is bolted to a stay. Both attachments consist of bolted joints, two guide pins and bursting screws.The design is controlled by parameters in CAD, meaning that if you change the size of the duct the attachments automatically adapts themselves to the new dimensions.The total result from this thesis is a design suggestion and not an actual manufactured product.The design is dimensioned by a load analysis and strength calculations. The dimensions of the bolts are determined by basic load calculation and the guide pins aredimensioned to withstand the shear forces that occur.The conclusion of this thesis is that the developed attachment solution is a good way to solve this problem andthe personal recommendation is that it should be developed further.Further design work that needs to be done with the attachment is a more thorough analysis of the strength and especially with fatigue, since no account has been taken considering fatigue.

  • 21.
    Lindholm, Marcus
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Column bolt calculation: Column bolt calculation on a 1200T HAP Raufoss aluminium extrusion machine2005Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This degree project is a verification of a hand made calculation made by Semcon CAE inGothenburg, Sweden. The main purpose has been to investigate how loads in a pre-tensionedbolt appear and how material displacement and contact pressures in the nuts affect bolt joints.A FEM-model has been created to imitate the reality as much as possible this to verifySemcon’s calculations. The result of the FEM-model has been compared with the result fromSemcon report 87-082-008, see appendix 2. Thus the Semcon original report has beenverified.The results between the Semcon report 87-082-008and the FEM calculations can be seen inchapter 2 and appendix 1.The basic data of the degree exam is the Semcon report and is the starting point of the wholeproject. All data regarding dimensions, geometry, materials and so on is based on the datafrom the Semcon report.A fatigue analysis based on the FEM-results was not conducted. This was due to thesimilarities in result between the previous Semcon report and this study

  • 22.
    Löfvenberg, Kristofer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Utveckling av kontorsstolsmekanism till stolen Saga för Support Design AB2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Rapporten avser ett examensarbete för Högskoleingenjörsprogrammet i innovationsteknik och design på Karlstads universitet och genomförs våren 2017. Uppdragsgivare för projektet är Support Design AB i Sunne.

    Arbetet handlar om att ta fram ett konceptförslag för funktionen som reglerar höjden på kontorsstolen Saga. Stolens gasfjäder bestämmer höjden på stolen och regleras idag med hjälp av en vajerinfästning. Vajerinfästningen medför att stolen endast kan demonteras av en kvalificerad montör och ger upphov till en osäker konstruktion. Projektets huvuduppgift är att kvalitetssäkra mekanismen och förenkla avlägsnande av gasfjäder.

    Projektet bygger på en designprocess som inleds med en förstudie. För att säkerställa en god grund till att utveckla ett hållbart konceptförslag undersöks befintliga lösningar på andra kontorsstolar. Förstudien behandlar även: undersökning av befintlig mekanism, kontorsstolsstandarder, hur man konstruerar mot en hållbar konstruktion och undersökning om hur en gasfjäder demonteras från en mekanism. Resultaten från förstudien används till en produktspecifikation. Ifrån den skapas olika koncept som leder fram till ett slutligt konceptval. Det slutliga konceptvalet är ett konceptförslag som ersätter stolsmekanismens vajerinfästning.

    Konceptförslaget presenteras med skisser, CAD-konstruktion och komponentlisa. Beräkningar, dimensionering och materialvalsegenskaper presenteras också.

  • 23.
    Malis, Isak
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Lyftverktyg till ytbehandlingsborstar: Konstruktion av ett lyftverktyg för byte av ytbehandlingsborstar till plåttillverkningsindustrin.2018Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Handling and replacement of cylindrical surface treatment brushes for rolled sheet metal is currently done by hand at the company voestalpine Precision Strip AB in Munkfors. The workis described as time consuming, non-ergonomic and with some risk of personal injuries. The surface treatment brushes that are handled are sensitive to both forces and dirt on their outer jacket area and therefore require caution when handling. To improve the ergonomic circumstances and minimize the risk of personal injury while ensuring the handling of thebrush, the company has requested a lifting tool.

    The goal of the project is to develop a travers emounted lifting tool that can lift the brush directly from the delivery pallet and mount in the intended machine without risking the quality of the brush or exposing personnel to risks. The tool is designed to be CE-labeled after manufacturing.

    To get a clear picture of today's working methodology and to define problem areas for a brush change, a preliminary study is conducted. The result of this study, together with the wishes of the company, is summarized into a requirement specification that becomes a direct starting point for continued development of the design.

    The concepts and ideas that are developed are evaluated and presented to the project organization. Some of the solutions are considered to have potential for further development and are kept for further development. It should be mentioned that the further development of the lifting tool until its final construction is aproduct of partly my own solutions, and partly the viewpoints, ideas and aspects from other members of the project organization.

    The final construction of the traverse lifting tool meets the requirements formulated in the specification and is considered safe and easy to handle and with good chances of being CEmarked. The tool can lift the brushes from the delivery pallet, rotate and mount in and out of the machine without grabbing the outer casing area or otherwise risking the brush's functionality. The tool also completely eliminates the non-ergonomic movements that arise as a result of the manual handling of the brushes that occur today.

    It is noted that the final lifting tool has potential for improvement, thus it ́s provided suggestions for continued work and further development of the product.

  • 24.
    Masoumi Tochahi, Seyed Amirhosein
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Self-locking in electrical actuators2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays all different kind of actuators is used in a widespread range. Their job is to transmit force, bear load, produce linear force, adjust height etc. Hydraulic fluid pressure, pneumatic pressure and electrical current usually change in to some sort of motion in actuators. This report is related to electrical actuators and self-locking problem, which is really common in them. The thesis report has been performed at Reac AB in Åmål, Sweden, a major supplier of wheel chair actuators.

     

    Electrical actuators have vast usage and they are versatile but in some cases they face with different working situation like dynamic forces. Recent generation of electrical actuators which used in wheelchairs (imagine moving wheelchair in bumpy road) have self-locking problem, which it means that they will lose their position after while under compression load. This fact will lead to de-calibration of the control system. Approximately 90% of  AB production is related to the electrical wheelchairs. Challenging point here is dynamic force which can lead to de-calibration of potentiometer and failure of device.

     

    Load capacity of certain actuator (RE25) is 2000 N. In this project different method has been used to simulate and calculate different aspects. Design of new part, material selection and improvement of some parts are most important. During the period lots of static and dynamic tests, CAD design and FEM analysis have been executed.

     

    Shock absorber, lock pin and new material have been run parallel and more or less all those three had a positive effect.

     

    Finally with design and selection of lock pin solution included cogwheel and pin, we overcome to the problem with great results. 

  • 25.
    Monfared, M. M.
    et al.
    University of Zanjan, Iran.
    Ayatollahi, M.
    University of Zanjan, Iran.
    Mousavi, Mahmoud
    Aalto University, Finland.
    The mixed-mode analysis of a functionally graded orthotropic half-plane weakened by multiple curved cracks2016In: Archive of applied mechanics (1991), ISSN 0939-1533, E-ISSN 1432-0681, Vol. 86, no 4, p. 713-728Article in journal (Refereed)
    Abstract [en]

    The problem of functionally graded orthotropic half-plane with climb and glide edge dislocations is solved. Dislocations are used as the building blocks of defects to model cracks of modes I and II. Following a dislocation-based approach, the problem is reduced to a system of singular integral equations for dislocation density functions on the surfaces of smooth cracks. These integral equations enforce the crack-face boundary conditions and are solved numerically for the dislocation density. The numerical results include the stress intensity factors for several different cases of crack configurations and arrangements.

  • 26.
    Mousavi, Mahmoud
    Aalto University, Finland.
    Dislocation-based fracture analysis of functionally graded magnetoelectroelastic solids2015In: Zeitschrift für angewandte Mathematik und Mechanik, ISSN 0044-2267, E-ISSN 1521-4001, Vol. 95, no 12, p. 1501-1513Article in journal (Refereed)
  • 27.
    Mousavi, Mahmoud
    Aalto University, Finland.
    Dislocation-based fracture mechanics within nonlocal and gradient elasticity of bi-Helmholtz type - Part II: Inplane analysis2016In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, p. 105-120Article in journal (Refereed)
    Abstract [en]

    Abstract This paper is the sequel of a companion Part I paper devoted to dislocation-based antiplane fracture mechanics within nonlocal and gradient elasticity of bi-Helmholtz type. In the present paper, the inplane analysis is carried out to study cracks of Modes I and II. Generalized continua including nonlocal elasticity of bi-Helmholtz type and gradient elasticity of bi-Helmholtz type (second strain gradient elasticity) offer nonsingular frameworks for the discrete dislocations. Consequently, the dislocation-based fracture mechanics within these frameworks is expected to result in a regularized fracture theory. By distributing the (climb and glide) edge dislocations, (Modes I and II) cracks are modeled. Distinctive features are captured for crack solutions within second-grade theories (nonlocal and gradient elasticity of bi-Helmholtz type) comparing with solutions within first-grade theories (nonlocal and gradient elasticity of Helmholtz type) as well as classical elasticity. Other than the total stress tensor, all of the field quantities are regularized within second-grade theories, while first-grade theories give singular double stress and dislocation density and classical elasticity leads to singularity in the stress field and dislocation density. Similar to gradient elasticity of Helmholtz type (first strain gradient elasticity), crack tip plasticity is captured in gradient elasticity of bi-Helmholtz type without any assumption of the cohesive zone. ", keywords = Crack; Inplane; Dislocation; Nonlocal elasticity of bi-Helmholtz type; Gradient elasticity of bi-Helmholtz type; Nonsingular, isbn = 0020-7683, doi=https://doi.org/10.1016/j.ijsolstr.2016.03.025

  • 28.
    Mousavi, Mahmoud
    Aalto University, Finland.
    Dislocation-based fracture mechanics within nonlocal and gradient elasticity of bi-Helmholtz type Part I: Antiplane analysis2016In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, p. 222-235Article in journal (Refereed)
    Abstract [en]

    Abstract In the present paper, the dislocation-based antiplane fracture mechanics is employed for the analysis of Mode III crack within nonlocal and (strain) gradient elasticity of bi-Helmholtz type. These frameworks are appropriate candidates of generalized continua for regularization of classical singularities of defects such as dislocations. Within nonlocal elasticity of bi-Helmholtz type, nonlocal stress is regularized, while the strain field remain singular. Interestingly, gradient elasticity of bi-Helmholtz type (second strain gradient elasticity) eliminates all physical singularities of discrete dislocation including stress and strain fields and dislocation density while the so-called total stress tensor still contains singularity at the dislocation core. Based on the distribution of dislocations, a fracture theory with nonsingular stress field is formulated in these nonlocal and gradient theories. Strain and displacement fields within nonlocal fracture theory are identical to the classical ones. In contrast, gradient elasticity of bi-Helmholtz type leads to a full nonsingular fracture theory in which stress, strain and dislocation density are regularized. However, the singular total stress of a discrete dislocation results in singular total stress of the plane weakened by a crack. Within classical fracture mechanics, Barenblatt’s cohesive fracture theory assumes that cohesive forces is distributed ahead of the crack tip to model crack tip plasticity and remove the stress singularity. Here, considering the dislocations as the carriers of plasticity, the crack tip plasticity is captured without any assumption. Once the crack is modeled by distributing the dislocations along its surface, due to the gradient theory, the distribution function gives rise to a non-zero plastic distortion ahead of the crack. Consequently, regularized solutions of crack are developed incorporating crack tip plasticity. ", keywords = Crack; Antiplane; Dislocation; Nonlocal elasticity of bi-Helmholtz type; Gradient elasticity of bi-Helmholtz type; Nonsingular, isbn = 0020-7683, doi=https://doi.org/10.1016/j.ijsolstr.2015.10.033

  • 29.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland & Aristotle University, Greece.
    Aifantis, E. C.
    Aristotle University, Greece.
    A note on dislocation-based mode III gradient elastic fracture mechanics2015In: Journal of the Mechanical Behavior of materials, ISSN 2191-0243, Vol. 24, no 3-4, p. 125-129Article in journal (Other academic)
  • 30.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Aifantis, Elias C.
    Aristotle University, Greece; St Petersburg, Russia.
    Dislocation-based gradient elastic fracture mechanics for in-plane analysis of cracks2016In: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 202, no 1, p. 93-110Article in journal (Refereed)
    Abstract [en]

    The in-plane classical dislocation-based linear elastic fracture mechanics analysis is extended to the case of strain gradient elasticity. Nonsingular stress and smooth-closure crack profiles are derived. As in the classical treatment, the crack is represented by a distribution of climb edge dislocations (for Mode I) or glide edge dislocations (for mode II). These distributions are determined through the solution of corresponding integral equations based on variationally consistent boundary conditions. An incompatible framework is used and the nonsingular full-field plastic distortion tensor components are calculated. Numerical results and related graphs are provided illustrating the nonsingular behaviour of the stress/strain components and the smooth cusp-like closure of the crack faces at the crack tip. The work provides an alternative approach to celebrated “Barenblatt’s treatment” of cracks, without the introduction of a cohesive zone and related to intermolecular forces ahead of the physical crack tip. It also supplements a recent paper by the authors in which the mode III crack, represented by an array of screw dislocations, was solved within the present gradient elasticity framework.

  • 31.
    Mousavi, Mahmoud
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013). Tehran Polytechnic, Iran.
    Fariborz, Shahriar
    Tehran Polytechnic, Iran.
    Anti-plane elastodynamic analysis of cracked graded orthotropic layers with viscous damping2012In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 36, no 4, p. 1626-1638Article in journal (Refereed)
    Abstract [en]

    Stress analysis is carried out in a graded orthotropic layer containing a screw dislocation undergoing time-harmonic deformation. Energy dissipation in the layer is modeled by viscous damping. The stress fields are Cauchy singular at the location of dislocation. The dislocation solution is utilized to derive integral equations for multiple interacting cracks with any location and orientation in the layer. These equations are solved numerically thereby obtaining the dislocation density function on the crack surfaces and stress intensity factors of cracks. The dependencies of stress intensity factors of cracks on the excitation frequency of applied traction and material properties of the layer are investigated. The analysis allows the determination of natural frequencies of a cracked layer. Furthermore, the interactions of two cracks having various configurations are studied.

  • 32.
    Mousavi, Mahmoud
    et al.
    Tehran Polytechnic, Iran.
    Fariborz, Shahriar
    Tehran Polytechnic, Iran.
    Propagation of Anti-plane Shear Waves in a Cracked Graded Strip with Viscous Damping2011In: 11TH INTERNATIONAL CONFERENCE ON THE MECHANICAL BEHAVIOR OF MATERIALS (ICM11) / [ed] Guagliano, M; Vergani, L, Elsevier, 2011, Vol. 10, no 0, p. 792-797Conference paper (Refereed)
    Abstract [en]

    The dislocation-distributed technique is utilized to study the elastodynamic fracture behavior of a graded isotropic layer with viscous damping. By investigation of the stress components due to the dislocation, the familiar Cauchy singularity is detected at the location of dislocation. Then the dislocation is utilized for the formation of cracks in the strip. The stress components of dislocation and time-harmonic antiplane point force leads to the integral equations. These equations results in the stress intensity factors (SIF) for the crack configuration in the strip.

  • 33.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Juha, Paavola
    Aalto University, Finland.
    Djebar, Baroudi
    Aalto University, Finland.
    Distributed non-singular dislocation technique for cracks in strain gradient elasticity2014In: Journal of the Mechanical Behavior of Materials, ISSN 2191-0243Article in journal (Refereed)
  • 34.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Korsunsky, Alexander M.
    University of Oxford.
    Non-singular antiplane fracture theory within nonlocal anisotropic elasticity2015In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, p. 854-861Article in journal (Refereed)
    Abstract [en]

    Abstract In the present paper, the distributed dislocation technique is applied for the analysis of anisotropic materials weakened by cracks. Eringen’s theory of nonlocal elasticity of Helmholtz type is employed. The non-singular screw dislocation within anisotropic elasticity is distributed to model cracks of mode III. The corresponding dislocation density functions are evaluated using the proper crack-face boundary conditions. The nonlocal stress field within a plane weakened by cracks is determined. The crack opening displacement is also discussed within the framework of nonlocal elasticity. The stress singularity of the classical linear elasticity is removed by the introduction of the nonlocal theory of elasticity. The general anisotropic case and the special case of orthotropic material are studied. The effect of material orthotropy is presented for a crack which is not necessarily aligned with the principal orthotropy direction. ", keywords = Cracks; Anisotropy; Fracture mechanics; Dislocations; Nonlocal elasticity; Integral equations, isbn = 0264-1275, doi=https://doi.org/10.1016/j.matdes.2015.09.068

  • 35.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Lazar, Markus
    Darmstadt University of Technology, Germany.
    Distributed dislocation technique for cracks based on non-singular dislocations in nonlocal elasticity of Helmholtz type2015In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 136, no 0, p. 79-95Article in journal (Refereed)
    Abstract [en]

    Abstract In the present paper, the distributed dislocation technique is extended for crack problems within Eringen’s theory of nonlocal elasticity of Helmholtz type. Employing distributed dislocation technique, non-singular stresses of cracks of modes I, II and III are obtained using the non-singular stresses of climb edge, glide edge and screw dislocations and dislocation density functions which are solutions of the non-singular integral equations of distributed dislocation technique. The cracks are modeled by a continuous distribution of straight dislocations. The nonlocal elasticity solutions of crack problems do not contain a stress singularity. We found that the non-singular crack stresses are zero at the crack tip or near the crack tip.

  • 36.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Paavola, Juha
    Aalto University, Finland.
    Analysis of a cracked concrete containing an inclusion with inhomogeneously imperfect interface2015In: Mechanics research communications, ISSN 0093-6413, E-ISSN 1873-3972, Vol. 63, p. 1-5Article in journal (Refereed)
    Abstract [en]

    Abstract The distributed dislocation technique is applied to determine the behavior of a cracked concrete matrix containing an inclusion. The analysis of cracked concrete in the presence of inclusions such as steel expansions is a practical problem that needs special attention. The solution to the problem of interaction of an edge dislocation with a circular inclusion having circumferentially inhomogeneously imperfect interface is available in the literature. This analytical solution is used in the distributed dislocation technique to obtain the stress intensity factor for the cracked concrete in the presence of inclusion. The interface of the matrix and the inclusion is assumed inhomogeneously imperfect and the stress intensity factor is determined for the cracked concrete for a case of two identical cracks on diametrically opposite sides of the inclusion. Consideration of this general inhomogeneously imperfect interface is the contribution of this paper. The variation of the inhomogeneity parameters is studied and presented. Additionally, the general assumption for the interface is simplified to the special case of perfectly bonded interface. The observations for the perfect interface are coincident with the previously reported results.

  • 37.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Paavola, Juha
    Aalto University, Finland.
    Analysis of cracked functionally graded piezoelectric strip2013In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 50, no 14-15, p. 2449-2456Article in journal (Refereed)
    Abstract [en]

    Abstract The fracture behavior of a cracked strip under antiplane mechanical and inplane electrical loading is studied. A functionally graded piezoelectric strip with exponential material gradation is under consideration. The mechanical and electrical loading is combined via loading coupling factor. The problem of a graded piezoelectric strip containing a screw dislocation is solved. This solution results in stress and electric displacement components with Cauchy singularity. Based on the solution achieved for the dislocation, the distributed dislocation technique (DDT) is utilized to form any geometry of multiple cracks and analyze the behavior of a cracked strip under antiplane mechanical and inplane electrical loading. This technique is capable of the analysis of a strip with a system of interacting cracks. Several examples including strips with single crack, two straight cracks and two curved cracks are presented.

  • 38.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Paavola, Juha
    Aalto University, Finland.
    Analysis of functionally graded magneto-electro-elastic layer with multiple cracks2013In: Theoretical and applied fracture mechanics (Print), ISSN 0167-8442, E-ISSN 1872-7638, Vol. 66, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Abstract In this paper, the distributed dislocation technique (DDT) is developed to be utilized for the analysis of a cracked functionally graded piezoelectric-€“piezomagnetic (FGPP) layer under anti-plane mechanical and in-plane electric and magnetic fields. By using the Fourier transformation, the closed-form expressions for the shear stress, electric displacement and magnetic displacement components are obtained for a generalized Volterra-type screw dislocation. The generalized dislocation in FGPP layer contains dislocation in the displacement component and jump in the electric and magnetic potentials. The expressions of generalized stress intensity factor are derived in the DDT. The solution of the dislocation problem is utilized in the DDT to solve the problem of arbitrary configurations of multiple embedded and edge cracks. The generalized intensity factors of the cracked layer are obtained. Numerical results for generalized intensity factors of straight and curved cracks are presented. The DDT is proved to be useful in the analysis of the interaction of the embedded and edge cracks in an FGPP layer.

  • 39.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Paavola, Juha
    Aalto University, Finland.
    Analysis of plate in second strain gradient elasticity2014In: Archive of applied mechanics (1991), ISSN 0939-1533, E-ISSN 1432-0681, Vol. 84, no 8, p. 1135-1143Article in journal (Refereed)
  • 40.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Paavola, Juha
    Aalto University, Finland.
    Reddy, J. N.
    Texas A&M University, USA.
    Variational approach to dynamic analysis of third-order shear deformable plates within gradient elasticity2015In: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 50, no 6, p. 1537-1550Article in journal (Refereed)
    Abstract [en]

    A variational approach based on Hamilton’s principle is used to develop the governing equations for the dynamic analysis of plates using the Reddy third-order shear deformable plate theory with strain gradient and velocity gradient. The plate is made of homogeneous and isotropic elastic material. The stain energy, kinetic energy, and the external work are generalized to capture the gradient elasticity (i.e., size effect) in plates modeled using the third-order shear deformation theory. In this framework, both strain and velocity gradients are included in the strain energy and kinetic energy expressions, respectively. The equations of motion are derived, along with the consistent boundary equations. Finally, the resulting third-order shear deformation (strain and velocity) gradient plate theory is specialized to the first-order and classical strain gradient plate theories.

  • 41.
    Mousavi, Mahmoud
    et al.
    Aalto University, Finland.
    Reddy, J. N.
    Texas A&M University, USA.
    Romanoff, Jani
    Aalto University, Finland.
    Analysis of anisotropic gradient elastic shear deformable plates2016In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 227, no 12, p. 3639-3656Article in journal (Refereed)
    Abstract [en]

    In this paper, Reddy’s third-order shear deformable plate theory is employed for the analysis of centrosymmetric anisotropic plate structures within strain gradient elasticity. The general three-dimensional anisotropic gradient theory is reduced to a two-dimensional formulation for the analysis of thick plate structures. The third-order shear deformation theory (TSDT) takes into account quadratic variation of the transverse shear strains of the plate and does not require shear correction factors. In order to investigate the case of small strains but moderate rotations, the von Kármán strains are considered. The TSDT is also simplified to anisotropic Kirchhoff plate theory within gradient elasticity. To study specific material properties in more detail, the (Kirchhoff and TSDT) gradient plate theory of general anisotropy is simplified to the more practical case of orthotropic plates. It is observed that the gradient theory provides the capability to capture the size effects in anisotropic plate structures. As case studies, the bending and buckling behaviors of the simply supported orthotropic (Kirchhoff and TSDT) plates are studied. Variationally consistent boundary conditions are also discussed. Finally, analytical solutions are presented for the bending and buckling of simply supported orthotropic Kirchhoff plates. The effects of internal length scales on deflections and buckling loads are presented.

  • 42.
    Nordlind, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Westmatic platta paket: Utveckling av ett modulbaserat stativsystem2013Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 43.
    Persson, Edvin
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Krabba: Automatisk pallkragsmontering2012Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The company Goodtech Solutions AB has developed a prototype. This prototype is a machine that automatically can assemble pallet collars on pallets with the help of a robot. The prototype needs to undergo some improvements and this work focus on the unit that handles the pallet collar during the assembling. This unit is called crab because of its design. The objective of this work is to accomplish the improvements and the purpose is to be a basis for all the improvements that the machine could undergo before a market release.

    To assemble a pallet collar the crab locks the pallet collar after it’s received from the robot. Then it bends the hinges and mounts the pallet collar onto a pallet. The crab’s main problems are the adjustments before handling the pallet collar and to correct the crab’s position in relation to the outer collar before assembling. This is because all adjustments are in relation to the center of the crab and that the crab pushes out the four corners when locking the pallet collar. To bend the hinges the crab uses a method that’s similar to a quick hammer stroke and this method is considered uncontrolled. A customer requirement emerged during the project. The customer requirement was that the machine should handle the bigger Volvo L pallet collar in addition to the EUR pallet collar.

    Because the crab should handle two different sizes of pallet collars the new concept would be for a new design. Therefor the work was limited to only include the crab. The attachment of the crab to the structure and the drive during assembly were excluded. Because of these restrictions the new crab must have the same movements as the present crab to collaborate with the rest of the machine.

    In the new concept two sides of the crab are fixed, one long and one short side, and the other two are variable. The two variable sides push outwards in a linear direction to lock the pallet collar. With two sides fixed all adjustments can relate to their corner as it is an origo. The crab remains in this fixed position because of the origo but the outer collar can adjust to this origo. This new concept appears to be better for adjustments because of the origo and that only two sides can vary. To bend the hinges there are four units in each corner. The units bend the hinges with a linear movement and an anvil so the forces can be absorbed locally. These units can vary their positions to handle both the EUR pallet collar and the Volvo L pallet collar. The linear movement to bend the hinge is considered stable.

    During the design of this concept the choices of components, material, material dimensions are based on rough estimates and oversizing due to the machine being a prototype. The crab was designed foremost with parts and profiles in construction steel. Hydraulic cylinders were used to bend the hinges. Pneumatic cylinders and ball rail systems were used to lock the pallet collar and other movements.

    This new concept and its design have improved the crab and extended its functionality. Therefor the objective and purpose of this work is considered to be achieved. Work still remaining is more precise estimates of material dimensions and components. The attachment in the structure and the drive during assembling should be looked over to make sure the crab is compatible with the rest of the machine.

  • 44.
    Rysjö, Henrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Pallsluss: Ett produktutvecklingsprojekt för säker och effektiv pallhantering mellan människa och robot2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    In Sweden, as in many other parts of the world, production is moving toward an ever more automated environment. As part of this development the use of robot cells is steadily increasing. In line with this development a growing need for standard components for these robotic cells can be distinguished.

    Handling of goods is an important part of a robotic cell. The use of standardized pallets with its well-developed logistic support is an ideal platform to meet this need. In the production flow these goods cross the boundary between the robot and the operator. Thus, rises the need to facilitate such border crossing without affecting the safety of the operator nor the production capacity.

    By the means of established product development methods this project has produced a conceptual design for a pallet-lock. The basic idea of the design is a pallet space enclosed by perforated sheet metal. On the top side and one short-side the pallet-lock situates roller doors. The side door permits the operator access to the pallet while the top door prevents access to the work-area of the robot whilst the side door is opened. In order to allow for handling of goods as well as liners and blisters a robot cell contains three pallet-locks. All three are operated and placed separately according to the best conditions of the site. This ensures a high level of flexibility. All in all, the pallet lock is simple, practical, flexible and, above all, safe in its construction.

    The work has undergone project planning, information retrieval, requirement specification, concept generation and selection, configuration and final layout design, which gave a CAD-model of the final result.

    Much of the work went to the initial information search and the establishment of the requirement specification. An overall philosophy throughout the project was to minimize the risk of reconversion by thorough preparatory work. This was distinctly noticeable during the initial information retrieval and requirement specification. The concept selection process was divided into two parts. The introductory part included the main technical solution. The following part, in turn, handled the different parts of the chosen concept individually. This way of working optimized working time and focused on detail solutions only when it was appropriate.

    This report together with the CAD model aims to provide a basis for continued development towards a finished product.

  • 45.
    Sadek, Mohamed
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Design and development of a testing device for a new invented Doctor Blade2013Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    This thesis project is about designing and developing an already existing testing device for a new invented Doctor Blade. A doctor blade is a blade used for creping tissue paper of a rotating cylinder, Yankee Cylinder. The old testing device was incomplete in a way that a rotating cylinder was missing, hence the tested blade is not loaded properly. The old testing device already contained the doctor blade holding device and the pulling device (pulling the creping blade). These two devices are transferred to the new testing device without any redesign within them. The adding of a rotating cylinder/roller required some new redesign regarding the testing device.

    The main beam (beam carrying all elements) is replaced with a larger one in order to fit the roller and is elongated in order to run longer tests. The new beam has a larger cross section in order to minimize the risk of bending.

    The main beam is supplied with five small beams, welded onto it, three for attaching the holding device and two for attaching the roller. The dimensions of these small beams are chosen in order to put the roller on the right position according to the creping blade.

    An electric motor is added to the new testing device in order to drive the roller with a chain. This required two sprockets, one for the motor and one for the roller shaft. The sprockets are chosen with a pitch diameter ratio matching the gearing required.

    FMEA-analysis is done on the whole design where five failure modes were chosen to be included, bending of the main beam and motor beam, screw joints of the same beams and sprocket-chain mechanism. Some FEM-analysis was required in order to detect the bending of the beams and measuring the loading on the screw joints. The screw joint loading achieved from the FEM-analysis is used for the theoretical screw joint calculations.

    The FMEA-analysis implied that four of the analyzed failure modes have acceptably low risk factor and dos not require any further actions. However one received a high risk factor, the chain-sprocket mechanism, the risk of clamping fingers. This is solved by adding a protecting house/shell made of sheet metal.

    Measurements were done on the old and the new testing device regarding the required force for pulling the creping blade and the pressure distribution between the creping blade and the beam (and roller in the new testing device).

    The improvement of the pulling force values is rather due to the new designed doctor blade than due to the new testing device. The new testing device is however more appropriate than the old one hence the added roller and the tests shows that it is functional as well. 

  • 46.
    Sandberg, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Hållfasthetsberäkning av handikapanpassad lyftanordning2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 47.
    Tahaei Yaghoubi, Saba
    et al.
    Aalto University, Finland.
    Balobanov, Viacheslav
    Aalto University, Finland.
    Mousavi, Mahmoud
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Niiranen, Jarkko
    Aalto University, Finland.
    Variational formulations and isogeometric analysis for the dynamics ofanisotropic gradient-elastic Euler-Bernoulli and shear-deformable beams2018In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, ISSN 0997-7538, Vol. 69, p. 113-123Article in journal (Refereed)
    Abstract [en]

    A strain and velocity gradient framework is formulated for centrosymmetric anisotropic Euler-Bernoulli and third-order shear-deformable (TSD) beam models, reducible to Timoshenko beams. The governing equations and boundary conditions are obtained by using variational approach. The strain energy is generalized to include strain gradients and the tensor of anisotropic static length scale parameters. The kinetic energy includes velocity gradients and a tensor of anisotropic length scale parameters and hence the static and kinetic quantities of centrosymmetric anisotropic materials are distinguished in micro- and macroscales. Furthermore, the external work is written in the corresponding general form. Free vibration of simply supported centrosymmetric anisotropic TSD beams is studied by using analytical solution as well as an isogeometric numerical method verified with respect to convergence.

  • 48.
    Tofique, Muhammad Waqas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Development of the distributed dislocation dipole technique for the analysis of closure of complex fractures involving kinks and branches2018In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 69, p. 168-178Article in journal (Refereed)
    Abstract [en]

    This paper presents the development of the distributed dislocation dipole technique (DDDT) for the analysis of straight, kinked and branched cracks where parts of the cracks may close during loading. The method has been developed for plane problems. Crack cases in which closure occurs are analyzed by reformulating the Buecicner's principle, taking into account the contact stresses at the contacting portions of the crack surfaces. Stress intensity factors corresponding to opening and the in-plane sliding mode of deformation at the crack tips are computed. Several test cases involving straight, kinked and/or branched cracks where parts of the cracks undergoes crack surface closure when subjected to the outer loading are analyzed. The results obtained from the DDDT are compared to those obtained from a Finite Element Method (FEM) analysis of the same crack cases. This comparison shows that the computation of stress intensity factors for the cases involving crack surface closure are less accurate than those for fully open crack cases. However, for the cases under consideration, the stress intensity factors were still computed with a maximum difference of approximately 2 per cent compared to the FEM calculations if Jacobi polynomial expansions of at least the twelfth order were used to represent the crack surface opening and sliding displacements. In most cases under consideration, sixth order Jacobi polynomial expansions were sufficient to obtain results within that margin of deviation.

  • 49.
    Tofique, Muhammad Waqas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hallbäck, Nils
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Development of the distributed dislocation dipole technique for the analysis of closure of complex fractures involving kinks and branchesManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents the development of the distributed dislocation dipole technique (DDDT) for the analysis of crack surface closure of crack cases involving kinks and branches. Crack cases in which closure occurs are analyzed by reformulating the Bueckner's principle taking the contact stresses at the contacting portions of the crack surfaces into account. Stress intensity factors corresponding to opening and sliding mode of deformation at the crack tips are computed. Three test cases involving kinked and/or branched cracks with at least one of the crack segments undergoing crack surface closure when subjected to remote tensile loading are analyzed. The results obtained from the DDDT are compared to those obtained from the Finite Element Method (FEM) analysis of the same crack cases. This comparison shows that the computation of stress intensity factors for the crack cases involving crack surface closure are less acurate compared to fully open crack cases. However, the stress intensity factors are still computed to an accuracy of within 2 percent if the Jacobi polynomial expansions of at least the sixth order are used to represent the crack surface opening and sliding displacements. Higher order Jacobi polynomials lead to increased accuracy.

  • 50. Werme, Fredrik
    Energiförluster orsakade av uppriktningsfel och obalanser i roterande maskiner2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    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.

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