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When a material is mechanically loaded or experience environmental changes such as for example thermal or pressure variations it is affected, in some way, due to these new conditions. In order to measure engineering properties related to these structural changes, such as for example deformation and strain, we need to gain information about them that are precise and reliable. There exist many different methods for such measurements. However, most often these methods measure the pure surface response due to the deforming mechanism, since this is what can be observed directly by use of cameras and various sensors. We therefore know a lot about how the material surface behaves but not much about how the structure beneath the surface behaves. As long as the material structure is reasonably homogeneous this may be enough but as the complexity of the material structure increase it gets more important to obtain information from the inside of the material. In this thesis two techniques with the ability to measure internal deformations in optically non-transparent materials are presented. The fundamental principle of both the techniques is the same. The techniques utilize a correlation based routine to estimate deformations from two and three dimensional image data collected with x-ray-based methods. The first technique, called Digital Speckle Radiography (DSR), measures two-dimensional deformation fields, in a single plane within the examined material. The deformations are estimated by the use of image correlation applied to two-dimensional digital x-ray images. The second technique, called Tomographic 3D-DSP, measures the three-dimensional unrestricted deformation, in every point of the examined object. Here the correlation procedure is carried out on volumetric object data collected with computed tomography (CT). Three separate experiments have been carried out, to investigate the behaviour of the two techniques. In two of the experiments the two-dimensional technique is applied. In the first of these the flow profile of an alumina powder is measured as it flows through a silo configuration. In the second experiment the motion in a thin film of glue, sandwiched between two wooden plates, exposed to shear, is measured. Finally in the third experiment the three-dimensional technique is used to measure the deformations in bone tissue when being exposed to a mechanical load. In this case two measurements have been carried out, and compared. These differ through a small damage that has been introduced to the bone tissue in the second measurement. / Godkänd; 2005; 20061221 (haneit)

Företaget Cranab, i vindeln, tillverkar i stor utsräckning skotar-, och skördarkranar till skogsmaskiner i varierande storlekar. Företaget tillverkar sedan ett år tillbaka även lastbilkranar. En kran består av olika delar i varierande storlekar så som kranpelare, lyftarmar, vipparmar, mellanbommar och innerbommar. Dessa krandelar är svetsade konstruktioner och består i sig av olika komponenter, de olika komponenterna skärs ut i en lasermaskin och svetsas sedan på de olika krandelarna. När krandelarna är kompletta bearbetas de i en CNC-maskin. När den färdiga krandel ska bearbetas i CNC-maskinen placeras den i en fixtur som säkerställer en stabilare bearbetning och förhindrar främst vibrationer. I nuläget används en uppsjö av olika fixturer som är konstruerade för en esnkild krandel, vilket medför en längre ställtid och fixturerna tar väldigt stor plats på golvet. Syftet med detta arbete är att ta fram ett konstruktionsförslag till en flexibel fixtur där ett antal krandelar med varierande storlek går att spänna fast. Många faktorer är viktiga vid konstruering av fixturerna för att kunna säkerställa en optimal bearbetning av krandelarna. Cranab står inför en stor investering gällande CNC-maskin vilket påverkar fixturen då den skall roteras 90 grader under bearbetningen, de nuvarande fixturerna är inte anpassade för denna rotation och därför måste även detta tas till hänsyn under konstruktion utöver de tidigare kraven. Under detta arbete behandlades lyftarmar till skotare vilket är den mest komplicerade krandelen. Första momentet av arbetet består av informationsinsamling och analys av nuvarande fixturer, efter detta utförs konstruktionsarbetet i CAD-programmet Inventor där ett koncept till fixturen tas fram. Resultatet av arbetet är en fixtur som kan hantera åtta stycken olika varianter av lyftarmen till skotare, i nuläget kan en fixtur endast användas till maxiamalt två olika varianter. I och med den nya konstruktionen kan justeringarna som krävs för olika varianter göras på ett smidigt sätt och inga traverser eller liknande verktyg krävs för att ställa om fixturen, vilket effektiviserar fixturen ytterligare. Resultatet ses som en klar förbättring jämfört med de nuvarande fixturerna, även om det som presenteras inte är en färdigställd genomarbetad fixtur så är det en grund att arbeta vidare med. / The company Cranab, located in Vindeln, manufactures cranes in varius sizes mostly to forest machines, since a year back they also manufactures cranes to trucks. A crane consists of different components in various sizes such as crane piller, lifting arms, rocker arms, middle boom and inner boom. These components are welded constructions and consists of different details, the different details are produced in a laser cutting process and then welded on to the arm itself. When the arm is complete it is put into a CNC-machine where it is processed. When the arm is ready for the CNC-machine it is placed in a fixture to ensure a more stable processing an mostly to readuce vibrations. The current situation at Cranab is that they use one specific fixture to one specific arm. For this reason it takes a lot of time to change between arms and the fixtures itself takes a lot of place in the workshop. The purpose of this project is to construct a flexible fixture that is able to handle a couple of arms by changing the fixture in a smooth way. A lot of varius factors are important when constructing a fixture that ensures a stable and safe process in the CNC-machine. Cranab are investing a lot of money in a new CNC-machine that will process these arms, the new machine is going to rotate the whole fixture 45 degreese. The fixture that are now used are not able to handle this kind of rotation so except the current requirements the new fixture must be able to hold the whole weight of the arm. During this project the lifting arm to forwarders will be analyzed which is the most complicated part of the crane. The first part of the project will consist of collecting information about the current situation and analyzing the fixtures that are now used, after that the construction of the fixture will be done in the CAD-program Inventor where a koncept will be be developed. The project results in a fixture that can handle eight arms, the current fixtures that are used can only handle a maximum of two arms. With the new fixture, the adjustmets that are necessary when different arms needs to be mounted will be easy to implement and they won’t need a traverse to adjust the fixture. This will make the workprocess of adjusting the fixture much more time efficient. The result is, in comparison with the old fixtures, a clear improvement. Although the project resulted in a raw model of the flexible fixture it is a clear improvement of the existing ones and it is something to continue working with.

n development of bumper systems for the automotive industry, iterative Finite Element (FE) simulations are normally used to find a bumper design that meets the requirements of crash performance. The crash performance of a bumper system is normally verified by results from standardized low speed crash tests based on common crash situations. Consequently, these crash load cases are also used in the FE simulations during the development process. However, lack of data for the car under development implies that simplified models must be used as a representation of the car in the FE simulations. Present simplified models of the car lead to uncertainties of the design even though the bumper system is modelled in a proper manner. The present work focuses on methods of how to represent the car in the FE crash simulations. The work is limited to the standardized crash tests in which the force acts longitudinally along the vehicle. Two different types of modelling perspectives are investigated. With the traditional approach, the aim is to obtain agreement of the results from the FE simulation and the physical test in terms of force from the barrier as a function of the compression of the bumper system. Here, the vehicle is represented by a point mass connected via rigid beam elements to the bumper system. The point mass, which only is allowed to translate longitudinally, is assigned with a reduced mass compared to the physical mass of the car to compensate for energy transformations in the car during the collision. In paper A, it is shown that the required mass reduction is dependent on vehicle and bumper characteristics as well as on the loading conditions. Also, the simple method of mass reduction leads to difficulties in attaining high agreement for time history of force and compression. In contrast to this, the idea with the second modelling technique is to reach a high agreement of the time history of force and compression of the bumper system. This methodology is based on a model structure that consists of mass elements, linear spring and viscous damper elements. It is shown that this model structure can provide high agreement between the FE simulation and the physical crash test in terms of force and compression as functions of time even for different loading conditions without adjusting the model parameters. Within the current thesis, a methodology of identifying parameters in the Mass Spring Damper (MSD) model from physical crash tests is presented. The methodology identifies a set of parameters that minimizes the deviation of the resulting displacements from the crash test and the simulation. This identification methodology is then used in a Design of Experiments (DOE) approach for relating model parameters in the MSD model to general properties of an arbitrary vehicle such as axial stiffness, bending stiffness and mass. For this, a public domain FE simulation model of a Ford Taurus is used. The knowledge gained from this study makes it possible to use the MSD model for representation of a coming car in the FE simulations associated with bumper development. / <p>Godkänd; 2006; 20061120 (pafi)</p>

In the vehicle industry there is a constant struggle to develop cars with high passive safety without increasing the fuel consumption. High passive safety requires a very rigid behaviour of the crash protecting components. Accomplishing this often leads to an increase in the weight of the components. An increase in weight results in a higher fuel consumption which is bad for the environment as well as for the economy of the car owner, therefore the manufacturers turn to new materials. One of these new materials is ultra high strength steel which is the material in focus for the present thesis. To be able to utilize all the advantages of ultra high strength steel the material behaviour must be investigated in detail. In this thesis, sheets of ultra high strength steel, which are produced by press-hardening, are investigated using a method called digital speckle photography. When using the method of digital speckle photography (DSP) a series of photographs are taken of a deforming specimen. Prior to the experiment a random pattern (speckles) has been applied to the specimen and by studying the deforming speckle pattern on the images, the deformation fields through time can be established. Within the present thesis the deformation fields up to the point of fracture have been investigated on a length scale of the order of 10e-4 meters. With length scales of this magnitude the deformation inside a localized neck can be investigated. This is done, both for a specimen shape that induces a fracture initiation at an inner point of the specimen and a specimen shape where fracture starts from the edge of a hole. These investigations show that there is a strong localization of the strain before fracture is initiated. The local strain values inside a localized neck are significantly higher than the strain values that can be observed with conventional experimental techniques involving extensometers. It is also noticed that the method used to make holes play an important role for the onset of fracture. Some methods hardly affect the material at all while others can decrease the level of local strain at the onset of fracture down to about a third of the value for unaffected material. Furthermore, a method for characterizing the material based on full-field measurements is presented. The method is a fast and simple alternative to previously used inverse modelling procedures where the material model of a finite element simulation is updated iteratively to make the simulation produce the same results as the experiment. / <p>Godkänd; 2007; 20070514 (ysko)</p>

In recent years an increasing interest has evolved concerning seat integrated safety belts in cars, regarding both 3- and 4-point belts in various configurations. One safety advantage of seat integrated safety belts appears in the case of so-called small overlap crashes. One consequence of a small overlap crash can be that the colliding cars strike each other's sides hitting both the A- and B-pillar. Hence, the A- as well as the B-pillar are pushed inwards and backwards. In this case, belt anchor points on the B-pillar may also be pushed backwards and the belt will be stretched over the occupant. The purpose of the present study was to investigate seat integrated safety belt configurations that may involve a seat structure design that intentionally deforms and absorbs energy during a crash. Common 3-point configurations were used as references. The aim was to investigate how the physical properties influence the interaction of the seat back frame and the safety belt. Numerical simulations were carried out using the explicit LS-DYNA FE-analysis software. A FE-model of a seat structure, floor pan and B-pillar was established. A 50th percentile Hybrid III FE-dummy model was used as occupant and for studying the biomechanical responses. Different physical properties of the seat structure and different belt load limit forces were used as parametric variables. Only frontal crashes were considered. Responses concerning chest deflection, head- and chest displacement, change of pelvis angle, pelvis submarining tendency, lap- and torso belt forces, seat back frame deflection, ride-down efficiency, seat structure natural frequency, upper neck loads and neck injury criteria were studied. The results indicate that the belt-webbing distribution between the lap and the torso belts via a slip-ring and in combination with a non-rigid seat back frame increases the ride-down efficiency compared to a system with no belt-webbing distribution. Further, the combined use of different energy absorption mechanisms influences the biomechanical response as well as the structural response of an integrated safety belt configuration. An optimal solution with respect to multiple objectives requires a proper combination of parameters. Beside the optimisation of traditional biomechanical responses, the multiple objectives can be the minimisation of weight and cost as well as optimal control of passenger kinematics. The present study will hopefully create a basis for future research and possibly for the design of seat integrated safety belts. / <p>Godkänd; 2006; 20070109 (haneit)</p>

Handling of iron ore pellets is an important part in the converting process for LKAB. Knowledge about this sub process is very important for further efficiency progress and increased product quality. The existence of a simulation tool with modern modelling and simulation methods will significantly increase the possibility to predict the critical forces in product development processes and thereby decrease the amount of crushed pellets (fines). In this work, simulations of granular material flows on a global scale are performed. From the simulations, properties like flow pattern and density distribution are studied. The methodology is suitable for different applications of particle flows. The particles could be stones, ore, ore pellets, metal powder and other granular materials. Previous studies exploring flow patterns and stress fields in granular solids are analysed with experiments or with numerical methods such as discrete element (DE) method or finite element (FE) computations. In this work, the smoothed particle (SP) method is used to simulate granular material flow. It is a mesh-free continuum-based computational technique where each calculation node is associated with a specific mass, momentum and energy. Properties within the flow such as density and movements of the nodes results from summations via a kernel function of the neighbours of each node to solve the integration of the governing equations. The fact that there are no connections between the nodes in the SP method, results in a method that handles extremely large deformations and still has the advantages of a continuum-based method. This is a major advantage versus FE and DE analysis. Within the current thesis, two applications of simulating granular material with SP analysis is presented: iron ore pellets flow in a flat bottomed silo and simulation of shoe filling of metal powder into simple and stepped dies. In the first application, primarily the flow pattern, when discharging a silo with pellets, is studied and compared with experimental results. Next application focuses on the filling behaviour and density distribution in metal powder shoe filling. For trustworthy numerical simulations of iron ore pellets flow, knowledge about their mechanical properties is needed. In this work, an elastic-plastic material characterization for blast furnace pellets is evaluated from experimental data. Constitutive data in vein of two elastic parameters and a yield function for the pellets bulk material is determined. The present study is an important step towards a simulation tool to predict the critical load in different handling systems of pellets. / Godkänd; 2008; 20080428 (ysko)

The rapid development of computing technology has made powerful tools, such as finite element codes, available for more and more companies. The use of simulation tools, predictive engineering, is a prerequisite today in product development. To describe the material deformation a variety of constitutive models, based both on physical foundations and empirical considerations, are available. Common for all models is that they contain material parameters, which have to be estimated by utilising experimental methods. Despite the advanced numerical tools, the most common method to characterise materials in industry today is to use standard tensile tests. Those tests have a major drawback. When the loading is no longer homogenous, and plastic instability has initiated, the stress-strain relationship is no longer valid. The aim for this work is to investigate methods for parameter estimation in material models. The test material used is hot-rolled cold-forming steel. A further aim is to yield stress-strain curves more appropriate for large deformations compared to a standard tensile test. The main features are the use of experiments, finite element analysis (FEA) and inverse modelling combined. The parameter estimation is formulated as an inverse problem and an objective function, describing the residual error between experimental data and data from a FEA of the experiment, is formulated as a least-square functional. The objective function is minimised by an optimisation algorithm yielding a vector of best fit, or estimated, material parameters. Two approaches are investigated. One global, where experimental data from a forming experiment is used. Data is in the form of tool force and displacement, hence global data. This is in contrast with a local approach where in-plane full-field measurements of displacements on a flat specimen (hence, local data), subjected to a tensile test, are collected through the whole deformation history until fracture. The measurements are made with digital speckle photography (DSP). Parameters are estimated for a total of three different material models, assuming isotropic material properties and yield surface according to von Mises. Results from the global approach show significant difference in the stress-strain curves and a force response with optimised models compared to an extrapolated tensile test curve. In the local approach the DSP-technique provided measurements, where the maximum equivalent plastic strain in a specimen was approximately 0.8. The true stress-strain curves based on the estimated parameters are validated in the low strain region by comparison with curves from standard tension tests. / Godkänd; 2004; 20070115 (ysko)