Rolling contact fatigue is a damage process that may arise in mechanical applications with repeated rolling contacts. Some examples are: gears; cams; bearings; rail/wheel contacts. The resulting damage is often visible with the naked eye as millimeter sized surface craters. The surface craters are here denoted spalls and the gear contact served as a case study. The work focused on the asperity point load mechanism for initiation of spalls. It was found that the stresses at asperity level may be large enough to initiate surface cracking, especially if the complete stress cycle was accounted for. The gear contact is often treated as a cylindrical contact. The thesis contains experimental and numerical results connected to rolling contact fatigue of cylindrical contacts. At the outset a stationary cylindrical contact was studied experimentally. The stationary test procedure was used instead of a rolling contact. In this way the number of contact parameters was minimized. The cylindrical contact resulted in four different contact fatigue cracks. The two cracks that appeared first initiated below the contact. The other two cracks developed at the contact surface when the number of load cycles and the contact load increased. The influence of a surface irregularity (asperity) was studied numerically with the Finite Element Method (FEM). Firstly, the stationary contact was modelled and investigated numerically. At the cylindrical contact boundary a single axisymmetric was included. The partially loaded asperity introduced a tensile surface stress, which seen from the asperity centre was radially directed. Secondly, FE simulations were performed where a single axisymmetric asperity was over-rolled by a cylindrical contact. The simulations were performed for pure rolling and rolling with slip. For both situations, tensile forward directed stresses in front of the asperity were found. The presence of slip and a surface traction greatly increased the stresses in front of the asperity. Finally, when rolling started from rest with applied slip, the distance to steady-state rolling was determined for elastic similar cylindrical rollers. / QC 20100702

We describe the design and implementation of a high dynamic range (HDR) imaging system capable of capturing RGB color images with a dynamic range of 10,000,000 : 1 at 25 frames per second. We use a highly programmable camera unit with high throughput A/D conversion, data processing and data output. HDR acquisition is performed by multiple exposures in a continuous rolling shutter progression over the sensor. All the different exposures for one particular row of pixels are acquired head to tail within the frame time, which means that the time disparity between exposures is minimal, the entire frame time can be used for light integration and the longest expo- sure is almost the entire frame time. The system is highly configurable, and trade-offs are possible between dynamic range, precision, number of exposures, image resolution and frame rate.

The in situ proximity ligation assay (in situ PLA) is an immunoassay that enables directvisualisation of single protein targets or protein interactions in cell or tissue samples. This project revolves around designing and introducing several novel multiplexable components tobe used in conjunction with Olink Bioscience's Duolink product line. In this report, a novel in silico approach to DNA oligomer interaction design is presented. Using this in silico method, a multiplexed system of DNA oligomers has been designed andevaluated using in situ PLA and fluorescence microscopy.

Today, 3D models of cities are created from aerial images using a camera rig. Images, together with sensor data from the flights, are stored for further processing when building 3D models. However, there is a market demand for a more mobile solution of satisfactory quality. If the camera position can be calculated for each image, there is an existing algorithm available for the creation of 3D models. This master thesis project aims to investigate whether the iPhone 4 offers good enough image and sensor data quality from which 3D models can be created. Calculations on movements and rotations from sensor data forms the foundation of the image processing, and should refine the camera position estimations. The 3D models are built only from image processing since sensor data cannot be used due to poor data accuracy. Because of that, the scaling of the 3D models are unknown and a measurement is needed on the real objects to make scaling possible. Compared to a test algorithm that calculates 3D models from only images, already available at the SBD’s system, the quality of the 3D model in this master thesis project is almost the same or, in some respects, even better when compared with the human eye.

Hot rolling process is heat input process. The heat energy in hot rolled steel coils can be utilized. At SSAB Strip Product Borlänge when the hot rolled steel coils came out of the hot rolling mill they are at the temperature range of 500°C to 800°C. Heat energy contained by the one hot rolled steel coil is about 1981Kwh whereas the total heat energy for the year 2008 is 230 GWh/year.The potential of heat is too much but the heat dissipation rate is too slow. Different factors on which heat dissipation rate depends are discussed.Three suggestions are proposed to collect the waste heat from hot rolled steel coils.The 2nd proposal in which water basin is suggested would help not only to collect the waste heat but to decrease in the cooling time.

Generally, investment in commodity ETFs cannot produce similar performance as well as spot goods. Evidence shows that ¡§rolling¡¨ futures positions experience ¡§contango and the effects on contango will harm ETFs¡¨ value. This study shows that two ETFs, USO and UNG, underperform the spot substantially because of rolling in the crude oil and natural gas market, respectively. In this study we employ four energy sector futures market data from the Thomson Reuters to investigate the impact of rolling positions on the relation between commodity index funds and in contango/backwardation. This paper finds that increasing trading in commodity index fund made futures market more contango in the WTI crude oil, natural gas and heating oil markets. This study termed the strategy as the Backwardation Sensitive Trading (BST) . Moreover, this research designs an investment strategy based on variation of backwardation. That is to examine whether BST can make a successful arbitrage: increase holding when the market is more contango and decrease holding when the market is more backwardation. Our strategy performs better than USO and UNG, and those performances perform lower tracking error on oil and natural gas over 2006 to 2010.

This work is initiated from an observation of the rolling-sliding kinematic behavior observed in the motion of the knee joint. We use the slip ratio as a parameter to analyze the rolling-sliding properties of a mechanism, and also propose a method to design new mechanisms with specific slip ratio. In this research, we first verify the many definitions of the slip ratio, then modify a best definition to suit various rolling-sliding motions. Most importantly, we propose two types of rolling-sliding mechanism design. By changing the parameters of the mechanism, we can adjust its slip ratio curve to be close to a desired curve. In addition, when the idea of adjustable link length is used in the design of the mechanism, exact slip ratio curve as specified can be generated by the use of some cams.

Screws are produced by four manufacturing processes : extrusion, drawing, heading and thread-rolling. This paper will develop the related manufacturing technology of LZ91 magnesium alloy screws. At first, finite element simulation is adopted to analyze the effects of each process parameters on the formability. Then, each process experiments are conduted to manufacture an M6 magnesium alloy screw. Comparisous between analytical and experimental results verify the suitability and accuracy of the analytical models. In the extrusion process, by the finite element simulations the extrusion load is obtained. Then bar extrudsion experiments with high extrusion ratioto manufacture two bars of 6.5 and 7 mm in diameter using a 350 ton extrusion machine . In the drawing process, the effects of reduction and friction factor on the optimal semi-die angle are discussed, and the relationship is found. Then a rod of 7.0 mm in diameter is drawn into 6.5 mm experimentally. In the heading process, three stages in it`s process are designed. The arc shape and axial length of the die for the first stage are found out. Finally, heading experiments are conducted and sizes between the product and the simulation results are compared. In thread-rolling process, the effects of the screw plate gap on the formability are discussed numerically. Then, thread-rolling experiments are conducted to compare the sizes of the product and the simulation results. In addition, microstructure observation and hardness test are conducted to understand the effects of drawing process on the strength of the product.

Rolling element bearings are the one of the most widely used machine elements in the industry. The most important criterion in bearing selection is the endurance life. The first attempts on the prediction of the endurance life of rolling elements bearings are done by Lundberg and Palmgren in 1950s (Harris, 1999). Their work adopted as an ANSI, ABMA and ISO standard which is widely used in industry today. The basic assumption of Lundberg-Palmgren formulation is that no matter how small the load applied on rolling element bearing, all material in the stressed volume is subject to fatigue failure. In this study, four main life theories / Weibull, Lundberg-Palmgren, Ioannides-Harris, and Zaretsky on rolling element bearings have been investigated. Three-dimensional finite element models of a bearing&rsquo / s inner ring and rolling element have been prepared. The stress fields within the inner ring and the ball with respect to the applied load are obtained numerically. The fatigue life of the inner ring has been predicted by two methods that are widely used for fatigue analysis / Total Life Analysis (S-N method) and Crack Initiation Analysis (&amp / #56256 / &amp / #56624 / -N method). Obtained results are compared with ISO formulation. As a result of the investigation, S-N and &amp / #56256 / &amp / #56624 / -N methods are determined to give more conservative results than ISO method for higher loads that cause stresses above the fatigue limit of the material. The used methods for bearing life prediction recognize the existence of the fatigue limit stress. Hence as the stresses within an operating bearing do not exceed the limit stress, the bearing can achieve infinite life. It is also observed that load variation has a direct influence on the bearing life. When the load significantly changes from the levels which create stress above the fatigue limit to the levels that result stress is below the fatigue limit, the bearing would have higher endurance life than predicted by ISO method.

<p>This doctoral thesis presents a modeling method fordemonstrating the behavior of inclusions and their surroundingmatrix during plastic deformation of steels.</p><p>Inclusions are inescapable components of all steels. Moreknowledge about their behavior in processes such as rolling andforging is necessary for carrying out the forming processes ina more proper way so that the properties of the final productare improved. This work is focussed on deformation ofinclusions together with void formation at the inclusion-matrixinterface. The topic of the work is analyzed by differentFE-codes.</p><p>The relative plasticity index is considered as an importantmeasure for describing the deformability of inclusions. Theindex could be analyzed quantitatively, enabling a deeperunderstanding of the deformation mechanisms. The workingtemperature is found to be an important process parameter. Thisis very clear when the deformation of silicate inclusions in alow-carbon steel is studied during hot rolling. Here a narrowtransition temperature region exists, meaning that theinclusion behaves as non-plastic at lower temperatures and asplastic at higher. The results are in agreement withexperiments published by other authors.</p><p>Regarding void formation, the simulations have been carriedout by utilizing an interfacial debonding criterion. Thedifference in yield stress between the matrix and the inclusionis one common reason for void initiation and propagation.During large compressive deformation the evolution of voidsgoes through a sequence of shapes, from convex with two cuspsto concave with three cusps together with self-welding lines.It is concluded that the formation of voids is alwaysassociated with a large relative sliding between the inclusionand the matrix.</p><p>In order to study the local behavior of the material closeto inclusions during hot rolling a mesomechanical approach isused. Uncoupled macro- and micro- models have been developed.By means of the macro-model, the stress-strain historythroughout each sub-volume of the steel is evaluated. Thestress components or velocity fields are recorded with respectto time as history data. No consideration is taken to theexistence of inclusions. The micro-model, which includes bothinclusion and steel matrix, utilizes the stress components orthe velocity fields from the macro-model as boundaryconditions.</p><p><b>Keywords</b>: Inclusion; Steel; Plastic deformation; Void;Rolling; Forging; Finite Element; Mesomechanical approach.</p>