In this work the influence of Under Sleeper Pads on the dynamic forces on a railway track is investigated. A special interest is devoted to the effect of using Under Sleeper Pads in a railway track with changing vertical stiffness. The contact force between wheel and rail and the ballast contact forces are examined. For the investigation a finite element model with the length of thirty sleepers is created and calculations are performed with the software LS-DYNA. Three different cases of varying vertical track stiffness are studied: the transition from an embankment to a bridge, a randomly varying track stiffness along the railway track and hanging sleepers.

Although there have been tremendous improvements in crash safety there has been an increasing trend in side impact fatalities, rising from 30% to 37% of total fatalities from 1975 to 2004 (NHTSA, 2004). Between 1979 and 2004, 63% of AIS≥4 injuries in side impact resulted from thoracic trauma (NHTSA, 2004). Lateral impact fatalities, although decreasing in absolute numbers, now comprise a larger percentage of total fatalities. Safety features are typically more effective in frontal collisions compared to side impact due to the reduced distance between the occupant and intruding vehicle in side impact collisions. Therefore, an increased understanding of the mechanisms governing side impact injury is necessary in order to improve occupant safety in side impact auto crash. This study builds on an advanced numerical human body model with focus on a detailed thoracic model, which has been validated using available post mortem human subject (PMHS) test data for pendulum and side sled impact tests (Forbes, 2005). Crash conditions were investigated through use of a modified side sled model used to reproduce the key conditions present in full scale crash tests. The model accounts for several important factors that contribute to occupant response based on the literature. These factors are; the relative velocities between the seat and door, the occupant to door distance, the door shape and compliance. The side sled model was validated by reproducing the crash conditions present in FMVSS 214 and IIHS side impact tests and comparing the thoracic compression, velocity, and Viscous Criterion (VC) response determined by the model to the response of the ES-2 dummy used in the crash tests. Injury was predicted by evaluating VCmax, selected for its ability to predict rate-sensitive soft tissue injury during thoracic compression (Lau & Viano, 1986). The Ford Taurus FMVSS 214 and Nissan Maxima IIHS tests were selected from side impact crash test data found in the NHTSA database because they included factors not present in standard side impact test procedures. These factors were; the presence of door accelerometers used to provide input velocities to the side impact model and the use of a ES-2 (rather than the SID) to facilitate comparison of VC response to the human body model. Also, the two crash test procedures (FMVSS 214 & IIHS) were selected to ensure accurate side impact model response to different impact scenarios. The side impact model was shown to closely reproduce the timing and injury response of the full-scale FMVSS 214 side impact test of a Ford Taurus, as well as the IIHS side impact test of a Nissan Maxima. The side impact model was then used to investigate the effects of door to occupant spacing, door velocity profile, armrest height, seat foam, restraint system, and arm position. It was found that the VCmax was controlled by both the first and second peaks typically found in door velocity profiles, but the effect of each varies depending on the situation. This study found that VCmax was reduced by 73-88% when door intrusion was eliminated compared to the VC response incurred by an intruding door. Also, the presence of a deformable door based on physical geometry and material characteristics rather than a simplified rigid door reduced VCmax by 16% in this study. The study on seat foam determined that significant effects on VC response can be made by modest adjustments in foam properties. Low stiffness seat foam was found to increase VCmax by 41% when compared to the VC response when using high stiffness foam. Arm position has been proven to be a relevant factor in side impact crash. Positioning the arms parallel to the thorax, in the “down” position, caused a 42% increase in VCmax when compared to the VC response determined with the arms positioned at 45 degrees. Finally, although restraint systems have limited influence on side impact crash safety compared to front and rear impacts, this study found that the presence of a pre-tensioning restraint system reduced VCmax by 13% when compared to the VC response of an un-belted occupant. It should be noted that the current study was limited to velocity profiles obtained from a specific FMVSS 214 test and therefore results and observations are restricted to the confines of the input conditions used. However, the side impact model developed is a useful tool for evaluating factors influencing side impact and can be used to determine occupant response in any side impact crash scenario when the appropriate input conditions are provided.

The steel through-truss Traffic Bridge, located in Saskatoon, Saskatchewan is over one hundred years old. The bridge has been subject to ongoing maintenance throughout its service life. However, inspection reports from 2005 and 2006 highlighted the severe deterioration experienced primarily by the steel members immediately above and below the deck surface. These reports prompted the City of Saskatoon (COS) to implement a rehabilitation project that involved the installation of a post-tensioning system to relieve the badly corroded bottom chord members of the axial loads due to the self-weight of the structure, in 2006. Due to the severe deterioration and the structural modifications that the Traffic Bridge has endured, a limited scope structural health monitoring (SHM) system, based on strain measurements, was implemented to reduce some of the uncertainty regarding the active load paths occurring at the deck level. The objectives of the SHM study were to obtain more information regarding the actual load paths and ascertain possible types of structural redundancy, to determine how to best model this type of structure, and to find ways to track ongoing deterioration using instrumentation. The SHM study involved controlled truck loading scenarios to permit measurement of the load paths and provide data to compare the measured results to a finite element (FE) model of the instrumented span. In addition, random loading scenarios were used to capture the vertical dynamic response of the structure in order to further refine the FE model. This study focused on the response of one-half of one interior span. A total of 72 strain gauges were installed. The downstream truss was highly instrumented at ten locations, three members of the upstream truss were instrumented to measure the distribution, and the floor joists in the downstream lane were instrumented to establish possible redundancy paths. Using an FE model in combination with the measured strain data, it was found that redundant load paths only existed at the level of the deck. The bottom chord members experienced non-zero strains once the control vehicle was past the span, possibly indicating some level of redundancy. The members believed to relieve a portion of the bottom chord tensile forces included the car joists, edge joists, and the timber deck. The amount of force transferred from the bottom chord to the deck members was found by FE analysis to be highly related to the lateral stiffness of the floor beams. The FE model was adjusted to match the measured results by modifying various modelling parameters. The most important features of the model were that all deck elements were modelled to be located at the elevation of the bottom chord, that the lateral stiffness of the floor beams was reduced by 50% to best represent the transfer of forces to deck elements, and that the stiffness of bottom chord members was reduced to 80% of their pristine values. In combination with calibrated modification factors applied to the measured values, this FE model is believed to be a useful tool to represent the behaviour of the structure to assist in detecting further damage by modelling the strain differential between members, and components of members.

<p>In this work the influence of Under Sleeper Pads on the dynamic forces on a railway track is investigated. A special interest is devoted to the effect of using Under Sleeper Pads in a railway track with changing vertical stiffness. The contact force between wheel and rail and the ballast contact forces are examined. For the investigation a finite element model with the length of thirty sleepers is created and calculations are performed with the software LS-DYNA. Three different cases of varying vertical track stiffness are studied: the transition from an embankment to a bridge, a randomly varying track stiffness along the railway track and hanging sleepers.</p>

Title from PDF of title page. / Document formatted into pages; contains 64 pages. / Thesis (M.S.C.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Predicting breast tissue deformation is of great significance in several medical applications such as surgery, biopsy and imaging. In breast surgery, surgeons are often concerned with a specific portion of the breast, e.g., tumor, which must be located accurately beforehand. Also clinically it is important for combining the information provided by images from several modalities or at different times, for the planning and guidance of interventions. Multi-modality imaging of the breast obtained by mammography, MRI and PET is thought to be best achieved through some form of data fusion technique. However, images taken by these various techniques are often obtained under entirely different tissue configurations, compression, orientation or body position. In these cases some form of spatial transformation of image data from one geometry to another is required such that the tissues are represented in an equivalent configuration. / ABSTRACT: We constructed the 3D biomechanical models for this purpose using Finite Element Methods (FEM). The models were based on phantom and patient MRIs and could be used to model the interrelation between different types of tissue by applying displacements of forces and to register multimodality medical images. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Glued connections are relatively new in structural timber engineering. They are expected to show high connection stiffness as well as a high connection strength compared to mechanical connections e.g. dowel‐type connections.The main aim of this thesis is to characterize the behavior of glued timber connections under pure tension by conducting experiments as well as numerical simulations. Hereby the influence of different parameters is studied such as the geometry (bond-line length and thickness) and the material properties (e.g. adhesives of highly diverse stiffness). Additionally, reference tests on a dowel-type connection are made. The purpose is to see the differences between dowelled and glued connections and to see if there are some advantages in using glued timber connections (the base geometry was chosen acc. to Eurocode 5).Finite element models were created in the software ABAQUS. The models were used to predict the connection stiffness and compare this to the experimental results. In addition, parametric studies were performed on e.g. overlapping lengths. The comparison between experiments and simulations showed good agreement.It was found that glued connections with the adhesives SikaPower-4720 and SikaFast-5215 NT (an epoxy and an acrylate, respectively) had higher stiffness than the dowel connections, whereas connections with the silicone adhesive SikaSil SG-500 had a lower stiffness. A general conclusion drawn from this work is that the glued timber connections simulated in this project should also be suitable for application to complex connections and situations involving other loading situations than pure tension.

Air permeability (ka) is a viable alternative to water- and texture-based methods to rapidly map saturated hydraulic conductivity (Ksat). The ability to measure this important hydraulic property without the use of more cumbersome and time-consuming methods may provide a practical approach to generate more complete data to describe hydrologic conditions. This study presents the development of an air permeameter which is suitable for desert soils. The Soil Corer Air Permeameter (SCAP) is compatible with a standard soil corer and employs digital components to measure flowrates under low-pressure gradients to improve accuracy, ease of use, and portability. SCAP allows for the extraction of undisturbed soil samples for laboratory analysis, providing direct comparisons of ka with other soil physical and hydraulic properties. The applicability of a regression equation to estimate Ksat from field-measured ka using SCAP was examined in unburned and burned soils. Ex situ field ka and laboratory Ksat measurements were compared and air to water permeability (ka/kw) ratios were calculated to determine structural changes due to water saturation. The study also characterized changes in permeability due to fire in woodland-chaparral and coniferous soils. For soils that could be extracted with minimal structural changes, results show ka and Ksat measurements for unburned and burned soils were within the 95% confidence intervals of a ka-Ksat regression developed for agricultural soils. However, correlations for in situ ka measurements in some burned soils showed a decrease in accuracy and may be attributed to soil anisotropy. A three-dimensional steady-state finite element air flow model was developed using FEMLAB 3.0A to consider the effects of anisotropy on in situ ka measurements. Results show that anisotropic conditions can introduce an error as high as a factor of 2 especially for air permeameters with high diameter to height (D/H) ratios, however, the error is much smaller than the anisotropy ratio. If anisotropy is important to characterize, it was shown that paired measurements of in situ and ex situ ka can be used to infer the anisotropy ratio.

The cutting action of a single abrasive grain was investigated using a combination of high-speed scratch tests and finite element models. The high-speed scratch tests were unique in that the cutting conditions of a grinding operation were closely replicated. Two geometries were tested: a round-nosed stylus to approximate a 15-grit abrasive grain and a flat-nosed stylus to approximate a worn 46-grit abrasive grain. The three-dimensional finite element model was unique in that a hybrid Euler-Lagrange method was implemented to efficiently model the interaction between an abrasive grain and a workpiece. The finite element model was initially validated using indentation tests to remove the complexities of relative motion from the validation process. The validation was completed through comparisons to the experimental scratch tests. The results of the analysis revealed several key findings. Rubbing, plowing, and cutting do not display distinct transitions; rather, they coexist with different weightings depending on the scratching speed and the depth of cut. The normal forces increased for a given depth of cut as the scratching speed was increased due to strain-rate hardening of the workpiece. The tangential forces decreased for a given depth of cut as the scratching speed was increased due to a reduction in the coefficient of friction and a change in the cutting mechanics from plowing to cutting. The change in the cutting mechanics was investigated by analyzing the evolution of the scratch profiles as the depth of cut and scratching speed were changed. It was found that higher scratching speeds produced less material pile-up and this was attributed to a change in the cutting mechanics. Due to the change in the cutting mechanics, the specific energy decreased as the depth of cut and scratching speed were increased. A numerical case study revealed that reducing the grain size resulted in: lower forces, lower specific energies, and smaller volumes of subsurface stresses. The finite element model was adapted to work in conjunction with the flat-nosed stylus creating the first model capable of simulating the cutting of an abrasive grain in three dimensions.

Oil companies need to evaluate the risk of annular fluid or gas migration if cement fails during the life of the well. Sustained casing pressure can lead to shutting in the wells to avoid health, safety, and environment (HSE) risks and government fines. To understand the long-term integrity of cement in high temperature and high pressure (HTHP) conditions and the mechanical properties that affect the ability of cements to seal fluids, this project used finite-element models (FEMs) to study the stress-causing phenomena. FEM analyses in ABAQUS version 6.11 were used to determine the potential of cement failure in oil wells. The model uses a 3D section of a well that can be used for different casing and formation types under different loading conditions. The model built in ABAQUS version 6.11 allows incorporating materials with nonlinear mechanical properties; it also uses FEM analysis to forecast fractures inside the cement under different loading scenarios like hydraulic fracture jobs or casing tests. The finite-element model included cases for cement cracking, cement debonding, and plastic deformation of the cement and rock that can generate loss of zonal isolation. Linear manner: set cements behave elastically until a failure criterion is reached, and then they can behave plastically. The FEM approach can reproduce stresses, strains, and volume changes in the material under different environmental HTHP conditions. Cemented wells have both tensile and compressive stresses that make some parts of the cement sheath experience fracture initiation, plastic deformation, or debonding. This dissertation provides a model that will help drillers design the set cement for long-term integrity in HPHT well conditions. The FEM predicts if the cement sheath can develop debonding, cracks or plastic deformations during the life of the well. The cement sheath needs to be designed for long-term zonal isolation to avoid interzonal communications, remedial costs and environmental problems related to cement seal. A CMS™-300 Automated Permeameter, a mechanical properties analyzer, HPHT cement consistometer, annular expansion molds, and tri-axial test equipment were used in this study to test cements for specific applications in three Colombian oil fields, including an oil field with in-situ combustion project.

The first step in many mining operations is blasting, and the purpose of blasting is to fragment the rock mass in the most efficient way for that mine site and the material end use. Over time, new developments to any industry occur, and design and implementation of traditional techniques have to change as a consequence. Possibly the greatest improvement in blasting in recent years is that of electronic detonators. The improvements related to safety and increased fragmentation have been invaluable. There has been ongoing debate within the explosives industry regarding two possible theories for this. Shorter timing delays that allow interaction between adjacent shock waves or detonation waves, or the increase in accuracy associated with electronic detonators. Results exist on the improved accuracy of electronic detonators over that of electric or non-electric, but data on the relationship between the collision of dynamic stress waves and fragmentation is less understood. Publications stating that the area of greatest fragmentation will occur between points of detonation where shock waves collide exist, but experimental data to prove this fact is lacking. This dissertation looks extensively at the head on collision of shock (in the rock mass) and detonation (in the detonation column) waves with relation to fragmentation through a number of small scale tests in concrete. Timing is a vital tool for this collision to occur and is the variable utilized for the studies. Small scale tests in solid masonry blocks, 15 x 7⅞ x 7⅞ inches in size, investigated shock and detonation wave collisions with instantaneous detonation. Blocks were wrapped in geotextile fabric and a wire mesh to contain the fragments so that in situ tensile crack formations could be analyzed. Detonating cord was used as the explosive with no stemming to maintain the shock pressure but reduce the gas pressure phase of the fragmentation cycle. Model simulations of these blocks in ANSYS Autodyn looked at the stress and pressure wave patterns and corresponding damage contours for a direct comparison with the experimental investigation. Detonation wave collision in a single blast hole was found to positively influence the fragmentation and throw of the material. Mean fragment size decreased compared to tests with no detonation wave collision. Area of greatest throw occurred at the point of detonation collision where a buildup of gas pressure exited the block from one location. Head on collision of shock waves did not positively influence the muck pile. Largest fragments were located at the point of shock collision. The lack of particle velocity with relation to shock collision in previous literature could be attributed to the increased particle size here. Directional particle velocities could actually increase the strength and density of the rock at this location, decreasing the degree of fragmentation rather than increasing it.