The aim of this master thesis was to investigate the mechanical properties of ExpandedPolystyrene (EPS) through experimental testing. The strain was measured on thespecimen’s surface with Digital Image Correlation (DIC), in order to investigate howthe first principal strain at fracture initiation depends on the loading of the material.To impose different loading conditions various tests were performed, such as biaxialtension-compression, uniaxial tension and bending tests. The study was done withfour densities of EPS, 35, 50, 75 and 100 g/L. To investigate how strain and stressat fracture initiation depend on temperature, the bending tests were performed atthree different temperatures, -20, 20 and 50 °C. All tests were performed in the SolidMechanics lab at KTH, Stockholm. For every experiment, five repetitions were madeto reduce the influence of the inhomogeneous microstructure of EPS and the stochasticbehaviour of fracture mechanics. The results indicate that the fracture initiation straindecreases with increasing density of EPS, while the fracture strength increases withincreasing density of EPS. Further, the results indicate that the loading conditions havean influence on the fracture initiation strain. / Målet med detta examensarbete var att undersöka materialegenskaper för EPS genomatt utföra experimentell testning. Töjningen mättes på provbitarnas yta med hjälp avDIC-teknik, för att undersöka hur första huvudtöjningen vid sprickinitiering beror påbelastningen av materialet. För att belasta material på olika sätt utfördes olika tester,såsom enaxligt drag, biaxiellt drag och tryck samt böjtester. Testerna gjordes med fyradensiteter av EPS, 35, 50, 75 and 100 g/L. För att undersöka hur töjning och kraft vidsprickinitiering beror på temperatur utfördes böjtesterna vid tre temperaturer, -20,20 and 50 °C. Alla tester utfördes på institutionen för hållfasthetslära vid KungligaTekniska högskolan. Varje experiment repeterades fem gånger för att minimerainverkan av den inhomogena mikrostrukturen hos EPS. Resultaten tyder på attbrottinitieringstöjningen minskar med ökande densitet av EPS, medan brottlastenökar med ökande densitet av EPS. Vidare indikerar resultaten att belastningen har eninverkan på brottinitieringstöjningen.

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The heavy use of de-icing salts in the winter to accommodate heavy traffic has been the most detrimental cause of chloride-induced corrosion in Canadian reinforced concrete (RC) bridge infrastructure. In addition, the rise of greenhouse emissions and subsequent increase in the mean surface temperature have increased the potential risk of carbonation-induced corrosion. It is believed that the synergistic effect of multiple deteriorating mechanisms will accelerate the incidence of reinforcement corrosion in Canadian infrastructure. Over time, premature deterioration of RC bridges due to reinforcement corrosion leads to concrete cover cracking and spalling, loss of bond between reinforcement and concrete, and reduction in the structural capacity and ductility of the structure. There is limited research work that has examined the effect of corrosion on the structural performance of RC columns. This research has evaluated the axial and flexural capacity of corroded RC columns exposed to different levels and patterns of reinforcement corrosion. An experimental testing campaign of ten RC columns was conducted in two stages. During the first stage, eight columns were subjected to an accelerated corrosion regime by impressing a constant current for 137 days. In the second stage, all ten columns were subjected to an axial quasi-static load until failure. Five columns were loaded concentrically, while the remaining five were loaded eccentrically. The structural performance (residual strength, ductility, resilience, stiffness, toughness and failure mode) of the columns were analyzed from load-displacement curves of the entire and mid-span length of the columns. The experimental results show that corrosion of the ties directly affects the column's post-peak response even at low corrosion levels. Columns with corroded ties had a brittle failure, and the residual ductility and toughness were significantly reduced. On the other hand, longitudinal reinforcement corrosion primarily affects the residual strength of the columns, which is prominent at a medium level of corrosion. At high levels of both longitudinal and transverse reinforcement corrosion, the residual strength, ductility, and axial stiffness are significantly reduced. This is accompanied by a significant deterioration of the cover and local buckling of the longitudinal rebars, which is attributed to a significant reduction in the confinement pressure of the core concrete. A three-dimensional non-linear finite element model (3D-NLFEM) of the columns was developed using the finite element package DIANA (v.10.4) and validated with the experimental results. The effect of reinforcement corrosion on the structural response of columns was modelled as a change in the mechanical and geometrical properties of concrete and steel materials. This was achieved by integrating constitutive and deteriorating models into the 3D-NLFEM. The model accounts for the bond-slip behaviour between longitudinal bars and concrete (for eccentrically loaded columns), the confinement of the concrete core and strength reduction of the concrete cover, and the buckling potential of longitudinal reinforcement. The validated model was used to conduct a parametric analysis to investigate the effect of several influencing variables such as damage level and patterns and to explore scenarios beyond those tested in a laboratory setting. Finally, an analytical model based on sectional analysis was developed and compared with both the experimental and FEM results. The proposed analytical approach was developed by integrating deteriorating models and incorporating data collected from field investigation. Based on this evaluation, a practical analytical approach is proposed to estimate the nominal residual capacity of corroded columns considering the reduction in confinement effects, bond loss and potential buckling. The results from the experimental, numerical, and analytical studies correlate well. This work's outcome will contribute to a better understanding of the axial and flexural performance in terms of the ultimate capacity, post peak response and failure mode of RC columns affected by the reinforcement corrosion and static loading. Moreover, it provides a simplified analytical tool for practicing engineers to predict the axial and flexural capacity of deteriorated bridges vulnerable to reinforcement corrosion and increased traffic volume.

Various congenital heart defects (CHDs) are characterized by the existence of a single functional ventricle, which perfuses both the systemic and pulmonary circulation in parallel. A three-stage palliation procedure, including the final Fontan Completion, is often adopted by surgeons to treat patients with such CHDs. However, the most common outcome of this surgery, an extra-cardiac total cavopulmonary connection (TCPC), formed by suturing the inferior vena cava (IVC) and superior vena cava (SVC) to the pulmonary arteries (PAs), results in non-physiological flow conditions, systemic venous hypertension, reduced cardiac output, and pressure losses, which ultimately calls for a heart transplantation. A modest pressure rise of 5-6 mm Hg would correct the abnormal flow dynamics in these patients. To achieve this, a novel conceptual design of a percutaneous dual propeller pump inserted and mounted inside the TCPC is developed and studied. The designed blood pump is percutaneously inserted via the Femoral vein and deployed at the center of Total Cavopulmonary Connection (TCPC). The two propellers, each placed in the Superior Vena Cava (SVC) and the Inferior Vena Cava (IVC) are connected by a single shaft and motor, and thus rotate at same speed. The device is supported with the help of a self-expanding stent which would be anchored to the walls of the IVC and the SVC. An inverse design methodology implementing Blade Element Momentum theory and Goldstein's radial momentum loss theory was employed to generate the blade profiles for the studied propeller pumps. The propeller blade profiles generated from the inverse design optimization code were examined for hydraulic performance, blood flow pattern and potential for hemolysis inside the TCPC using 3-D computational fluid dynamics (CFD) analysis. The Lagrangian particle tracking approach in conjunction with a non-linear mathematical power law model was used for predicting the blood damage potential of the analysed blood pump designs by calculating the scalar shear stress history sustained by the red blood cells (RBC). The study demonstrated that the IVC and SVC propeller pumps could provide a pressure rise of 1-20 mm Hg at flow rates ranging from 0.5 to 5 lpm while rotating at speeds of 6,000-12,000 rpm. Moreover, the average Blood Damage Index (BDI), quantifying the level of blood trauma sustained by the RBCs for the analyzed propeller pump designs, was found to be around 3e-04% to 4e-04% which is within the acceptable limits for an axial flow heart assist device. Thus, such a dual propeller blood pump configuration could potentially provide assistance to Fontan patients by unloading the single functional ventricle thereby acting as a bridge to transplantation and recovery until a donor heart is available. / Master of Science

Adaptive controllers allow robots to perform a wide variety of tasks, but the extensive computations required have generated an interest in developing decentralized adaptive controllers. Horner has designed an adaptive controller for a four-degree-of-freedom mobile robot and tested it through simulations. The study described in this thesis uses the techniques described by Horner to design and test a decentralized model reference adaptive controller (DMRAC) for a physical four-degree-of-freedom mobile robot. The study revealed several difficulties in implementing this design. Most notably, the robot available for the research did not allow for the measurement of joint velocity, so it was necessary to estimate the velocity as the derivative of the position measurement. The noise created by this estimation made completion of testing impossible. Future research should be performed on a robot that provides joint velocity measurement. Alternatively, a study could include state estimation as part of the controller, thus reducing and possibly eliminating the need for velocity measurement. / Master of Science

Mitigation of displacement and acceleration responses of a three story benchmark structure excited by seismic motions is pursued in this study. Multiple 20-kN magnetorheological (MR) dampers are installed in the three-story benchmark structure and managed by a global fuzzy logic controller to provide smart damping forces to the benchmark structure. Two configurations of MR damper locations are considered to display multiple-input, single-output and multiple-input, multiple-output control capabilities. Characterization tests of each MR damper are performed in a laboratory to enable the formulation of fuzzy inference models. Prediction of MR damper forces by the fuzzy models shows sufficient agreement with experimental results. A controlled-elitist multi-objective genetic algorithm is utilized to optimize a set of fuzzy logic controllers with concurrent consideration to four structural response metrics. The genetic algorithm is able to identify optimal passive cases for MR damper operation, and then further improve their performance by intelligently modulating the command voltage for concurrent reductions of displacement and acceleration responses. An optimal controller is identified and validated through numerical simulation and fullscale experimentation. Numerical and experimental results show that performance of the controller algorithm is superior to optimal passive cases in 43% of investigated studies. Furthermore, the state-space model of the benchmark structure that is used in numerical simulations has been improved by a modified version of the same genetic algorithm used in development of fuzzy logic controllers. Experimental validation shows that the state-space model optimized by the genetic algorithm provides accurate prediction of response of the benchmark structure to base excitation.

Most tyre models developed to date require a fair amount of data before an accurate representation of the tyre can be obtained. This study entails the development of a simplified, yet accurate, non-linear Finite Element (FE) model of an “off-road” tyre to study the behaviour of the tyre due to radial loading conditions. The study aims to develop a FE tyre model that can solve fast and be accurate enough to be used in multibody dynamic vehicle simulations. A model that is less complex than conventional detailed FE models is developed. The work explores the use of superimposed finite elements to model the varying stiffness in the respective orthogonal directions of the sidewall and tread of the tyre. Non-linear elements defined by Neo-Hookean or Ogden models and elements with different linear orthogonal stiffnesses are superimposed onto each other to simulate the global material properties of the tread and the sidewall of the tyre investigated. The geometry of the tyre studied was measured experimentally using laser displacement transducers and digital image correlation techniques. Material properties of segments of the tyre were obtained by performing tensile tests on samples. Since the rubber slipped against the clamps during the experiment, deformation of the segments was also measured using digital image correlation. These geometrical and material properties were used as input to develop a finite element model of an “off-road” tyre. Measurements were conducted using laser displacement transducers, load cells mounted to actuators, etc. to obtain accurate sidewall deformation profiles and global radial load vs. displacement curves for different radial loading conditions. The data obtained from the results was used to validate the tyre model developed. Numerous analyses are performed with different combinations of moduli of elasticity in the respective orthogonal directions of the sidewall stiffness and the tread to investigate its influence on the global behaviour of the tyre model. The main focus of the project was to develop a tyre model from data obtained from laser and photogrammetry measurements in a laboratory that accurately represents tyre behaviour due to radial forces. A finite element model that can simulate the effect of radial forced and obstacles on a tyre was developed. The use of two subsets of elements, superimposed onto each other to simulate global material properties of the rubbers, steel wires, polyester and nylon threads, was investigated. The combination of material properties that gave the best fit for all the load cases investigated were determined. The finite element model correlated well with the load vs. displacement graphs and sidewall displacement profiles determined experimentally. The solving time is still fairly high and is still not quite suitable for real-time dynamic simulation. However, it solves faster than more complex tyre models where details of steel wires, etc. are included in the model. For future studies it is recommended that different element types be investigated in the tyre model. The study proves that equivalent material properties can be used to simulate the composite properties of the materials in tyres. Most tyres can be divided into a few regions that each has its own material structure right through the region. These regions can be characterized by simple tests and the input can be used as a first estimation of the tyre’s material properties for the model. Accurate validation criteria should be used to validate the tyre model if time does not allow for excessive testing of the material properties of all the rubber, steel wires, polyester threads, etc. Geometric displacement data at various loading conditions can be used for validation of the tyre model. The model developed can be used to investigate the effect of different stiffnesses and other material changes in the sidewall or tread of a tyre. Useful insight can be obtained from the finite element model developed for dynamic simulation where the force vs. global displacement data is important. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Mechanical and Aeronautical Engineering / MEng / Unrestricted

<p>The focus of this study is on evaluating the performance of nine, one-third scale, arching, reinforced masonry (RM) walls subjected to blast loads and three, one-third scale arching, RM walls subjected to out-of-plane static airbag loads. These RM walls were supported on four sides to enforce two-way arching allowing the ability to monitor individual response to varying levels of blast loads and standoff distances. The uniformity of the blast pressure and impulse were ensured by a specifically designed test enclosure, diminishing the wrap-around and clearing effects, allowing valuable data to be documented. The damage levels noted, ranged from Superficial to Blowout compared directly to the CSA S850-12 performance limits. The outcome of this experiment demonstrates the beneficial effect of two-way arching on the flexural behaviour of RM walls under impulsive loading. The use of two-way arching RM walls significantly reduces structural damage and increases out-of-plane resistance, which in turn enhances the overall structural integrity and building preservation. Further, when subjected to blast, two-way arching RM walls considerably reduces debris and their dispersal, thus increasing public safety and minimizing hazard levels. When using the experimental test data results to calibrate finite element models (FEM), more analytical data points can be obtained and therefore getting a larger range of scaled distances and trials. The validation of the LS-DYNA model can be used as an alternative to the costly experimental data, as the information collected concluded that the FEM gave damage patterns and failure modes that were comparable with experimental results. The test data collected provides a better understanding of RM wall response to blast loads and to the ongoing Masonry Blast Performance Database (MBPD) project at McMaster University. The generated MBPD will in turn contribute to masonry design clauses in the future editions of the recently introduced Canadian Standards CSA S850-12 “Design and Assessment of Buildings Subjected to Blast Loads”.</p> / Master of Applied Science (MASc)

This research undertakes the problem of vibration control of vehicular and structural systems using intelligent materials and controllable devices. Advanced modeling tools validated with experimental test data are developed to help with understanding the fundamentals as well as advanced and novel applications of smart and conventional suspension systems. The project can be divided into two major parts. The first part is focused on development of novel smart suspensions using Magneto-Rheological (MR) fluids in unique configurations in order to improve efficiency, controllability, and safety of today's vehicles. In this part of the research, attention is paid to fundamentals as well as advanced applications of MR technology. Extensive rheological studies, both theoretical and experimental, are performed to understand the basic behaviors of MR fluids as complex non-Newtonian fluids in novel applications. Using the knowledge obtained from fundamental studies of MR fluids, unique application concepts are investigated that lead to design, development, and experimental testing of two new classes of smart devices: MR Hybrid Dampers and MR Squeeze Mounts. Multiple generations of these devices are built and tested as proof of concept prototypes. Advanced physics-based mathematical models are developed for these devices. Experimental test data are used to validate the models and great agreement is obtained. The models are used as design tools at preliminary as well as detailed design stages of device development. The significant finding in this part of the research is that MR fluids can deliver a much larger window of controllable force in squeeze mode compared to shear and valve modes which can be used in various applications. The second part of the research is devoted to the development of innovative design tools for suspension design and tuning. Various components of suspension systems are studied and modeled using a new physics-based modeling approach. The component of main interest is the shim stack assembly in hydraulic dampers which is modeled using energy and variational methods. A major finding is that the shims should be modeled individually in order to represent the sliding effects properly when the shim stack is deflected. Next, the individual component models are integrated into a full suspension model. This model is then used as a tool for suspension design, synthesis, and tuning. Using this design tool, suspension engineers in manufacturing companies and other industrial sections can easily perform parametric studies without the need to carry out time consuming and expensive field and laboratory tests. / Ph. D.

Unreinforced masonry walls subjected to blast loading are vulnerable to collapse and fragmentation. The objective of this thesis is to conduct experimental and analytical research for developing a blast retrofit methodology that utilizes polyurea. A total of four unreinforced masonry walls were constructed and tested under various shock tube induced blast pressures at the University of Ottawa Shock Tube Testing Facility. Two of the retrofitted walls had surface-sprayed polyurea. The results indicate that the use of polyurea effectively controlled fragmentation while significantly increased the load capacity and stiffness of masonry walls. Polyurea proved to be an excellent retrofit material for dissipating blast induced energy by providing ductility to the system and changing the failure mode from brittle to ductile. Single degree of freedom (SDOF) dynamic analyses were conducted as part of the analytical investigation. The results show that the analytical model provides reasonably accurate predictions of the specimen response.