A novel coupler measurement station and technique for manufacturing fused biconical tapered multi-port multimode couplers with improved uniformity among ports is presented. Improvement in the uniformity of the couplers is achieved by diffusion of the minimum taper region of the coupler. The phenomenon of dopant transport from the core to the cladding (or from the cladding to the core) at high temperatures is known as diffusion. Diffusion of a germanium-doped core results in the germanium dopants migrating from the core into the cladding thus increasing the effective diameter of the core which is accompanied by a decrease in the refractive index. The cores of individual fibers in the minimum taper region are a few micrometers apart. Diffusion thus results in a minimum taper region that has approximately uniform refractive index leading to better uniformity among ports. The experimental setup and results of diffusion tests on multimode fiber with different core/cladding ratios are presented. A coupler station that is capable of making bi- directional measurements of the coupler is demonstrated successfully. The coupler station also enables a user to dynamically monitor the ports of the coupler during manufacture, and can be adapted to manufacture star couplers ranging in size from two to sixteen fibers. / Master of Science

The concept of a ready-to-assemble kit fabricated in a factory and delivered to the customer is well known and commonly used by the furniture industry. In wood construction, the lack of a simple and reliable method of assembling the frame members creates a barrier to wide acceptance of prefabricated kit structures. This thesis focuses on a novel technology of assembling structural components of a wood frame using a metal nail plate connector (NPC). This technology was referred to as a ready-to-assemble (RTA) wood framing system. The RTA system simplifies the framing process and allows for rapid erection of a wood structural frame by a small nonprofessional crew. A 16 x 24 foot RTA building was constructed to demonstrate the feasibility of the RTA system concept. An effective assembly sequence was proposed and successfully implemented. The design procedure for the RTA buildings was presented. The lateral load path for the RTA building includes diaphragms and shear walls. The contribution of the RTA frame can be ignored from the lateral load analysis. This conclusion was validated for the diaphragms with aspect ratios up to 4:1. The finite element method was used to model the RTA structures. The models incorporated semi-rigid behavior of the NPC. An analytical model was developed to predict the nonlinear moment-rotation relationship of the NPC. The proposed model showed a good agreement (R2=0.98) with the experimental data. Tests were conducted to measure the load-drift response of the RTA shear walls. / Master of Science

Reinforced concrete (RC) moment frames comprise a significant portion of the built environment in areas with seismic hazards. The beam-to-column joints of these frames are key components that have a significant impact on the structure's behavior. Modern detailing provides sufficient strength within these joints to transfer the forces between the beams and the columns during a seismic event, but existing structures built with poor detailing are still quite prevalent. Identifying the need and extent of retrofits to ensure public safety through nondestructive means is of primary importance. Existing models used to analyze the performance of RC beam-to-column joints have either been developed for modern, well-detailed joints or are simplified so that they do not capture a broad range of phenomena. The present study is aimed to extend a modeling technique based on the nonlinear truss analogy to the analysis of RC beam-to-column joints under cyclic loads. Steel and concrete elements were arranged into a lattice truss structure with zero-length bond-slip springs connecting them. A new steel model was implemented to more accurately capture the constitutive behavior of reinforcing bars. The joint modeling approach captured well the shear response of the joint. It also provided a good indication of the distribution of forces within the joint. The model was validated against three recently tested beam-column subassemblies. These tests represented the detailing practice of poorly-detailed RC moment frames. The analytical results were in good agreement with the experimental data in terms of initial stiffness, strength and damage pattern through the joint. / Master of Science

Present stress analysis of adhesively bonded joints suffers from inadequate adhesive material characterization. The lack of correlation between bulk adhesive properties and the corresponding in-situ behavior has led to numerous adhesive test geometries. The current study was an attempt to predict the nonlinear viscoelastic response of an adhesive in-situ using properties obtained from a pure shear test geometry. Four candidate adhesive test geometries were studied both analytically and experimentally in terms of accurate shear property determination and realistic adhesive bond simulation. The thick adherend joint was chosen as the experimental reference of actual viscoelastic response in-situ; the Arcan specimen provided a pure shear stress state for material viscoelastic characterization. Results of finite element analysis and extensive experimental evidence suggest that residual thermal stresses alter the in-situ adhesive properties compared to the bulk adhesive: Furthermore, preliminary results indicate that the free volume nonlinear viscoelastic theory accounts for the effect of residual strains on the in-situ adhesive mechanical response. / M.S.

Poly(vinylidene fluoride) (PVDF) films can be easily etched into sensor devices. Since these sensors are relatively inexpensive, thin and light-weight, they can be attached to adhesively bonded joints permanently to measure bond integrity. The present study shows the different steps to design such sensors and proper techniques to attach them near the adhesive bondline. PVDF sensors have been successfully used as NDT transducers in pulse-echo, through-transmission, and acousto-ultrasonic techniques to monitor curing, to detect porosity and crack propagation in different model joint geometries. The potential of using these techniques for practical bonded structures has then been evaluated. / Master of Science

Though using bulk adhesive properties to predict adhesively bonded joint response has yet to be proven infallible, based upon the success of previous works, this effort attempts to shed some light on the stresses present in a typical automotive bonded joint. Adhesive material properties obtained in previous works were used in a finite element analysis of a simulated automotive joint to predict the stresses in that joint. The automotive joint analyzed was a simplified representation of a joint provided by General Motors. The specifications included the rate or stiffness of the joint and the materials to be used. The basic design of the joint is a rectangular solid section steel frame to which an SMC panel is bonded using Ashland Chemical urethane based adhesives. Due to computer time constraints and problem complexity, a complete analysis including a time dependent, viscoelastic analysis was not possible. The linear elastic case analyzed gave important insight into the magnitudes of stresses to be expected in a typical joint. It was found that for an applied load to produce a 1 degree deflection in the steel frame, the stresses in the adhesive were below 20% of the ultimate tensile strength of the adhesive. This low stress state is significant because the adhesive behaves as a linear viscoelastic material in that range, making further analysis less complicated and time consuming. / Master of Science

No description available.

Each year, falls from elevated structures, like scaffolding, kill or seriously injure over a thousand construction workers (Bureau of Labor Statistics, 2007). To prevent such falls, the development of a robotic system is proposed that can climb and navigate on the complex structures, performing hazardous inspection and maintenance in place of humans. In this work, a serpentine robotic system is developed that will be able to climb pole-like structures, such as scaffolding and trusses, commonly found on work sites. Serpentine robots have been proven to be effective at traversing unstructured terrains and manipulating complex objects. The work presented in this thesis adds a new method of mobility for serpentine robots, specifically those with actuated universal joint structures. Movement is produced by inducing a wobbling motion between adjacent modules through oscillatory motions in the actuated axis of the universal joint. Through the frictional interactions between the modules of the serpentine and the surface of the pole, the wobbling motion lets the serpentine effectively roll up the pole's surface. This work investigates theoretical and experimental results for a serpentine robot climbing a pole structure. It discusses the structure and design parameters of the robot and develops relationships between them. These geometric and performance-based relationships are then used to create a design space that provides a guide for choosing a combination of module dimensions for a desired set of performance parameters. From this, case studies are shown which give examples of how the design space can be used for several different applications. Based on the design space procedure, a serpentine robot, HyDRAS (Hyper-Redundant Discrete Robotic Articulated Serpentine) was designed and built. The robot was used to prove the validity of the design space procedure and to validate the climbing motion algorithms. Several tests were performed with HyDRAS that showed the practicality of the helical rolling motion, as well as the feasibility of serpentine pole climbing. Observations and discussion based on the experiments are given, along with the plans for future work involving pole-climbing serpentine robots. / Master of Science

published_or_final_version / abstract / Nursing Studies / Master / Master of Philosophy

The overall aim of the project is to examine the rivetability of new steels and to investigate the mechanical behaviour of self-piercing riveted (SPR) aluminium-steel hybrid structures for automotive applications. Interstitial Free Steel (I.F.) of 1.2 mm thickness was joined to Aluminium 5754 of 2 mm thickness and Aluminium 5182 (coated and uncoated) of 1.5 mm thickness. The work began by initially conducting a quality assessment of the various joints that were produced in order to establish the optimum conditions for joining the various sample combinations to be investigated. A relationship was established between the head height and the interlock distance on the one hand and between the interlock distance and the lap shear strength of samples. It was also established that for higher lap shear strength, it is preferable to use the stronger material (I.F. steel) as the pierced sheet and the weaker material (5182) as the locked sheet. However, the results showed that this rule could not be applied for predicting the fatigue behaviour of SPR joints between I.F. steel and 5182. An investigation of the fatigue failure mechanisms was undertaken and possible reasons for this behaviour are discussed. The influence of fretting was also investigated by using scanning electron microscopy and reported. The fatigue behaviour of Dual Phase (DP600 + 5182) SPR joints was investigated. It was observed that the position of fatigue crack initiation differed with the maximum applied load. An explanation for this observation was provided by considering the failure mechanism of the samples under different load levels. The study also showed how fretting led to the initiation of fatigue cracks. The corrosion behaviour of (I.F. steel + 5182) samples was investigated by conducting tests in a salt spray according to the ASTM B117-97 standard. Three types of corrosion were observed; galvanic corrosion, differential aeration corrosion, uniform corrosion and are discussed. The weight change with time was monitored and was used to describe the corrosion behaviour. The lap shear strength was measured as a function of corrosion time. The presence of the corrosion product within the overlap was observed to greatly influence the lap shear strength behaviour. A further study was carried out in order to examine the influence of the individual alloys on the corrosion of the SPR samples. In this part the potential influence of pulse current treatment on corrosion was also investigated and was observed to increase greatly the corrosion resistance of the I.F. steel. Principal findings for this observation are also provided.