DEVELOPMENT OF A BIAXIAL LOADING FRAME FOR THIN SHEET CRUCIFORM SPECIMENS

Characterization of the evolving yield loci and forming limit diagrams for sheet materials under biaxial loading is necessary for the development of accurate sheet metal forming process simulations. Biaxial tension testing has been shown to have significant advantages over the current computational and experimental methods for such material characterization; however, the few commercially available loading frames are far too large and expensive to be practical for most metal forming research laboratories. To address this problem, the University of New Hampshire’s Mechanics, Materials, and Manufacturing Lab is working to design a practical servohydraulic biaxial loading frame for such metal forming laboratories. The physical system design, fabrication, and component selection was performed previously by a team of mechanical engineering seniors in collaboration with Greenerd Press and Machine Co. To continue the project, this thesis presents the design, implementation, and validation of a PLC-based control system and LabVIEW graphical interface for operating the biaxial loading frame. Experimental data shows that the displacement control system can accurately maintain equal displacement of opposing actuators to within 0.1[mm] for fixed position, 80[mm/min] ramp, and 0.2[Hz] sinusoidal profiles. The selection and mounting position of the hydraulic control valves were found to be the major limiting factor in the abilities of the control system. Preliminary uniaxial and biaxial tension tests with Al-6022-T4 show inconsistent stress-strain responses that cause differing force measurements of up to 8[%] between opposing load cells. The inconsistencies were attributed to the mechanical design of the current frame of the testing machine. Corresponding mechanical, hydraulic, and software/control design improvements are suggested, and plans for the future of the project are discussed

Modification of the rotary machining process to improve surface form

Planing and moulding operations carried out within the woodworking industry make extensive use of rotary machining. Cutter-marks are produced on the timber surface which are generally accepted as unavoidable. More noticeable surface defects may be produced by such factors as cutter-head imbalance, and until recently most research has concentrated on removing these defects. When a high quality finish is required, a further machining operation, such as sanding, is often required to remove cutter-marks. What is required, is a modified machining process which combines a surface closer to the ideal fixed knife finish, whilst retaining the flexibility, practicality and cost effectiveness of rotary machining. [Continues.

Sustainable Management of Urban Water Resources

It is well known that 55% of the world’s population currently lives in urban areas, and this figure is predicted to grow to 68% by 2050, adding more than 2.5 billion people to urban populations. It is also projected that there will be 43 megacities worldwide by 2030, with populations of more than 10 million inhabitants. The United Nations World Water Development Report, 2018, warned that by 2030, the global demand for fresh water is likely to exceed supply by 40%. Added to population growth, climate change has the potential to lead to changes in rainfall regimes, with the potential of increased flooding and drought. Currently, 1.2 billion people are at risk from flooding, but this is predicted to increase to about 1.6 billion, i.e., nearly 20% of the total world population, by 2050. In line with this, replacing deteriorating water management infrastructure that can no longer cope is economically unfeasible, impracticable from a construction point of view, and likely to fail in the long term. To address these issues, approaches are needed that are flexible and have multiple benefits. In its World Water Development Report, 2018, the UN promotes the use of nature-based solutions to some of these problems, with the focus of Sustainable Development Goal 6 (making sure that everyone has access to a safe and affordable supply of potable water and sanitation by 2030) requiring investment in suitable infrastructure across the world. This Special Issue covers the challenges faced in managing urban water in all its forms, from potable supplies to reuse and harvesting, as well as resilient and sustainable approaches developed to address flooding and drought

Pneumatic Artificial Muscle Driven Trailing Edge Flaps For Active Rotors

This research focuses on the development of an active rotor system capable of primary control and vibration reduction for rotorcraft. The objective is to investigate the feasibility of a novel Trailing Edge Flap (TEF) actuation system driven by Pneumatic Artificial Muscles (PAMs). A significant design effort led to a series of experimental apparatuses which tested various aspects of the performance of the actuators themselves and of TEF systems driven by them. Analytical models were developed in parallel to predict the quasistatic and dynamic behavior of these systems. Initial testing of a prototype blade section with an integrated PAM driven TEF proved the viability of the concept through successful benchtop testing under simulated M = 0.3 loading and open jet wind tunnel tests under airspeeds up to M = 0.13. This prototype showed the ability of PAM actuators to generate significant flap deflections over the bandwidth of interest for primary control and vibration reduction on a rotorcraft. It also identified the importance of high pneumatic system mass flow rate for maintaining performance at higher operating frequencies. Research into the development and improvement of PAM actuators centered around a new manufacturing technique which was invented to directly address the weaknesses of previous designs. Detailed finite element model (FEM) analysis of the design allowed for the mitigation of stress concentrations, leading to increased strength. Tensile testing of the swaged actuators showed a factor of safety over 5, and burst pressure testing showed a factor of safety of 3. Over 120,000,000 load cycles were applied to the actuators without failure. Characterization testing before, during, and after the fatigue tests showed no reduction in PAM performance. Wind tunnel testing of a full scale Bell 407 blade retrofitted with a PAM TEF system showed excellent control authority. At the maximum wind tunnel test speed of M = 0.3 and a derated PAM operating pressure of 28 psi, 18.8° half-peak-to-peak flap deflections were achieved at 1/rev (7 Hz), and 17.1° of half-peak-to-peak flap deflection was still available at 5/rev (35 Hz). A quasistatic system model was developed which combined PAM forces, kinematics and flap aerodynamics to predict flap deflection amplitudes. This model agreed well with experimental data. Whirl testing of a sub-span whirl rig under full scale loading conditions showed the ability of PAM TEF systems to operate under full scale levels of centrifugal (CF), aerodynamic, and inertia loading. A commercial pneumatic rotary union was used to provide air in the rotating frame. Extrapolation of the results to 100% of CF acceleration predicts 15.4° of half-peak-to-peak flap deflection at 1/rev (7 Hz), and 7.7° of half-peak-to-peak flap deflection at 5/rev (35 Hz). A dynamic model was developed which successfully predicted the time domain behavior of the PAM actuators and PAM TEF system. This model includes control valve dynamics, frictional tubing losses, pressure dynamics, PAM forces, mechanism kinematics, aerodynamic hinge moments, system stiffness, damping, and inertia to solve for the rotational dynamics of the flap. Control system development led to a closed loop control system for PAM TEF systems capable of tracking complex, multi-sinusoid flap deflections representative of a combined primary control and vibration reduction flap actuation scheme. This research shows the promise that PAM actuators have as drivers for trailing edge flaps on active helicopter rotors. The robustness, ease of integration, control authority and tracking accuracy of these actuators have been established, thereby motivating further research

Wave and tidal power review

A review of the technology of useful conversion of wave power and tidal power is presented. These two power resources are reviewed separately, but on the same basis: principles of operation, existing devices or plants and research and development. Promising wave power devices in Britain, the United States and Europe are discussed. If wave power is to be competitive, one of the first requirements may be energy densification. Proposed energy densification schemes include resonance, high pressure water and wave focussing. Wave focussing is a Norwegian invention, technically feasible, and although more research and development is required, it appears to be more promising than alternative forms of wave power utilisation. According to a preliminary cost analysis, it could be competitive with conventional hydro-electric power. The large scale exploitation of tidal power has been considered seriously for about half a century; the literature on the topic is voluminous. The main limitations of tidal power are its intermittent nature and the high costs involved in the construction of a plant. The existing pilot plants at the Rance and Kislaya Guba have respectively proved that tidal power is technically feasible and that construction costs could be reduced. With the rapid increase in the price of fossil fuels, tidal power plants may be realised at the two best sites in the world, the Bay of Fundy and the Severn Estuary

EFFECTS OF RAILROAD TRACK STRUCTURAL COMPONENTS AND SUBGRADE ON DAMPING AND DISSIPATION OF TRAIN INDUCED VIBRATION

A method for numerical simulation of train induced track vibration and wave propagation in subgrade has been proposed. The method uses a mass to simulate the bogie of a train and considers the effect of rail roughness. For this method, rail roughness is considered as a randomly generated signal and a filter is used to block the undesired components. The method predicts the particle velocity around the track and can be applied to many kinds of railroad trackbeds including traditional ballast trackbed and modern Hot mix asphalt (HMA) trackbed. Results from ballast and HMA trackbeds are compared and effects of HMA layer on damping track vibration and dissipating wave propagation are presented. To verify the credibility of the method, in-track measurements were also conducted. Site measurements included performing geophysical tests such as spectral analysis of surface wave test and seismic refraction test to determine the subsurface conditions at the test site. Ballast and HMA samples were tested in the laboratory by resonant column test to obtain the material properties. Particle velocities were measured and analyzed in the frequency domain. Results from in-track tests confirm the applicability of the numerical method. The findings and conclusions are summarized and future research topics are suggested

Strategies for rapid seismic hazard mitigation in sustainable infrastructure systems

The goal of this study is to design and evaluate economic and rapid seismic retrofit strategies for relatively small rehabilitation projects for steel structures consistent with the tenets of sustainable design. The need to retrofit existing structures in earthquake prone regions may arise directly from the problem of aging and deteriorating conditions, recognition of the vulnerability of existing infrastructure, from updates in seismic code requirements, or changes in building performance objectives. Traditional approaches to seismic hazard mitigation have focused reducing the failure probabilities, consequences from failures, and time to recovery. Such paradigms had been established with little regard to the impact of their rehabilitation measures on the environment and disruptions to occupants. The rapid rehabilitation strategies proposed here have sustainability benefits in terms of providing a more resilient building stock for our communities as well as minimizing environmental and economical impacts and social consequences during the rehabilitation project. To achieve these goals, a unique approach to design supplemental systems using tension-only elements is proposed. In this design approach undesirable global and local buckling are eliminated. Two rapid rehabilitation strategies are presented. The first is a bracing system consisting of cables and a central energy dissipating device (CORE Damper). The second is a shear wall system with the combined use of thin steel plate and tension-only bracing. Analytical studies using both advanced and simplified models and proof-of-concept testing were carried out for the two devices. The results demonstrated stable, highly efficient performance of the devices under seismic load. Preliminary applications of the CORE damper to the retrofitting of a braced steel frame showed the ability of the system to minimize soft story failures. Both techniques can be implemented within a sustainability framework, as these interventions reduce the seismic vulnerability of infrastructure, are low cost, utilize materials and fabrication processes widely available throughout the world, can be handled by unskilled labor and carried out with minimal disruptions to the environment. The approach taken in this study can provide a road map for future development of sustainability-based rehabilitation strategies.Ph.D.Committee Co-Chair: DesRoches, Reginald; Committee Co-Chair: Leon, Roberto T.; Committee Member: Craig, James I.; Committee Member: Goodno, Barry; Committee Member: White, Donald W

Design, modeling, fabrication, and testing of a multistage micro gas compressor with piezoelectric unimorph diaphragm and passive microvalves for microcooling applications

This dissertation investigates the development of a multistage micro gas compressor utilizing multiple pump stages cascaded in series to increase the pressure rise with passive microvalves and piezoelectric unimorph diaphragms. This research was conducted through modeling, simulation, design, and fabrication of the microcompressor and its components. A single-stage and a two-stage microcompressor were developed to demonstrate and compare the performance and effectiveness of using a cascaded multistage design. Steady fluid flow through static microvalves structure was studied to gain insight on its gas flow dynamics and characteristics. Transient analysis combined with the structure\u27s interaction was investigated with an analytical model and FEM model. The static analysis and transient analysis enabled lumped model parameter extraction for modeling and simulations. The transient FEM solution of the microvalve fluid-structure interaction (FSI) allows for extraction of the damping ratio for the lumped model. The microvalves were fabricated with MEMS microfabrication methods and integrated into a machined microcompressor housing. Study from the simulation of the microvalve fluid-structure dynamics in Simulink showed the frequency of the microvalves, at which frequency the mierovalve is more prone to leakage. Simulation indicated that the reverse leakage from the sealing of the microvalve can have a significant impact on the pressure rise performance of the compressor. A model of the single- and the two-stage microcompressor were developed with Simulink to observe the dynamics and performance of the multistage microcompressor. The simulation shows the dead volume between the two chambers to decrease in the overall pressure rise of the multistage microcompressor. Operating scenarios with different frequency and in phase and out of phase actuation between stages were simulated to understand the dynamics and performance of the multistage design. The fabricated single- and two-stage microcompressor produced a maximum pressure rise of 10 kPa and 18 kPa, respectively, and a maximum flow rate of 32 sccm for both. To obtain these maximum pressure rises, the microcompressors were operated at high frequency at the resonance of the piezoelectric diaphragm. This dissertation investigated the feasibility and operation of a multistage gas microcompressor with passive microvalves, allowing the exploration of its miniaturization

Low power energy harvesting and storage techniques from ambient human powered energy sources

Conventional electrochemical batteries power most of the portable and wireless electronic devices that are operated by electric power. In the past few years, electrochemical batteries and energy storage devices have improved significantly. However, this progress has not been able to keep up with the development of microprocessors, memory storage, and sensors of electronic applications. Battery weight, lifespan and reliability often limit the abilities and the range of such applications of battery powered devices. These conventional devices were designed to be powered with batteries as required, but did not allow scavenging of ambient energy as a power source. In contrast, development in wireless technology and other electronic components are constantly reducing the power and energy needed by many applications. If energy requirements of electronic components decline reasonably, then ambient energy scavenging and conversion could become a viable source of power for many applications. Ambient energy sources can be then considered and used to replace batteries in some electronic applications, to minimize product maintenance and operating cost. The potential ability to satisfy overall power and energy requirements of an application using ambient energy can eliminate some constraints related to conventional power supplies. Also power scavenging may enable electronic devices to be completely self-sustaining so that battery maintenance can eventually be eliminated. Furthermore, ambient energy scavenging could extend the performance and the lifetime of the MEMS (Micro electromechanical systems) and portable electronic devices. These possibilities show that it is important to examine the effectiveness of ambient energy as a source of power. Until recently, only little use has been made of ambient energy resources, especially for wireless networks and portable power devices. Recently, researchers have performed several studies in alternative energy sources that could provide small amounts of electricity to low-power electronic devices. These studies were focused to investigate and obtain power from different energy sources, such as vibration, light, sound, airflow, heat, waste mechanical energy and temperature variations. This research studied forms of ambient energy sources such as waste mechanical (rotational) energy from hydraulic door closers, and fitness exercise bicycles, and its conversion and storage into usable electrical energy. In both of these examples of applications, hydraulic door closers and fitness exercise bicycles, human presence is required. A person has to open the door in order for the hydraulic door closer mechanism to function. Fitness exercise bicycles need somebody to cycle the pedals to generate electricity (while burning calories.) Also vibrations, body motions, and compressions from human interactions were studied using small piezoelectric fiber composites which are capable of recovering waste mechanical energy and converting it to useful electrical energy. Based on ambient energy sources, electrical energy conversion and storage circuits were designed and tested for low power electronic applications. These sources were characterized according to energy harvesting (scavenging) methods, and power and energy density. At the end of the study, the ambient energy sources were matched with possible electronic applications as a viable energy source