The objective of this work is to characterize and understand structure- mechanical property relationships in (meth)acrylate networks. The networks are synthesized from mono-functional (meth)acrylates with systematically varying sidegroup structure and multi-functional crosslinkers with varying mole fraction and functionality. Fundamental trends are established between the network chemical structure, crosslink density, glass transition temperature, rubbery modulus, failure strain, and toughness. The glass transition temperature of the networks ranged from -29 to 112 °C, and the rubbery modulus ranged from 2.8 to 129.5 MPa. At low crosslink density (Er < 10 MPa) network chemistry has a profound effect on network toughness. At high crosslink densities (Er > 10 MPa), network chemistry has little influence on material toughness. The characteristic ratio of the mono-functional (meth)acrylates components is unable to predict trends in thermoset toughness as a function of chemical structure, as is accomplished for thermoplastics. The cohesive energy density is a better tool for prediction of network mechanical properties. Due to superior mechanical properties, networks with phenyl ring sidegroups are further investigated to understand the effect of phenyl ring distance on toughness. This work provides a fundamental basis for designing (meth)acrylate shape memory polymer networks with specific failure strain, toughness, glass transition temperature, and rubbery modulus.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 70).

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Gall, Ken; Committee Chair: May, Gary S; Committee Member: Brand, Oliver; Committee Member: Degertekin, F Levent; Committee Member: Milor, Linda S. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2011 / Smart (SMA-Shape Memory Alloy) Technology continues to advance rapidly as engineers move closer to and understand better the industrial and commercial needs for SMA. As a matter of fact, all types of products, which exercise some type of control over their function, are rapidly making their way into the marketplace [36] Nonetheless, nowhere has been evidence in the development of a SMA impeller. Unlike traditional impellers with no control over their function and sometimes fixed angle of attack, this paper demonstrates numerical investigations using analytical algorithms (Matrix laboratory programming and excel spread sheet) and advanced computer simulation package, Engineering Fluid dynamics (EFD) into the feasibility of using a smart impeller to study the performance of a pumping system and the best angle of attack for a Shape Memory Impeller. Primarily, Bench mark data and dimensions are obtained from a standard centrifugal pump run on a FM21 demonstration unit. Using the same standard centrifugal pump, and keeping all other dimensions the same but altering the angle of attack, EFD simulations where made. From analytical algorithm and EFD comparison, it was evident that the best angle of attack is 12 degree at the outlet angle with respect to the inlet angle. From EFD results, it is palpable that, by increasing the angle of attack from 35 degree to 45 degree at the outlet there will be huge increase in flow rate by 63.47% There is also a slight decrease in the impeller Torque from 35 degrees to 42 degrees by 0.72%. It is economically feasible to work at an outlet angle of 42 degrees due to increase in efficiency of 62.1% and a drop in torque of 0.72% by varying the outlet angle from 35 degrees to 42 degree. Understanding how critical actuator design is, it should be suggested that any shape memory impeller should never be used in critical components without a prior history of thermal and mechanical loading. Therefore, a NiTi impeller constitutive model can be designed, with impeller blades made from NiTi plates, trained to remember its best angle of attack (Martensitic phase). NiTi shape memory metal alloy (plates-blades) can exist in a two different temperature-dependent crystal structures (phases) called martensite [9](lower temperature-normal pumping condition) and austenite [9] (higher temperature or parent phase-trained best angle of attack.)

A shape memory alloy (SMA) is an intermetallic compound able to recover, in a continuous and reversible way, a predetermined shape during a thermal cycle while generating mechanical work. In this thesis, its use in developing an actuator for a machining process is investigated. The actuator is to drive the tool cross feed into an aluminium workpiece in a finishing lathe operation. The actuator structure was designed with an output shaft to transfer the movement and force of the SMA wire outside the device. The actuator was fabricated and the experimental setup was assembled which also included a power supply control circuit, displacement sensor, temperature sensor and current sensor for feedback, and data collection and monitoring within software. PID control was implemented within the software that regulated the power supplied to the SMA, thereby providing the position control. This study covers the mechatronics system design and development of the actuator, the experiments carried out to determine performance and the results. Open loop tests were conducted to determine the maximum stroke, the effect of cooling and response to radial forces. These tests revealed the expected non-linearity of the SMA. The actuator achieved the rated maximum stroke of 3-4 percent. The forced cooling test showed a general improvement of approximately 65 percent with fans. The radial force tests showed the value of the maximum stroke remained unaffected by force. The results from the closed loop tests responses with a tuned PID controller produced a stable system for various displacement setpoints. The actuator had a feed rate of 0.25 mm/s and an accuracy of 0.0153mm, which was within the acceptable accuracy for turning operations. The system was deemed accurate for a conventional lathe machine cross feed.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18587号 / 工博第3948号 / 新制||工||1607(附属図書館) / 31487 / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 北條 正樹, 教授 北村 隆行, 教授 琵琶 志朗 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Actuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying composition and thermo-mechanical processing parameters can be cost intensive, especially when expensive, high-purity elemental additions are involved. Thus, in order to save on development costs there is value in establishing a methodology that facilitates the fabrication, processing and testing of smaller specimens, rather than larger specimens from commercial billets. With the objective of establishing such a methodology, this work compares thermo-mechanical test results from bulk dog-bone tensile Ni29.5Ti50.5Pd20 samples (7.62 mm diameter) with that of thin wires (100 μm-150 µm diameter) extracted from comparable, untested bulk samples by wire electrical-discharge machining (EDM). The wires were subsequently electropolished to different cross-sections, characterized with Scanning Electron Microscopy, Transmission Electron Microscopy and Energy Dispersive X-Ray Spectroscopy to verify the removal of the heat affected zone following EDM and subjected to Laser Scanning Confocal Microscopy to accurately determine their cross-sections before thermo-mechanical testing. Stress-strain and load-bias experiments were then performed on these wires using a dynamic mechanical analyzer and compared with results established in iv previous studies for comparable bulk tensile specimens. On comparing the results from a bulk tensile sample with that of the micron-scale wires, the overall thermomechanical trends were accurately captured by the micron-scale wires for both the constrained recovery and monotonic tensile tests. Specifically, there was good agreement between the stress-strain response in both the martensitic and austenitic phases, the transformation strains at lower stresses in constrained recovery, and the transformation temperatures at higher stresses in constrained recovery. This work thus validated that carefully prepared micron-diameter samples can be used to obtain representative bulk thermo-mechanical properties, and is useful for fabricating and optimizing composition and thermomechanical processing parameters in prototype button melts prior to commercial production. This work additionally assesses potential applications of high temperature shape memory alloy actuator seals in turbomachinery. A concept for a shape memory alloy turbine labyrinth seal is also presented. Funding support from NASA’s Fundamental Aeronautics Program, Supersonics Project (NNX08AB51A) and Siemens Energy is acknowledged.

No description available.

No description available.

No description available.