Health, Physical Education and Recreation

This departmental history was written on the occasion of the UND Centennial in 1983.https://commons.und.edu/departmental-histories/1031/thumbnail.jp

Micro-Scale Waste Heat Recovery from Stationary Internal Combustion Engines by Sub-Critical Organic Rankine Cycle utilizing Scroll Machinery

The movement towards renewable energy sources has created new challenges for energy production and has promoted the concept of distributed energy production. High efficiency Generators for Small Electrical and Thermal Systems (GENSETS) provide a viable solution to residential-scale power production at low cost. In an effort to improve the energy production efficiency of small scale internal combustion engine generators, a waste heat recovery (WHR) bottoming cycle can boost the operating efficiency of such systems by up to 7%. Organic Rankine Cycle (ORC) technology is a popular method of achieving WHR from low temperature heat sources. However, the application of ORC systems using the high-temperature exhaust stream of ICE generators as heat input is currently unexplored. Thermodynamic modeling of a sub-critical ORC system proved its viability as a bottoming cycle for ICE generators. The simulations also enabled the selection of the optimal working fluid for the specified application given the system restrictions. The refrigerant R245fa was selected for its high-temperature chemical stability and thermal efficiency. Detailed modeling that reflected the selected ORC components then provided insight into system performance with a range of ICE generators and further proved the system’s viability. The high temperature application required the creation of several prototype components to create an efficient ORC WHR system. By utilizing a novel evaporator heat exchanger, it is possible to establish a cycle with high superheat in an effort to minimize exergy destruction in the evaporation heat transfer process. Additionally, the sub-critical architecture of the ORC benefits from custom scroll-type expander and pump that match the designed pressure and volume ratios. However, the prototype ORC components required further development and testing and therefore, an experimental test stand was constructed to perform component evaluation and system performance measurement. Using the test stand, it was possible to evaluate two different types of scroll expander: the Oldham ring orbiting scroll, and the spinning scroll. A performance comparison is presented and the strengths and weaknesses of each are considered. Additionally, a performance comparison between the working fluid R245fa and its HFO replacement R1233zd(E) is presented in an effort to evaluate the feasibility of a working fluid change. The work performed on evaluating the different scroll machines presents a good first step in the successful development of an ORC bottoming cycle for ICE generators. Through further development, ORC WHR will become more feasible and assist in the goal of distributed energy production

Processing and Microstructure of WC-CO Cermets by Laser Engineering Net Shaping

Submicron-sized tungsten carbide-cobalt (WC-Co) powder and nanostructured WC-Co powder were applied to make thick wall samples by the Laser Engineered Net Shaping (LENS®) process. It was found that decomposition and decarburization of WC was limited during laser deposition because of the features of the LENS® process: high cooling rate, short heating time, and low oxygen concentration. The effects of working distance, as well as laser power, powder feed rate, and traverse speed on microstructure were studied in this paper. Thermal behavior leading to the observed microstructures that result from the variations in the processing parameters was investigated in detailMechanical Engineerin

Synthesis of Discontinously Reinforced Metal matrix Composites Using Spray Atomisation and Co injection

A variety of processing techniques have evolved over the last two decades to optimize the structure and properties of particulate reinforced metal-matrix composites (MMCs). Among these, spray processes offer a unique opportunity to combine the benefits associated with fine particulate technology with in situ processing, and in some cases, near-net shape manufacturing. Spray processing generally involves mixing reinforcements and matrix under highly non-equilibrium conditions, and as a result, these processes offer the opportunity to modify the properties of existing alloy systems, and develop novel alloy compositions. In principle, such an approach will inherently avoid the extreme thermal excursions, with concomitant macrosegregation, normally associated with casting processes. Furthermore, this approach also eliminates the need to handle fine reactive particulates, normally associated with powder metallurgical processes. The present paper discusses recent developments in the area of spray atomisation and deposition processing of discontinuously reinforced MMCs, with particular emphasis on the synergism between microstructure, mechanical properties and processing

Deformation mechanisms in bulk nanostructured metals and strategies to improve their ductility

Bulk nanostructured (NS) metals, with structural units falling in the nanometer range, are of interest in part as a result of drastically improved strength over that corresponding to conventional coarse-grained (CG) materials. Examples of ultrahigh-strength bulk NS metals will be provided in this lecture and strengthening mechanisms will be briefly discussed. In the case of conventional CG metals, plastic deformation is based on the motion of lattice dislocations, which are usually unit dislocations nucleated inside grain interiors or at GBs. In the case of bulk NS metals, with significantly reduced grain size and therefore very limited space in grain interiors, and drastically increased grain boundary (GB) volume fraction, the deformation mechanisms are different from those -corresponding to CG metals. In this presentation, deformation mechanisms in bulk NS metals will be reviewed and discussed, including full/partial dislocation emission from GBs, deformation twinning, GB sliding, grain rotation induced grain coalescence, stress-coupled GB migration, and de-twinning. Deformation mechanisms during dynamic and cyclic deformation of bulk NS metals, e.g., grain rotation induced grain coalescence and de-twinning, will be discussed in detail. Stress/deformation induced grain growth, with underlying deformation mechanisms of grain rotation-coalescence and stress-coupled GB migration, will be discussed in detail, and a theoretical framework that incorporates the influence of second-phase particles and solute/impurity segregation at GBs on grain growth during hot deformation will be formulated and discussed. Owing to the different deformation mechanisms in bulk NS metals, and particularly to the limited dislocation accumulation and therefore little strain hardening during deformation, bulk NS metals tend to have limited ductility. Strategies to improve ductility will be discussed in detail, e.g., bimodal/multimodal grain size distribution, nanoscale twins, low dislocation density, second-phase nanoscale precipitation within grains, and phase transformations during deformation

Aluminum with dispersed nanoparticles by laser additive manufacturing.

While laser-printed metals do not tend to match the mechanical properties and thermal stability of conventionally-processed metals, incorporating and dispersing nanoparticles in them should enhance their performance. However, this remains difficult to do during laser additive manufacturing. Here, we show that aluminum reinforced by nanoparticles can be deposited layer-by-layer via laser melting of nanocomposite powders, which enhance the laser absorption by almost one order of magnitude compared to pure aluminum powders. The laser printed nanocomposite delivers a yield strength of up to 1000 MPa, plasticity over 10%, and Young's modulus of approximately 200 GPa, offering one of the highest specific Young's modulus and specific yield strengths among structural metals, as well as an improved specific strength and thermal stability up to 400 °C compared to other aluminum-based materials. The improved performance is attributed to a high density of well-dispersed nanoparticles, strong interfacial bonding between nanoparticles and Al matrix, and ultrafine grain sizes

Diseño y vida

[ES] Diseño de envases de botellas de agua. Beber para vivirLavernia, N. (2011). Diseño y vida. EME Experimental Illustration, Art & Design. (1):84-88. doi:10.4995/eme.2011.1483SWORD8488

Ciencia y naturaleza en Goethe: apuntes sobre la epistemología natural goetheana a partir de La metamorfosis de las plantas

This paper updates and defends Goethe’s Metamorphosis of Plants (1791) from a philosophical perspective. After presenting some of his key concepts, we will expand on Goethe’s reflection on nature through other epistemological moments: his morphology as theory of form, his understanding of science as a living experience of phenomena, and his assertion of a metamorphosis of the scientist.El artículo reactualiza y defiende la potencialidad filosófica de La metamorfosis de las plantas (1791), de Johann Wolfgang Goethe. A partir de la reflexión sobre sus claves conceptuales se desplegarán, a continuación, otros momentos de talante epistemológico relativos a su reflexión sobre la naturaleza, entre otros: la morfología como teoría de la forma, su comprensión de la ciencia como experiencia viva de los fenómenos y su reivindicación de la metamorfosis del científico