The Computational Design Optimization of Engineering Systems (CODES) laboratory, led by Dr. Samy Missoum at the University of Arizona is working on the design optimization of wind turbines under uncertainty. Specifically, this research will investigate the topology optimization of wind turbines blades as well as the tower. Topology optimization enables one to find, without any a priori knowledge, the optimal distribution of material within a domain and is particularly suited for additive manufacturing. The design optimization will account for a set of static and dynamic design constraints. It will also include the presence of load as well as material property uncertainties in the definition of the optimization problem. Small scale, fully functioning wind turbines will be printed and the computational predictions will be validated against experimental results.

The development of clean energies will see an increase in the use of hydrogen. However, storage and transportation of hydrogen is a challenge. Currently, hydrogen is compressed but other options need to be developed for wider use. Small organic molecules have a high capacity to store hydrogen, but flammability might be an issue of concern. Polymers present an alternative to store hydrogen and release it with the assistance of reversible reactions. This project aims to synthesize polymers and characterize their molecular structure. Additionally, formation of micro- and nanofibers of these polymers, which will present higher surface areas is being studied with the objective of increasing their adsorption and releasing hydrogen capacity.

Plastics are an integral part of our everyday. These are materials that are resistant to many harsh chemical environments, lightweight, and low cost. However, most plastics are made for single use and disposal. While this might not be a big problem for items being used for several years, it is a huge problem for certain plastics, such as poly(ethylene terephthalate). This polymer is widely used in plastic bottles for carbonated beverages, textiles, balloons, etc. Most of these plastic bottles are discarded and not recycled, creating an environmental problem by contaminating oceans and filling up landfills. Thermomechanical recycling is a widely used approach, but every recycling cycle decreases the thermal and mechanical properties of the polymer, and also decreases the value of the material. Chemical recycling is an attractive alternative, since it yields the raw material and upon re-polymerization the material has its original properties. This project investigates the catalytic chemical recycling of poly(ethylene terephthalate) using microwave assisted radiation, thus decreasing significantly the reaction times. Potentially, in addition to obtaining the starting materials for re-polymerization, these materials can be used for other chemical applications, effectively upcycling the plastic bottles.

Development of Metal Matrix Composite (MMC) coatings via Laser-assisted Cold Spray (LCS) for Aerospace Applications under Extreme Conditions

Javier Ortega

Laser-assisted Cold Spray (LCS) is a coating and deposition process that combines the supersonic powder beam found in Cold Spray (CS) with laser heating of the deposition zone. Cold Spray (CS) is a solidstate process in which micrometer sized particles are accelerated by a supersonic carrier gas in a de Laval nozzle to high velocities (300-1200 m/s) and impact a substrate material. If the impact velocity of the particles exceeds a threshold, referred to as critical velocity, the particles bond to the substrates in solid state without having to induce high homologous temperatures or melt either material. As a result, limitations associated with high temperatures such as phase transformation, tensile residual stresses, and significant distortion can be avoided, making cold spray a competitive deposition technology for different classes of materials. As preheating of particles and substrate plays an important role in coating formation during CS, it would be desirable to introduce additional heat sources into CS to soften the spraying particles and/or substrate thermally. As one of the most ideal heat sources for materials process due to its unique advantages such as high energy density, chemically clean and flexible operation, laser has been coupled with CS for pre-/post-treatments in the past few years. Therefore, the main objective of the proposed research project is to develop new CS coatings on aerospace materials using LCS technology and study the effect of different processing parameters on the coating’s microstructure and properties. The target conditions to be investigated include: 1. Determine how the metal/ceramic powder ratio, gas temperature, and velocity affect the microstructure and properties of the coatings. 2. Determine how laser pre- and post-treatments affect the coatings microstructure, properties, and adhesion to the substrate.

Development of a metal arc welding (GMAW) metal-based 3D printer

 Javier Ortega

The main goal of the proposed project is to design a metal-based 3D printer combining two approaches: an automated 3-axis CNC-3D printer and a low-cost commercial gas metal arc welder (GMAW). Gas metal arc welding (GMAW) is a welding process in which the heat is generated by an electric arc incorporating a continuous-feed consumable electrode shielded by an externally supplied gas. Much of the traditional welding literature can be directly applied to GMAW-based metal 3D printing to understand printed metal parts' fundamental concepts and behaviors. 3D printing via GMAW most closely resembles single-layer, multi-pass welding, also known as multi-run welding. This welding process reheats previously welded material, thus altering the grain structure, which can improve weld mechanical properties such as ductility while reducing residual stress. Although GMAW-based metal 3D printing is analogous to single-layer multi-pass welding technology, 3-D printing with this technology requires special considerations since the weld material comprises the entire part rather than a small portion. This results in a unique distribution of thermal stresses, microstructures, and mechanical properties as a function of process parameters and part geometry. The current research project proposes developing a GMAW metalbased 3D printer prototype for research purposes and more units for manufacturing projects, demonstrations, and outreach.

Hybrid 3- Dimensional Electrodes with Optimum Compositions for Green Energy Generation

 M. Jasim Uddin

We propose to synthesize and establish the optimal arrangement of three critical segments of three-dimensional (3D) photovoltaic solar cells that would elicit the fastest electron transport kinetics. We want 19 to determine the ideal quantum dot (QD) arrangement, organic dye–a ligand to QD, and functionalization of carbon nanotubes (CNTs) that would lead to the greatest enhancement of the electron transport kinetics in our 3D photovoltaic carbon nanotube microwires. By modifying the QD arrangement (pure CdS, pure CdSe, pure MoS2, or a mixture of CdS-CdSe-MoS2) with or without organic/inorganic ligand, the ruthenium-based organic dye sensitizer (N-719, N3, and modified/synthesized), and the CNTs functionalization (–OH, –COOH, etc.), we will extract the necessary information to determine the faster photoelectron generation and transport kinetics and develop a better understanding of the underlying mechanisms that govern these photocatalytic processes with 3D and solid state cells.

Corrosion Study of Additive Manufactured 316 Alloy for Dry Storage Canister Applications

Brendy C. Rincon Troconis

The storage of spent fuel in austenitic stainless steel dry storage canisters (DSC) is in jeopardy by the risk of CISCC when stored in locations near seawater because of salt deposition and deliquescence. The DSC’s are fabricated through arc welding processes that due to high weld heat input promote microstructural sensitization and high residual stresses in the weld heat-affected zone (HAZ), the combination of which can promote pitting and CISCC. Additively manufactured parts are being adopted broadly among many industries and used in an array of applications. AM parts are attractive to these industries for several reasons. Very complex geometries that otherwise cannot be manufactured using traditional methods can be printed. Also, the ability to use AM to produce parts mitigates the need to maintain a stock of replacement parts and length delivery times. AM 316 alloys have shown superior corrosion resistance when exposed to chloride containing immersion conditions, but its performance under atmospheric exposure, specifically for DSC applications, have not been studied. The goal of this project is to evaluate and compare the performance of AM 316 under atmospheric conditions to the conventional 316. The maintenance and repair of the DSCs are of importance to safely maintaining the national strategic fuel supply chain. End-of-life storage is an integral component of the infrastructure supporting the long-term viability of the existing U.S. reactor fleet. If successful, the proposed program provides an alternative material to extend the life cycle of the spent fuel storage canisters.

Tunability of material properties in additive manufacturing through numerical simulations of multi-phase turbulent flows

 Ruyan Guo 

Smart or multifunctional materials are used in sensors and actuators due to their tailored response to different types of physical stimulations. In 3D printing of electronic technology for example, devices are fabricated in two and three dimensions (2D and 3D) ranging from millimeters to sub-micro scale from inks with conductive, dielectric, or even magnetic properties. Great effort has been put into modifying the properties of inks containing nanoparticles to gain better control of flow parameters, deposition time and viscosity of the ink solvents to successfully obtain polycrystalline structures of materials for sensor and actuators. 

The current state of art of piezoelectric research with numerical tools largely focuses on the analysis of sensor responses under specific stimuli. However, there is room for improvement on optimization of the shape, weight, and performance of the sensors by adjusting material properties in particular directions and custom geometries. The focus of this investigation is to characterize the sensitivity of different manufacturing parameters such as ink speed, viscosity and droplet size and their effects in the functionality of piezoelectric bodies to further understand limitations of additive manufacturing methods for geometries with sharp edges and narrow topologies.  Multi-physics design sensitivity analysis will be conducted on the relationship between output variables or system response with respect to the input design parameters such as material properties, geometry dimensions, and boundary conditions.

Vision Based Automation of Drop-On-Demand Inkjet Printing for Drop Optimization and Ink Characterization

Ruyan Guo

Additive manufacturing has applications in medicine, electronics, transportation, and education—just to name a few.  One of the main advantages of additive manufacturing is that it provides an inexpensive, rapid prototyping solution.  There is, currently, much interest in using drop-on-demand (DOD) inkjet printing to explore functional material applications.  Each novel ink possesses its own DOD drop ejection behavior—associated with the ink’s rheological properties.  Currently, printhead voltage profiles are adjusted, manually, to compensate for these differences.  In this project a Recurrent Dilated Convolutional network will be explored for the vision-based automation of printhead voltage regulation.   The network will be used in two ways.  The first mode of operation will attempt to optimize drop formation by adjusting printhead piezo voltage profiles.  The second mode of operation will explore the effect that different printhead piezo voltage profiles have on drop formation—in order to characterize the material.  The network will be implemented with learned basis functions and attention weights. Generative/discriminative networks, recurrent networks, attention weights, and autoencoders, are being explored to achieve custom developed vision based automation in hybrid 3D fabrications. 

Design and implementation of self-sustainable low power remote multi-sensing system powered by efficient hybrid energy harvesting

Ruyan Guo 

This research focuses on alternative energy harvesting using piezoelectric devices and thermoelectric generators to harvest energy to power remote multi-sensing systems. Custom designed and fabricated stacked PZT transducer harvest the mechanical vibration from the roadway surface and the thermoelectric generators (TEG) harvest the thermal gradient of the soil underneath the asphalt of the roads. Energy-efficient AC-DC and DC-DC converters are used to convert the electrical signals from the stacked PZT transducer and the TEG into electrical power that charges batteries. A remote multi-sensing system is powered by harvested energy. The system is designed to operate in low power (In the range of milliwatts) and hence can operate sustainably using the harvested power from the alternative energy sources.

Research is ongoing to prototype a custom-designed integrated power converter for both AC-DC and DC-DC power conversions. Multiple sensory capabilities are incorporated into the system capable of sensing traffic data such as weight of the vehicle, axle counts, speed of the vehicle, and temperature gradient between the road surface and surrounding soil. 3D fabrication and printed electronics will be used to fabricate the strain gauge sensor used in the system. Modeling and design tasks will be carried out to overcome the RF signal loss when transmitting through multiple medium including metal, soil and air. Circuit simulation and design will be conducted to enable compact low power remote multi-sensing system.

Comparison of electrical energy consumption, additive manufacturing process versus traditional machining process

 F. Frank Chen 

Manufacturing facilities are responsible for roughly 37% of the world’s energy consumption. This daunting figure reinforced the decision to investigate the energy requirements for additive manufacturing, and compare them with traditional manufacturing using metal removal processes. The initial finding indicted that a traditional industrial part made by using fused filament fabrication (FFF) used only about 32% of electrical energy consumed by a CNC milling machine used to make the same part. While energy consumption is just one of several factors to evaluate and sustainability of a manufacturing process, we believe a more in-depth study by exploring energy consumption of various additive manufacturing processes/technologies versus energy consumption of traditional metal removal machining processes can provide more insight into the impact of energy savings on a more widespread adoption of additive manufacturing technologies and processes to produce industrial parts.

Improving Humidity Control Unit Assembly, which combines cooling and desiccant dehumidification technologies into one energy-efficient system, through Arena Simulation and Python Sequencing

 F. Frank Chen 

A local company’s production cycle for Humidity Control Units (HCUs) is a complex process split into five stages of development. In sequential order, these stages may entail the construction, assembly, and installation of the unit base, condensing components, electrical wiring and control panel, the outside shell doors and exterior skin, and production culminates with product shipment. To sustain the evergreen, mission-critical, need for reliable and robust approaches to humidity control, the company identified an opportunity to improve its production efficiency. A focus on the Final staging area has been highlighted by project’s team as the key area of improvement due to data collected from the last year. Based on initial analysis of data derived from last year, a deeper dive into the causes for these issues is needed.  A key problem noticed was the lack of sequencing the assembly team was doing, as it appeared they just did processes in no real order. The project team believes that by finding the optimal sequence of processes for the area, the assembly time needed in completing a unit will be curtailed, thus reducing the energy and resources needed to meet the production requirements. 

In-situ shear exfoliation and direct ink writing assisted  2D nanomaterial-conductive polymer based anodes for biophotovoltaic applications

 Ali Ashraf and Farid Ahmed 

Biophotovoltaics can use photosynthetic microorganisms, such as cyanobacteria or microalgae, to produce bioelectric power through liberating electrons, protons, and oxygen during light-induced charge-transfer processes by catalyzing the oxidation of water. Additionally, photosynthesis produces carbohydrates, which through respiratory reaction, re-generates carbon dioxide and water. Therefore, the biophotovoltaic system can be a self-sustainable and self-maintainable system that can supply long-term power. Use of biophotovoltaics is limited since they produce a small number of electrons. Performance of  biophotovoltaics can be improved by integrating additional capacitive materials in the anode, forming a dual-function photobioanode. The goal of this project is to design a supercapacitive anode using in-situ shear exfoliated 2D nanomaterials and conductive polymers. Suitable conductive polymers (PSS:PEDOT, polyaniline, etc.) will be selected that will provide biocompatibility and bioaffinity for microbial adhesion and subsequent biofilm formation. Nanomaterials (graphene, MoS2,etc.) will be exfoliated from low cost bulk layered materials through innovative shear exfoliation techniques and will be mixed in conductive polymer matrix using planetary mixing. Finally a porous electrode with suitable geometry will be manufactured using a direct ink writing system suitable for printing viscous materials. After biofilm adhesion and growth, the performance of the composite anode will be evaluated using electrochemical means in a physiological media.