Water jetting as a means for removing anomalous materials from cast-in-drilled-hole (CIDH) piles was examined. The primary objective of this research was to establish empirical relationships between different jetting parameters and the removal of commonly occurring anomalous zone materials, including low-strength concrete, slurry mixed concrete, grout, and clay soil. Also investigated was the current standard-of-practice used by water jetting contractors within California. The testing specimens consisted of typical anomalous material with unconfined compressive strengths between 5 and 6,000 psi. The experimental work consisted of water blasting submerged specimens using rotary jets, nozzles, and pumping equipment typically used in construction practice. Two testing protocols were developed. The first testing protocol called for the nozzle to be held stationary and the second allowed the nozzle to be cycled up and down across the anomaly. During testing, material removal rates were measured as a function of jet pressure and standoff distance. Water blasted specimens were cut apart after testing to confirm erosion measurements and to permit inspection of the water blasted surfaces. Based on the results, erosion rates and the effectiveness of water jetting are primarily influenced by unconfined compressive strength, when using standard test equipment and jetting pressures. Further, aggregate size and material type in the anomalous material does not appear to influence both total erosion and erosion rate.

<p>Binder jet printing (BJP) is an additive manufacturing (AM) method which has the potential to be applied to high annual volumes in the automotive industry. Binder jet printing provides an excellent opportunity to innovate transmission valve body components. The three-layer design and complex hydraulic control system channels of valve body housing formulated a new electro-hydraulic system with the brand-new features inherited from BJP. For the valve body, the features of BJP brought a revolutionary new idea for both the valves and hydraulic channel design. The spool valve was housed with a sleeve that integrates orifices and port controls. The hydraulic channel layout of the valve body assembly was greatly simplified and space-saving. The support components had also been replaced with a lightweight design while maintaining the same functionality. Integrated design of Binder jet print produced hydraulic automatic valve system presented an entirely new design, whose static performance was compared to that of the conventional 948TE ZF9HP48 transmission valve body. Similar performance indicated that a valve body design featuring BJP would have great potential for various industrial applications.</p>

The development of a process chain for Inconel 718 production utilizing Binder Jetting has been investigated. Different powder sources were compared by the effect they had on machine compatibility, powder bed packing, recyclability, green density, sintering parameters, final density, porosity, and mechanical properties. The three powder lots investigated originated from two different production sites. One of the three powder lots has a finer powder size distribution, due it being produced simultaneously with another powder lot with a coarser powder size distribution fraction. This synergy production results in a higher yield of the atomization process and thus is economically and environmentally beneficial. The compatibility between powder lots and Binder Jetting machine was investigated using new powder and recycled powder. By using recycled powder in the process an increase in green density by 5% could be achieved. Several temperature and hold time relations were tested to develop a sintering program with an acceptable final density above 94% of theoretical density. 1270◦C with a hold time of 4h generated the best results. Sintered samples did not reach acceptable strength properties. The elongation value was twice as high as required for one of the powder lots using recycled powder. Post heat treatment generated samples with an acceptable yield strength but highly reduced elongation properties.

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Additive manufacturing has gained considerable attention in recent years due to its capabilities of producing complex parts with tailormade mechanical properties. Because of its infancy state, additive manufacturing production chains are seldom optimized to the same extent as conventional manufacturing techniques. Companies with additive manufacturing production sitesusing powder as a building material often find themselves devoting a lot of resources towards depowdering, a post processing step that has potential of being a significant bottleneck.The purpose of this master thesis was to develop a de-powdering system that would function automatically, relieving operators from performing the process step manually. The following work has been conducted at Sandvik in Sandviken at the department for additive manufacturing.Results were acquired with high credibility due to a mixture of qualitative and quantitative gathering techniques that supplemented each other. Together with a literature review, empirical data gave rise to the possibility of developing a new de-powdering system for binder jetting technology.Optimization of the system indicated that larger inlets produced a higher removal efficiency. This was later confirmed with computational fluid dynamics, where smaller nozzles created a more turbulent air flow, making it difficult for powder particles to exit the system. Though final trials with green bodies revealed that the system, in its current state, did not have the capabilities of replacing manual de-powdering completely, it certainly displayed how efficient it can be with further development.

The purpose of this work is to explore the feasibility of using binder jetting to print copper-graphene composites. This work discusses in detail the approach used to print the composite samples which are optimised through various processes to generate denser parts than a copper reference print and finally discussing various opportunities to enhance development of the process. The preliminary results suggest that graphene improves the printing process giving faster sintering and more dense samples. From the findings, it can be concluded that at 1060OC for dwell time of 8 hours the density of copper composite(98.9±0.3%), copper reference (94.8±0.6%) and pressed composite pellets (99.1±0.1%) have the maximum density. Also, the presence of graphene seems to increase hardness and improve conductivity but further studies are required to confirm this. However, due to contamination of external elements in bulk due to porous surface of printed samples with binder jetting, hardness and electrical conductivity can be improved by further densification.

The continuous miniaturization of electronic devices and the corresponding increase in computing powers have led to a significant growth in the density of heat dissipation within these devices. This increase in heat generation has challenged conventional air fan cooling and alternative solutions for heat removal are required to avoid overheating and part damage. Micro/Mini channel heat sinks (M/MCHS) that use liquids for heat removal appear as an attractive solution to this problem as they provide large heat transfer area per volume. Mini/microchannels traditionally have suffered from geometrical and material restrictions due to fabrication constraints. An emerging new additive manufacturing technique called binder jetting has the potential to overcome some of those restrictions. In this study, a straight minichannel heat sink is manufactured from stainless steel using binder jetting, and it is experimentally evaluated. The hydraulic performance of the heat sink is tested over a range of Reynolds numbers (150-1200). The comparison between the hydraulic results and standard correlations confirms that the targeted geometry was produced, although the high surface roughness created an early transition from laminar-to-turbulent flow. The heat transfer performance was also experimentally characterized at different heat flux conditions ($3000W/m^2$, $5000W/m^2$, $6500W/m^2$), and a range of Reynolds numbers (150-800). These results indicated that convection heat transfer coefficients on the order of $1000 W/m^2-K$ can be obtained with a simple heat sink design. Finally, the effects of the contact resistance on the results are studied, and contact resistance is shown to have critical importance on the thermal measurements. / Master of Science / The continuous miniaturization of electronic devices and the corresponding increase in computing powers have led to a significant growth in the density of heat dissipation within these devices. This increase in heat generation has challenged conventional air fan cooling and alternative solutions for heat removal are required to avoid overheating and part damage. Micro/Mini channel heat sinks (M/MCHS) that use water instead of air for heat removal appear as an attractive solution to this problem as they provide large heat transfer area per volume due to the small channels. Mini/microchannels are distinguished from conventional channels by the hydraulic diameter, where they range from $10mu m$ to $2mm$. M/MCHS are typically manufactured from a highly conductive metals with the channels fabricated on the surface. However, mini/microchannels traditionally have suffered from geometrical and material restrictions due to fabrication constraints. Complex features like curves or internall channels are difficult or even impossible to manufacture. An emerging new additive manufacturing technique called binder jetting has the potential to overcome some of those restrictions. Binder jetting possess unique advantageous as it uses precise control of a liquid binder applied to a bed of fine powder to create complex geometries Furthermore, it does not require extreme heating during the fabrication process. The advantages of binder jetting include that it is low cost, high speed, can be applied to a variety of materials, and the ability to scale easily in size. In this study, a straight minichannel heat sink is manufactured from stainless steel using binder jetting, and this heat sink is experimentally evaluated. The hydraulic performance of the heat sink is tested over different water flow rates (Reynolds numbers between 150-1200). The comparison between the hydraulic results and standard correlations confirms that the targeted geometry was produced, although the high surface roughness created an early transition from laminar-to-turbulent flow. The surface roughness effect should be considered in future designs of additively manufactured minichannels. The heat transfer performance was also experimentally characterized at different heat flux conditions ($3000W/m^2$, $5000W/m^2$, $6500W/m^2$), and different water flow conditions (Reynolds numbers 150-800). These results indicated that convection heat transfer coefficients on the order of $1000 W/m^2-K$ can be obtained with a simple heat sink design. However, a mismatch between the experimental data and the correlation requires further investigation. Finally, the effects of the contact resistance on the results are studied, and contact resistance is shown to have critical importance on the thermal measurements.

Additive manufacturing (AM) creates 3D objects out of polymers, ceramics, and metals to enable cost-efficient and rapid production of products from aerospace to biomedical applications. Personalized products manufactured using AM, such as personalized dosage pharmaceuticals, tissue scaffolds, and medical devices, require specific material properties such as biocompatibility and biodegradability, etc. Polymers possess many of these qualities and tuning molecular structure enables a functional material to successfully deliver the intended application. For example, water-soluble polymers such as poly(vinyl pyrrolidone) and poly(ethylene glycol) both function as drug delivery materials because of their inherit water-solubility and biocompatibility. Other polymers such as polylactide and polyglycolide possess hydrolytically cleavable functionalities, which enables degradation in the body. Non-covalent bonds, such as hydrogen bonding and electrostatic interactions, enable strong connections capable of holding materials together, but disconnect with heat or solvation. Taking into consideration some of these polymer functionalities, this dissertation investigates how to utilize them to create functional biomedical products using AM. The investigation of structure-property-processing relationships of polymer molecular structures, physical properties, and processing behaviors is transforming the field of new materials for AM. Even though novel, functional materials for AM continue to be developed, requirements that render a polymeric material printable remain unknown or vague for most AM processes. Materials and printers are usually developed separately, which creates a disconnect between the material printing requirements and fundamental physical properties that enable successful printing. Through the interface of chemistry, biology, chemical engineering, and mechanical engineering, this dissertation aims to relate printability of polymeric materials with three types of AM processes, namely vat photopolymerization, binder jetting, and powder bed fusion. Binder jetting, vat photopolymerization, and powder bed fusion require different viscosity and powder requirements depending on the printer capabilities, and if the material is neat or in solution. Developing scaling relationships between solution viscosity and concentration determined critical overlap (C*) and entanglement (Ce) concentrations, which are related to the printability of the materials. For example, this dissertation discusses and investigates the maximum printable concentration in binder jetting of multiple polymer architectures in solution as a function of C* values of the polymer. For thermal-type printheads, C* appeared to be the highest jettable concentration, which asserted an additional method of material screening for binder jetting. Another investigation of the photokinetics as a function of concentration of photo-active polymers in solution revealed increased viscosity leads to decreased acrylate/acrylamide conversion. Lastly, investigating particle size and shape of poly(stearyl acrylate) particles synthesized through suspension polymerization revealed a combination of crosslinked and linear polymers produced high resolution parts for phase change materials. These analytical screening methods will help the progression of AM and provide future scientists and engineers a better guideline for material screenings. / Doctor of Philosophy / Additive manufacturing (AM), also known as 3D printing, enables the creation of 3D objects in a rapid and cost-efficient manner for applications from aerospace to biomedical sectors. AM particularly benefits the field of personalized biomedical products, such as personalized dosage pharmaceuticals, hearing aids, and prosthetic limbs. In the future, advanced detection and prevention medical screenings will provide doctors, pharmacists, and engineers very precise data to enable personalized healthcare. For example, a patient can take three different medications in one pill with the exact dosage to prevent side-effects and drug-drug interactions. AM enables the delivery and manufacturing of these personalized systems and will improve healthcare in every sector. Investigations of the most effective materials is needed for personalized medicine to become a reality. Polymers, or macromolecules, provide a highly tunable material to become printable with slight chemical modifications. Investigation of how chemical structure affects properties, such as strength, stretchability, or viscosity, will dictate how they perform in a manufacturing setting. This process of investigation is called "structure-property-processing" relationships, which connects scientists and engineers through all disciplines. This method is used to discover which polymers will not only 3D print, but also carry medication to a patient or deliver therapeutics within the body.

Material jetting (MJ) is an additive manufacturing (AM) process that involves the selective jetting of a liquid material into the shape of a layer and subsequent solidification, often via ultraviolet (UV) irradiation, in a layer-wise fashion. The MJ process has the potential to emerge as a robust fabrication method: the inherent, facile, multi-material capability in a high-resolution process should distinguish the technology as a competitive, multi-functional, manufacturing process. However, it is mainly constrained to prototyping use, limited by both material and process constraints. This research expands material and process knowledge by characterizing the multi-material process-structure-property relationships in photopolymer-based MJ, which provides a basis for advancing the capability of MJ to fabricate accurate and consistent multi-material parts for functional applications. One of the challenges for advancing MJ is the general lack of processable materials. For example, MJ is increasingly being used for fabricating anatomic models for use as pre-procedural planning or medical student trainee tools, but commercial MJ elastomers are unable to mimic human tissues' mechanical properties, which limits the instructional value of printed anatomic models. By combining photo-curing and non-curing materials, a cardiac tissue-mimicking material was achieved and integrated into a fully-printed heart model used to practice the transseptal puncture procedure. Several mechanical properties of this multi-material combination were evaluated to facilitate quicker screening of future tissues that would be desired to be mimicked. Also impeding technological advancement of MJ systems is a lack of understanding the effects of indiscriminate UV exposure on material properties. Depending on factors such as part design and build layout, an indiscriminate UV toolpathing strategy poses the risk for providing inconsistent UV dosing to parts and causing unintended variations in mechanical performance. Experiments were conducted to quantify these effects, and an empirical model was developed to predict the accumulated exposure parts receive. A connection was then made between accumulated exposure received by material voxels and final part properties, where it was observed that overexposure effects exist, and are largely dependent on material, build layout, and toolpathing. This work will lead to improved design guidelines and process modifications to ensure consistency of UV dosing and achieve desired mechanical performance. This knowledge will enable future photopolymer AM systems to account for potential overcuring effects toward fabricating repeatable and reproducible functional products. Finally, documented in this work are efforts toward expanding the knowledge about the use of AM to safely produce personal protective equipment during the COVID-19 pandemic. Amid prospects of large-scale, distributed production of respirators via AM, the lack of filtration efficiency testing generated concerns about the respirators' effectiveness. The goal of this work was to measure particle transmission through respirators fabricated with powder bed fusion and fused filament fabrication processes and compare their performance to that of cloth masks and standardized N95 respirators. Through systematic post-processing, the connection between printed respirator deficiencies and changes in filtration efficiency were discerned. Identifying the system-level quality control challenges responsible for the respirator failure modes highlights some the current limitations in AM for fabricating functional parts. The findings will assist future efforts toward both creating enhanced designs and optimizing printer parameters, ultimately working toward qualifiable, end-use parts. / Doctor of Philosophy / The material jetting (MJ) additive manufacturing (AM) process operates in a similar fashion to inkjet printing. For MJ of photopolymer materials, liquid droplets are selectively deposited onto a build plate, and an ultraviolet (UV) light bulb provides the energy to solidify the droplets into a three-dimensional layer by curing the materials. Droplets are then deposited on top of these solidified droplets to fabricate a part layer by layer. Multiple materials and colors can be jetted simultaneously within a single part layer. If these materials exhibit different mechanical behavior, such as one material being rigid and another being flexible, a printed part could have regions with different material properties, as well as intermediate gradients of these properties. The MJ process offers high resolution, smooth surface finishing, a large build volume, and the opportunity to print multiple parts in one build. However, the process is mainly limited to prototypes and non-functional applications. One of the challenges for advancing MJ is the general lack of processable materials. In the medical field, surgeons are increasingly looking to MJ to fabricate physical, patient-specific models to assist in pre-surgical planning and to serve as practice models for medical student trainees. In particular, a printed cardiovascular model was sought to enable the practice of the transseptal puncture procedure; however, the available materials were not able to mimic the heart tissue. In this work, a non-curing liquid was patterned into an elastomer to soften the material and attain tissue-mimicking performance for a model to practice the transseptal puncture procedure. By characterizing this expanded material space, this work enables the potential for mimicking a broader spectrum of tissues in future anatomic models. Another aspect limiting widespread functional use for MJ is the lack of understanding how UV exposure affects material performance. For the MJ process, the UV light is on the same assembly as the printheads and remains on throughout the duration of a print, which means that the amount of administered energy is not consistent across the build plate. If, for example, parts have different heights, the shorter part will finish printing first and receive excess UV exposure, which has been shown to alter the mechanical performance for some materials. A model was developed to predict the accumulated exposure received by parts of different materials and build scenarios. Observed changes in mechanical properties could then be connected to specific instances of overexposure. With this knowledge, future strategies can be implemented to achieve consistency of UV exposure and thus better ensure reliable, functional parts. Additionally presented in this work is a study involving the use of AM to safely produce personal protective equipment for COVID-19 relief efforts. During the initial stages of the pandemic, AM was sought to address respirator shortages; however, there were no studies measuring printed respirators' effectiveness. By measuring particle transmission through respirators fabricated with a variety of AM processes, it was found that even when N95 filters were inserted, printed respirators were not able to consistently filter 95% of virus-sized particles, even with modifications. The quality control challenges for the AM processes identified in this study will assist future efforts in part design and printer parameter optimization to work toward accurate and qualifiable products.