Search

ABSTRACT: Hydropower with a small elevation change from inlet to outlet, known as “low-head” hydropower, is a relatively untapped resource for reliable green power generation. One major barrier to entry is the cost of the components needed to generate the power. Each installation site is unique, with various head levels, flow rates, and other unique site characteristics that drive up the cost of development and installation. As a result, custom-made components are necessary because the sites are intrinsically inefficient. However, customized parts are generally more expensive to manufacture than ready-made parts. Often times, the cost of custom-made components is so high that the low-head hydropower installation becomes non-viable. Additive manufacturing offers the ability to make custom components, ideal for one-off applications, at low costs that are well suited for the needs of low-head hydropower. Indirect additive manufacturing, such as making tools or dies rather than end use components, can also be used to make low-cost composite tooling as needed for these custom applications. This paper explores the use of additive manufacturing, both directly and indirectly, to produce the components of a turbine system for a low-head hydropower site. The parts were designed to form a unique modular system, which saves time for future designs and iterations. The system has operated for more than three years without failure at a test site in Wisconsin, USA. This work serves as a basis for future application of AM to low-head systems, in which the modular components can be customized for each unique hydropower installation.

Computer-aided manufacturing (CAM) techniques for hybrid manufacturing have led to new application areas in the manufacturing industry. In the tooling industry, cooling channels are used to enable specific heating and cooling cycles to improve the performance of the process. These internal cooling channels have been designed with limited manufacturing processes in mind, so, until recently, they were often straight in shape for cross-drilling operations and manufactured from a cast billet. To show a novel application of this common technology, a tool with integrated conformal cooling channels was manufactured using hybrid manufacturing (blown-powder DED and CNC machining) techniques. The computer-aided manufacturing strategy used, and the lessons learned are presented and discussed to enable future work in this industrial application space.

At the onset of the COVID-19 (Coronavirus Disease 2019) pandemic, USA faced supply chain issues causing a nationwide shortage of N95 respirators and PAPR devices. Researchers at Oak Ridge National Laboratory's (ORNL) Manufacturing Demonstration Facility (MDF) were sent to work from home to help slow the spread of the pandemic, and during that time they were tasked with using their manufacturing expertise to research alternative methods of producing face masks. To rapidly iterate on face mask designs without access to a research or manufacturing facility, 3D (3-Dimensional) printing and silicone casting were used. Molds and components for the masks are modeled with computer-aided design (CAD), printed with common home desktop 3D printers, and test poured with skin-safe silicone rubber. The resultant masks are form fitting and comfortable to wear. To ease the shortage of N95 filter media, the masks are designed to use existing filter materials such as home HVAC (heating, ventilation, and air conditioning) filters. The masks can be sanitized, and the filter replaced to allow the same mask to be reused. The result is not equivalent to an N95 mask, and not meant to be a replacement, but is meant to be a stopgap mask that is still able to provide the wearer filtered protection. Filtration testing has not been performed because it is not the intention of the authors to make medical claims. This research is meant to demonstrate the rapid design, iteration, and manufacturing processes of a stopgap mask.

The combined benefit of both additive and subtractive manufacturing within the same gantry system enables hybrid directed energy deposition to create complex geometries with smooth surface finish and superior dimensional accuracy. Moreover, with layer-by-layer access to the structure during both the addition and subtraction of material, the insertion of components is now possible, assuming the components can survive the high temperatures associated with the subsequent metal deposition. Ceramic inserts are of interest for a variety of reasons including (1) to create complex interwoven ductile/brittle composites for ballistics or high-temperature applications or (2) to integrate high-temperature strain or temperature sensors protected within ceramic substrate subsumed into a larger metal structure. In this work, stainless steel substrates were machined to create an internal cavity for the insertion of a ceramic component. During the investigation of several different over-the-ceramic deposition strategies, components were inserted, and different process sequences were allowed to continue to envelop the inserted ceramic with varying success. Unmelted powder was used to serve both as a thermal buffer and to provide a flush surface upon which the laser cladding could continue. Subsequent depositions were attempted with both dry and wet powder (addition of machining coolant to wet). The wet powder has previously been demonstrated to not significantly impact the mechanical properties of a final structure and provided a thermal barrier to protect the ceramic piece from the extreme temperatures of the final metal deposition. The wetting of the powder provided stability and minimized displacement caused by the powder flow from the laser cladding head. Finally, the use of an oblique angle for laser cladding allowed for the redirection of some fraction of the introduced thermal energy away from the ceramic component and, consequently, improved the survival of the ceramic inserts. With this combination of techniques, ceramic inserts survived full embedding within a 3D-printed stainless steel structure. [ABSTRACT FROM AUTHOR]

Computer-aided manufacturing (CAM) techniques for hybrid manufacturing have led to new application areas in the manufacturing industry. In the tooling industry, cooling channels are used to enable specific heating and cooling cycles to improve the performance of the process. These internal cooling channels have been designed with limited manufacturing processes in mind, so, until recently, they were often straight in shape for cross-drilling operations and manufactured from a cast billet. To show a novel application of this common technology, a tool with integrated conformal cooling channels was manufactured using hybrid manufacturing (blown-powder DED and CNC machining) techniques. The computer-aided manufacturing strategy used, and the lessons learned are presented and discussed to enable future work in this industrial application space. [ABSTRACT FROM AUTHOR]

Although additive manufacturing (AM) is a net/near-net forming process, significant deviations may occur between the finally manufactured product and the designed object. This study is inspired by the deposition errors in a typical closed-contour structure manufactured via laser-directed energy deposition (DED). A series of experiments were carried out and a multi-physics mechanistic model was developed to reveal the origins and the spatiotemporal variations of the errors in representative processes. The results demonstrate that the irregularity of the deposition can be initiated by the liquid metal flow in the molten pool driven by forces including the recoil pressure and surface tension. The deviations are subsequently aggravated due to the inheritance between layers. Supported by the revealed underlying mechanisms, solution strategies including layer-wise dynamic compensations are thus proposed. The novel scientific findings can be insightful to researches for other metal AM processes and structures considering the universality of the uncovered mechanisms. [ABSTRACT FROM AUTHOR]

This article explores how men serving mandatory life sentences in England and Wales anticipate life after release and the imposition of a life licence. It reports the various ways that lifers feared licencing as being exceedingly 'tight' and restrictive, sometimes resulting in them retreating from release altogether. At the same time, some participants reported a motivation to embrace the 'tightness' of their impending licence conditions, and use penal power as a means of structuring life on release. Whether they resisted or embraced penal intervention, all participants altered their aspirations to what seemed achievable upon release when subject to numerous conditions. Specifically, the article argues that the anticipation of a particular mode of penal power has a material effect on lifers' approach to release. [ABSTRACT FROM AUTHOR]

The manufacturing of composite parts and assemblies requires various kinds of tools, which determine the accuracy, performance, and cost of the end component. Additive manufacturing (AM), also known as 3D printing technology, has a direct impact on the manufacturing the of composite structures by offering rapid production of molds. 3D printing of molds, jigs and fixtures for composites manufacturing increases flexibility and design opportunities and reduces costs and lead time. Large-format AM systems, that can create an object larger than 1 m3, are the only systems that are suitable for rapid production of molds. Most of these systems are based on single-screw thermoplastic pellet extruders. Massivit 3D has developed a unique technology called Cast-In-Motion (CIM) and a designated system, the Massivit 10000, for direct digital printing of tools and molds, made of a proprietary epoxy-based, Thermoset casting material, CIM 500. The technology consists of printing a double-wall shell made of a proprietary UVcured Water Breakable (WB) material, Dimengel 50, followed by casting a calculated amount of CIM 500. The WB printing process and the thermoset-casting processes operate intermittently to create a near net shape, thermoset mold encapsulated by the WB shell. After the encapsulated mold is cured to optimize its mechanical properties at elevated temperatures, it is immersed in a water bath which causes the shell to crumble away and can be post finished to obtain the desired surface finish and geometry for the mold. The system can also be used for the printing of geometric cores and soluble mandrels for the composites industry by utilizing the printing of the WB and other various acrylic base UV cured materials without the conjunction of the CIM 500. This paper presents the advancements in CIM technology with its proprietary materials to enable direct manufacturing of complex finished molds. It also presents various applications from the design phase through printing to post finishing that meet customers' requirements. [ABSTRACT FROM AUTHOR]

In this research, anisotropic NdFeB + SmFeN hybrid and NdFeB bonded magnets are additively printed in a polyphenylene sulfide (PPS) polymer binder. Printed NdFeB + SmFeN PPS bonded magnets displayed excellent magnetic properties (Br [remanence] = 6.9 kG [0.69 T], Hcj [coercivity] = 8.3 kOe [660 kA/m], and BHmax [energy product] = 9.9 MGOe [79 kJ/m3]) with superior corrosion resistance and thermal stability. The anisotropic NdFeB bonded magnet shows a high coercivity of 14.6 kOe (1162 kA/m) with a BHmax of 8.7 MGOe (69 kJ/m3). The coercivity and remanence temperature coefficients for NdFeB + SmFeN hybrid bonded magnets are −0.10%/K and −0.46%/K, and for NdFeB bonded magnets are −0.14%/K and −0.53%/K in the range of 300–400 K, indicating that the hybrid bonded magnets are thermally stable. The average flux aging loss for hybrid magnets was also determined to be very stable over 2000 h at 448 K (175°C) in air with 2.04% compared to that of NdFeB magnets with 3.62%. [ABSTRACT FROM AUTHOR]

Additive manufacturing technologies are increasingly used in the development of new products. However, variations in part quality in terms of material properties, dimensional tolerances, surface roughness and defects limit its broader acceptance. Process control today based on heuristics and experimental data yields limited improvement in part quality. In an effort to identify the needed measurement science for real-time closed-loop control of additive manufacturing (AM) processes, this paper presents a literature review on the current AM control schemes, process measurements and modelling and simulation methods as it applies to the powder bed fusion process, though results from other processes are reviewed where applicable. We present our research findings to identify the correlations between process parameters, process signatures and product quality. We also present research recommendations on the key control issues to serve as a technical basis for standards development in this area. Complimentary details to this paper with summary tables, range of values, preliminary correlations and correlation figures can be accessed from a National Institute of Standards and Technology Report (http://nvlpubs.nist.gov/nistpubs/ir/2015/NIST.IR.8036.pdf). This paper is developed based on the report. [ABSTRACT FROM AUTHOR]

Fabricating a bonded magnet with a near‐net shape in suitable thermoplastic polymer binders is of paramount importance in the development of cost‐effective energy technologies. In this work, anisotropic Sm2Fe17N3 (Sm–Fe–N) bonded magnets are additively printed using SmFeN anisotropic magnetic particles in a polymeric binder polyamide‐12 (PA12). The anisotropic SmFeN bonded magnets are fabricated by Big Area Additive Manufacturing followed by post‐printing alignment in a magnetic field. Optimal post‐alignment results in an enhanced remanence of ∼0.68 T in PA12 reflected in a parallel‐oriented (aligned) measured direction. The maximum energy product achieved for the additively printed anisotropic bonded magnet of Sm–Fe–N in PA12 polymer is 78.8 KJ m−3. Our results show advanced processing flexibility with 3D printing of the development of SmFeN nylon bonded magnets designed for applications with no critical rare earth magnets. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) processes intended for large-scale components deposit large volumes of material to shorten process duration. This reduces the resolution of the AM process, which is typically defined by the deposition nozzle size. If the resolution limitation is not considered when designing for Large-Scale Additive Manufacturing (LSAM), difficulties can arise in the manufacturing process, which may require the adaptation of deposition parameters. This work incorporates the nozzle size constraint into Topology Optimisation (TO) in order to generate optimised designs suitable to the process resolution. This article proposes and compares two methods, which are based on existing TO techniques that enable control of minimum and maximum member size, and of minimum cavity size. The first method requires the minimum and maximum member size to be equal to the deposition nozzle size, thus design features of uniform width are obtained. The second method defines the size of solid members sufficiently small for the resulting structure to resemble a structural skeleton, which can be interpreted as the deposition path. Through filtering and projection techniques, the thin structures are thickened according to the chosen nozzle size. Thus, a topology tailored to the deposition nozzle size is obtained along with a deposition proposal. The methods are demonstrated and assessed using 2D and 3D benchmark problems. [ABSTRACT FROM AUTHOR]

Copyright of História da Historiografia is the property of Sociedade Brasileira de Teoria e Historia da Historiografia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Featured Application: This work applies to the production of large, complex, metallic preform structures in the aerospace and tool and die industries. In the aerospace industry, this technology has a potential role in the rapid production of custom, near-net shape preforms for machined Ti-6Al-4V components. Specifically, site-specific control enables localized control of bead geometry, which has enhanced defect mitigation capabilities and may enable local control of material properties. A variety of techniques have been utilized in metal additive manufacturing (AM) for melt pool size management, including modeling and feed-forward approaches. In a few cases, closed-loop control has been demonstrated. In this research, closed-loop melt pool size control for large-scale, laser wire-based directed energy deposition is demonstrated with a novel modification, i.e., site-specific changes to the controller setpoint were commanded at trigger points, the locations of which were generated by the projection of a secondary geometry onto the primary three-dimensional (3D) printed component geometry. The present work shows that, through this technique, it is possible to print a specific geometry that occurs beyond the actual toolpath of the print head. This is denoted as extra-toolpath geometry and is fundamentally different from other methods of generating component features in metal AM. A proof-of-principle experiment is presented in which a complex oak leaf geometry was embossed on an otherwise ordinary double-bead wall made from Ti-6Al-4V. The process is introduced and characterized primarily from a controls perspective with reports on the performance of the control system, the melt pool size response, and the resulting geometry. The implications of this capability, which extend beyond localized control of bead geometry to the potential mitigations of defects and functional grading of component properties, are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Teachers are responsible for providing an education to students of all ability levels. Recent data suggest that roughly 95% of students with a disability are receiving some form of education in their general education setting. Individuals with disabilities tend to engage in higher levels of disruptive behaviors (e.g., talking out in class, noncompliance, throwing materials) than peers without disabilities. With an increase in the number of students with disabilities receiving some form of education in their general education setting, teachers may be spending more time managing disruptive behaviors and less time teaching. Research suggests a strong relationship between classroom‐management techniques and academic achievement. These data highlight the importance of classroom‐management interventions that promote the learning of all students in the classroom. Despite the importance of classroom‐management techniques, a lack of training, as well as the feasibility of the interventions may prevent the ultimate adoption and long‐term success of effective techniques. Self‐management is a potential solution, as self‐management techniques can be easily trained and implemented. [ABSTRACT FROM AUTHOR]

Surgical removal remains the best curative option for patients diagnosed with early‐stage lung cancer. However, it is also associated with significant morbidity and reduced quality of life. Interventions to improve patient outcomes are required. This study aimed to explore the views, attitudes and beliefs of key stakeholders on exercise intervention for people who are surgically treated for lung cancer to inform the development of future interventions. Focus groups and individual interviews were carried out at two Scottish sites. The study was guided by the Health Action Process Approach behaviour change model. A total of 23 (12 patients and 11 health professionals) participated in the study. The data analysis resulted in three main themes: attitudes and beliefs, external factors and intervention design. The results highlighted certain key elements that should be included in an exercise intervention, such as the need for supervised sessions, an element of individualisation and the perceived social benefits of exercising with others. This study emphasises the importance of including key stakeholders in the development of complex interventions such as exercise and provides important information for the development of future exercise intervention trials for people who are surgically treated for lung cancer. [ABSTRACT FROM AUTHOR]