Karthick Rasu, Ashwin Prabhu Gnanasekaran, Sudarsan Deenadayalan
et al.
This study focuses on the machinability optimization of bio-waste corn husk fiber–reinforced epoxy composites during drilling, with the objective of minimizing delamination and improving hole quality required for mechanical fastening applications. While natural fiber composites have been widely investigated, systematic statistical optimization of drilling parameters for corn husk fiber composites remains limited. The novelty of this work lies in identifying the dominant drilling parameter and establishing a clear damage-control strategy using a Taguchi L16 design coupled with ANOVA. Drilling experiments were conducted by varying spindle speed (1000, 1500, 2000, and 2500 rpm), drill diameter (6, 8, 10, and 12 mm), feed rate (00.05, 0.10, 0.15, and 0.20 mm/rev), and point angle (90°, 100°, 110°, and 120°). The results show that the drill diameter is the governing factor affecting delamination, contributing 73.52% of the total variation, followed by spindle speed (22.68%), whereas feed rate (3.14%) and point angle (0.38%) have minimal influence. The optimal condition (2500 rpm, 6 mm drill diameter, and 0.05 mm/rev feed rate) produced the lowest delamination and improved surface integrity. Microscopic observations confirmed reduced fiber pull-out and matrix cracking under these conditions. The main advantage of the proposed approach is the clear identification of parameter priority, enabling the industry to control drilling damage by primarily selecting appropriate drill diameter and spindle speed. The findings provide practical machining guidelines for the use of corn husk fiber composites in lightweight panels, automotive interior parts, and secondary structural components where reliable bolted joints are required.
Nikolaos Bolanakis, Emmanuel Maravelakis, Vassilis Papadakis
et al.
This study aimed to develop a biochar-modified polyethylene terephthalate glycol (PETG) composite for 3D printing. Biochar prepared from olive tree prunings was compounded with PETG at different loadings and then processed into filaments through a controlled extrusion process. The resultant filaments were used to print test specimens, which were characterized thoroughly by mechanical, thermal, morphological, and rheological methods. The tensile strength (17.8%), flexural strength (15.9%), impact resistance (20.9%), and thermal stability of the biochar-reinforced composites were substantially improved. Overall, the 6.0 wt.% biochar compound exhibited the highest improvement. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed the excellent dispersion of biochar in the PETG matrix. The results demonstrated that biochar is an effective, environmentally friendly material to use as a reinforcing agent for additive manufacturing. The PETG/biochar composites have a promising future for various industrial applications, offering sustainable alternatives with superior performance characteristics.
Yeasir Mohammad Akib, Ehsan Marzbanrad, Farid Ahmed
The trend of adapting powder bed fusion (PBF) for product manufacturing continues to grow as this process is highly capable of producing functional 3D components with micro-scale precision. The powder bed’s properties (e.g., powder packing, material properties, flowability, etc.) and thermal energy deposition heavily influence the build quality in the PBF process. The packing density in the powder bed dictates the bulk powder behavior and in-process performance and, therefore, significantly impacts the mechanical and physical properties of the printed components. Numerical modeling of the powder bed process helps to understand the powder spreading process and predict experimental outcomes. A two-dimensional powder bed was developed in this work using the LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) package to better understand the effect of bimodal and unimodal particle size distribution on powder bed packing. A cloud-based pouring of powders with varying volume fractions and different initialization velocities was adopted, where a blade-type recoater was used to spread the powders. The packing fraction was investigated for both bimodal and unimodal systems. The simulation results showed that the average packing fraction for bimodal and unimodal systems was 76.53% and 71.56%, respectively. A particle-size distribution-based spatially varying powder agglomeration was observed in the simulated powder bed. Powder segregation was also studied in this work, and it appeared less likely in the unimodal system compared to the bimodal system with a higher percentage of bigger particles.
Liudmyla Kapitanova, Viktor Riabkov, Andriy Koryagin
Enhancing flight efficiency is a pressing issue in the development of the aircraft manufacturing industry. Aircraft manufacturers in Europe, the USA, China, and Ukraine are following this path of improvement for such aircraft, as it is the most economically efficient approach. This method significantly reduces the time required for design, prototype production, flight testing, and the start of operation of the first units. At the National Aerospace University "KhAI", the Department of Aircraft and Helicopter Design has established a school focused on implementing necessary modification changes in transport category aircraft. The distinctive feature of this approach is that only outdated parameters of a well-proven baseline aircraft are modified, while the majority of the parameters are carried over to the modification from the original version. This foundation underpins the research presented in this publication. The research aims to develop parametric models to support decision-making during the preliminary design stage for enhancing the load capacity and flight efficiency of transport category aircraft modifications. Research methods: a method of changes assessing in wing induced drag with modifications in its planform shape; a method of "payload-range" characteristics creation. The object of the research is the development of parametric models to support decision-making during the preliminary design stage of transport category aircraft modifications. The following results were obtained a package of models was developed, including: ensuring the specified load capacity and "payload-range" characteristics; a temporal model of parameter changes in modifications considering the time frame for modifications; cost indicators for changes at individual stages and throughout the entire life cycle; representation of modifications in terms of their competitiveness; formation of wing geometric shapes with minimal induced drag at a given lift; ensuring that the takeoff and landing characteristics of modifications remain at the level of the baseline aircraft; coordination of wing lift coefficients and engine throttle characteristics to ensure minimum fuel consumption in cruise flight mode. Each model serves as a tool to address the main tasks of increasing load capacity and the range of useful payload transport at the moment of modification introduction and throughout its entire life cycle. Examples of real modification changes in domestic transport aircraft, such as the An-32, An-32B, and An-132U, demonstrate that using the proposed decision support models during the preliminary design stage has ensured their competitiveness throughout their operational life. Practical significance of the obtained results: Based on the developed models, the load capacity and flight efficiency of modifications like the An-32 and An-32B have been increased, and the parameters of the An-132U modification with Motor Sich engines have been optimized, surpassing the load capacity and flight efficiency of all other analogs of light military transport aircraft. Scientific novelty of the obtained results: For the first time, a method was developed to minimize induced drag during cruise flight with the required lift force, i.e., for a given load, allowing an increase in the range of modified aircraft.
Souradeep Dutta, Deba Kumar Sarma, Jay Vora
et al.
The miniaturization of smart materials has become a new trend in the modern manufacturing industry due to its enormous application in the aerospace, biomedical, and automobile sectors. Nickel–titanium (NiTi)-based binary shape memory alloys (SMAs) are one of the smart materials with certain supreme features like shape memory effect, pseudo-elasticity, high ductility, strong corrosion-resistance, and elevated wear resistance. For this, several micro-machining processes have been developed to machine NiTi SMAs. This paper summarizes all of the conventional and non-conventional micro-machining processes employed to machine NiTi SMAs. In this review process, the surface integrity, dimensional accuracy of the machined surface, cutting force and tool wear analysis during conventional and non-conventional micro-machining of NiTi SMA are evaluated mostly with the aid of input process variables like cutting speed, depth of cut, width of cut, types of coolants, tool coating, discharge voltage, capacitance, laser fluence, pulse duration, scan speed, electrolysis concentration and gap voltage. The optimization of process parameters using different methods during conventional and non-conventional micro-machining of NiTi SMAs is also analyzed. The problems faced during conventional micro-machining of NiTi SMAs are overcome by non-conventional micro-machining processes as discussed. The present study aims to recognize potential developments in the improvement of the micro-machinability of NiTi SMAs.
Sergei Egorov, Fabian Soffel, Timo Schudeleit
et al.
In the context of directed energy deposition (DED), the production of complex components necessitates precise control of all processing parameters while mitigating undesirable factors like heat accumulation. This research seeks to explore and validate with various materials the impact of a geometry-based analytical model for minimizing heat input on the characteristics and structure of the resultant DED components. Furthermore, it aims to compare this approach with other established methods employed to avoid heat accumulation during production. The geometry of the fabricated specimens was assessed using a linear laser scanner, cross-sections were analyzed through optical microscopy, and the effect on mechanical properties was determined via microhardness measurements. The specimens manufactured using the developed analytical model exhibited superior geometric precision with lower energy consumption without compromising mechanical properties.
Evgeny Zaytsev, Vasiliy Krutikov, Alexey Spirin
et al.
Magnetic pulse welding (MPW) employs a strong pulsed magnetic field to accelerate parts against each other, thus forming an impact joint. Single-turn tool coils and field-shapers (FSs) used in MPW operate under the most demanding conditions, such as magnetic fields of 40–50 T with periods lasting tens of microseconds. With the use of conventional copper and bronze coils, intense thermo-mechanical stresses lead to the rapid degradation of the working bore. This work aimed to improve the efficiency of field-shapers and focused on the development of two- and four-slit FSs with a nanocomposite Cu 18Nb brazed wire acting as an inner current-carrying layer. The measured ratios of the magnetic field to the discharge current were 56.3 and 50.6 T/MA for the two- and four-slit FSs, respectively. FEM calculations of the magnetic field generated showed variations of 6–9% and 3% for the two- and four-slit FSs, respectively. The ovality percentages following copper tube compression were 27% and 7% for the two- and four-slit FSs, respectively. The measured deviations in the weld-joining length were 11% and 1.4% in the two- and four-slit FSs, respectively. Compared to the previous experiments on an entirely steel inductor, the novel FS showed significantly better results in terms of its efficiency and the homogeneity of its magnetic field.
Mohamed Awad, Abdelrahman Said, Mohamed H. Saad
et al.
Hydrogen provides the greatest performance in conditions of capacity and duration when related to other energy storage techniques. Renewable energy sources including solar, geothermal, wind, wave and tidal energy, and hydropower, are used to create green hydrogen. However, biogas is converted into renewable hydrogen via chemical procedures. A comparison of several water Electrolyzer types is provided by this research. All kinds of Electrolyzers have an impact on how well a green hydrogen production system works were discussed. This review gives a broad review of environmentally friendly hydrogen generation techniques based on renewable energy sources. These sources incorporate solar energy, hydropower, wind energy, tidal and wave energy, biogas systems, geothermal energy, and hybrid systems of these sources. The method used to obtain the hydrogen and its effects on the environment is the primary distinction between green hydrogen and other colors. Climate, control, management systems, and tracking systems. The innovations and difficulties that green hydrogen systems encounter are highlighted. In the final section, the costs associated with manufacturing hydrogen are explained through an economic study of the understudied production systems LCOE and LCOH. Furthermore, the advantages and disadvantages of all electrolyzers are discussed.
This paper studies the issue of capacity allocation in multi-rank distribution channel management, a topic that has been significantly overlooked in the existing literature. Departing from conventional approaches, hierarchical priority rules are introduced as constraints, and an innovative assignment integer programming model focusing on capacity selection is formulated. This model goes beyond merely optimizing profit or cost, aiming instead to enhance the overall business orientation of the firm. We propose a greedy algorithm and a priority-based binary particle swarm optimization (PB-BPSO) algorithm. Our numerical results indicate that both algorithms exhibit strong optimization capabilities and rapid solution speeds, especially in large-scale scenarios. Moreover, the model is validated through empirical tests using real-world data. The results demonstrate that the proposed approaches can provide actionable strategies to operators, in practice.
PurposeOmnichannel sales have provided new impetus for the development of catering merchants. The authors thus focus on how catering merchants should manage capacities at the ordering, production and delivery stages to meet customers’ needs in different channels under third-party platform delivery and merchant self-delivery. This is of great significance for the development of the omnichannel catering industry.Design/methodology/approachThis paper formulates the capacity decisions of omnichannel catering merchants under the third-party platform delivery and merchant self-delivery mode. The authors mainly use queuing theory to analyze the queuing behavior of online and offline customers, and the impact of waiting time on customer shopping behavior. In addition, the authors also characterize the merchant’s capacity by the rate in queuing model.FindingsThe authors find that capacities at ordering stage and food production stage are composed of base capacities and safety capacities, but the delivery capacities only have the latter. And in the self-delivery mode, merchants can develop higher safety capacities by charging delivery fees. The authors prove that regardless of the delivery mode, omnichannel sales can bring higher profits to merchants by integrating demand.Originality/valueThe authors focus on analyzing the capacity management of omnichannel catering merchants at the ordering, production and delivery stages. And the authors also add the delivery process into the omnichannel for analysis, so as to solve the problem of capacity decision-making under different delivery modes. The management of delivery capacity and its impact on other stages’ capacities are not covered in other literature studies, which is one of the main innovations of this paper.
Gabriela Costa Pinto Fiuza, Karine Araújo Ferreira
Este artigo tem como objetivo apresentar os métodos de gestão da construção adotados por empresas de construção civil de uma cidade do interior de Minas Gerais, bem como identificar e analisar se as mesmas utilizam algum princípio ou prática presente na construção enxuta. Para tanto, foram realizados estudos de casos em nove construtoras por meio de aplicação de entrevistas semiestruturadas. Dentre os resultados obtidos, destaca-se que a maioria das construtoras investigadas não utilizam métodos de gestão estruturados, sendo esta gestão baseada principalmente nas experiências profissionais dos gestores. Em relação às ferramentas e técnicas da construção enxuta adotadas pela maioria das construtoras investigadas, o uso das mesmas ocorre de maneira mais intuitiva, sem relação com a adoção da filosofia enxuta. Dentre as mais comumente adotadas nas empresas investigadas, destacam-se: trabalho padronizado, 5S, just in time e reuniões diárias.
Production management. Operations management, Production capacity. Manufacturing capacity
Emily C Tucker, Sarah Haylock‐Jacobs, Mirjana Rapaic
et al.
Abstract Background and Aim This study evaluates whether a stool donor program to supply fecal microbiota transplantation (FMT) product is feasible in the Australian regulatory environment. The primary outcome was capacity to supply FMT product. The secondary outcomes were donor eligibility, retention, and output. Methods Prospective observational cohort study using data collected from the stool donor and FMT production records from BiomeBank, South Australia. Participants were people who engaged with BiomeBank's donor screening and FMT manufacturing process between 01 January 2021 and 31 December 2021. Results In total 176 people registered interest in the program, 74 of 176 (42.0%) proceeded to written questionnaire, 14 of 176 (8.0%) underwent clinical assessment, and 8 of 176 (4.5%) enrolled in the program. Two people were ineligible based on laboratory tests: both had an extended spectrum beta‐lactamase producing organism in stool and one also tested positive for hepatitis B core antibody. Two donors remained eligible from 2020, resulting in 10 enrolled donors in 2021; 5 of 10 (50%) male with a median age of 36.9 years (interquartile range, 30.3–42.7 years). All donors were ineligible to donate at some time point. There were 144 stool donations processed into 1480 50 mL FMT; 413 FMT were shipped to 33 Australian hospitals for treatment, 470 for clinical trials, and 89 were destroyed prior to release from quarantine. Conclusion Recruitment into the program, retention, and maximizing the yield from a donation period was challenging. Despite this, BiomeBank was able to produce and supply FMT to Australian hospitals under the TGA‐regulated Class 2 Biologicals framework.
Diseases of the digestive system. Gastroenterology
Markus Mirz, Simone Herzog, Christoph Broeckmann
et al.
Duplex stainless steels (DSSs) have excellent mechanical properties, owing to their austenitic-ferritic microstructure. The phase equilibrium strongly depends on solidification conditions and chemical composition, where elemental nitrogen significantly stabilizes the austenitic phase. When DSSs are processed by laser powder bed fusion (L-PBF) under an argon atmosphere, the rapid cooling rates result in an undesirable fully ferritic microstructure. To better understand the microstructure formation, this study examined the influence of the L-PBF process atmosphere on the porosity, microstructure, and mechanical properties of DSS AISI 318LN. Gaseous argon and nitrogen were used as a protective atmosphere, and specimens were analyzed in the as-built and post-processed conditions via optical and electron microscopy, electron backscatter diffraction, and tensile testing. Specimens processed under a nitrogen atmosphere showed a lower initial density in the as-built conditions, and tended to form more lack-of-fusion and gas pores compared to specimens processed under argon. The different defect types in nitrogen-processed specimens were still present after solution-annealing and quenching, leading to a 13% lower tensile strength and 43% lower elongation at fracture. Differences in phase equilibrium caused by the process atmosphere could not be established. All differences in porosity can be minimized by hot isostatic pressing, thus resulting in comparable mechanical properties of argon- and nitrogen-processed specimens.
Copper is a key material for cooling of thermally stressed components in modern aerospace propulsion systems, due to its high thermal conductivity. The use of copper materials for such applications requires both high material strength and high stability at high temperatures, which can be achieved by the concept of oxide dispersion strengthening. In the present work, we demonstrate the oxide reinforcement of two highly conductive precipitation-strengthened Cu-Cr-Nb alloys using laser additive manufacturing. Gas-atomized Cu-3.3Cr-0.5Nb and Cu-3.3Cr-1.5Nb (wt.%) powder materials are decorated with Y<sub>2</sub>O<sub>3</sub> nanoparticles by mechanical alloying in a planetary mill and followed by consolidation by the laser additive manufacturing process of laser powder bed fusion (L-PBF). While dense specimens (>99.5%) of reinforced and nonreinforced alloys can be manufactured, oxide dispersion-strengthened alloys additionally exhibit homogeneously distributed oxide nanoparticles enriched in yttrium and chromium next to Cr<sub>2</sub>Nb precipitates present in all alloys examined. Higher niobium contents result in moderate increase of the Vickers hardness of approx. 10 HV0.3, while the homogeneously dispersed nanometer-sized oxide particles lead to a pronounced increase of approx. 30 HV0.3 in material strength compared to their nonreinforced counterparts.
Prezada comunidade científica, é com muito prazer que comunicamos que em 2021, a revista Exacta iniciou a publicação online com DOI dos artigos aceitos com o objetivo de agilizar as publicações para a comunidade científica. Com isso, os artigos aceitos são publicados online após a aceitação responsivamente antes do processo editorial. Os artigos aceitos são elencados em um repositório na página intitulado “Publicações online”.
Após ocorrer a publicação online com DOI os artigos são enviados para o processo editorial. Os artigos ficam no repositório “Publicações online” até que os artigos editados sejam publicados.
Em seguida, os artigos editados são excluídos do repositório “Publicações online” para compor o volume e número conforme o período normal de publicação, que consiste na publicação por volume (ano): número 1 de (jan./mar.), número 2 de (abr./jun.), número 3 de (jul./set.), e número 4 de (out./dez.).
Ressalta-se que mesmo após a publicação final no respectivo volume (ano) e número, os artigos continuam com acesso aberto visando contribuir com a comunidade científica.
Production management. Operations management, Production capacity. Manufacturing capacity
Ramy Hussein, Ahmad Sadek, Mohamed A. Elbestawi
et al.
In this paper, the tool wear mechanisms for low-frequency vibration-assisted drilling (LF-VAD) of carbon fiber-reinforced polymer (CFRP)/Ti6Al4V stacks are investigated at various machining parameters. Based on the kinematics analysis, the effect of vibration amplitude on the chip formation, uncut chip thickness, chip radian, and axial velocity are examined. Subsequently, the effect of LF-VAD on the cutting temperature, tool wear, delamination, and geometrical accuracy was evaluated for different vibration amplitudes. The LF-VAD with the utilization of minimum quantity lubricant (MQL) resulted in a successful drilling process of 50 holes, with a 63% reduction in the cutting temperature. For the rake face, LF-VAD reduced the adhered height of Ti6Al4V by 80% at the low cutting speed and reduced the crater depth by 33% at the high cutting speed. On the other hand, LF-VAD reduced the flank wear land by 53%. Furthermore, LF-VAD showed a significant enhancement on the CFRP delamination, geometrical accuracy, and burr formation.
This paper reports on a dual-axial tool servo diamond turning method for the one-step fabrication of hierarchical micro-nano-structured surfaces. With respect to the dual-axial servo motion (XZ), the <i>z</i>-axis motion can generate the primary surface with a complex shape, and the <i>x</i>-axis motion is used to synchronously form the secondary structure via controlling the residual tool marks. The toolpath determination algorithm for the developed turning method is described in detail, and the effect of the machining parameters on the basic feature and sizes of the generated secondary structures is investigated through conducting the numerical simulation for both toolpath and surface generation. The simulation result indicates that the additional <i>x</i>-axial motion is effective for the deterministic generation of a variety of secondary structures. Finally, taking advantage of an ultra-precision lathe with a self-developed tri-axial FTS, a hierarchical surface with high accuracy is practically generated.
Ultrasonic welding of titanium alloy Ti6Al4V to carbon fibre reinforced polymer (CFRP) at 20 kHz frequency requires suitable welding tools, so called sonotrodes. The basic function of ultrasonic welding sonotrodes is to oscillate with displacement amplitudes typically up to 50 µm at frequencies close to the eigenfrequency of the oscillation unit. Material properties, the geometry of the sonotrode, and the sonotrode tip topography together determine the longevity of the sonotrode. Durable sonotrodes for ultrasonic welding of high-strength joining partners, e.g., titanium alloys, have not been investigated so far. In this paper, finite element simulations were used to establish a suitable design assuring the oscillation of a longitudinal eigenmode at the operation frequency of the welding machine and to calculate local mechanical stresses. The primary aim of this work is to design a sonotrode that can be used to join high-strength materials such as Ti6Al4V by ultrasonic welding considering the longevity of the welding tools and high-strength joints. Material, sonotrode geometry, and sonotrode tip topography were designed and investigated experimentally to identify the most promising sonotrode design for continuous ultrasonic welding of Ti6AlV4 and CFRP. Eigenfrequency and modal shape were measured in order to examine the reliability of the calculations and to compare the performance of all investigated sonotrodes.