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Arc plasma flow between electrodes has been investigated in several studies. However, in the industrial field, arc plasma flow between electrodes is hindered by interfering materials such as filler metal in arc welding, substrates in chemical vapor deposition, and powders in sintering. Therefore, in this study, high temperature arc plasma flow analysis via three obstruction structure shapes was performed to understand the inter-electrode interference phenomena. COMSOL Multiphysics was used for the analysis; COMSOL interface such as electric field, magnetic field, heat transfer, and fluid flow (laminar flow) was applied and Multiphysics such as plasma heat source and temperature coupling were considered. The temperature and velocity of the arc plasma were determined and the energy transfer between the electrodes was analyzed. We confirmed that the concave shape has a lower average heat flux than the other shapes, with the arc pressure evenly distributed in the anode. It is concluded that the concave shape can reduce the flow of the plasma from the anode and obtain even distribution of the arc plasma in the radial direction.

Terahertz waves (T-ray) were extensively studied for the nondestructive evaluation of the characterization of trailing edges composed with composite materials. The NDE system consisted of both continuous wave (CW) and time domain spectroscopy (TDS). The FRP composites were utilized for both trailing edges of wind energy (non-conducting polymeric composites) and carbon fiber composites with conducting properties. The signals of T-ray in the TDS mode almost resembles that of ultrasound waves; however, a terahertz pulse could not penetrate a material with conductivity, unlike ultrasound. The refractive index (n) was utilized as one of the material properties, so a method was suggested to obtain the “n” in the materials. The data of refractive index (n) were utilized due to obtained data for the trailing edges. The trailing edges were scanned for charactering and inspecting. C-scan and B-scan images were obtained and the optimal NDE techniques were suggested for complicated geometry samples by terahertz radiation. In particular, the penetrating time-of-flight (TOF) of T-ray corresponded with the calculated TOF for the trailing edges with greater thickness (about 70 mm).

Artificial liquid-repellent surfaces inspired by biomimetic structures provide a wide range of functional surfaces for various practical applications, such as self-cleaning, antisticking, oil/water separation, and droplet manipulation. However, functional biomimetic structures cannot be fabricated using conventional techniques. For example, mushroom-like topologies on the skin of springtails, which are referred to as "doubly reentrant structures," have attracted significant attention owing to their extraordinary liquid-repellent properties. Current methods of fabricating these reentrant structures have several limitations, such as complex material systems, processing steps, and additional chemical treatments. This study proposed a simple micro-shape-deformed approach to fabricate mushroom-like reentrant structures by digital light processing, a three-dimensional (3D) printing technique, with volumetric shrinkage. The nonuniform cross-linking process and light propagation during photopolymerization caused the deformation of the topological patterns atop the micropillar arrays, resulting in bent structures for mushroom-like shape-deformed microarchitectures. This 3D-printed shape-deformed microstructure exhibits a highly stable liquid repellency without perfluorinated coatings.

Terahertz wave (T-ray) technologies have become a popular topic in scientific research over the last two decades, and can be utilized in nondestructive evaluation (NDE) techniques. This study suggests an optimal scanning technique method for honeycomb sandwich composite panels, where skins were utilized with two different skins, namely, carbon fiber-reinforced plastic (CFRP) skin and glass fiber-reinforced plastic (GFRP) skin, as layers of the panel surfaces. Foreign objects were artificially inserted between the skins and honeycomb cells in the honeycomb sandwich composite panels. For this experiment, optimal T-ray scanning methods were performed to examine defects based on the angle between the one-ply thin fiber skin axis and the angle of the electric field (E-field) according to the amount of conductivity of the honeycomb sandwich composite panels. In order to confirm the fundamental characteristics of the terahertz waves, the refractive index values of the GFRP composites were experimentally obtained and analyzed, with the data agreeing with known solutions. Terahertz waves (T-rays) were shown to have limited penetration in honeycomb sandwich composite panels when utilized with a skin of carbon fibers. Therefore, T-rays were found to interact with the electrical conductivity and electric field direction of honeycomb sandwich composite panels with glass fiber skins. The T-ray images were obtained regardless of the electric field direction and the fiber direction. In the honeycomb sandwich composite panels with carbon fiber skins, the T-ray images with higher signal-to-noise (S/N) ratios depended on the scanning angle between the angle of the carbon fiber and the angle of the electric field. Thus, the angle of optimum detection measurement was confirmed to be 90&deg, between the E-field and the fiber direction, particularly when using a carbon fiber skin.

Drilling work on Inconel, a well-known super-heat-resistant alloy, requires a significant quantity of cutting oil to prevent heat-induced abrasion and damage to the cutting tool, caused by the strength and toughness of the alloy. This high requirement of cutting oil, however, negatively affects the processing environment, therefore, minimum-quantity lubrication (MQL), an eco-friendly cutting-oil-supply method, is attracting attention. The conventional MQL method, however, has the disadvantage that an oil-mist is produced along with high-pressure air, hence, the mist is scattered in the air, making the application of the oil to the cutting point inefficient and rendering the cooling effect to be less than that in wet processing. In this study, therefore, an eco-friendly compound, polyhedral oligomeric silsesquioxane (POSS)&mdash, a nanostructured organic&ndash, inorganic hybrid material that exhibits better adhesion to materials than conventional MQL-specific oil and is resistant to the heat generated during drilling&mdash, was developed by adding POSS to the conventional MQL-specific oil, and the effects were verified.

When the metal is melted by an arc plasma heating, convective flow is generated in the molten metal zone by various drag forces. The state of arc plasma used in this process is dependent on the current, voltage, shielding gas, and the evaporated component of the base material also affects the arc plasma. In this study, we show that oxygen content of the anode material affects the constriction of the arc plasma and changes the flow of molten metal by experiment and numerical analysis. First, after the generation of the arc plasma on ferritic stainless steels, which had different oxygen content and all other components were the same, the size of the arc plasma was compared by captured image using high speed camera. This size can be deduced from the brightness of the image, and it can be seen that the sizes of the two plasmas are slightly different from each other. Numerical simulation was carried out to confirm that these differences could affect the flow of the molten metal and final weld bead shape. As a result, the flow of the molten metal was completely different even with this slight change of plasma shape. These differences in molten metal flow was also observed in an experiment using a high speed camera. This change in flow can be explained by the interpretation that the Lorentz force is strengthened by the constriction of the arc plasma and the magnitude of the Marangoni force is increased by the increasing of thermal gradient. In conclusion, it was clearly confirmed that the oxygen content in the anode material affects the size of the fusion zone during arc plasma heating.

Due to their superior thermal and mechanical properties, super alloys widely used in the aerospace industry have been well-documented in terms of AdvantEdge-based analysis of cutting characteristics rather than experimental methods. However, the well-known super alloy Inconel 601 does not have any database of its material properties in AdvantEdge, which underscores the urgency to build such a database. Hence, the current study uses the Johnson-Cook equation to build a database of Inconel 601’s material properties in AdvantEdge. To that end, drawing on a room temperature tensile test, elevated temperature tensile test and orthogonal cutting test, the current study determines the Johnson-Cook constitutive equation for Inconel 601, and verifies the reliability of the determined Johnson-Cook constitutive equation by comparing the experimental values with the analytical values.

Research on additive manufacturing (AM) is being actively conducted in various fields in order to efficiently manufacture complex three-dimensional structures. In particular, metal powder feedstock and lasers are being used by the manufacturing industry to fabricate mechanical components and parts, such as propellers, fuel nozzles, and vehicle equipment. We developed an approach, scanning- directed energy deposition (S-DED), in which a high-throughput DED method with a scanning nozzle was established that could create metal beads of exceptional quality with high productivity using metal powder. The S-DED nozzle was designed based on a numerical simulation of the particle fluid flow, which was verified through a deposition experiment. Before the simulation, the deposition efficiency and shape of the bead were assumed according to the shape of the nozzle and the distance between the nozzle and the surface of the base material. The optimal inlet supply angle was determined by changing the powder flow inside the nozzle; the optimal number of outlet channels was determined by analyzing the amount of powder deposited by the laser beam irradiated on the base material. It was found that the laser beam improved the productivity by shaping the existing Gaussian beam into an 8 × 3 square flat-top beam. As a result of the simulation, it was proved that the angle of the inlet (that supplied powder to the nozzle) influenced the flow of powder finally captured in the laser beam. Based on the simulation, the angle of inlet was selected as 75°, and the number of outlet and cooling channels was five and three, respectively. A cross section of the specimen was analyzed using a single bead and multiple layers.

The mechanism for the promoted formation of equiaxed ferrite grains during rapid solidification has been investigated in the gas‑tungsten arc welds of a newly developed ferritic stainless steel. The preferential nucleation of ferrite at the interface of TiN encapsulating MgAl2O4 spinel compound was observed in the developed steel showing a higher potential to form TiN-MgAl2O4 complex inclusions. The epitaxial alignment of 110 ferrite / / 31 1 _ TiN and 01 1 _ ferrite / / 02 2 _ TiN was first found, which is different from Kurdjumov-Sachs, Nishiyama-Wasserman and Baker-Nutting relationships. The faceted interfaces to keep the epitaxy is energetically favored, which may reduce the activation barrier for the formation of ferrite. A finite element model calculation of heat transfer was used to examine the role of heterogeneous nucleants as well as the local thermal condition. The developed steel is predicted to have 1.4 times more heterogeneous nucleants than the conventional steel.

In 4D printing, a target 3D object that can self-transform or self-assemble over time is created using a printer with smart materials. Since the advent of 4D printing, much research has been conducted on smart materials and application of 4D printing in diverse areas. However, research and development of 4D printing software is very limited due to the fact that 4D printing technology is still a novelty. Nevertheless, the time characteristics of 4D printing require appropriate 4D printing software to produce effective 4D printing outputs. In this article, we first introduce 4D printing technology and discuss its application in various fields. Then, we focus on the software required for 4D printing. More specifically, we present six types of software solutions needed to fully support corresponding stages in the 4D printing process: simulation, modeling, slicing, host/firmware, monitoring, and printing management software (PMS), respectively. We discuss how each software solution can sufficiently carry out the designated functions at each stage of the 4D printing process and propose that these software solutions can together provide all of the required operations for 4D printing.

Wire grid polarizer has high extinction ratio, brightness, excellent durability and large acceptance angle of light. The interest in grid-type polarizer has maintained continuously over recent decades since it can cover from ultraviolet to terahertz range. As nanotechnology advances, size, shape and material of wire grid can be controlled by various fabrication processes. A review of fabrication, materials, simulation schemes and new designs of wire grid polarizer is presented. Additionally, research trend of wire grid polarizers in terahertz time domain spectroscopy is addressed.

For many years, scientists have been aware of the importance of terahertz waves (T-rays), which have now emerged as an NDE (nondestructive evaluation) technique for certain ranges of the electronic spectrum. The present study deals with T-ray scanning techniques of honeycomb sandwich composite panels with a carbon-fiber-reinforced plastic (CFRP) skin as well as the refractive index (n), and the electrical conductivity (&alpha, ) of glass fiber-reinforced plastic (GFRP) composites. For this experiment, the degree of penetration to FRP composites is investigated for the THz transmitted power based on the angle in the electric field (E-field) direction vs. the direction of the unidirectional carbon fibers. Also, when CFRP skin honeycomb sandwich panels are manufactured for use in aerospace applications, aluminum wires are twisted together into the one-sided surface of the honeycomb sandwich panels to protect against thunderstorms. The aluminum wires are partly visible because they are embedded in the CFRP skin on the honeycomb sandwich panels. After finishing work with a paintjob, the wires become invisible. Thus, detecting the aluminum wires is a key issue for product monitoring. Based on a simple resistor model, an optimal scanning method is proposed to determine the preferred scan orientation on the baseline of the E-field in the direction of fibers to evaluate the level of transmission of T-rays according to the frequency bandwidth. Thus, the combination of angles required to detect the aluminum wires embedded with carbon fibers on the surface of the composite panels can be determined.

In gas tungsten arc welding (GTAW), columnar grains typically grow from the fusion line of a weld to its centerline because of high temperature gradient and small growth rate. This columnar grain often causes premature failure during bending or expansion in the center of the fusion zone. Equiaxed grains, on the other hand, reduce the occurrence of cracks and improve the ductility, strength, and toughness in the fusion zone. Microstructural solidification has a significant effect on the mechanical properties; the columnar-to-equiaxed grain transition (CET) is one factor that significantly improves fusion zone mechanical properties. During GTAW, a thermal gradient occurs on a molten pool owing to the uneven mixing of the elements or the unequal compositions of the base materials, leading to a non-uniform surface tension. This is called the Marangoni effect, which creates a flow inside the molten metal and affects the overall weld shape. The Marangoni effect is associated with a coefficient called the surface tension gradient or the thermal gradient of surface tension that affects the direction of molten metal flow. The content of oxygen and flux affect the surface tension gradient. If the content of oxygen and flux are high, the surface tension gradient becomes positive, with a narrow and deep-penetrating pool. In this study, various experiments and a numerical simulation were performed to analyze the weld pool behavior and CET in GTA welding of ferritic stainless steels with aluminum contents of 100 and 300 ppm. In the experiment, 300 ppm of aluminum was observed to have a wider bead width than that observed for the 100-ppm sample; further, the growth of equiaxed grains in the centerline was promoted. In the numerical simulation, it was confirmed that when the aluminum content was 300 ppm, the outward flow occurring in the arc center formed a wide and shallow penetration. Furthermore, it was revealed that aluminum combines with oxygen to form aluminum oxide, thereby reducing the oxygen content. Therefore, as the aluminum content increased, the surface tension gradient was observed to become negative and affect CET.

Recently, aluminum alloy has used various industry, such as automobile, shipbuilding and aircraft because of characteristics of low density and high corrosion resistance. Al 6061-T6 is heat treatment materials so it has high strength and mostly used for assembly by mechanical fastening such as a bolting and riveting. In GMA (Gas Metal Arc) welding of alloy, some defects which are hot cracking, porosity, low-mechanical properties and large heat affected zone is generated, because of high heat conductivity. It reduces mechanical properties. In this study, the major factor effected on properties are analyzed after welding in Al 6061-T6 in GMAW, then optimize heat treatment conditions. Plate of Al 6061-T6 with a thickness of 12 mm is welded in V groove and applied welding method is butt joint. Mechanical properties and microstructure are analyzed according to heat treatment condition. Tensile strength, microstructure and Hardness are evaluated. Result of research appears that Al 6061-T6 applied heat treatment show outstanding mechanical properties.

Wire grid polarizers often have reflective characteristics, such that some incident light is transmitted through the polarizer, while the rest is reflected. For some applications, such as anti-reflective films in OLEDs, non-reflective (or absorptive) wire grid polarizers are necessary; these can be realized by the deposition of an absorptive material on the nanoscale metal wire grid. However, because this deposited absorptive layer can severely affect the polarization characteristics, its material must be selected carefully. The polarization characteristics of a given nanowire grid polarizer can be simulated using rigorous coupled-wave analysis (RCWA). In this study, several types of metal oxides and nitrides were tested as candidate materials for the absorptive layer of a non-reflective polarizer. Nanopatterned double layers with absorptive and reflective functions were modeled using RCWA. Simulations were conducted for various pattern widths, depths, and periodicities. CuO and Fe3O4 showed optimal polarization characteristics among the simulated absorptive layers. Simulations indicated that the performance of non-reflective wire grid polarizers could be enhanced using CuO or Fe3O4. The design of absorptive polarizers was fully characterized by simulation for future experimental research.

Several industries including the automotive industry have recently applied the process of welding high-strength steel for their requirements. Ultra-high-strength steel is harder than normal high strength steel; it is considerably much stronger and stiffer. In particular, ultra-highstrength steel (UHSS) can be formed in pieces that can be up to 10 to 15% thinner than normal steel without sacrificing strength, which enables weight reduction and improved fuel economy in automobiles. Furthermore, UHSS can be formed into complex shapes that can be welded into structural areas. This study is based on previous experiments and is aimed at establishing the maximum allowable vertical and longitudinal loads for stitch-welded ultra-high-strength steel in laser-arc hybrid welding. Research on the stress distribution and maximum allowable load and for stitch-welded ultra-high-strength steel is conducted via Solid-Works, a program that analyzes the stress of a virtual model. We determine that the maximum allowable load and stress distribution vary depending on the shape of the welded lap joint. The effects of the stress distribution and maximum allowable load on stitch-welded ultra-high-strength steel can be utilized as a standard for high energy welding of ultra-high-strength steel, and we can further predict fault regions in the stitch-welded.

Manufacturing paradigms have historically been shaped by social, economic, and technological aspect, including limitations and needs. Design for manufacturing (DFM) has been the main paradigm for last three decades since design is defined by the limitations of available manufacturing processes. Since reducing the time required for the development of new products has been one of the key issues for businesses, removing the gap between designers and manufacturers has been one of today’s main goals. Many methods were developed to reduce this gap including information and communication technologies (ICT). However, current issues have been shifting towards design-related issues such that researchers have been trying to make products desired by the customers rather than that which is cheaper to manufacture. In this article, hybrid manufacturing (HM) and the concept of smart factory are introduced as key technologies for the future paradigm of manufacturing: Manufacturing for Design (MFD). Issues related to the development of HM process and examples of HM process are explained, and the importance of smart factories for the implementation of MFD is shown. Finally, future trends of HM and smart factory are predicted at the end of this article.

Microstructures present on surfaces can change the surface properties of a material. In this study, various patterns – and arrangements of those patterns in different shapes – were designed in order to analyze the associated differences in surface properties related to superhydrophobicity. We categorized these surface microstructures into three different groups of patterns: (1) pillar, (2) wall, and (3) wall–pillar; and four shapes of pattern arrangement: (1) triangular, (2) square, (3) hexagonal, and (4) octagonal. Pillar-pattern microstructures exhibit a small water-contact area and the wall-pattern structures contain interconnected pillars, and as a result, an air layer is trapped when the structure comes into contact with water. Wall–pillar pattern microstructures exhibit characteristics of both walls and pillars. For the different patterns, Si master molds were used to fabricate structures from a UV-curable polyurethane acrylate resin. Measured contact angles for 5 μl water droplets on the patterned surfaces were compared according to shape, pattern, and pitch, and the pattern exhibiting the highest contact angle was further investigated.

Additive manufacturing techniques are used to fabricate functional microstructures with customised mechanical and chemical properties. One common technique is projection microstereolithography, which has recently been developed to support smaller features, larger build areas, and/or faster speeds. The limitation of such systems is that they typically utilise a single-aperture imaging configuration, which restricts their ability to produce microstructures in large volumes owing to the tradeoff between image resolution and image field area. In this paper, we propose an integral lithography technique based on integral image reconstruction coupled with a planar lens array. The individual microlenses in the planar lens array maintain a high numerical aperture and are employed to create digital light patterns that can expand the printable area by the number of microlenses (10^3-10^4). The proposed lens array-based integral imaging system can simultaneously scale up and scale down incoming image fields, thereby allowing for the scalable stereolithographic fabrication of three-dimensional features that surpass the resolution-to-area scaling limit. We extend the printing capability of integral lithography to fabricate deterministic nonperiodic structures through the rotational overlapping or stacking of multiple exposures with controlled angular offsets. The proposed system provides new possibilities for producing periodic and deterministic aperiodic microarchitectures spanning four orders of magnitude from micrometres to centimetres. These microarchitectures can be applied to biological scaffolds, chemical reactors, functional surfaces, and metastructures.

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing challenge in the field is the fabrication of hybrid micro-nano structures using a facile, cost-effective, and high-throughput method. To overcome these challenges, this paper proposes a protocol to fabricate multiscale structures using only an imprint process with an anodic aluminum oxide (AAO) filter and an evaporative self-aggregation process of nanofibers. Unlike previous attempts that have aimed to straighten nanofibers, we demonstrate a unique fabrication method for multiscale aggregated nanofibers with high aspect ratios. Furthermore, the surface morphology and wettability of these structures on various liquids were investigated to facilitate their use in multifunctional surfaces.