Metal Beads Research Articles

Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder

In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.

Comparative study on visual fatigue caused by watching liquid crystal display and projection display

Objective: To explore the effect of different types of visual display terminals (VDT) on visual fatigue. Methods: A total of 68 subjects were enrolled and divided into flat screen group, metal screen group and glass bead screen group. The subjects watched a video in the same environment for 60 minutes. Before and after watching, they were asked to fill in a visual fatigue rating scale and underwent visual function examinations. The blink rate of subjects was recorded during the experiment. Results: After watching the video, for the metal screen, glass bead screen, and flat screen group respectively: (1)The median (interquartile range, IQR) of visual fatigue rating increased significantly (before: 1.0 (1.2), 1.3 (1.6), 0.5 (0.9); after: 2.1 (1.9), 2.1 (1.7), 1.2 (1.0); Z=-4.72, -4.83, -3.75; all P<0.05). (2) The median (IQR) of blink frequency increased significantly (before: 11.5 (10.6), 15.3 (11.9), 7.0 (13.0) times/minute; after: 15.0 (13.0), 17.0 (16.0), 15.0 (12.0) times/minute; Z=-2.64, -2.74, -4.12; all P<0.05). (3) The mean (±standard deviation) of critical flicker fusion frequency (CFF) decreased significantly [before: (35.76±2.98), (35.84±2.79), (35.44±2.21) Hz; after: (35.09±2.78), (34.94±2.67), (34.57±2.33) Hz; t=-2.64, -2.38, -4.12; all P<0.05). (4)The median (IQR) of near point of convergence (NPC) became significantly larger [before: 3.9 (2.6), 4.0 (2.5), 4.3 (2.7) cm; after 5.4 (3.8), 4.8 (2.7), 6.1 (3.9) cm; Z=-3.39, -2.27, -3.36; all P<0.05]. (5)The median of negative relative accommodation (NRA) reduced significantly [before: 2.00 (0.50), 2.00 (0.56), 2.00 (0.25) cm; after 1.75 (0.50), 1.75 (0.25), 1.75 (0.50) cm; Z=-1.98, -2.09, -2.53; all P<0.05]. Meanwhile, no significant changes were found for the positive relative accommodation (PRA), accommodative amplitude, accommodative response, negative relative vergence in all groups after watching the video. The comparisons between the three groups showed that, after watching the video, the participants in the two kinds of projection screen group (the metal and glass bead screen group) had more subjective visual fatigue than those in the flat screen group respectively (Z=-2.09, -2.21; all P<0.05), while there was no significant difference in subjective visual fatigue between the two projection screen groups (P>0.05). In addition, positive fusional vergence recovery point and break point decreased after watching the video in the metal screen and glass bead screen group, respectively (t=4.15, 2.07; all P<0.05). However, no such change was found in the flat screen group. Conclusions: Short-term and long-distance VDT operations have significant effects on visual fatigue, which may be due to the decreased positive convergence ability. VDT operations over projection screens may result in more visual fatigue than LED flat panel display, while the effect of different projection screen types have insignificant influences on visual fatigue. (Chin J Ophthalmol, 2019, 55:595-600).

Deciphering the conditions of tochilinite and cronstedtite formation in CM chondrites from low temperature hydrothermal experiments

AbstractTochilinite/cronstedtite intergrowths are commonly observed as alteration products in CM chondrite matrices, but the conditions under which they formed are still largely underconstrained due to their scarcity in terrestrial environments. Here, we report low temperature (80 °C) anoxic hydrothermal experiments using starting assemblages similar to the constituents of the matrices of the most pristine CM chondrite and S‐rich and S‐free fluids. Cronstedtite crystals formed only in S‐free experiments under circumneutral conditions with the highest Fe/Si ratios. Fe‐rich tochilinite with chemical and structural characteristics similar to chondritic tochilinite was observed in S‐bearing experiments. We observed a positive correlation between the Mg content in the hydroxide layer of synthetic tochilinite and temperature, suggesting that the composition of tochilinite is a proxy for the alteration temperature in CM chondrites. Using this relation, we estimate the mean precipitation temperatures of tochilinite to be 120–160 °C for CM chondrites. Given the different temperature ranges of tochilinite and cronstedtite in our experiments, we propose that Fe‐rich tochilinite crystals resulted from the alteration of metal beads under S‐bearing alkaline conditions at T = 120–160 °C followed by cronstedtite crystals formed by the reaction of matrix amorphous silicates, metal beads, and water at a low temperature (50–120 °C).

Technological estimation of skull effect on steel melting parameters in basic oxygen furnace

Increasing the lining life of basic oxygen furnaces (BOF) reduces the expenses for refractories. Application of skull lining layer on the working surface is a good way to improve the efficiency of refractories. Features of the application of slag skull by the method of blowing a slag from previous melt with gas jet are discussed in the paper. It is shown that the presence of skull on the surface of the oxygen converter working lining affects not only the campaign duration of the unit, but also the technological parameters of steel melting, connected with its slag and thermal conditions. To quantify this effect, calculations of melting indices were performed for the conditions of BOF shop of PJSC MMK using a mathematical model based on the balance-statistical equations of physicochemical and thermal processes of oxygen-converter steel smelting. Taking into account the fact, that the skull is involved in the process as an additional material, that introduces slag-forming components and physical heat, the corresponding article of the heat balance was added to the program for melting parameters calculating. Assessment of the change of the amount of slag in the BOF in the course of steelmaking, knowing the possible arrival of the components from skull, was carried out. The calculations results of the change of the of melt metal components mass from the percentage of skull in the BOF are presented. The dependence of the change of the consumption of charge components on the amount of skull in the BOF is presented. It is shown that with an increase of the skull amount for smelting of the same steel mass some increase of metal charge will be required. This fact can be explained by increased iron loss with oxides, metallic beads and additional oxygen consumption for oxidative refining of the melt.

Are hypervelocity impacts able to produce chondrule-like ejecta?

Chondrules are one of the major components of primitive meteorites. Their sphericity indicates they formed as molten fragments or droplets but conditions and mechanisms of chondrule formation remain unknown. A possible scenario is their formation during hypervelocity impacts and ejections. To challenge this idea, we prepared an experiment that reproduces analogous of iron metal -rich chondrules by impact between a glassy silicate projectile and a metallic steel target. The hypervelocity experiment setting allowed an impact velocity of 5 km/s, and was also designed to collect the ejecta. A scanning electron microscopy survey shows that silicate ejecta share several similarities with chondrules. They formed from a population of small melt fragments whose size distribution has the same shape as the size distribution of chondrules, with a shift in size: ejecta are about one order of magnitude smaller than typical chondrules (log(dchondrules/dejecta) = 1.3−0.7+0.5). We attribute this difference in size to the large discrepancy in the size of the impactors (only small 3 mm particle in our experiment versus km-scale planetesimal expected in an impact forming scenario for chondrules). The silicate ejecta formed in the ejecta plume contains numerous small size spherical iron metal beads. Such beads are also observed in numerous chondrules of CO chondrites specifically presented here but also documented in L and LL ordinary chondrites. Size distributions of metal beads in ejecta and chondrules of a carbonaceous chondrite used as reference material (Yamato 81020 CO) display a same shape but with a size shift, quite similar to the one observed between the ejecta droplets and the chondrules: the diameter of metal beads in ejecta is about one order of magnitude smaller than the diameter of the ejecta themselves (log(dejecta/dmetal beads in ejecta) = 1.2−0.8+0.9), and the diameter of metal beads in chondrules is about one order of magnitude smaller than the diameter of the chondrules themselves (log(dchondrules/dmetal beads in chondrules) = 1.4−1.0+0.6). We attribute this size differences to the blast dynamics: for a same velocity and surface tension, fragments of silicate liquid will be stable when iron liquid fragments of similar size will be separated into smaller droplets. In our experiment, the biggest iron metal beads (∼7 μm) are within the mean size range of silicate ejecta and can be considered as analogous of the rare large rounded metallic grains (nearly the same size as chondrules) documented in CB chondrites. The textural analogies exposed here provide support for a production of chondrules by impact.

Corrosion behavior of base metal and weld bead of CLAM steel in flowing Pb-Bi at 550 °C

Corrosion behavior of base metal and weld bead of China low activation martensitic (CLAM) steel was studied in the flowing Pb-Bi at 550 °C. The corrosion tests were performed in an apparatus which was designed and manufactured by ourselves and could simulate the condition of corrosion test in the nuclear industry. CLAM steel is one of the reduced-activation ferritic/martensitic steels (RAFM) that is widely considered as the candidate structural metal for the new generation nuclear facilities. The flow velocity, corrosion temperature and corrosion time were 2.98 m/s, 550 °C and 1500 h, respectively. The corrosion test results indicate that a double-layer oxide film consisted of Fe3O4 outer layer and (Fe,Cr)3O4 inner layer on surface of all the samples. The corrosion process of base metal and weld bead of CLAM steel in flowing liquid Pb-Bi included the oxidation-corrosion and erosion. The degree of oxidation-corrosion and erosion on the surface of the weld bead samples was more serious than that on the surface of the base metal, due the small grain size was related to greater corrosion resistance. The corrosion test results will provide a reference for the feasibility of the practical application of CLAM steel in the field of nuclear power in the future, and they will also provide data support for estimating the actual service life of CLAM steel.

Analysis of pressureless sintering of titanium diboride ceramics with nickel, cobalt, and tungsten carbide additives

The mechanisms during pressureless sintering of TiB2 with 0–50 wt.% Ni were analysed by differential dilatometry after mechanical alloying with hard metal beads. Three main stages of sintering could be identified by means of the changing dilatation rate. The first interval (200–600 °C) comprises reactions with oxygen and moisture (H3BO3, B2O3 formation, melting, evaporation). The second stage (600–700 °C) is governed by solid state sintering and reactions of Ni and/or Co with TiB2 yielding Ni3B, Ni2B, the corresponding Co-compounds and the ternary ω-phase of W2NiB2-type. The third main shrinkage interval is due to liquid phase sintering (987–1640 °C) and is accompanied by a significant weight-loss. Both precipitation of ω-phase as well as a (Ti,W)B2 solid solution in form of a core-shell structure are responsible for a grain growth retardation and the homogeneous microstructure. The results explain well all features reported in the corresponding literature while encountering the role of WC, too.

Optimization of current parameters during variable polarity GMAW of magnesium alloy

Magnesium alloy welding suffers from problems such as burn through and loss of alloying elements during conventional welding process due to high heat input. Variable polarity gas metal arc welding (VP-GMAW) features low heat input. Therefore, it is an attractive method for welding of magnesium alloy. However, the principles governing the correlations among welding current parameters, metal transfer modes, and bead formation are not well understood. Identifying optimal welding current parameters by trial and error is unrealistic. Therefore, peak current, base current, and negative current were selected as independent variables. Their impact mechanism on metal transfer and bead formation were investigated by experiments with high-speed photographs. Then, weld quality evaluation was conducted by a fuzzy comprehensive evaluation. A mathematical method was proposed to calculate optimal current parameters for VP-GMAW of magnesium alloy. In addition, a significant sequence of current parameters is obtained. The results indicate that almost defect-free weld joint is produced by the optimal welding current parameters. The significance sequence of current parameters on weld quality is negative current, peak current, and base current.

Microflow-mediated optical assembly of nanoparticles with femtogram protein via shrinkage of light-induced bubbles

Bottom-up processing of nanobiomaterials enables the creation of a variety of macroscopic structures in natural systems. Here, we use optical means to produce macroscopic-assembled structures of nanoparticles (NPs) from protein molecules by using light-induced bubble (LIB) generation under asymmetric pressure-driven flow in a microchannel. The broadband optical response of assembled NPs facilitates the application of photon pressure and photothermal convection when irradiated by using an infrared laser. The presence of a large amount of protein allows the generation of a vast number of stable LIBs from optically assembled metallic NP-fixed beads (MNFBs). In the case of more diluted albumin solutions, the shrinking of a single LIB can cause the aggregation of MNFBs via fg-level albumin (3.4 fg in the observation region), like a microscale bubblegum. The size of the resulting aggregate can be controlled by changing the concentration of protein. These findings can be used to devise production methods not only for broadband optical nanocomposites but also for label-free methods to detect an extremely small amount of protein.

Контроль положения наплавленного валика в процессе аддитивного формообразования по сигналу коллектора отраженных электронов

The urgency of solving the problem of determining the deposited layer’s height for control the process of additive forming products from metallic materials in a vacuum is substantiated. A scheme of electron beam additive manufacturing process with wire feed is shown. A method for control the distance between deposited bead and electron gun by the signal taken from collector of backscattered electrons is proposed. The analysis of the signals recorded during the process of deposited metal bead scanning has been carried out and technical feasibility of this method has been substantiated. The technical solutions to introduce a method for continuous monitoring and control of additive forming process are proposed.

Corrosion behavior of CLAM steel weld bead in flowing Pb-Bi at 550 °C

China Low Activation Martensitic (CLAM) steel was one of the Reduced-Activation Ferritic/Martensitic (RAFM) steels which were widely considered as the candidate structural metal for the new generation nuclear facilities. Flowing Pb-Bi corrosion tests of CLAM steel weld bead with Tungsten Inert Gas (TIG) welding were conducted in oxygen-saturated liquid Pb-Bi eutectic alloy at 550 °C for 500 h, 1000 h and 1500 h to study the effect of different flow velocities (1.70 m/s, 2.31 m/s and 2.98 m/s) and corrosion time on corrosion behavior. The results indicate that the double-layer oxide films consist of Fe3O4 outer layer and (Fe,Cr)3O4 inner layer on the surface of all samples. With the increase of relative flow velocity, the dissolution and migration of elements are faster, which leads the degree of corrosion to become more severe. In the corrosion process of CLAM steel weld bead in flowing liquid Pb-Bi, the oxidation-corrosion and erosion have happened. Meanwhile, the degree of erosion on the surface of weld bead samples was more serious than that of the base metal samples. The experiment has obtained the function between corrosion time and oxide layer thickness of CLAM base metal and weld bead in Pb-Bi with 2.98 m/s.

Hopewell Meteoritic Metal Beads: Clues to Trade 2,000 Years Ago

Hopewell Meteoritic Metal Beads: Clues to Trade 2,000 Years Ago

Variations in slice sensitivity profile for various height settings in tomosynthesis imaging: Phantom study

Understanding the properties of slice sensitivity profile (SSP), or slice thickness, is crucial for an accurate and highly reproducible diagnosis using tomosynthesis imaging. The objectives of the present study are therefore to quantitatively evaluate how the SSP with the use of a small metal bead is affected by different settings of the height from the table and the height of the center of rotation (COR) in tomosynthesis imaging except for the digital breast tomosynthesis, and visually verify the effects on tomosynthesis images. The reconstruction filters used were three types of filtered back-projection and iterative reconstructions. The SSP was measured from the full width at half maximum (FWHM-SSP) of the profile curve of the bead in the perpendicular direction (z direction) relative to the table. Two types of anthropomorphic phantoms simulating the human body, with bones and soft tissues, were used to study the effects of different settings for the COR height. In all reconstruction filters, the FWHM-SSP changed as the height of the bead varied when the bead and COR were set to the same height from the table. If the bead and the COR were set to different heights, the FWHM-SSP increased (decreased) when the height of the bead was set to be greater (less) than the height of the COR. These changes were also confirmed on the anthropomorphic phantom images of the bones and soft tissues.

Potential use of Fe isotopes for ancient non-ferrous metals tracing through the example of a lead-silver production site (Imiter mine, Anti-Atlas, Morocco)

Determining the provenance of non-ferrous metals is a major issue in archaeology and history. The classical method using Pb isotopes shows several limitations, and new isotopic tracers need to be developed in archaeometallurgy. Recently, Fe isotopes were found to be promising for iron metal tracing. In this context, we evaluated the pertinence of Fe isotopes as a new tool for provenance studies of non-ferrous metals. We collected slag and furnace lining samples from the Imiter silver mine in Morocco (Anti-Atlas), where many archaeological remains attest ancient lead-silver production. Their mineralogical composition was investigated by optical microscopic observations, SEM-EDS and EPMA. Besides, we measured both Pb and Fe isotope compositions of these samples by high resolution MC-ICP-MS after wet sample decomposition and purification chemistry. The occurrence of Ag, Pb, Cu and Ag/Pb metallic beads in the slag samples and their high Fe content suggests that these metallurgical materials result from the exploitation of Ag-rich polymetallic ores associated with gossan formations. Isotopic analyses of these slags highlighted their heterogeneous Pb isotope compositions and homogeneous Fe isotope composition. This points to the exploitation of two distinct ore sources with different Pb but similar Fe isotope compositions, despite the Fe isotope variability often encountered in metallic ores worldwide. Hence, Fe isotopes provide a complementary approach to trace lead-silver products from Imiter. Overall, the combination of Pb and Fe isotope analyses constitutes a promising method for further provenance investigations of non-ferrous metals.

Removal of foreign objects from root canals- A Case Report

Foreign bodies in root canals are rarely seen, and usually objects are accidently lodged and broken in root canals by the patients themselves. The occurrence of a foreign body, such as a metal screw, staple pin, sewing needle, pencil lead, bead or toothpick in the root canal system, makes the eradication of microorganisms impossible. Due to difficulties of eradicating microorganisms, foreign bodies may become sources of infection. These objects must be removed. This case report describes a rare clinical case in which a sewing needle, inserted into the root canal by the patient, was removed the orthograde approach with the aid of ultrasonic devices.

Effect of Lateral Column Lengthening Calcaneal Osteotomy on Radiographic Measurements of Foot Alignment

Category: Hindfoot Introduction/Purpose: Lateral column lengthening (LCL) with calcaneal osteotomy has been increasingly used for reconstruction in flexible flat foot reconstruction. The aims of this study were to 1) evaluate the effects of variably sized LCL blocks on the restoration of alignment in an acute flat foot cadaveric model; 2) create a computer algorithm to more objectively measure foot alignment; and 3) develop an acute flat foot model that does not require cyclic loading for creating a type IIB flat foot. Determining if overcorrection with lateral column lengthening can occur would provide guidance surgeons to avoid lateral column overload. A computer guided measurement program could make studies more comparable. An acute flat foot model would clarify the ligament deficiencies necessary to create a type IIB flat foot. Methods: A type IIB flat foot model was used in which the medial and medial-plantar fibers of the calcaneonavicular (CN), the interosseous talo-calcaneal (ITCL) and the cervical (CL) ligaments were transected. Metallic markers were placed in the PF origin. 3D weightbearing CT scans were obtained with the specimens in a custom jig that permitted loading with 100 lbs. (445 N). The jig allowed full pronation under load. Scans were obtained: intact, flat, and with 6, 8 and 10 mm LCL blocks. Simulated AP and lateral radiographs were created using a custom MATLAB program. A custom ImageJ plugin was created which guided measurement of Meary’s angle, naviculo-cuneiform overlap, AP talo-first metatarsal angle, and a novel plantar fascia (PF) distance and PF angle. The program automatically calculated midpoints and perpendicular lines from guided user input. Four observers performed all measurements in blinded and randomized fashion on two occasions greater than 12 weeks apart. Results: The ligament sectioning model reliably produced a type IIB flat foot as noted by talo-navicular sag, increased talar head uncovering (forefoot abduction) and divergence of the talus and calcaneus as seen on the AP weightbearing view (Figure 1). Cyclic loading was not required in any specimens and the remaining medial column ligaments were not sectioned. Intraobserver and interobserver comparisons indicated naviculo-cuneiform overlap and plantar fascia distance had excellent interobserver agreement and Meary’s and plantar fascia angle had good interobserver agreement (Figure 1). Lateral column lengthening trended toward overcorrection at 10 mm suggesting a possible threshold for over-correction. Conclusion: The trend toward overcorrection with 10 mm LCL may indicate a threshold for lateral column overload. Computer guided measurement may improve consistency when comparing studies. The PF measurements are not possible in vivo. The use of a heel centering ring might be a surrogate for the implanted metallic beads. The CL sectioning was essential for creating type IIB flat foot without cyclic loading. The CL has been noted to be a main subtalar stabilizer, but has not entered into mainstream discussions regarding flat foot. Changes that occurred with cyclic loading performed in other flat foot studies have not been defined.

Impact‐induced chemical fractionation as inferred from hypervelocity impact experiments with silicate projectiles and metallic targets

AbstractHypervelocity impacts are common in the solar system, in particular during its early phases when primitive bodies of contrasted composition collided. Whether these objects are chemically modified during the impact process, and by what kind of processes, e.g., chemical mixing or gas–liquid–solid fractionation, are still pending questions. To address these issues, a set of impact experiments involving a multielemental doped phonolitic projectile and a metallic target was performed in a 3–7 km s−1 range of impact speeds which are typical of those occurring in the asteroid belt. For each run, both texture and chemistry of the crater and the ejecta population have been characterized. The results show that the melted projectiles largely cover the craters at all speeds, and that melted phonolitic materials are injected into fractures in the crater in the metallic target. Ejecta are generally quenched droplets of silicate impact melt containing metal beads. Some of these beads are extracted from the target, but we propose that some of the Fe metal beads are the result of reduction of FeO. A thin FeO‐SiO2‐rich condensate layer is found at the edge of the crater, suggesting that a limited amount of vapor formed and condensed. LA‐ICP‐MS analyses suggest, however, that within analytical uncertainties, no volatility‐controlled chemical fractionation of trace elements occurred in the ejecta. The main chemical fractionation during impact at such velocities and energies are the result of projectile‐target mixing.

Simulating direct shear tests with the Bullet physics library: A validation study.

This study focuses on the possible uses of physics engines, and more specifically the Bullet physics library, to simulate granular systems. Physics engines are employed extensively in the video gaming, animation and movie industries to create physically plausible scenes. They are designed to deliver a fast, stable, and optimal simulation of certain systems such as rigid bodies, soft bodies and fluids. This study focuses exclusively on simulating granular media in the context of rigid body dynamics with the Bullet physics library. The first step was to validate the results of the simulations of direct shear testing on uniform-sized metal beads on the basis of laboratory experiments. The difference in the average angle of mobilized frictions was found to be only 1.0°. In addition, a very close match was found between dilatancy in the laboratory samples and in the simulations. A comprehensive study was then conducted to determine the failure and post-failure mechanism. We conclude with the presentation of a simulation of a direct shear test on real soil which demonstrated that Bullet has all the capabilities needed to be used as software for simulating granular systems.

The Aesthetic values of bead handicrafts inspired by Saudi heritage in Taif Governorate ornamentations utilized in design on the dress form

Beadwork are one of the traditional handicrafts since ancient times, which reflects people’s customs, traditions, and cultures. Beads have been used aesthetically to embellish traditional dresses, garments, and accessories in the Kingdom of Saudi Arabia using regular or irregular decorative embellishments including straight, parallel, intersecting lines or ornamental triangular or square shapes. Several villages in the south of Taif province, including Bani Malik, Belharith, and Bani Saad, have been famous for Embroidery and ornamentation traditional dresses with colored crystal or metal beads. This theme has motivated the researcher to explore ways of using beads to create a variety of modern embroidery inspired by the aesthetic and popular heritage, and ways of taking advantage of beadwork in designing fashion using by design on the dress form. Objectives: identify the artistic features and aesthetic values of the traditional beadwork ornamentations in Taif province, Kingdom of Saudi Arabia, and to take inspiration from traditional Saudi decorative beadwork heritage to create modern artistic beadwork. Furthermore, it aims to make use of the artistic characteristics and decorative embroidery beadwork to design women’s night dresses (for ages between 20 – 30), using the design on the dress form to revive heritage and protect it from disappearing or identity loss, by giving these historical beadworks a modern touch. The importance of the study The documentation of the handicrafts of woven beads and the revival of handicrafts, which are characterized by artistic creativity in a modern style. Methodology: The research followed the analytical descriptive approach along with the applied study through the analysis and characterization of the traditional beadwork. The experimental part of this study includes a beadwork design and making use of its aesthetics by presenting fifteen designs. The results showed a statistical difference in terms of aesthetic and functional aspects, at a significance level of (0.00), among the designs proposed by specialists. The findings also show a statistical difference in terms of aesthetic and functional aspects, at a significance level of (0.00), among the designs suggested by female customers, and these differences came in favor of the second design, which ranked first position among the designs proposed in both the aesthetic and functional aspects by the research sample (specialists and consumers).

Effects of anode material oxygen content on molten metal convection generated via arc plasma heating

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.