Milling Of Materials Research Articles

Inflammatory Response to Cobalt-Chromium Alloys Fabricated With Different Techniques.

ABSTRACTObjectivesTo explore the in vitro cytokine expression of human peripheral blood mononuclear cells exposed to cobalt-chromium alloys, manufactured with different techniques, in comparison with commercially pure titanium grade 4 and titanium alloy grade 23.Material and MethodsPeripheral blood mononuclear cells (PBMC) were collected from 10 healthy blood donors and exposed to machine-ground coin-shaped: (a) cobalt-chromium (Co-Cr) specimens (n = 5) manufactured by four techniques, i.e. cast, milled, laser melted and presintered milled; (b) commercially pure titanium grade 4; and (c) titanium alloy grade 23. The cells were cultured for 4, 24 and 72 hours followed by investigations of pro- and anti-inflammatory cytokine release using Bio-Plex Pro™.ResultsIn general, the PBMC produced significantly more cytokines when exposed to the cast and presintered milled Co-Cr materials compared to laser melted, milled Co-Cr and titanium materials.ConclusionsWithin the limitation of the present study, it may be suggested that cast and presintered milled cobalt-chromium alloys provoke a stronger inflammatory response compared to milled and laser melted cobalt-chromium alloys and titanium materials.

ИССЛЕДОВАНИЯ ВЛИЯНИЯ ТЕХНОЛОГИЧЕСКИХ ПАРАМЕТРОВ НА ГРАНУЛОМЕТРИЧЕСКИЕ ХАРАКТЕРИСТИКИ СУБМИКРОННОГО ОКСИДА АЛЮМИНИЯ В α-ФОРМЕ

Experimental studies of the influence of technological parameters of grinding alumina raw materials in a ball mill on the kinetics of the grinding process and the granulometric characteristics of activated alumina in the α-form have been carried out. It is found that the use of spherical grinding bodies leads to the formation of a specific four-modal granulometric composition with maxima: 0.5; 4.0; 50.0 and 400.0 microns, respectively. The disadvantage of using spherical grinding bodies is the uneven distribution of the introduced intensifier additive (PEG), which in turn causes adhesion of fine particles and the appearance of aggregates. This is especially pronounced at n = 100 rpm. When using grinding bodies of cylindrical shape, on the contrary, there is a tendency towards a bimodal nature of the distribution of particles with maxima in the regions of 0.4 and 4 μm, respectively, regardless of the rotation speed of the drum (n). The use of cylpebs does not provoke agglomeration of the fine particle fraction, which is observed in the case of spherical grinding bodies. When analyzing the kinetics of grinding alumina raw materials, two main stages of the process are identified. The first stage corresponds to the active fragmentation of large initial aggregates into constituent crystallites by the cleavage mechanism. The second stage corresponds to a change in the grinding mechanism from crushing to abrasion. It is found that carrying out the grinding process for 10 hours using cylindrical grinding bodies at n = 100 rpm and φ = 0.35 provides a high yield of the submicron fraction of the target product (1 μm) - up to 20 wt. %.

The Effect of Compaction Effort on Fatigue Performance of Cold Emulsified Bitumen Mixes with Reclaimed Asphalt Pavement

During the service period, flexible pavements tends to produce series of distresses, such as rutting, cracking, pothole, etc. When the distresses are severe, the best method is to recycle the distressed layer using stabilizers like emulsified asphalt or some additives and that layer can be used as a base\sub base or surface course based on the purpose. The milled material is known as Reclaimed Asphalt Pavement (RAP) and the application of emulsified asphalt comes under cold mix asphalt technologies. This can help to create a cleaner production including lesser usage of natural aggregates and lower carbon emissions. Compaction is one of the significant factors in order to prevent premature failures and for better performance of the mix. A properly compacted base develops adequate density and strength; the present study investigated the influence of compaction effort on the fatigue performance of Emulsified Asphalt Treated Bases (EATB). The performance indicators include Indirect Tensile Strength (ITS), Resilient Modulus (MR), and fatigue characteristics. Finally, the study developed the models between ITS and MR for different fluid contents.

Comparative evaluation of the effect of thermocycling on the mechanical properties of conventionally polymerized, CAD-CAM milled, and 3D-printed interim materials

Statement of problemStudies on the energy absorption characteristics by means of elastic and plastic material deformation of interim materials are lacking. PurposeThe purpose of this in vitro study was to compare the effect of different thermocycling periods on the flexural strength (σfs), resilience (Ur), and toughness (UT) of conventionally polymerized, computer-aided design and computer-aided manufacturing (CAD-CAM) milled, and 3-dimensionally (3D) printed interim materials. Material and methodsRectangular specimens (n=30 for each material) were fabricated from autopolymerized polymethyl methacrylate (PMMA), bis-acryl resin (Bis-acryl), CAD-CAM polymethyl methacrylate-based polymer (CAD-CAM/Milled), and 3D-printed composite resin (3D-Printed). Each material was divided into 3 groups (n=10) according to the applied thermocycling (5 °C to 55 °C) procedure: control (0 cycles), 2500, and 10 000 cycles. Parameters of the materials such as σfs, Ur, and UT were tested in a 3-point bend test according to International Organization for Standardization (ISO) 10477. Data were statistically analyzed with the Shapiro-Wilk test followed by Kruskal-Wallis test, the Mann-Whitney U test, the Friedman test, and Wilcoxon signed-rank test (α=.05). ResultsThe tested material and thermocycling had a statistically significant influence on the σfs, Ur, and UT values (P<.05). PMMA showed the lowest mean σfs, Ur, and UT values (P<.05), and CAD-CAM/Milled showed σfs values similar to those of 3D-Printed at all thermocycling periods. CAD-CAM/Milled showed the highest Ur values at 10 000 cycles and the highest UT values at all thermocycles. No significant differences were found in the mean change of σfs and Ur of CAD-CAM/Milled among different thermocycling periods. ConclusionsThe results suggested that digitally fabricated interim materials had better mechanical properties than conventionally polymerized materials and that milled materials had the highest stability in maintaining their initial capacity to absorb energy.

Environmental Assessment of Recycling (EAoR) for Safe Recycling of Steelmaking Slag in the Republic of Korea: Applications, Leaching Test, and Toxicity

Steel slag is a major waste product of the steelmaking process. Owing to its chemical composition, it can be reused as a raw material in steel mills and a substitute for aggregates in engineering. In 2016, the Republic of Korea (ROK) introduced the Environmental Assessment of Recycling (EAoR) system for the safe recycling of waste products, which divides recycling methods into either matrix contact or non-matrix contact types; numerous challenges have been raised regarding weaknesses in the matrix contact type. Consequently, the standards for matrix contact recycling of slag (inorganic waste) have become stricter, and the recycling applications have also become more diverse. This study investigates the treatment, recycling, and management of steel slag in the ROK. In 2019, the annual generation of slag in the ROK exceeded 23.03 million tons with a recycling rate of 98.3%, showing a high level of recycling, compared with that of the United States (81.3%), the European Union (87%), Australia (100%), and Japan (98.4%). However, a comparative analysis of overseas slag recycling systems and recycling standards found that the recycling applications and recycling standards of slag in the ROK were somewhat stricter than those in the European Union and the United States. Furthermore, an investigation comparing the applications of recycled slag in different countries showed that the ROK could expand its applications of recycled slag. The limitation of the EAoR system was that the excluding products, environmentally certified from Korean Standards in the EAoR regulations, might be attributing to environmental pollution. The leaching and toxicity tests for recycling application of steelmaking slag were evaluated and showed no significant negative effects. Lastly, there is an urgent need for environmental standards relating to slag that can be recycled as a product, and the recycling and environmental label certification for products should also be amended. In addition, the applications of steelmaking slag were necessary to partially extend according to the hazardous characteristics.

Role of compaction and drying-wetting cycles on the capability of precompression stress to indicate load history of heavily disturbed soils

Wetting and drying are common processes in agricultural soils, which change particle rearrangement, cementation and related properties. Some recent studies have noted that soil precompression stress (σp) – the soil capacity to support stress – can be affected by wetting and drying cycles and should be seen as state variable instead of a soil mechanical characteristic. In this study, we investigated how wetting and drying cycles change the σp of remolded samples, i.e. soil without distinct loading history. Soil material from three highly weathered soils with different textures (62, 35 and 15% of clay) of the most common soil classes of Brazil were used. The soils were milled and then used to create two set of samples with different compactness. In one set, named not compacted (NC), the milled material was just poured (loose material) into the cylinders, while in the other set the milled material inside the cylinders was compacted (COMP). In the NC samples, zero and three drying (under 33 kPa matric suction) and wetting (saturation) cycles (0D-S and 3D-S) were applied. The COMP samples were subjected to 0, 2, 4, and 6 D-S cycles. In the NC samples, the σp (35–49 kPa) in 0D-S was similar to the matric stress soil samples had experienced prior to the compression test (33 kPa), but σp increased to 60–92 kPa after 3D-S. In the COMP samples, σp increases ranged between 65 and 53 kPa from 0 D-S to 2 D-S and then decreased to a value similar to that of 0 D-S again after 6 D-S. Changes of σp tended to be more remarkable in the soils with 62 and 35% of clay, but only a weak association between σp and texture was noticed. These results indicate that internal forces a soil experiences during shrinkage and swelling are key drivers of the σp parameter of the topsoil of agricultural areas. Thus, one σp value cannot characterize a site over time as it might be altered thoroughly during the year and thus fail in reflecting documented load history by means of traffic.

РАЗВИТИЕ ОБОРУДОВАНИЯ ДЛЯ ТОНКОДИСПЕРСНОГО ИЗМЕЛЬЧЕНИЯ МИНЕРАЛЬНОГО СЫРЬЯ

Introduction. The huge energy costs of fine and ultrafine grinding operations have led to numerous studies aimed at developing new devices and methods for producing powdered materials. The first way leads to an increase in specific productivity while maintaining energy consumption at approximately the same level. The second way allows not only to increase the specific productivity, but also to reduce the specific energy consumption, since with a decrease in the exposure time, the body is more easily deformed and destroyed. The grinders in which the intensification of the destruction process is carried out in the first way can include planetary and vibrating mills. The second method of intensification is used in jet and various types of centrifugal mills. It is determined that vertical centrifugal mills are the equipment of a new type that can effectively perform grinding operations at high technological indicators and low energy consumption. The purpose of the research. Development of measures for obtaining a finely dispersed product by destroying mineral raw materials in vertical centrifugal mills by mechanical means. Research methodology. The paper uses a comprehensive research method: analysis of the state of grinding equipment according to literary and patent sources; development of mathematical models of the movement of bulk material in the working space of a vertical centrifugal mill based on the Navie-Stokes equations; computer modeling of the movement of the crushed material using the OpenFOAM package for solving hydrodynamic equations; a solver program was created to perform calculations, implementing the SIMPLER algorithm and using the MRF model; laboratory experiments; granulometric method for the analysis of grinding products; fractional analysis of crushed material with a grain size of 0.08 mm using an X-ray analytical centrifuge ВrооkhаvеnBI-ХDС. The development of measures for the effective evacuation of the crushed product from the working space of a centrifugal mill was evaluated by comparative tests of mills using various design solutions. Research results and discussion 1. It is established that vertical centrifugal mills are the devices of a new type capable of effectively performing grinding operations at high technological indicators and low energy consumption. 2. A mathematical model of the movement of bulk material in the working space of a vertical centrifugal mill has been developed based on the Navier-Stokes equations, which allows determining the speed and direction of movement of material layers at any point in the working space, the energy costs for their movement, the influence of the height of the material column on the nature of its movement in the space above the rotor. 3. The directions of increasing the efficiency of grinding mineral raw materials in a vertical centrifugal mill are determined by reducing the number of radial ribs installed in the cavity of the mill rotor; making cutouts in the radial ribs of the rotor, in the area near the rotor hub; installing coaxial rings in the working space of the mill above the rotor. 4. A method of effective evacuation of the crushed product from the mill body by installing additional screening surfaces in the peripheral part of the working space of the mill has been developed. 5. For the first time, the distribution of the granulometric composition of fine and medium - dispersed crushed product obtained as a result of processing lump dolomite in a centrifugal mill was obtained. It was found that particles with a size class of -0.08 + 0.03 mm are absent in the output of the crushed product from the mill. Conclusions. A mass-produced vertical centrifugal mill will find its effective application at enterprises of the Russian Federation for the preparation of powdered materials and will allow to obtain a significant effect by reducing the price of the final product, simplicity of design and maintenance of equipment, as well as small occupied production areas.

Study of the Influence of the Time of Mechanical Processing of Powder Mixture of Composition Ti – 25 wt. % TiN in a Planetary Mill on the Characteristics of Composite Particles

In this work, by the method of mechanical processing in a high-energy planetary mill of titanium powder (PTS – 1) and ceramic powder of titanium nitride, composite particles with a size of 10 to 100 μm were obtained, in the volume of which ultrafine particles of titanium nitride are distributed. It is assumed that the use of such particles in powder spraying by cold or thermal spray will increase the homogeneity of the distribution of refractory elements in the coating volume. Depending on the time of mechanical treatment of the powder mixture containing three weight fractions of ultrafine particles of titanium nitride, agglomerated composite particles were obtained. Their granulometric composition and surface morphology were studied; a map of the distribution of elements over the surface and volume of the particle material is obtained. It is noted that during mechanical processing of materials in a planetary mill, the behavior of titanium nitride particles is similar to the role of a surfactant. It is shown that the time of mechanical processing of the powder mixture for three minutes is optimal: composite particles have an average size of 38 microns; mass fraction of particles of fraction 20 – 90 μm more than 60 %.

Role of Si3N4 on microstructure and hardness of hot-pressed ZrB2−SiC composites

The impact of Si3N4 content on the hardness and microstructural developments of ZrB2-SiC material has been investigated thoroughly in the present investigation. Having prepared the raw materials in a jar mill, the ZrB2-SiC samples containing various amounts of Si3N4 were hot-pressed at 1850 °C. Furthermore, XRD, FESEM, and HRTEM were utilized to evaluate the microstructure of samples. The formation of in-situ h-BN was proved by the mentioned methods. Also, it was shown that the Vickers hardness of ZrB2-SiC increases up to 20 GPa in presence of 4.5 wt% Si3N4 which is 3 GPa more than the sample without Si3N4. Results show that the positive effect of increased relative density on hardness is more than the negative effect of h-BN soft phase formation.

Retention forces between primary and secondary CAD/CAM manufactured telescopic crowns: an in vitro comparison of common material combinations

ObjectivesTo analyze the retention forces between primary and secondary telescopic crowns milled from various materials and to compare them with the retention forces between cast telescopic crowns made of precious metal alloys.Materials and methodsPrimary and secondary crowns (N = 60; n = 10 per group) were fabricated using various material combinations (1: zirconia [ZIR]/polyether ether ketone [PEEK]; 2: titanium grade IV [TI]/PEEK; 3: PEEK/PEEK; 4: non-precious alloy [NPA]/PEEK; 5:NPA/NPA), while precious alloy (PA) was used for the control group (6: PA/PA). The retention forces at 10, 1000, 5000, and 10,000 connection and disconnection cycles and the relative weights were analyzed, applying nonparametric repeated measures ANOVA and post hoc Mann–Whitney and Wilcoxon signed-rank tests (α < 0.05).ResultsGlobally, significant differences in the retention forces among the materials (p < 0.0001), time points (p < 0.0001), and wear resistance for the various materials (p < 0.0001) were observed. No significant changes in retention forces compared to baseline were observed in groups 2, 4, 5, and 6. A significantly higher weight loss for both primary and secondary crowns was observed in groups 4 and 6.ConclusionsThe material combination in telescopic attachments influences retention forces and wear. Interactions between materials and time were evident, indicating that the change in retention forces differs among the materials. The combinations of milled TI/PEEK and NPA/NPA qualify for further preclinical testing in a more clinically realistic setup, determining a material-specific double-crown design.Clinical relevanceThe design of precious alloy telescopic crowns cannot be directly transferred to other milled material combinations due to different retention behaviors.

A combination of density-based clustering method and DEM to numerically investigate the breakage of bonded pharmaceutical granules in the ball milling process

Ball milling is widely used in industry to mill particulate material. The primary purpose of this process is to attain an appropriate product size with the least possible energy consumption. The process is also extensively utilised in pharmaceuticals for the comminution of the excipients or drugs. Surprisingly, for ball mill, little is known concerning the mechanism of size reduction. Traditional prediction approaches are not deemed useful to provide significant insights into the operation or facilitate radical step changes in performance. Therefore, the discrete element method (DEM) as a computational modelling approach has been used in this paper. In previous research, DEM has been applied to simulate breaking behaviour through the impact energy of all ball collisions as the driving force for fracturing. However, the nature of pharmaceutical material fragmentation during ball milling is more complex. Suitable functional equations which link broken media and applied energy do not consider the collision of particulate media of different shapes or collisions of particulate media (such as granules) with balls and rotating mill drum. This could have a significant impact on fragmentation. Therefore, this paper aimed to investigate the fragmentation of bounded particles into DEM granules of different shape/size during the ball milling process. A systematic study was undertaken to explore the effect of milling speed on breakage behaviour. Also, in this study, a combination of a density-based clustering method and discrete element method was employed to numerically investigate the number and size of the fragments generated during the ball milling process over time. It was discovered that the collisions of the ball increased proportionally with rotation speed until reaching the critical rotation speed. Consequently, results illustrate that with an increase of rotation speed, the mill power increased correspondingly. The caratacting motion of mill material together with balls was identified as the most effective regime regarding the fragmentation, and fewer breakage events occurred for centrifugal motion. Higher quantities of the fines in each batch were produced with increased milling speed with less quantities of grain fragments. Moreover, the relationship between the number of produced fragment and milling speed at the end of the process exhibited a linear tendency.

Bronze Age of Direct Mechanocatalysis: How Alloyed Milling Materials Advance Coupling in Ball Mills

The copper‐catalyzed Glaser coupling is conducted mechanochemically, with the milling balls and vessels being the catalyst. Thus, neither catalyst powders nor soluble catalyst salts are required. Substituting Cu0 milling tools by copper alloys not only increases the yield of the reaction, but also greatly reduces abrasion, and in turn increases catalyst long‐term stability and reusability. Tracking the reaction by Raman spectroscopy allows to identify the active intermediate directly on the milling ball surface and propose a reaction mechanism.

Effect of protective layer deposition in cross-sectional analysis of focused ion beam in germanium substrate

In this work, a single micro-size circular and rectangular holes were fabricated in phosphorus/tin implanted germanium substrate using ion milling of FIB, for potential application in photonic crystal and FINFET. One of the important analysis that need to be done in the future is a cross-sectional analysis in order to evaluate the milling rate of material, redeposition of milled material, and the quality of the milled surface in the pattern structure. However, a well-known practise in preparing a cross-sectional sample for transmission electron microscope analysis using FIB involves a deposition of protective layer on the substrate surface before performing the cross-sectional ion milling, in order to prevent the surface damage. Taking this into consideration, this work performed a preliminary study to analyze the effect of depositing a protective layer onto the hole for performing FIB cross-sectional analysis of the fabricated hole structures. Two-step deposition technique of platinum layer involving electron beam, followed by ion beam was performed on the hole prior to the cross-sectional milling. Hole structure without protective layer was also prepared as a comparison. It is found that although the depth of the milled area can be evaluated in both cross-sectioned holes with/without protective layer, an evaluation on roughness and redeposition are difficult, specifically in the one with protective layer. While the existence of secondary damage might affect the quality of milled surface during the cross-sectional milling in the sample without protective layer.

Optimization Issues of a Hammer Mill Working Process Using Statistical Modelling

Our paper presents the hammer mill working process optimization problem destined for milling energetic biomass (MiscanthusGiganteus and Salix Viminalis). For the study, functional and constructive parameters of the hammer mill were taken into consideration in order to reduce the specific energy consumption. The energy consumption dependency on the mill rotor spinning frequency and on the sieve orifices in use, as well as on the material feeding flow, in correlation with the vegetal biomass milling degree was the focus of the analysis. For obtaining this the hammer mill was successively equipped with 4 different types of hammers that grind the energetic biomass, which had a certain humidity content and an initial degree of reduction ratio of the material. In order to start the optimization process of hammer mill working process, 12 parameters were defined. The objective functions which minimize hammer mill energy consumption and maximize the milled material percentage with a certain specific granulation were established. The results obtained can serve as the basis for choosing the optimal working, constructive, and functional parameters of hammer mills in this field, and for a better design of future hammer mills.

Nanostructured Strain-Hardened Aluminum–Magnesium Alloys Modified by C60 Fullerene Obtained by Powder Metallurgy: Part 1. The Effect of the Magnesium Concentration on the Structure and Phase Composition of Powders

This paper provides the first part of a study on the effect of magnesium on the structural phase composition and physical and mechanical properties of nanostructured aluminum–magnesium composite materials with the composition AlxMgy + 0.3 wt % C60 fullerene. Composite powders are obtained by the simultaneous mechanical activation of the initial materials in a planetary ball mill in an argon atmosphere. It is found that the powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It is found that the increase in magnesium concentration in the composite up to 18 wt % makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation is 15 wt % (17 at %). Using the differential scanning calorimetry method, it is found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400°C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum, and the formation of intermetallic β-(Al3Mg2), γ-(Al12Mg17) and carbide (Al4C3) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C60 fullerene—aluminum–fullerene complexes. The data that have been obtained will be used in further research to determine the parameters for the thermobaric treatment of nanocomposite powder mixtures in order to obtain and test bulk samples.

Microstructural Analysis of Changes in the Morphology of Quartz Raw Materials of Different Genesis at Dry Milling

The influence of the genesis of quartz-containing rocks on the strength of particles and changes in morphology during destruction from the standpoint of the mineralogical approach in the development of the scientific direction "geonics" ("geomimetics") has been investigated. The kinetics of dry grinding of raw materials in a laboratory ball roller mill was carried out. The features of the formation and development of cracks, particle size distribution, changes in the morphology and microstructure of fragments have been studied. It was found that in natural quartz cracks develop along the surface, where the highest concentration of impurities creates a defect structure with destruction into small particles. The purest structure of hydrothermal quartz is susceptible to brittle fracture into fragments similar in morphology to the base particle. Reducing the defectiveness of the structure increases the strength of the crystals. The internal energy potential of techno genic raw materials is determined by its defective structure, which undergoes the greatest deformations during grinding, allowing obtaining the maximum values of the specific surface area and reduce the grinding time. A difference in the degree of crystallinity of quartz, which composes the polymineral techno genic raw materials, makes it possible to obtain the optimal granulometry of fine particles. The conducted research is aimed at identifying the mechanisms of destruction of quartz rocks and can be used in solving engineering problems not only in construction materials science, but also in geotechnics.

Determination of the ball mills performance, taking into account the particle size of the finished product

The article discusses the issue of determining the newly formed specific surface of the cement clinker taking into account the lateral surface of the seal area. When developing this technique, the assumption that the newly formed particles have a shape close to spherical, has been made. The obtained ratio determines the work that considers the formation of thecement clinker material new surface, depending on the size of the original and newly formed material. An arithmetic expression is given, defined as the minimum amount of energy that must be introduced into the deformation zone for the destruction of a cement clinker particle to occur. The presented technique is specified taking into account the fact that defects are introduced into the crushed material particle. Taking into account the fact that the grinding ball makes an impact in one cycle of its movement, the value of the newly formed surface of the material in the ball mill is determined in one hour of its operation.

Extraction of lipids from New Zealand fern fronds using near-critical dimethyl ether and dimethyl ether–water–ethanol mixtures

Dimethyl ether (DME), under near-critical conditions, can be used to extract lipids containing valuable fatty acids from wet biomass. In this work, DME, and a mixture of DME with a water–ethanol co-solvent, are used to extract fronds of the fern Cyathea dealbata, and the fatty acid composition of the extract was compared with the fern total lipids obtained by chloroform–methanol extraction. Extraction was carried out by circulating DME through a packed bed of milled undried fern material at pressure of 4.0 MPa, temperature of 58 °C, flow rate of 13.6 kg per kg undried fern material per hour, for 60 min followed by extraction using DME with addition of 5 wt% of a 70% ethanol in water co-solvent mixture until 572 g of co-solvent had been introduced. The total combined yield of DME and DME–ethanol–water extracts was 6.3 wt% of the fronds with the recovery of 88–93% of the major fatty acids (18:3n-3, 16:0, 18:2n-6, 18:1n-9). The remaining residue contained<7% of the fern total lipids. The extracts were slightly enriched in eicosapentaenoic acid (EPA, 95% recovery), while a significant portion of arachidonic acid (ARA, 19%) remained in the residue. The DME and DME–ethanol–water extracts contained 6.9 and 6.1 mg/g of ARA, and 13.4 and 14.2 mg/g of EPA, respectively.

Position-Dependent Stability Prediction for Multi-Axis Milling of the Thin-Walled Component with a Curved Surface

Time-varying dynamic behaviors are essential to investigate the stability in the thin-walled workpiece milling process, which is usually affected by material removal and position-dependent characteristics of the workpiece along with the tool feed direction. To predict the milling stability with position-dependent, thin-walled component multi-axis milling, an improved structural dynamic modification method with variable mass is proposed in the paper. Firstly, the extraction of multi-axis milling material and the removal process of thin-walled parts with a complex curved surface and variable thickness is completed with CAM software. Then, the material removal of one cutting path as a modification of the structure is divided into multi-cutting steps with equal length to obtain the corrected FRFs in the machining process on the basis of the extended Sherman-Morrison-Woodbury formula. Furthermore, the dynamic characteristics of the initial un-machined workpiece and final machined workpiece are calculated by both experimental modal analysis and FEM. Finally, the multi-axis milling stability is predicted using the extended numerical integrated method, and an aero-engine blade is used to validate the accuracy and effectiveness of the proposed method for multi-axis milling molding parts.

DHFSlicer

3-axis milling enables cheap and precise fabrication of target objects from precut slabs of materials such as wood or stone. However, the space of directly millable shapes is limited since a 3-axis mill can only carve a height-field (HF) surface during each milling and their size is bounded by the slab dimensions, one of which, the height , is typically significantly smaller than the other two for many typical materials. Extending 3-axis milling of precut slabs to general arbitrarily-sized shapes requires decomposing them into bounded-height 3-axis millable parts, or slices , which can be individually milled and then assembled to form the target object. We present DHFSlicer , a novel decomposition method that satisfies the above constraints and significantly reduces both milling time and material waste compared to alternative approaches. We satisfy the fabrication constraints by partitioning target objects into double height-field (DHF) slices, which can be fabricated using two milling passes: the HF surface accessible from one side is milled first, the slice is then flipped using appropriate fixtures, and then the second, remaining, HF surface is milled. DHFSlicer uses an efficient coarse-to-fine decomposition process: It first partitions the inputs into maximally coarse blocks that satisfy a local DHF criterion with respect to per-block milling axes, and then cuts each block into well-sized DHF slices. It minimizes milling time and material waste by keeping the slice count small, and maximizing slice height. We validate our method by embedding it within an end-to-end DHF milling pipeline and fabricating objects from slabs of foam, wood, and MDF; demonstrate that using the obtained slices reduces milling time and material waste by 42% on average compared to existing automatic alternatives; and highlight the benefits of DHFSlicer via extensive ablation studies.