Contents Of Volume Research Articles

Lightweight thermo- and heat-resistant composite materials based on polyimide foam

A prepolymer foaming composition based on 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride methyl ester and diamines: 4,4'-diaminodiphenylmethane and m-phenylenediamine for the production of high-temperature polyimide foam (PIF) is proposed. The p ossibility o f u sing P IF a s a b inder f or c omposite materials (foam composites) reinforced with carbon or organic fibers with low density (0.4–1.1 g/cm3) a s a result of foaming of the binder during the formation of the foam composite is shown. The density and mechanical properties of the foam composite can vary within a relatively wide range depending on the volume content of the fiber and air pores. The high glass transition temperature of 260°C, combined with the high thermal stability of carbon or polyimide fibers, contributes to the retention of the mechanical properties of such composites at elevated temperatures. The temperature of the start of mass loss of the foam composite must be at least 550°C, and it depends on the type of fibrous material. The combination of the excellent thermal and mechanical properties of lightweight PIF composites, together with the exceptional fire resistance of polyimide materials, may provide new applications in advanced aircraft and shipbuilding technologies.

Study on Nonlinear Vibration of Vertical Lifting Section of Bulk Grain Entrainment Ship Unloader

In view of the prominent problem that nonlinear vibration of a belt conveyor can easily occur during the vertical grain-conveyance process due to the coupling effect of airflow clamping and traction of the conveyor belt, which seriously affects the efficiency and stability of conveying materials by the belt conveyor, a method of solving the vibration analysis of the vertical lifting section of the bulk grain belt unloader by using nonlinear vibration is proposed. Firstly, based on the laminated plate theory, the vertical lifting belt and the grain material clamped by the belt are laminated. The nonlinear vibration differential equation of the vertical lifting section of the bulk grain-carrying ship unloader is established by elastic–plastic mechanics, and solved by perturbation theory and Galerkin discrete analysis. The vibration response curve and structural natural frequency of the vertical lifting section of the bulk grain-carrying machine are obtained by numerical solution, and the influence of the volume content of the clamped material on the vibration response and structural natural frequency of the lifting section is analyzed. This study provides theoretical support for the design of pressure-supply parameters, overall structure and operation parameters of the subsequent entrainment ship unloader, promotes the rapid development of the entrainment ship unloader, provides theoretical support for the design, manufacture, later operation, and maintenance of the entrainment ship unloader, and thus provides equipment and technical support for building an efficient and intelligent port.

THE CHEMICAL ETCHING OF CdTe, ZnxCd1-xTe and CdxHg1-xTe SINGLE CRYSTALS WITH HNO3 – KI – DIMETHYLFORMAMIDE SOLUTIONS

The chemical dissolution of CdTe single crystals, ZnxCd1-xTe and CdxHg1-xTe solid solutions in HNO3 – KI – dimethylformamide solutions has been investigated under reproducible hydrodynamic conditions for the first time. It is shown that the etching compositions of this system are cheaper, create a less aggressive environment, are more stable over time and are more ecologically safe. The diagrams «solution composition versus dissolution rate» has been plotted and the concentration limits of polishing etchant have been determined. Chemical-dynamic polishing with the investigated solutions can be carried out with a volume content of HNO3 9-15 %, while the polishing speed the surface of CdTe single crystals, ZnxCd1-xTe and CdxHg1-xTe solid solutions is within 1.6-2.5 μm/min. The dependence of the ions concentration that passed into the solution after the interaction of solid solutions ZnxCd1-xTe with the investigated etchants, versus the content of the oxidant in the etchant has been determined, and it was shown that the content of ions in the solution corresponds to the molar ratio in the semiconductor and indicates uniform dissolution of the surface. Based on the results of kinetic study, the apparent activation energy of the polishing was calculated for a solution of the composition (in vol. %): 12 НNO3 + 88 KI (DMF), which does not exceed 15.1 kJ/mol for СdTe and 7.7 kJ/mol for solid solutions on its basis, which indicates the limitation of the process by diffusion stages. The effect of the lactic acid and the nature of the semiconductors on the kinetics of chemical-mechanical polishing of the studied single crystals were determined. When the polishing solution is diluted with organic acid to 40 vol. %, the speed of chemical and mechanical polishing decreases from 3.5 to 0.5 μm/min. The compositions of etching mixtures and modes of implementation of chemical-dynamic polishing, which is recommended to be carried out in a suitable installation at the temperature 293 K and the disk rotation speed 82 min‑1, and chemical-mechanical polishing of the mention above semiconductor single crystals with the addition of lactic acid and polishing rates of 3.5-0.5 μm/min.

Room temperature nanoindentation creep behavior of CoNiCrMo-based high entropy amorphous alloy coatings prepared by HVAF

The present study aimed to explore the creep behavior of CoNiCrMo-based high entropy amorphous alloy coatings at room temperature using nanoindentation creep experiments. The coatings were subjected to different loading rates to assess their performance. The findings indicate that the high entropy effect of the (Co0.33Ni0.33Cr0.23Mo0.1)80-xNbx(B0.7Si0.3)20 (x = 0, 2 and 4 at. %) high entropy amorphous alloy coatings has a notable impact on the creep resistance and facilitates a uniform plastic deformation during creep. The shear transition zone (STZ) size and the free volume content during creep deformation exhibit an increase in response to the concentration of Nb. This phenomenon can be attributed to the elevated atomic packing density and the hindered movement of atoms resulting from the incorporation of Nb. Nb content has a favorable impact on the creep stress index, increasing creep stress. Also, the high concentration of Nb is found to mitigate the propensity of the stress exponent to drop with increasing loading rates. The high entropy effect of the as-sprayed coatings promotes high creep resistance and homogenous creep deformation.

Humic Acid for Soil Quality Improvement with Application of Scan Automation on Seedless Watermelon Cultivation

Purpose: Sustainable agricultural intensification needs to be well developed. Therefore, food and agricultural production activities can be continuously produced without damaging the ecosystems and environment. One that can be used is a plant biostimulant based on humus. This research was conducted to examine the effect of humic acid as a soil biostimulant and the impact of its use on the yield of seedless watermelon cultivated on marginal land. This study involve IoT technology through monitoring soil quality which is carried out based on the concept of precision agriculture using the farm management system (FMS) Agrooscan tool. Methods: The study used humic acid factor for five treatments (0, 2, 4, 6, and 8 g/L). Observations included soil conditions monitored with Agrooscan instruments such as soil pH, nutrients (N, P, K), as well as measuring plant height, fruit weight, fruit volume and total sugar content (Brix). Results: The results showed that application of humic acid increased the nutrient content in the soil and significantly affected soil pH and seedless watermelon yields. The 8 g/L treatment gave the highest soil N and K values, and was significantly different from no treatment (control). Conclusions: Thus, exogenous use of humic acid as a soil nutrient supplement can be used to help increase marginal land use, including in the development of seedless watermelon cultivation. The use of Agrooscan as a tool to scan soil conditions plays a very important role in maintaining the quality of nutrients so that the growth of watermelon cultivation can run better.

Contents of Volume 83.

Contents of Volume 83.

Contents of Volume 87

Contents of Volume 87

Вероятностная оценка эффективности применения метода циклического заводнения нефтяных пластов

Extraction of hard-to-recover hydrocarbons is becoming an urgent task for the entire world oil community. The development of new technologies and methods, as well as the improvement of existing ones, have become the main issue in the extraction of hydrocarbons at existing fields. The aim of the work was to develop the technology of hydrodynamic impact on the hydrocarbon deposit. The process of oil reservoirs flooding is one of the most widespread and traditional in the application of extraction of hard–to-recover oil. The most effective in terms of impact is the cyclic regime of flooding of oil reservoirs – periodic changes in fluid flow rates at injection and production wells with a phase shift of oscillations for individual groups of wells. The use of cyclic flooding in combination with an increase in the average level of injection pressures can give a significant increase in the coefficient of reservoir coverage in power. The degree of hydrodynamic connectivity of the layers along the section has a significant impact on the effectiveness of cyclic flooding. The coefficient of lithological connectivity of formations is determined by the ratio of the area of the reservoir confluence to the total area of the deposit and can characterize the hydrodynamic connectivity of formations along the section. Using the example of the D3 of the Korotkoye field, an assessment of the start-up of the wells of the PPD system was done as well as the analysis of the nature of its influence on the volume and water content of the extracted products of the D3 formation of the Korotkoye field under various injection modes using cyclic flooding. It is determined that when both injection wells are stopped for a long period, the output of the produced products decreases to 25%. The analysis of the total oil flow rate showed that in the variants with well shutdowns there is a stronger decrease in oil flow rate than in the variants with cyclic injection, in the variants with cyclic operation of the PPD system the highest indicators of accumulated oil production are achieved for a certain period.

Fiber fraction-dependent flexural behavior of high-performance fiber-reinforced concrete under static and repeated loading

The effect of the fiber volume fraction on the flexural behavior of high-performance fiber-reinforced concrete (HPFRC) under both static and repeated loading is highlighted through a series of experiments. All rectangular prism-shaped flexural specimens were 40 × 40 × 160 mm3 and subjected to a three-point bending (3 PB) fixture with a span length of 120 mm. Macro-hooked and micro-smooth steel fibers with volume contents of 0.0%, 0.5%, 1.0%, and 1.5% were investigated. The flexural strength and deflection capacity of the HPFRCs under static loading generally increased with increasing fiber volume content. The micro-smooth fiber mostly produced a higher flexural strength and a lower deflection capacity compared to the macro-hooked fiber. Under repeated loading, a larger fiber volume fraction generally resulted in higher HPFRC endurance limits, which exceeded 40,000 cycles with a fatigue stress ratio of <0.5, at a fiber volume fraction of 1.5 vol%. The flexural fatigue equations of the HPFRCs of various fiber contents were calculated with the fatigue stress amplitude as well as the fatigue stress ratio, based on the experimental data. The HPFRCs’ sensitivity to endurance limits generally decreased with increasing fiber content; this finding was greater when using the micro-smooth fiber than when using the macro-hooked fiber.

Water loss, not overheating, limits the activity period of an endothermic Sonoran Desert bee

Abstract Desert animals must manage the physiological stress caused by heat and desiccation; evaporative heat loss mitigates overheating but exacerbates water stress. Small endothermic flying insects may be particularly vulnerable to overheating and water stress as a result of high surface area to volume ratios, but we lack quantitative understanding of the relative magnitude of these abiotic stressors in flying desert invertebrates, despite their ecological importance. During the hottest and driest weeks of year, many thousands of males of the Sonoran Desert digger bee (Centris caesalpiniae) flew near‐continuously at elevated thorax temperatures for hours at mating aggregation sites, while fighting other males and digging for females. To determine whether incapacitating high temperatures or water loss limited the activity period of male C. caesalpiniae, we assessed wet and dry body mass and water content through the activity period, flight durations using mark–recapture methods, crop volume and sugar content, microclimate selection, water balance during flight, critical water content and maximum critical temperature. Body masses and sizes of males declined through the morning. Body water content scaled isometrically with total body wet mass. Crop volume and sugar content did not vary throughout the day or with bee size. Maximum critical temperature during flight was 51°C for large‐morph C. caesalpiniae males, similar to those measured for other bees, and well above body temperatures reached in the field, suggesting that avoidance of overheating does not limit activity in this desert bee. The critical water content of Centris bees averaged 50%, at the low end of those measured for other bees. Measures of net water loss rate indicated that males approached lethal water loss limits within 4 h, a duration in the range of measured daily flight activity, suggesting that desiccation tolerance limits activity. Remarkably, male C. caesalpiniae were not observed to forage at floral or water sources during the activity period, yet they returned over multiple days, suggesting that these males have a mechanism to rehydrate when not at the mating aggregation. Read the free Plain Language Summary for this article on the Journal blog.

Studies on the Growth, Production and Component Contents of Chrysanthemum indicum Using Arduino-controlled Moisture Content Irrigation Systems

The flowers of Chrysanthemum indicum L., when used as herbal medicines, are said to effectively relieve heat, pain, eye fatigue, and inflammation and be detoxifying. Recent studies have been conducted to control the growth environment of plants with the use of computers, Arduino company producing one such open-source control device. In this study, we evaluated the effect of a traditional ck irrigation system and three soil moisture volume content irrigation controlled by Arduino UNO on flowering, growth, production, and indicators of flower quality of C. indicum grown in pots in a greenhouse. For this study, we aimed to maintain soil moisture volume content to 35%-40%. Irrigation was set to be initiated when soil moisture volume content dropped to 25-30% (Is 30% group), 15-20% (Is 20% group) or 5-10% (Is 10% group). Flowering time was earlier in Is 30% and Is 20% plants than the traditional ck plants, while Is 10% plants did not flower throughout the cultivation period. Both the Is 30% and traditional ck plants produced significantly more total number of flowers and total dry weight of the flowers than Is 20% (Is 10% none). Traditional ck flowers have a significantly higher content of chlorogenic acid, myricetin and quercetin, indicators of quality. The other indicators, luteolin and apigenin were significantly higher than traditional ck and Is 30% plants. This study concluded that the Arduino UNO’s irrigation control system had a better effect on C. indicum growth and component content when irrigation was set Is 30%.

Study of Using Quartz Powder as a Mineral Admixture to Produce Magnesium Oxysulfate Cement

Magnesium oxysulfate (MOS) cement features potential advantages, including light weight, green and environmental protection, low thermal conductivity, and high frost- and fire-resistance, but its poor mechanical strength limits the extensive utilization in the architectural engineering. In this study, low-cost quartz (Q) was used as a mineral admixture to increase the mechanical strength of MOS pastes. The impact of the filler Q on the early and later mechanical strength of MOS cement was investigated, in which also had an impact on fluidity, setting times, volume stability, hydration processes, phase transformations, and microstructure. The results show that hydration of periclase to form 5Mg(OH)2·MgSO4·7H2O (phase 5-1-7) in this system was a multi-stage reaction process. 3Mg(OH)2·MgSO4·8H2O was the first sediment in this system and was converted into phase 5-1-7. The dilution and dispersion effects of the filler Q increased the early hydration rate, shortened the setting time, and increased the content and crystallite size of phase 5-1-7, increasing the early mechanical strength of MOS cement, while the volume-filling effect of the filler Q reduced the content of large pore and total pore volume, and improved the pore structure of the MOS cement, improving the later mechanical strength of MOS cement. MOS cement containing 15 wt.% of filler Q exhibited the highest early and later mechanical strength, and the lowest volume shrinkage, which is more suitable for application in architectural engineering. Based on these results, filler Q can be used as an enhancer in MOS cement, however its enhancement mechanisms are effective only when the content of filler Q is no more than 20 wt.%.

Induced synthesis of SO2-promoting and H2O-tolerant sorbents for elemental mercury removal from flue gas

In this study, novel S-doped sorbents synthesized via one-step co-pyrolysis of biomass and scrap tires under SO2 atmosphere were developed for elemental mercury (Hg0) removal from coal-fired flue gas. The presence of SO2 could regulate the sulfur species in S-doped sorbents and improve their Hg0 removal performance. Sample characterization exhibited that SO2 activation increased the sulfur content and decreased the carbon content in sorbents due to the occurrence of carbothermal reduction reaction. The specific surface area, pore volume, and micropore content in S-doped sorbents were obviously improved compared with raw sorbents. After SO2 activation, partial inorganic sulfide was converted into sulfur-containing functional groups and more oxygen-containing functional groups were generated on the sorbents. The S-doped sorbents presented more excellent performance for Hg0 removal compared with raw sorbents. The optimal pyrolysis temperature and SO2 concentration in activation atmosphere were 700 °C and 10%, respectively. It was surprising that SO2 facilitated Hg0 removal and the S-doped sorbents showed good water-resistance due to the presence of ZnS. O2 and NO had positive effects on Hg0 removal. A close fitting to the pseudo-second-order model was obtained for the behavior of Hg0 removal over S-doped sorbents. Aliphatic sulfur, sulfoxide, carbonyl and carboxyl/ester groups functioned as active components for Hg0 removal.

TMT-based quantitative proteomics reveals the protective mechanism of tenuigenin after experimental intracerebral hemorrhage in mice

Ethnopharmacological relevanceTenuigenin (TNG) is an extract obtained from Polygalae Radix. It possesses anti-inflammatory, antioxidant, and neuroprotective properties. However, the potential mechanism of TNG in intracerebral hemorrhage (ICH) has not been well studied. Aim of the studyIn the present study, we aimed to identify the prospective mechanism of TNG in treating ICH. Materials and methodsA total of 120 mice were divided into five groups: Sham group, ICH + vehicle group, ICH + TNG(8 mg/kg), ICH + TNG(16 mg/kg), and ICH + TNG(32 mg/kg). The modified Garcia test and beam walking test were carried out at 24 h and 72 h after ICH. Brain water content, haematoma volume and hemoglobin content examinations were performed at 72 h after ICH. TMT-based quantitative proteomics combined with bioinformatics analysis methods was used to distinguish differentially expressed proteins (DEPs) to explore potential pharmacological mechanisms. Western blotting was performed to validate representative proteins. ResultsOur results showed that the optimal dose of TNG was 16 mg/kg, which could markedly improve neurological functions, and reduce cerebral oedema, haematoma volume and hemoglobin levels 72 h after ICH. A total of 404 DEPs (353 up-and 51 downregulated) were identified in the ICH + vehicle vs. sham group, while 342 DEPs (306 up-and 36 downregulated) and 76 DEPs (28 up-and 48 downregulated) were quantified in the TNG vs. sham group and TNG vs. ICH + vehicle group, respectively. In addition, a total of 26 DEPs were selected according to strict criteria. Complement and coagulation cascades were the most significantly enriched pathways, and two proteins (MBL-C and Car1) were further validated as hub molecules. ConclusionsOur results suggested that the therapeutic effects of TNG on ICH were closely associated with the complement system, and that MBL-C and Car1 might be potential targets of TNG for the treatment of ICH.

Significance of organo-mineralogical constituents on pore distribution, fractals and gas sorption mechanism of Permian shale beds in Korba sub-basin of the Son-Mahanadi Valley, India

In this study, shale samples obtained from the Korbasub-basin of Central India have been evaluated for the significance of organo-inorganic constituents in terms of their source potential of gas genesis, pore-matrix setup, and gas adsorption and desorption. The samples were analysed for various properties, such as megascopic features, lithological variations, depositional facies, and sources of organic and inorganic sediments. Also, maceral content, mineralogical constituents, kerogen type, pore distribution, pore structure, fractal characteristics and gas storage capacity were examined. The analysis revealed a trend of alternating bands of carbonaceous matter, silts, intercalations, and fluvial bedding lithofacies patterns indicating that the sediments were deposited under fluvio-terrestrial-lacustrine depositional conditions. Ternary facies analysis of maceral composition and van Krevelen diagram suggested the evolutionary path of type IV kerogen and are thermally matured source material located within the dry hydrocarbon generation window. Evaluation of pore types and pore structures using BET sorption plots (hysteresis H3 and isotherm type IV) revealed the presence of cylindrical, slit and combined cylindrical-slit pores with two distinct fractal characteristics. The discrete macerals underwent partial decomposition during transportation and mixing with inorganic components (clay and minerals), which influenced organic matter preservation, gas genesis, pore fractals and storage mechanism. The chemical index of alteration (CIA – 88.36 to 91.97), weathering (CIW – 96.60 to 98.80) and compositional variation (ICV – 0.31 to 0.70) demonstrated the influence of partial decomposition and strong weathering patterns on the organo-inorganic matter. A significant correlation was observed between pore fractals and elemental composition, particularly related to the resistance of weathering elements such as MgO, Al2O3, Fe2O3, SiO2, P2O5, TiO2, etc., which partially contributed to the formation of pore rugged surfaces. Microscopic and XRD analyses were employed to determine the mineral type, grain shape and size, and their amount leading to the development of the shales brittleness index (MBI). The importance of brittle characteristics, governed by minerals and clays within the shale, is discussed in relation to the hydro-fracturing technique for permeability enhancement. The results of high-pressure methane sorption indicated a moderate gas storage potential. The variation in sorption capacity (VL – 6.65 to 8.25 cc/g) is described through relationships with the ICV, pore diameter, pore volume, liptinite and total maceral content. Fractal dimensions D1 (2.4571–2.5611) and D2 (2.5804–2.7529) exhibited a direct relationship with adsorption properties, indicating the presence of rugged surfaces associated with meso- and macro-scale pores, which primarily control gas storage in shale. This research offers detailed insights into shale gas, providing valuable information for CBM and petroleum operators engaged in methane gas exploration and production. While commercial CBM production has been ongoing in India for over a decade, the exploration and understanding of shale gas reservoir characteristics are still in progress. This investigation adds significant value and highlights the extensive opportunities for research and potentially commercially recovering shale gas in the Korba sub-basin.

Strengthening mechanism of polyvinyl alcohol fibers on mechanical properties of geopolymer concrete subjected to a wet-hot-salt environment

Concrete materials are subjected to a complex coupled environment of temperature, humidity, and salt ions when in a coastal area during the summer. Geopolymer concrete (GPC), as one of the best alternatives to ordinary silicate concrete, was explored in this study to investigate its mechanical damage under wet-hot-salt environment, and to understand the strengthening mechanism of its mechanical properties by polyvinyl alcohol fibers (PF), which are crucial for the application of GPC in coastal engineering. To achieve this, a series of experiments were conducted to investigate the effect of wet-hot-salt coupled environment and PF content on the mechanical properties of fiber-reinforced geopolymer concrete containing nano-SiO2 (PF-GPC). In the experimental design, a coupled environment of 45 °C temperature, 100% humidity, and 5% NaCl solution content was firstly established for simulation acceleration test by an environmental simulation test chamber. Then different PF volume contents (from 0% to 0.8%) were considered for the cube compressive strength test, split tensile test, elastic modulus test and impact test. The results indicated that the wet-hot-salt environment significantly weakened the mechanical properties of GPC specimens, while the addition of appropriate content of PF effectively mitigated the degradation caused by the wet-hot-salt environment. The compressive strength, splitting tensile strength and elastic modulus of PF-GPC reached their maximum value at a PF content of 0.6%. Particularly, the addition of PF significantly improved the impact resistance of PF-GPC in wet-hot-salt coupled environment, with the highest impact resistance indices observed at a PF content of 0.4%. Moreover, the correlation between the elastic modulus and compressive strength of PF-GPC in wet-hot-salt environment was established by using the power function equation. And based on the applicability of the two-parameter Weibull distribution in the impact life model, an impact damage evolution equation of PF-GPC was established and validated under the wet-hot-salt conditions, which can provide valuable guidance for the design of GPC structures under different damage probabilities. The findings of this study indicated that PF-GPC can be applied in the wet-hot-salt environment, which is important for the low-carbon sustainable development of building materials.

Dynamic impact tests and temperature rise induced damage constitutive model of ice-rich frozen sandy soil

In this study, a soil-ice particle mixing method was used to prepare ice-rich frozen sandy soil specimens. Subsequently, the mechanical behaviors of ice-rich frozen sandy soil with a wide range of total moisture contents (15%–150%) were studied at three negative temperatures (−5, −10, and −15 °C) under the impact pressures from 0.2 MPa to 0.4 MPa. The melting of ice particles caused by the rise in temperature of frozen soil specimens was identified as temperature damage. Moreover, damage mechanism of ice-rich sandy frozen soil specimen during failure process was considered as the combined action of crack propagation and temperature rise. The analysis of the relationship between temperature rise value and dynamic strain was then calculated based on the heat conduction theory. Additionally, the phase transition equilibrium between unfrozen water and effective ice was used to determine the variation in ice volume content as the temperature rises, and the temperature damage variable was defined according to the reduction of dynamic elasticity modulus of ice-rich frozen sandy soil. Lastly, the compound damage variable was deduced and considered in the damage constitutive model. Accordingly, the theoretical and test data were compared to determine the model parameters. The results of the curve comparison indicate that the proposed model is feasible and suitable to be applied to predict the dynamic mechanics of ice-rich frozen sandy soil.

Study on failure characteristics of basalt fiber reactive powder concrete under uniaxial loading

The uniaxial compression experiments of basalt fiber reactive powder concrete (BFRPC) were carried out by acoustic emission (AE) and DIC techniques, focusing on the AE characteristics in the process of BFRPC failure. The cracking modes of internal and surface cracks of BFRPC are judged by clustering analysis of average frequency (AF) and rise angle (RA) based on Gaussian mixture model (GMM) and displacement on both sides of cracks measured by DIC. Research investigates that the peak frequencies of BFRPC are mainly distributed in 5 ∼ 35 kHz, 60 ∼ 100 kHz, 185 ∼ 215 kHz and 230 ∼ 280 kHz. With the increase of stress level, the absolute energy in the peak frequency range increases gradually. The volume content of 0.5% and 1.0% basalt fiber increased the absolute energy in each peak frequency range. Basalt fiber can improve the compressive strength and the strength and density of AE energy of RPC to some extent. The shear failure of BFRPC mainly occurs in the later stage of loading. Basalt fiber can change the failure mode of BFRPC from tensile failure to tensile shear failure. Meanwhile, basalt fiber can effectively increase the stress level during cracking and reduce the damage degree of BFRPC. Judging the AE characteristics and crack types of concrete failure is of great consequence to predict the precursory failure of BFRPC.

Research Status of and Prospects for 3D Printing for Continuous Fiber-Reinforced Thermoplastic Composites.

Continuous fiber-reinforced thermoplastic composites (CFRTPCs) have advantages such as high specific strength, high specific modulus, corrosion resistance, and recyclability and are widely used in the fields of aerospace, rail transit, new energy, and so on. However, traditional methods for preparing CFRTPCs, such as placement and molding, rely more on forming molds, resulting in high manufacturing costs and a slow response speed, which limits the promotion and application of the new generation of CFRTPCs with complex configurations and designable performance. Three-dimensional printing can efficiently create products with multiple materials, complex structures, and integrated functions, introducing new ways and opportunities for the manufacturing of CFRTPCs. However, poor mechanical properties are the bottleneck problem in achieving 3D printing of CFRTPCs. This paper summarizes the research status of the fused deposition modeling (FDM) 3D printing process and the corresponding mechanical properties of CFRTPCs. The focus is on analyzing the influences of the FDM process parameters, such as the material type, printing temperature, speed parameters, layer thickness, scanning space, stacking direction, and fiber volume content, on the mechanical properties of CFRTPCs. Finally, the main problems and future prospects of current CFRTPCs-FDM are analyzed and forecasted, providing new references and ideas for 3D printing of high-performance CFRTPCs.

Size effect on the forming limit of a nickel-based superalloy thin sheet at the mesoscopic scale

With the development of product miniaturization in aerospace and other fields, nickel-based superalloy thin sheets with excellent comprehensive properties have become crucial materials for micro-components in these fields. Due to the complexity of the initial microstructure and strengthening mechanism, there is a lack of in-depth research on the mesoscale formability of nickel-based superalloys under the coupled effects of multiple factors such as feature size (i.e., the ratio of specimen thickness to grain size, t/d), particle size and volume content of the precipitated phase. In this paper, a test platform was constructed for the application of high-precision strain measurements to the analysis of the mesoscale forming limit, and the mechanisms for the influences of feature size and precipitation on the mesoscale forming limit of a nickel-based superalloy were studied. The results showed that feature size influenced the forming limit of the nickel-based superalloy thin sheet at the mesoscopic scale, and the formability decreased with decreasing t/d and increasing γ′′/γ′ particle size and volume content. Based on surface layer theory and ductile fracture theory, the influences of t/d and γ′′/γ′ phases on the forming limit of nickel-based superalloy thin sheets at the mesoscopic scale were revealed. The coupled effects of surface roughening caused by free surface grains and hindered dislocation movement induced by precipitated phases resulted in strain localization and reduced the forming properties of nickel-based superalloy thin sheets at the mesoscopic scale.