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Several studies using Friction Stir Welding (FSW) on dissimilar Aluminium and Copper weld configurations and the mechanical and microstructure characteristics, as well as the identification of intermetallic phases that appear in the weld region, have been conducted. Indeed, earlier several studies had been conducted in both lap and butt FSW joint designs. Even so, Al–Cu lap welding has received further attention than butt–welding, which has attracted only a few studies thus far. The studies ended with varying findings and were unable to reach high strengths despite the fact that very few studies addressed tool placement factors. The present investigation starts with butt–welding of AA1050 and pure Cu sheet by employing the FSW procedure. Experimental trails were designed using the L16 array (Taguchi’s technique) with distinct combinations of tool spinning speed, tool offset, welding speed, and plunge depth. Weld parameters such as compressive strength (CS), ultimate tensile strength (UTS), and average hardness at nugget zone (AHNZ) were evaluated using three different optimization methodologies, i.e. the WASPAS method, Alibaba and the Forty Thieves algorithm, and the Taguchi–WASPAS method, to find out the best weld constraint arrangement for maximizing the welded joint mechanical characteristics. ANOVA test was also conducted, which revealed that welding speed is the most significant and influential FSW factor for Al–Cu butt–welding using FSW. Finally, confirmatory tests were piloted to check the consistency of the predicted FSW parameters. [ABSTRACT FROM AUTHOR]

This research aims to produce green cement, as an alternative to traditional cement, with outstanding performance. Five alkali-activated cement pastes were fabricated based on NaOH-activation of slag (GGBFS), bypass (B), and/or silica fume (S). Codes of five pastes are C, C-20B, C-30B, C-10B10S, and C-20B10S, as C is the control paste containing 100% slag. The compressive strength of the fabricated pastes was measured at different curing regimes: Conventional curing for 3 months and autoclave curing at 4 bar/153◦C, 7 bar/178◦C, and 10 bar/198◦C for 4 h. XRD, TGA/DTG, SEM/EDX, and BET/BJH techniques were utilized to clarify the phase development, morphological and texture features of the formed alkali-activated composite pastes. Besides, the removal capacity of some pastes for methylene blue and indigo-carmine dyes from aqueous media was evaluated. The results confirmed that C and C10B10S (80%GGBFS + 10%B + 10%S) pastes have significant mechanical properties and distinctive meso-porosity that can remove both anionic and cationic dyes. [ABSTRACT FROM AUTHOR]

In this research, wear resistance of chromium nitride (CrN) coated aluminum alloy with hydrogen charging was investigated. Delamination rates of the CrN coating layer after 6 and 12 h of hydrogen charging were measured to be 42.37% and 86.96%, respectively. In particular, damage by hydrogen attack was observed in the exposed area of aluminum alloy. Increasing in applied load and hydrogen charging time decreased the friction coefficient, and when the two factors interacted, a significantly higher increasing rate of wear damage was observed. The increasing rate in wear depth due to hydrogen charging was greater at the applied of 1 N than at 5 N. This is because hydrogen permeation affects the wear resistance of the CrN coating layer and aluminum alloy in the depth direction. In addition, re-transfer and re-adhesion of the CrN coating, whose adhesion strength had decreased due to hydrogen charging, actively occurred. • The high durability of hydrogen valve is a very important factor for the commercialization of fuel cells. • The surface damage and delamination of the CrN coating layer by hydrogen charging were obviously observed. • The delamination of the CrN coating layer occurred in a bulk, and the wear resistance decreased accordingly. • In particular, hydrogen charging affected the adhesive wear of CrN-coated specimens. • Nevertheless the CrN coating technology is significantly excellent performance for resistance of hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

The introduction of bio-based matrices in automotive applications would, in principle, increase their sustainability and, in case the use of secondary raw materials is also involved, even result in reduced resource depletion. The bio-based polymer composite matrix that has been mainly brought forward towards industrial application is poly(lactic acid) (PLA), which has often been proposed as the replacement for matrices based on polyolefins in fields such as packaging and short-term commodities since, in general, it matches the needs for conventional thermoplastic production processes. The passage to the automotive sector is not obvious, though: problems affecting durability, the relation with water and the environment, together with the requirement for outstanding mechanical and impact performance appear very stringent. On the other hand, PLA has obtained durable success in additive manufacturing as a competitor for acrylonitrile butadiene styrene (ABS). Also, the perspective for 3D and 4D printing does not appear to be confined to bare prototyping. These contrasting pieces of evidence indicate the necessity to provide more insight into the possible development of PLA use in the automotive industry, also considering the pressure for the combined use of more sustainable reinforcement types in automotive composites, such as natural fibers. [ABSTRACT FROM AUTHOR]

In the South China Sea, a significant amount of methane hydrate exists in the sediment containing fine-grained soil. Increasing temperature and/or decreasing pore pressure can remarkably degrade the mechanical characteristics of this methane hydrate–bearing fine-grained sediment (HBFS). In this study, several compression tests under triaxial stress condition on HBFS are performed with changing temperature and pore pressure. The experimental results reveal that the HBFS specimen has an enhanced stiffness and failure strength characteristic under lower temperature and/or higher pore pressure conditions. An improved phase state parameter H is presented as a characterization for the temperature and pore pressure condition, which considers the capillary effect for HBFS with wide pore size distribution. The secant modulus and failure strength tend to linearly increase with the rising improved phase state parameter H. The internal friction angle is independent of the temperature and pore pressure, while the cohesion exhibits a significantly linear increase with the rising improved phase state parameter H. In addition, the shear–dilatancy curve shifts to the right with the rising improved state parameter H owing to the enhanced cementing strength of hydrate–soil cluster. These research findings are beneficial for grasping the mechanical behavior of HBFS. Furthermore, this research also provides data support for building the constitutive model of HBFS during methane hydrate recovery. [ABSTRACT FROM AUTHOR]

The response surface technique approach was used in this study to determine the best processing parameters for the three responses. For the friction stir welded dissimilar AA7075-T651 and AA1200- H19 aluminium alloys, the rotating and the welding speed, as well as the tool tilt angle, were used as input variables. Mechanical tests were performed on the weldment and the average hardness ranges from 64.26 to 99.72 HV, while the Ultimate Tensile Strength (UTS) ranges from 111.51 to 152.48 MPa. The impact energy was found to varry between 2.9 and 21.4 J. The results from the Signal to Noise (S/N) ratio revealed optimal welding parameters for hardness, UTS and impact energy as 1500 rpm speed of tool rotation, 30 mm/min transverse speed, and 2° tool tilt angle, while for UTS, it is a rotational speed of 1500 rpm, 90 mm/min transverse speed, tool tilt angle of 2° and finally for impact energy as 1500 rpm rotational speed, 30 mm/min transverse speed and 2° tool tilt angle. The results from the grey relational analysis gave optimal process parameters of 1500 rpm rotational speed, 60 mm/min transverse speed and 2° tool tilt angle. The results from the ANOVA revealed that tool rotational speed has the highest significant contribution of 41.79% to the hardness of the weldment followed by the rotational speed (34.46%) and then the transverse speed (19.44%). For UTS, tool rotational speed has the highest significant contribution (35.03%) followed by tool tilt angle (33.72%) and then transverse speed (30. 23%). Also, tool rotational speed has the highest significant effect on the impact energy of the weldment (37.45%) followed by transverse speed (32.00%) and then a tool tilt angle of (27.02%). Empirical models were developed using the Minitab 17 software with the central composite design (CCD) from which the UTS of 150.99 MPa, hardness of 99.102 HV and impact energy of 20.039 were obtained and were found to be close to the experimental values obtained. This study is significant as it gives insight into the optimum processing parameters of joining AA7075-T651 and AA1200- H19 aluminium alloys using the FSW and can be recommended for producing high quality welds with good joint integrity. [ABSTRACT FROM AUTHOR]

Crepe weave fabrics, known for their pebbly or crinkled (rough) surface, are widely used in clothing and bedding applications. Crinkled appearance for crepe weave can be achieved by different interlacement patterns. Generally, six methods/interlacement patterns are commercially used for fabricating crepe woven fabrics. However, there isn't any significant study reporting clothing comfort and mechanical attributes of crepe variants. In this study, crepe fabrics were developed by these six methods i.e., Base sateen (BS), Reversing method (R), Superimpose (SI), Subset (SS), Quarter turn (QT), and Plain base (P) methods. The yarn linear density, fabric density, and other fabric parameters were kept the same to determine the best development method for fabricating crepe woven fabric having higher thermal, sensorial, and mechanical properties. Characterization data revealed that each crepe variation possesses unique structural and physical parameters making performance differences i.e., the BS specimen exhibited the highest air permeability owing to higher porosity, the R specimen had superior Overall moisture management capability (OMMC) index due to compact yarn linkage, and the SS specimen showed best thermal conductivity performance due to its sophisticated crinkled appearance. Among mechanical attributes QT exhibited higher tensile and puncture strengths due to its compact structure with higher interlacements however, sateen interlacement governing yarn slippage made the tear strength higher for the BS specimen. [ABSTRACT FROM AUTHOR]

This study investigates the impact of long-term water immersion on the mechanical and hydrochemical properties of cemented calcareous soil, emphasizing the critical role of carbonate content in mechanical performance. Utilizing hydrochemical analysis and triaxial testing, the research revealed that prolonged immersion disrupts the acid-base balance of the solution, resulting in an increased concentration of ions and chemicals. Significant dissolution of carbonates and soluble minerals occurs, which reacts with carbon dioxide to generate bicarbonate ions, thereby elevating the alkalinity of the soaking solution. Additionally, the gradual dissolution of clay minerals compromises the cementitious structure, leading to particle reorientation and interlocking. The study quantitatively assesses the changes in soil properties, demonstrating a substantial reduction in soil cohesion by up to 86.1% and an increase in the internal friction angle by 37.5%. Furthermore, the gradual dissolution of clay minerals compromises the cementitious structure, resulting in particle reorientation and interlocking that contribute to the observed mechanical changes. The findings underscore the importance of understanding the effects of extended immersion on the stability and engineering applicability of cemented calcareous soils. [ABSTRACT FROM AUTHOR]

The mechanical properties of cemented paste backfill (CPB) directly determine the effect of backfilling in coal mining. However, the current studies on the mechanical properties of CPB are all based on standard cylinder or cube specimens, which cannot accurately characterise the distribution of mechanical properties in different spatial positions of CPB in situ. In addition, high-water-content material (HWM) has developed rapidly as a new binder in recent years. Therefore, in this paper, the uniaxial compressive strength (UCS) and elastic modulus of CPB with gangue as the aggregate and HWM as the binder (GHW-CPB) were investigated under different gangue particle sizes. The following conclusions were drawn: (1) The spatial evolution and distribution characteristics of mechanical properties of GHW-CPB are analysed. (2) The spatial evolution regression models of mechanical properties of GHW-CPB are established. (3) We improved the GHW-CPB spatial evolution regression models for mechanical properties due to their limitations and confirmed its validity and rationality. Through the research results of this paper, the failure position of the CPB in the goaf can be accurately predicted, so that manual interventions can be carried out in the vulnerable areas in advance to reduce the risk of coal mining production. [ABSTRACT FROM AUTHOR]

The mechanical properties and insulation damage of stator end windings in permanent magnet synchronous generator (PMSG) are investigated by theoretical analysis, finite element analysis (FEA) and experiment verification. First, a theoretical model of the winding electromagnetic force (EF) and vibration response before and after eccentricity faults are established. Then, the stress/strain distribution of the end windings under different working conditions is analyzed. Finally, the insulation damage behavior of end windings with initial cracks is studied and characterized using the stress intensity factor (SIF). The results indicate that the winding EF and vibration responses vary under different faults. The stress/strain at the joint of the winding is the largest, and the insulation layer has the maximum stress/strain under the same section. Additionally, the SIF amplitude of the crack at the winding joint is the largest. And the SIF amplitude of the crack will increase with the increase of fault degree/crack depth/crack length. The contribution of this paper lies in the comprehensive analysis of the winding EF distribution, vibration response, stress and strain, and insulation damage before and after eccentricity. This analysis can provide valuable reference for the health monitoring of PMSG eccentricity faults and the prevention of winding insulation damage. [ABSTRACT FROM AUTHOR]

The potential benefits of biodegradable and functional food packaging materials have garnered increasing attention in recent years. Sodium alginate (SA), a commonly utilized polysaccharide, is particularly noteworthy for producing biodegradable films for food packaging. This study aimed to investigate SA-based edible films enriched with various proportions of cactus pear peel extract (CPPE). We assessed the films and extracts for total phenolic content, antimicrobial and antioxidant activities, as well as mechanical properties. Cactus pear peels powder (CPPP) exhibited higher contents of total polyphenols (1243.82 mg GAE/100 g), total flavonoids (18.92 mg QE/100 g), and betalains (2.28 mg/100 g). The main constituents detected were catechol, pyrogallol, catechin, and alpha-coumaric acid, with concentrations of 1013.82, 223.45, 148.21, and 101.02 ppm, respectively, contributing about 45.71%, 9.85%, 6.54%, and 4.46% of the total phenolic compounds. The thickness of the SA films increased from 0.220 mm to 0.265 mm. The tensile strength values ranged from 1.98 to 3.12, while the elongation at break values for SA-CPPE films decreased relative to the plain SA film. Moreover, the inclusion of CPPE improved the barrier characteristics (with water vapor permeability values for SA films with 1%, 2%, and 3% CPPE ranging from 0.72 × 10−5 g•h−1 •m−1 •Pa−1 to 1.68 × 10−5 g•h−1 •m−1 •Pa−1) and induced variations in flexibility and resistance. The plain SA film did not exhibit any inhibitory activity against bacteria and fungi. However, the inclusion of CPPE in alginate films showed favorable antibacterial properties, which improved progressively with increasing CPPE concentration. These findings highlight the potential of incorporating active alginate-based films in food preservation. [ABSTRACT FROM AUTHOR]

Summary: A comprehensive analysis was conducted using optical microscopy based on wood anatomy to enhance the preservation of wooden components in Tingbao Yang's former residence. This study identified wood samples, and statistical examination of wood species, variations in their configuration, physical and mechanical properties, and natural durability were examined. The principles for wood species selection were assessed. Findings indicate that Cunninghamia lanceolata , Pseudotsuga spp., Populus spp. and Ulmus spp. are the primary choices for these wooden components. However, certain portions incorporate Larix sect. Multiseriales , Picea brachytyla , Pinus bungeana , Pinus massoniana , Castanea sp. and Quercus subg. Lepidabalanus , sect. Prinus. Pseudotsuga spp., C. lanceolata , Ulmus spp. and Populus spp. are primarily utilized for wooden columns and melon columns. However, C. lanceolata , Ulmus spp. and Populus spp. possess inadequate parallel grain compressive strength for load-bearing compression wooden components. C. lanceolata and Ulmus spp. are widely utilized in beams, lintels, purlins, and rafters owing to their exceptional bending strength. It was noted that Castanea sp. and Quercus subg. Lepidabalanus , sect. Prinus wood varieties demonstrate superior resistance to rotting and insects compared with other types of wood. The selection of wood species for the ancient buildings of Tingbao Yang's former residence relies on crucial principles, such as the suitability of wood properties and local selection. This selection process involves analyzing the wood properties, assessing the natural durability of wooden components, and considering the distribution of forest resources in Henan Province. [ABSTRACT FROM AUTHOR]

Fiber reinforced composites are made by reinforcing fibers in a polymeric matrix and shaping them to fit. Natural fibers, on the other hand, such as jute sisal, hemp, flax etc. are increasingly commonly utilized as reinforcements and perform similarly to artificial fibers. Man‐made fibers like as carbon, glass, and kevlar are utilized as reinforcements in the start and have shown to be the best in terms of characteristics, reinforcing capacity, and usefulness. Research investigations also show that when man‐made and natural reinforcements are combined in a hybrid form, the composite characteristics increase significantly. The composite material obtains all of the better qualities of individual fibers as a result of this combination, and when the composite is subjected to varying loads, each fiber gives its own maximal resistance. The chemical and physical properties are further enhanced by including particular reinforcements into polymer matrix composites, which provide whole new features (which has transformed the aerospace, marine, defence, and automobile industry). As a result, the composite would be better in all attributes. The current study provides a thorough examination of the different challenges concerning the synthesis and mechanical characterization of natural fiber reinforces hybrid polymer composites. Future difficulties, as well as areas of use for polymer matrix composites, have been investigated that may aid in the elimination of plastic waste and the reduction of environmental pollution. [ABSTRACT FROM AUTHOR]

Under the long-term influence of overburden load and water infiltration, coal undergoes creep damage, and the disturbance caused by mining activities can lead to sudden instability, triggering geological disasters such as mine flooding. Therefore, this study prepared four types of coal samples with different saturations under creep damage conditions and conventional coal samples. A comparative study was conducted using uniaxial compression tests to examine the deterioration characteristics of physical and mechanical parameters, failure modes, and energy evolution patterns in these two types of coal samples. Additionally, a microscopic deterioration model of coal samples under the combined influence of water and creep damage was constructed to elucidate the mechanism of creep damage on the deterioration of mechanical properties in water-containing coal samples. The research findings indicate that coal samples affected by creep damage and conventional coal samples exhibit significant consistency in mechanical parameters and energy evolution patterns. Specifically, an increase in saturation is positively correlated with peak stress, elastic modulus, and dissipated energy. Conversely, peak strain, total input energy, and elastic strain energy are negatively correlated with rising saturation levels. Under the same saturation conditions, the change in mechanical parameters and energy characteristics is more pronounced in creep-damaged coal samples. Furthermore, the stress-strain curves of both coal sample types exhibit prolonged compaction stages, shortened elastic stages, and more significant yield stages. Under equivalent saturation levels, the stress-strain trends in creep-damaged coal samples show more substantial variations. Upon loading and failure, the conventional coal sample transitions from single inclined plane shear failure to tension-shear mixed failure as the saturation increases. Conversely, the creep-damaged coal sample shifts from "X"-type conjugate shear failure and tension-shear mixed failure to tension failure, signifying a tendency toward more complex failure modes. In cases where the coal sample has a water saturation of 41%, the deterioration of its mechanical parameters is primarily attributed to creep damage. However, when the water saturation reaches 41–100%, water plays a dominant role in the deterioration of the coal sample's mechanical parameters. After experiencing creep damage, the internal micro-cracks of the coal sample are extensively developed, which is also the primary factor contributing to the deterioration of the coal sample's mechanical properties and an increased proportion of dissipated energy. [ABSTRACT FROM AUTHOR]

The microstructure development and mechanical behaviour of dissimilar metal welds between ferritic and austenitic steel, as well as their application in nuclear power plants, are discussed in this review paper. Nuclear reactor components, such as steam generators and pressure vessels, consist primarily of SA508 due to their low cost and high operating temperatures and pressures. The welding of dissimilar metals is crucial due to variations in physical characteristics such as thermal conductivity, thermal expansion coefficient, mechanical properties and chemical compositions. The principal challenges of dissimilar ferritic and austenitic steel welding are the subject of this review work. Weldability issues include a sharp change in mechanical and metallurgical characterization across the fusion line, carbon migration, cyclic thermal stresses and residual stresses, which necessitate a thorough investigation of the welded joint. Generally, austenitic steel and nickel-based fillers are used to join austenitic and ferritic steel materials; however, owing to many weldability concerns, nickel-based consumables are replacing austenitic consumables. Another critical issue in the weld joint is the selection of appropriate welding consumables, and detailed explanations of the benefits of employing a buttering layer on the ferritic side are provided. The effect of heat treatment on the metallurgical and mechanical characteristics of the weld joint, as well as the formation of residual stress, has also been thoroughly explored. [ABSTRACT FROM AUTHOR]

The BlueDeck profiled steel sheeting system offers an innovative composite flooring solution, integrating high-strength steel sheets with reinforced concrete to form a unified structure. This study aimed to evaluate the development of full composite action, the ultimate bearing capacity, and the flexural stiffness of the system. A comprehensive experimental programme involving 18 four-point bending tests and 6 shear tests was conducted to quantify the mechanical interaction between the steel deck and concrete slab. This study specifically examined bending capacity and vertical deflection, comparing the results with predictions from AS/NZS 2327. It was found that the system consistently achieved full composite action, with composite specimens demonstrating higher flexural stiffness and load-bearing capacity as the concrete depth increased. For example, specimens with 200 mm slab depths exhibited a 60% improvement in ultimate capacity compared to those with 150 mm slabs, while those with 175 mm depths saw a 27% increase. Additionally, the BlueDeck system showed an 81% improvement in de-bonding resistance in thicker slabs. The experimental results exceeded the bending moment and deflection limits prescribed by AS/NZS 2327, confirming that the system is structurally sound for use in buildings. This study provides quantitative evidence supporting the system's compliance with Australian standards, highlighting its potential for improving construction efficiency through reduced material use, while maintaining structural integrity under imposed loads. [ABSTRACT FROM AUTHOR]

Double perovskites present promising opportunities for harnessing energy from both sunlight and wasted heat. In this study, we conducted a comprehensive theoretical analysis to evaluate the mechanical, electronic, optical, and transport properties of K2LiTlX6 (X = Cl, Br, I) employing the WEIN2K code. The optimized FCC unit cell's lattice parameters exhibited an increase from 10.34 to 11.98Å when substituting Cl with Br/I. To ascertain thermodynamic and structural stability, we computed the enthalpy of formation (-2.64 to -1.89 eV) and the tolerance factor (0.97 − 0.93). The results provide evidence for the thermodynamic and structural stability of the compounds. Mechanical parameter calculations, comprising bulk, Young, and shear moduli, along with Poisson's ratio in three dimensions, reveal their anisotropic nature, with greater significance observed in K2LiTlBr6 and K2LiTlI6. Moreover, the numerical values of Poisson and Pugh ratios indicated their ductile characteristics. The materials also exhibit noteworthy properties such as hardness, ultra-low lattice thermal conductivities, and greater melting and Debye temperatures, enhancing their potential applications. The direct bandgap values underwent a transformation from the visible to the infrared region (2.57 − 0.14 eV) as the halogen size increased. Using the BoltzTraP code, we calculated temperature-dependent thermodynamic parameters, showing high electrical conductivity related to thermal conductivity. The combination of a higher Seebeck coefficient and ZT highlighted the appropriateness of these compounds for future energy harvesting applications. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond compact (PDC) bit is one of the most widely used drill bits for improving the rate of penetration in deep oil and gas well and geothermal well. However, the dynamic rock fragmentation mechanics characteristics of PDC bits are still unclearly. A coupled fragmentation mechanics model of PDC cutter-rock interaction is established by combining the mixed fragmentation modes with dynamic strength. The coupling influence laws of cutter angle, cutting depth, dynamic strength ratio, breaking modes on the horizontal force coefficient (HFC), vertical force coefficient (VFC) and specific energy are analyzed. The model of this paper can optimize cutter inclination angle, cutting depth and minimum specific energy. With the increase of the cutter inclination angle, the dynamic VFC changes into two modes. The definition of the dynamic modes depends on the dynamic strength ratio. As the cutting angle increases, the cutting force increases. The cutting force increases nonlinearly with increasing cutting depth. The specific energy of rock fragmentation increases nonlinearly with increasing cutting depth. With the increase of dynamic strength, the specific energy of rock fragmentation increases nonlinearly. When the input-energy increases, the rate of penetration response is divided into three stages. The results have important guiding significance for the PDC bit design and drilling parameters optimization to increase the rate of penetration and the efficiency of exploration and development. [ABSTRACT FROM AUTHOR]

Aluminum alloys (AAs) are pivotal materials in modern aircraft due to their superior mechanical properties and low weight. The structural integrity of these alloys, crucial for aircraft safety, heavily depends on heat treatment processes that alter their mechanical characteristics. Nondestructive evaluation (NDE) techniques, such as eddy current (EC) conductivity measurements, play a vital role in assessing these alloys throughout their lifecycle. EC methods enable the measurement of electrical conductivity, a structure-sensitive parameter that correlates with mechanical properties affected by heat treatments and operational stresses. This paper reviews the application of EC conductivity measurements in the aerospace industry, focusing on their role in assessing AA structural integrity. It discusses how EC methods can penetrate non-conductive coatings, crucial for in-service measurements without surface removal. Recent developments include a novel small-size EC probe and signal processing algorithms aimed at enhancing sensitivity to conductivity changes through dielectric coatings, up to 0.5 mm thick, commonly found in aircraft structures. Key findings include analyses of specific electrical conductivity (SEC) changes in AAs due to heat treatment deviations and long-term operational stresses, crucial for predicting residual life and maintaining safety standards. Case studies on aircraft wing skins and helicopter rotor blades demonstrate the practical application of EC conductivity meters in identifying critical damage zones. The methodology proves effective in evaluating localized degradation based on SEC distributions, thereby enhancing maintenance efficiency and aircraft safety. Overall, this research underscores the significance of EC conductivity measurements in advancing NDE practices for AAs in aircraft applications. The methodologies and findings presented aim to improve safety, durability assessment, and maintenance efficiency in the aerospace industry. [ABSTRACT FROM AUTHOR]

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Abstract This research aims to produce green cement, as an alternative to traditional cement, with outstanding performance. Five alkali-activated cement pastes were fabricated based on NaOH-activation of slag (GGBFS), bypass (B), and/or silica fume (S). Codes of five pastes are C, C-20B, C-30B, C-10B10S, and C-20B10S, as C is the control paste containing 100% slag. The compressive strength of the fabricated pastes was measured at different curing regimes: Conventional curing for 3 months and autoclave curing at 4 bar/153◦C, 7 bar/178◦C, and 10 bar/198◦C for 4 h. XRD, TGA/DTG, SEM/EDX, and BET/BJH techniques were utilized to clarify the phase development, morphological and texture features of the formed alkali-activated composite pastes. Besides, the removal capacity of some pastes for methylene blue and indigo-carmine dyes from aqueous media was evaluated. The results confirmed that C and C10B10S (80%GGBFS + 10%B + 10%S) pastes have significant mechanical properties and distinctive meso-porosity that can remove both anionic and cationic dyes.

Abstract This study investigates the impact of long-term water immersion on the mechanical and hydrochemical properties of cemented calcareous soil, emphasizing the critical role of carbonate content in mechanical performance. Utilizing hydrochemical analysis and triaxial testing, the research revealed that prolonged immersion disrupts the acid-base balance of the solution, resulting in an increased concentration of ions and chemicals. Significant dissolution of carbonates and soluble minerals occurs, which reacts with carbon dioxide to generate bicarbonate ions, thereby elevating the alkalinity of the soaking solution. Additionally, the gradual dissolution of clay minerals compromises the cementitious structure, leading to particle reorientation and interlocking. The study quantitatively assesses the changes in soil properties, demonstrating a substantial reduction in soil cohesion by up to 86.1% and an increase in the internal friction angle by 37.5%. Furthermore, the gradual dissolution of clay minerals compromises the cementitious structure, resulting in particle reorientation and interlocking that contribute to the observed mechanical changes. The findings underscore the importance of understanding the effects of extended immersion on the stability and engineering applicability of cemented calcareous soils.

The mechanical properties and insulation damage of stator end windings in permanent magnet synchronous generator (PMSG) are investigated by theoretical analysis, finite element analysis (FEA) and experiment verification. First, a theoretical model of the winding electromagnetic force (EF) and vibration response before and after eccentricity faults are established. Then, the stress/strain distribution of the end windings under different working conditions is analyzed. Finally, the insulation damage behavior of end windings with initial cracks is studied and characterized using the stress intensity factor (SIF). The results indicate that the winding EF and vibration responses vary under different faults. The stress/strain at the joint of the winding is the largest, and the insulation layer has the maximum stress/strain under the same section. Additionally, the SIF amplitude of the crack at the winding joint is the largest. And the SIF amplitude of the crack will increase with the increase of fault degree/crack depth/crack length. The contribution of this paper lies in the comprehensive analysis of the winding EF distribution, vibration response, stress and strain, and insulation damage before and after eccentricity. This analysis can provide valuable reference for the health monitoring of PMSG eccentricity faults and the prevention of winding insulation damage.

The objective of this study was to investigate the combined impact of nano-silica, steel microfibers, and ‎polypropylene microfibers on the mechanical properties, permeability, and resistance to chloride attack ‎of cement composite. To achieve this goal, a 2% weight ratio of nano-silica was used as a cement substitute, ‎while ‎1.0% steel and 0.2% polypropylene microfibers, respectively, by volume of the binders‎ were separately and simultaneously‎ ‎employed as additives in the cement composite. Experimental analyses, including compressive, flexural, and ‎tensile strength tests, were conducted to evaluate the mechanical properties. Additionally, the ultrasonic ‎pulse velocity (UPV) and sorptivity tests were employed to assess permeability, and the durability ‎against chloride attack was examined using the Rapid Chloride Migration Test (RCMT). The results ‎demonstrate that the simultaneous incorporation of nano-silica, steel microfibers, and polypropylene ‎microfibers in the cement composite mixture resulted in a significant enhancement in compressive strength, ‎flexural strength, flexural toughness, and tensile strength by 59.3%, 32.3%, 67.2%, and 25.9%, ‎respectively, compared to the control sample after a curing period of 90 days. Moreover, significant ‎decreases were observed in terms of the initial and secondary water absorption rates. Furthermore, the ‎penetration depth of chloride ions was notably reduced from 33.6 mm (in the control composite) to 14.2 ‎mm (in the composite containing the combined effects of nano-silica, steel microfibers, and polypropylene ‎microfibers) after 90 days. The enhancement of mechanical properties, permeability, and durability ‎against chloride attack in cement composite can be attributed to the synergistic mechanisms promoted by ‎the utilization of nano-silica, steel microfibers, and polypropylene microfibers. The filling effect, ‎nucleation sites, and pozzolanic activity of silica nanoparticles significantly contribute to the reduction of ‎porosity and refinement of the cementitious matrix's microstructure. Simultaneously, the inclusion of ‎steel microfibers and polypropylene microfibers reinforces the cement matrix and effectively controls ‎existing microcracks, thereby impeding the propagation of macrocracks and brittle failure in the cement ‎composite. Furthermore, the bridging effect of steel and polypropylene fibers aids in the control of cracks ‎caused by plastic shrinkage during the early stages and secondary or thermal cracks, thereby further ‎improving the properties of cement composite.

Currently, studies of structural superplasticity (SP) are of great interest, since the use of this mode in metalworking technologies allows for the production of parts of various shapes in one operation (with high repetition accuracy of even very complex shapes), while requiring less energy and material resources (relatively low pressures and tool wear) compared to deformation in the ‘normal plasticity’ mode. Other advantages of using a structural SP are improved physical and mechanical characteristics of the finished product: better surface quality after deformation, high ductility at elevated temperatures, increased strength at temperatures close to room one without reducing ductility (most often there is an increase in ductility), increased cyclic strength, hardness, impact resistance, elevated corrosion-resistance durability, and absence of anisotropy of properties after superplastic deformation.

A bending study was carried out on samples of rectangular cross-section made of structural steel 10Г2 (10G2) after laser hardening and laser alloying. It has been established that the presence of a laser impact zone leads to an increase in the elastic work area of the samples within 20–30 % in accordance with the implemented material processing mode and an even more significant increase in the level of perceived maximum load.

Geotechnical engineers are exploring the potential benefits of incorporating mineral additives like zeolite into soil stabilization, which is critical in construction activities. This laboratory experiment aims to assess the impact of zeolite on the microstructural and mechanical characteristics of clayey soil under both standard and temperature curing conditions. The study involves blending fine-grained clayey soil with different proportions of natural zeolite (0, 5, 10, 15, 20 percent by weight compared to the dry weight of the soil) to test the unconfined compressive strength (UCS), direct shear test (DST), and ultrasonic pulse velocity (UPV) under standard curing conditions (7, 28 and 90 days) at laboratory temperature and different curing temperatures (3 days at temperatures of 20°C, 40°C and 60°C). The microstructure of the specimens was also examined using a scanning electron microscope (SEM). Results from the study show that incorporating 5% zeolite into clayey soil enhances shear strength parameters and increases UCS significantly, 1.85 and 2.4 times higher than that of clayey soil, under both standard 90-day curing and accelerated curing at 60°C, respectively. Also, due to the improvement of shear strength parameters due to the addition of zeolite in two conditions of standard 90-day curing and accelerated curing at 60°C, the growth of 1.55, 1.86, 1.53, and 1.72 times has been observed for cohesion and internal friction angle of the soil, respectively. Analysis of the microstructure of the specimens revealed better compaction and improved particle connection due to the formation of aluminosilicate hydrate (ASH) gel with the addition of zeolite to the soil, illustrating the positive impact on mechanical characteristics. [ABSTRACT FROM AUTHOR]

Al7075 is employed as the matrix material and sugarcane bagasse ash (SBA) is a reinforcing material in this work, which is targeted at creating lightweight metal matrix composites (MMCs) at a reasonable cost. Hybridized improved composite castings have been produced and industrial as per ASTM standards with changing wt.% of 0%, 4%, 8%, 12%, and 16% wt.%, correspondingly, after mechanical testing for the evaluation of their strength. It is tested for hardness, tensile, impact, and flexural strength. Composites with hybrid enhanced metal matrix have greater tensile, hardness, and flexural strengths than single-reinforced MMCs. The composite's tensile and flexural strengths were boosted by a 12 wt.% increase in bagasse ash, which resulted in maximum values of 96.42% tensile and 23.58% flexural strength, respectively. As the bagasse weight percentage grew over 12%, these values fell, although Bagasse ash AA7075's impact and ductility improved slightly. [ABSTRACT FROM AUTHOR]

Urban operations such as counterterrorism, hostage rescue, and building clearance are the primary forms of modern warfare. The large scale of unstructured terrain makes quadruped combat platforms have great military potential and combat effectiveness in modern warfare. To explore the mechanical characteristics and firing disturbances of quadruped combat platforms under multiple shooting modes, the structure of the quadruped combat platform strike system was developed. Then, the rigid–flexible coupling launch dynamics model was built using ANSYS and ADAMS; in addition, simulations under single and continuous shooting modes were conducted by changing loads. According to the dynamic model, the launching process of the quadruped combat platform was simulated, the joint torque characteristics and firing disturbance of the quadruped combat platform were examined, and the method for suppressing the firing disturbance was explored. At last, the quadruped combat platform was confirmed by a live firing experiment in a 100-m indoor shooting range. Findings revealed that the joint torque distribution of the quadruped combat platform presents an uneven trend under static load conditions. The effect of the launching load resulted in a significant torque impact and oscillation to the joint of the quadruped combat platform. Moreover, firing disturbances were produced. Under the single shooting mode, the maximum amplitude of the muzzle center point of the quadruped combat platform along the z-axis direction is 8.42 mm, the maximum amplitude along the y-axis direction is 1.87 mm, and the firing disturbance momentum is 0.39 mm. Under the continuous shooting mode, the impact torque and firing disturbance of the first shooting are near the single shooting mode, whereas the impact torque of the subsequent firing increases by 25.8% compared with the first shooting. Meanwhile, with the superposition effect of the continuous firing vibration, the average firing disturbance also increases to 2.15 mm. Considering the reduction in firing disturbance, the effects of various buffers were discussed. The suppression effect of the unidirectional buffer was found not obvious due to the presence of the impact force during the return and forward processes, whereas the bidirectional buffer with damping can effectively lower the firing disturbance, and its average firing disturbance is 1.02 mm, decreased by 52.56% compared with the rigid connection. The live firing experiment confirmed the possibility of the quadruped combat platform, and the R50 of the platform with a bidirectional buffer was reduced by 47.0% compared with that with a rigid connection, demonstrating its effectiveness in suppressing the firing disturbance and enhancing the firing accuracy.

Multifunctional metastructure integrated broadband microwave absorption and effective mechanical resistance has attracted much attention. However, multifunctional performance is limited by the lack of theoretical approaches to integrated design. Herein, a multi-layer impedance gradient honeycomb (MIGH) was designed through theoretical analysis and simulation calculation, and fabricated using 3D printing technique. A theoretical calculation strategy for impedance gradient structure was established based on the electromagnetic parameter equivalent method and the multi-layer finite iterative method. The impedance of MIGH was analyzed by the theoretical calculation strategy to resolve the broadband absorption. Intrinsic loss mechanism of matrix materials and distributions of electric fields, magnetic fields and power loss were analyzed to investigate the absorption mechanism. Experimental results indicated that a 15 ​mm thick designed metastructure can achieve the absorption more than 88.9% in the frequency range of 2-18 ​GHz. Moreover, equivalent mechanical parameters of MIGH was calculated by integral method according to the Y-shaped model. Finite Element analysis of stress distributions were carried out to predict the deformation behavior. Mechanical tests demonstrate that MIGH achieved the compression modulus of 22.89 ​MPa and flexure modulus of 17.05 ​MPa. The integration of broadband electromagnetic absorption and effective mechanical resistance was achieved by the proposed design principle and fabrication methodology.

Abstract The industrial production of cement contributes significantly to greenhouse gas emissions, making it crucial to address and reduce these emissions by using fly ash (FA) as a potential replacement. Besides, Graphene oxide (GO) was utilized as nanoparticle in concrete to augment its mechanical characteristics, deformation resistance, and drying shrinkage behaviours. However, the researchers used Response Surface Methodology (RSM) to evaluate the compressive strength (CS), tensile strength (TS), flexural strength (FS), modulus of elasticity (ME), and drying shrinkage (DS) of concrete that was mixed with 5–15% FA at a 5% increment, along with 0.05%, 0.065%, and 0.08% of GO as potential nanomaterials. The concrete samples were prepared by using mix proportions of design targeted CS of about 45 MPa at 28 days. From investigational outcomes, the concrete with 10% FA and 0.05% GO exhibited the greatest CS, TS, FS, and ME values of 62 MPa, 4.96 MPa, 6.82 MPa, and 39.37 GPa, on 28 days correspondingly. Besides, a reduction in the DS of concrete was found as the amounts of FA and GO increased. Moreover, the development and validation of response prediction models were conducted utilizing analysis of variance (ANOVA) at a significance level of 95%. The coefficient of determination (R2) values for the models varied from 94 to 99.90%. Research study indicated that including 10% fly ash (FA) as a substitute for cement, when combined with 0.05% GO, in concrete yields the best results. Therefore, this approach is an excellent option for the building sector.

Abstract Owing to their exceptional mechanical properties, the various welding wires used to combine aluminum can meet the needs of many engineering applications that call for components with both good mechanical and lightweight capabilities. This study aims to produce high-quality welds made of AA7075 aluminum alloy using the GTAW technique and various welding wires, such as ER5356, ER4043, and ER4047. The microstructure, macrohardness, and other mechanical characteristics, such as tensile strength and impact toughness, were analyzed experimentally. To check the fracture surface of the AA7075 welded joints, the specimens were examined using optical and scanning electron microscopy (SEM). A close examination of the samples that were welded with ER5356 welding wire revealed a fine grain in the weld zone (WZ). In addition, the WZ of the ER4043 and ER4047 welded samples had a coarse grain structure. Because the hardness values of the welded samples were lower in the WZ than in the base metal (BM) and heat-affected zone (HAZ), the joints filled with ER5356 welding wire provided the highest hardness values compared to other filler metals. Additionally, the ER4047 filler metal yielded the lowest hardness in the weld zone. The welding wire of ER5356 produced the greatest results for ultimate tensile stress, yield stress, welding efficiency, and strain-hardening capacity (Hc), whereas the filler metal of ER4043 produced the highest percentage of elongation. In addition, the ER4047 fracture surface morphology revealed coarser and deeper dimples than the ER5356 fine dimples in the welded joints. Finally, the highest impact toughness was obtained at joints filled with the ER4047 filler metal, whereas the lowest impact toughness was obtained at the BM.

Abstract The sandstone is in a state of dry–wet cycle under the repeated action of rainfall, and its mechanical properties are deteriorated to varying degrees, which causes cracks in the sandstone. Therefore, it is of great significance to study the mechanical properties and fracture propagation of sandstone under the action of dry–wet cycles. Currently, there are limited studies using numerical simulation methods to study the fracture extension of rocks under various dry and wet cycling conditions.Therefore, in this paper, the effects of different amounts of dry and wet cycling on the mechanical properties and fracture behavior of sandstone are investigated through uniaxial compression tests and numerical simulations of fracture extension. The findings indicate that the deformation stage of sandstone remains unchanged by the dry–wet cycle. The uniaxial compressive potency and coefficient of restitution gradually diminish as the quantity of cycles rises, while the Poisson's ratio exhibits the opposite trend, and the impact on the mechanical performance of sandstone wanes with cycle increments, and the correlation coefficient surpasses 0.93, signifying a substantial influence of the dry–wet cycle on sandstone's mechanical performances. The discrepancy between the numerical simulation and experimental results is minimal, with a maximum error of only 3.1%, demonstrating the congruence of the simulation and experimental outcomes.The mesoscopic examination of the simulations indicates that the quantity of fractures in the sandstone specimens rises with the escalation of dry–wet cycles, and the steps of analysis linked to crack inception and fracture propagation are accelerated, and the analysis steps from fracture initiation to penetration are also reduced.

Due to excellent performance, hydrogen is treated as the most promising energy carrier. However, during the storage of liquid hydrogen, there are still some thorny issues that need to be addressed urgently, such as fluid thermal stratification and sloshing phenomenon. To efficiently grasp fluid sloshing mechanical characteristics, a simple visual sloshing experiment rig was established by using a rectangle transparent water vessel. The variations of the interface shape and the impact force during sloshing were monitored and analyzed. The effects of sloshing frequency, horizontal acceleration, and initial liquid height on fluid sloshing mechanical mechanism were investigated. The results show that when the external sloshing excitation is close to the first order natural frequency, obvious interface fluctuation and large amplitude sloshing force variation are observed. The present work is of significance to strengthen the understanding of fluid sloshing mechanical performance and may lay a solid foundation for fluid sloshing suppression and long‐term storage of cryogenic fuels. [ABSTRACT FROM AUTHOR]

Graphene platelets (GPLs) are gaining popularity across various sectors for enhancing the strength and reducing the weight of structures, thanks to their outstanding mechanical characteristics and low manufacturing cost. Among many engineering structures, wind turbine blades are a prime candidate for the integration of such advanced nanofillers, offering potential improvements in the efficiency of energy generation and reductions in the construction costs of support structures. This study aims to explore the potential of GPLs for use in wind turbine blades by evaluating their impact on material costs as well as mechanical performance. A series of finite element analyses (FEAs) were conducted to examine the variations of mechanical performances—specifically, free vibration, bending, torsional deformation, and weight reductions relative to conventional fiberglass-based blades. Details of computational modeling techniques are presented in this paper. Based on the outcomes of these analyses, the mechanical performances of GPL-reinforced wind turbine blades are reviewed along with a cost–benefit analysis, exemplified through a 5MW-class wind turbine blade. The findings affirm the practicality and benefits of employing GPLs in the design and fabrication of wind turbine blades. [ABSTRACT FROM AUTHOR]

The industrial production of cement contributes significantly to greenhouse gas emissions, making it crucial to address and reduce these emissions by using fly ash (FA) as a potential replacement. Besides, Graphene oxide (GO) was utilized as nanoparticle in concrete to augment its mechanical characteristics, deformation resistance, and drying shrinkage behaviours. However, the researchers used Response Surface Methodology (RSM) to evaluate the compressive strength (CS), tensile strength (TS), flexural strength (FS), modulus of elasticity (ME), and drying shrinkage (DS) of concrete that was mixed with 5–15% FA at a 5% increment, along with 0.05%, 0.065%, and 0.08% of GO as potential nanomaterials. The concrete samples were prepared by using mix proportions of design targeted CS of about 45 MPa at 28 days. From investigational outcomes, the concrete with 10% FA and 0.05% GO exhibited the greatest CS, TS, FS, and ME values of 62 MPa, 4.96 MPa, 6.82 MPa, and 39.37 GPa, on 28 days correspondingly. Besides, a reduction in the DS of concrete was found as the amounts of FA and GO increased. Moreover, the development and validation of response prediction models were conducted utilizing analysis of variance (ANOVA) at a significance level of 95%. The coefficient of determination (R2) values for the models varied from 94 to 99.90%. Research study indicated that including 10% fly ash (FA) as a substitute for cement, when combined with 0.05% GO, in concrete yields the best results. Therefore, this approach is an excellent option for the building sector. [ABSTRACT FROM AUTHOR]

In particular, the impact of Silicon Carbide (SiC) particles on the mechanical properties of stir-cast Al5052 alloy Metal Matrix Composites (MMCs) for rotor blade applications is examined in this work. The goal of integrating SiC particles is to improve mechanical characteristics including wear resistance, tensile strength, and hardness while preserving the ideal weight-tostrength ratio, which is essential for rotor blade performance. The Al5052 matrix was filled with SiC in a variety of compositions (0%, 2%, 4%, 6%, and 8% by weight), and the resultant composites underwent mechanical testing and microstructural examination. Due to the efficient load transfer and reinforcing processes, the results show a considerable improvement in tensile strength and hardness with the addition of SiC particles. Furthermore, microstructural analyses demonstrate a uniform dispersion of SiC in the matrix, which supports the improved performance attributes. Wear resistance of Al5052 alloy is greatly increased when Silicon Carbide (SiC) particles are added as reinforcement. This makes the composite material perfect for applications requiring great durability and longevity to survive hard mining conditions, such as wear plates, conveyor liners, and drill bits in mining machinery components. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the structural evolution, phase transformation, and mechanical strength of Al–12Si obtained using wire electron beam additive manufacturing has been investigated. The as-built Al–12Si alloy was characterized by structural inhomogeneities in the form of interlayer bands with coarsened Si particles resulted from cyclic reheating of the solidified metal. Quenching the as-built samples resulted in the increase of the volume fraction of Al/Si eutectics by 9% with simultaneous refinement of Fe-containing particles. This structure allows obtaining the combination of strength and plasticity better than that of the asbuilt sample. Annealing leads to coarsening of both Si and Fe-containing particles, thereby increasing the Al/Si volume fraction and impairing the mechanical characteristics. [ABSTRACT FROM AUTHOR]

There has been a significant interest in the development of eco-friendly building materials. Recyclable and environmentally friendly, geopolymer composites are extraordinary binding materials. The purpose of this experimental study was to examine the mechanical and durability properties of metakaolin based self-compacting geopolymer concrete (SCGPC) comprising steel fibers (SF) and recycled aggregate concrete (RCA) varying percentages of recycled coarse aggregate. The mechanical and durability properties of the geopolymer composites, including fracturing tensile strength, and flexural strength, were subsequently evaluated. At weight proportions of 0%, 25%, 50%, 75% and 100%, the recycled coarse aggregates were substituted for the natural coarse aggregates. The amounts of SF incorporated into the mixtures were 0, 0.5, 1.0, and 1.5% by volume fraction. While the incorporation of SF does not yield a substantial improvement in compressive strength, it substantially enhances fracture tensile strength and flexural behavior. The load-displacement graph demonstrated that the incorporation of steel fibers into geopolymer composites increased their fracture toughness, resulting in a higher maximal load capacity. The findings suggest that the incorporation of RCA into SCGPC reduces its flexural behavior, splitting and compressive tensile strengths, and durability, particularly under peak load, deflection, and load. Furthermore, it is observed that RCA negatively synergize with respect to compressive and fracturing tensile strength. However, SF exhibit a significant positive synergy in terms of flexural properties. [ABSTRACT FROM AUTHOR]

In this study, a bulk-area stirring zone (BSZ) was generated within the Al–Mg–Si alloy using friction stir processing with a combination of pin overlapping and water cooling. Detailed examinations were conducted on various aspects, including microstructural evolution, intermetallic behavior, crystallographic texture, and mechanical properties. The bulk-area stir zone (BSZ) microstructure contains an equiaxed fine-grained structure with more fraction of high-angle grain boundaries due to intense plastic straining and dynamic recrystallization. The grain refinement remained consistent across each overlapping pass, typically within the range of 3 to 4 µm. Notably, the BSZ exhibited the formation of A1-{111}(112) texture components with a maximum intensity of 5.4 owing to the material flow caused by the tool's revoluting nature around the pin. The hardness distribution across the BSZ was found to be uniform and aligned with the grain size values. The combined effects of material softening and intermetallic dissolution in the BSZ led to a substantial enhancement of 127% in ductility. [ABSTRACT FROM AUTHOR]

Some applications, such as aerospace testing and monitoring the operating conditions of equipment on space missions, require mechanical sensors capable of measuring accelerations at frequencies of several hundred hertz. For such measurements, optomechanical sensors can be used, providing the ability to measure accelerations without calibration. To enable such measurements, improved designs of drum-type sensors with the assigned performance have been elaborated. Such designs make it possible to provide the necessary levels of natural frequencies for optomechanical sensors and eliminate crosstalk. Using mathematical modeling, the dependencies of the mechanical characteristics of the proposed types of acceleration sensors versus their parameters were obtained. The use of such sensor designs ensures their compactness, making their manufacturing more technologically sound and suitable for use, in particular, in space missions. [ABSTRACT FROM AUTHOR]

The effect of sintering temperature on the mechanical and tribological characteristics of 2D phase reinforced copper-based composite has been investigated in the present study. The Cu-based composites containing 2 wt. % of(GO + MoS2)NP were sintered at different temperatures (1023, 1073, 1123, and 1173 K) by microwave sintering process. The microstructural features observed by SEM and HRTEM of composites suggest that as the sintering temperature increases (GO + MoS2)NP pocket formation tendency also increases, which also governs the mechanical and tribological characteristics of composites. As the sintering temperature elevated, the ultimate tensile strength of the composite decreases, whereas friction and wear rate decrease with increase in temperature up to 1123 and beyond 1123 increase in friction and wear has been observed. The decrease in strength with increasing sintering temperature has been attributed to the grain size increment and increase in (GO + MoS2)NP pocket size at the grain boundaries. However, the decrease in friction and wear rate has been ascribed to the ease of extrusion of (GO + MoS2)NP from the pockets for the composites sintered at high temperature, rather than extrusion of (GO + MoS2)NP of fillers from the intra-grainular sites, i.e., for the composites sintered at lower temperature. [ABSTRACT FROM AUTHOR]

Magnesium Metal Matrix Composites (MMMCs) possess remarkable mechanical and metallurgical properties that have garnered the interest of researchers worldwide. The current research endeavors to synthesize nanocomposites based on magnesium (Mg), specifically AZ31B, by employing Friction Stir Processing (FSP) and integrating nano-titanium carbide (TiC) as a reinforcing element. Additionally, the impact of various FSP parameters, encompassing transverse speeds (35 and 70 mm/min) and tool rotation speeds (850 and 1700 rpm), on the metallurgical, wear, and mechanical properties of the developed MMMCs was investigated. The microstructural analysis revealed that employing the FSP technique led to a uniform dispersion of nano-TiC reinforcement particles within the base matrix of the AZ31B Mg alloy. This concurrent distribution played a crucial role in both refining and evolving the grain sizes, subsequently leading to improvements in the composites's mechanical and wear characteristics. To be more specific, the grain size witnessed a reduction by nearly 18 times, the microhardness increased by approximately 2.54 times, and the ultimate tensile strength (UTS) showed a 2.08-fold increase when compared to the base alloy. Furthermore, in contrast to the base material characterized by an adhesive wear mechanism, the presence of scratches indicates that the abrasive wear mechanism predominated in the case of the AZ31B/TiC nanocomposite. The outcome of the results depicts that the nanocomposite fabricated at a tool rotation speed of 1700 rpm and 70 mm/min transverse shows better mechanical and tribological characteristics than other developed composites and the base alloy. [ABSTRACT FROM AUTHOR]

The steel rib and the lattice girder are two typical steel arch frames used in the primary lining of the New Austrian Tunnelling Method (NATM) highway tunnel. In the process of tunnel construction, it is necessary to choose the support method according to the mechanical properties, durability, construction difficulty, and economic benefits. In order to analyze the mechanical characteristics of steel arch frames, a loading and measurement test system for steel arch was designed, and destructive tests were carried out on a three-bar lattice girder, four-bar lattice girder, and I-beam steel rib. The steel utilization coefficient was introduced to compare the mechanical properties of the different types of steel frames. The results show that the I-beam steel rib has the largest steel utilization coefficient, but it is not well combined with concrete. Among the lattice girders, the three-bar W-shaped lattice girder uses the least amount of steel under the same load, which reduces the construction cost and is worth applying and popularizing. Additionally, the steel utilization coefficient of different types of lattice girders can be optimized through the ratio of steel bar diameters. It is proved that the steel utilization coefficient can provide a reference for the evaluation and selection of steel frames for the primary lining of highway tunnel engineering. [ABSTRACT FROM AUTHOR]

In view of the safety of the construction of the long foundation pit of the new upper span to the existing subway under urban complex environment conditions, combined with the construction of the intersection section of the first line of the existing subway across the north–south Expressway in Shenyang, the mechanical properties during construction were studied by means of numerical simulation and on-site monitoring. The results showed that the general deformation characteristic of the existing metro tunnel was "uplift first, then restrain". The local deformation characteristic was an unloading rebound in the cross region, and a compression deformation occurs outside the cross region. The index could be controlled in the range of the control value of the existing line protection by adopting the measures consisting of an uplift pile + capping beam balance, reinforcing the surrounding soil, the excavation of the foundation pit in sections, and the comprehensive construction. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation of the possibility of the reliable determination of the residual stress–strain state in polymers and composites using a combination of bridge curvature, optical scanning, and finite element methods. A three-factor experiment was conducted to determine the strength of printed PLA plastic products. The effect of the residual stresses on the strength of the printed products was evaluated. By comparing the values of the same strength stresses, a relationship between the nature of the stresses and the strength of the samples was found. A tendency of the negative influence of tensile stresses and the opposite strengthening effect of compressive stresses was obvious, so at the same values of tensile strength, the value of residual stress of 42.9 MPa is lower than that of the fibre compression at the value of 88.9 MPa. The proposed new methods of the residual stress determination allow obtaining a complete picture of the stressed state of the material in the investigated areas of the products. This may be necessary in confirming the calculated models of the residual stress–strain state, clarifying the strength criteria and assessing the quality of the selected technological modes of manufacturing the products. [ABSTRACT FROM AUTHOR]

With the growth of the wind energy market and the increase in the size of wind turbines, the demand for advanced composite materials with high strength and low density for wind turbine blades has become imperative. Graphene platelets (GPLs) stand out as highly premising reinforcements due to their exceptional physical properties, resulting in their widespread adoption in the composite industry in recent years. The present study aims to analyze the applicability of a graphene-platelet-reinforced composite (GPLRC) to wind turbine blades in terms of structural performance. A finite element blade model is constructed by referring to the National Renewable Energy Laboratory (NREL) 5 MW wind turbine, and its reliability is verified through a convergence test. The performance of the wind turbine blade is quantitatively examined in terms of the deflection and stress, natural frequencies, and twist angle. The applicability of the GPL-reinforced wind blade is explored through a comparison with wind blades manufactured with glass fiber and carbon nanotubes (CNTs). The comparison indicates that the performance of a wind blade can be remarkably improved by reinforcing with GPLs instead of traditional fillers, and the weight of not only the wind blade itself but also the wind turbine system can be remarkably reduced. The present results can be useful in the development of next-generation high-strength lightweight wind turbine blades. [ABSTRACT FROM AUTHOR]

Flaw length has a significant effect on the cracking behaviour of fractured rock. PFC2D was used to simulate the uniaxial compression of red sandstone samples with secondary flaw lengths L2 of 0 mm, 5 mm, 10 mm, 15 and 20 mm under different primary flaw angles α(α = 0°, 15°, 30°, 45°, 60°, 75°, and 90°). Based on the simulation results, the effects of the secondary flaw length on the mechanical parameters, crack initiation location and crack evolution process of the fractured rock were analysed. Then, a method for judging the initiation location of the first cracks was proposed. Finally, the characteristics of the particle displacement field at preexisting flaw tips during first and secondary crack initiation were analysed. The results of this study are helpful for more deeply understanding the cracking behaviour of fractured rock. [ABSTRACT FROM AUTHOR]

Renewable energy markets, particularly wind energy, have experienced remarkable growth, predominantly driven by the urgent need for decarbonization in the face of accelerating global warming. As the wind energy sector expands and turbines increase in size, there is a growing demand for advanced composite materials that offer both high strength and low density. Among these materials, graphene stands out for its excellent mechanical properties and low density. Incorporating graphene reinforcement into wind turbine blades has the potential to enhance generation efficiency and reduce the construction costs of foundation structures. As a pilot study of graphene reinforcement on wind turbine blades, this study aims to investigate the variations of mechanical characteristics and weights between traditional fiberglass-based blades and those reinforced with graphene platelets (GPLs). A finite element model of the SNL 61.5 m horizontal wind turbine blade is used and validated by comparing the analysis results with those presented in the existing literature. Case studies are conducted to explore the effects of graphene reinforcement on wind turbine blades in terms of mechanical characteristics, such as free vibration, bending, and torsional deformation. Furthermore, the masses and fabrication costs are compared among fiberglass, CNTRC, and GPLRC-based wind turbine blades. Finally, the results obtained from this study demonstrate the effectiveness of graphene reinforcement on wind turbine blades in terms of both their mechanical performance and weight reduction. [ABSTRACT FROM AUTHOR]

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