Search Results (34)

Given the limitation of existing slope collapse monitoring technology, which relies on surface sensors, and the difficulty in capturing the precursors of deep rock and soil instability, this study used rock anchor embedded sensing technology to conduct collapse tests on artificial simulated slopes. Two groups of control conditions were designed: (1) shotcrete reinforced slope and natural slope; and (2) GFRP anchor and spiral steel anchor support system. The deformation characteristics of the slope at the initial stage of collapse were analyzed. The results show that the monitoring method based on the stress–strain response of deep rock mass significantly improved the early warning effect. GFRP anchor had a lower elastic modulus and responded more sensitively to small displacements than spiral steel anchor. Shotcrete reinforcement transformed slope deformation from ‘local dispersed deformation’ to ‘overall coordinated deformation’ and delayed slope instability via the ‘deformation hysteresis effect’. This study provides key technical parameters for the intelligent monitoring system of high-risk slopes as well as support for pre-disaster emergency evacuation decision-making and the establishment of intelligent early warning systems. Full article

This study investigates the axial compressive behaviour of rectangular concrete specimens confined with low-cost Glass Chopped Strand Mat (GCSM) sheets. While the GCSM has been explored in other contexts, this is the first study specifically investigating its effects on rectangular concrete specimens. A total of 24 specimens were tested, grouped by different unconfined concrete strengths. Each group included unconfined specimens and GCSM-confined specimens wrapped with 2, 3, and 4 layers. The results demonstrate that GCSM confinement significantly enhances both compressive strength and ductility, particularly in low-strength concrete, where normalized gains in strength and strain exceeded 50% and 160%, respectively. The post-peak modulus decreased with increasing confinement ratio, indicating improved energy dissipation and delayed failure. Additionally, experimental elastic modulus values showed good agreement with ACI 318 predictions. Analytical models were developed to predict peak strength, peak strain, and post-peak modulus as functions of confinement pressure, achieving excellent correlation with experimental data (R² > 0.98). Full article

Metallic nanofoams with amorphous structures demonstrate exceptional properties and significant potential for diverse applications. However, their mechanical properties at different temperatures are still unclear. By using molecular dynamics simulation, this study investigates the mechanical responses of representative CuZr amorphous metallic nanofoam (AMNF) under uniaxial tension and compression at various temperatures. Our results reveal that the mechanical properties, such as Young’s modulus, yield stress, and maximum stress, exhibit notable temperature sensitivity and tension–compression asymmetry. Under tensile loading, the Young’s modulus, yield strength, and peak stress exhibit significant reductions of approximately 30.5%, 33.3%, and 32.9%, respectively, as the temperature increases from 100 K to 600 K. Similarly, under compressive loading, these mechanical properties experience even greater declines, with the Young’s modulus, yield strength, and peak stress decreasing by about 34.5%, 38.0%, and 41.7% over the same temperature range. The tension–compression asymmetry in yield strength is temperature independent. Interestingly, the tension–compression asymmetry in elastic modulus becomes more pronounced at elevated temperatures, which is attributed to the influence of surface energy effects. This phenomenon is further amplified by the increased disparity in surface-area-to-volume ratio variations between tensile and compressive loading at higher temperatures. Additionally, as the temperature rises, despite material softening, the structural resistance under large tensile strains improves due to delayed ligament degradation and more uniform deformation distribution, delaying global failure. Full article

The flight feather rachis is a lightweight, anisotropic structure that must withstand asymmetric aerodynamic loads generated during flapping flight—particularly under unidirectional compression during the wing downstroke. To accommodate this spatiotemporal loading regime, the rachis exhibits refined internal organization, especially along the dorsoventral axis. In this study, we used finite element modeling (FEM) to investigate how dorsoventral polarization in cortical keratin allocation modulates the mechanical performance of shaft-like structures under bending. All models were constructed with conserved second moments of area and identical material properties to isolate the effects of spatial material placement. We found that dorsal-biased reinforcement delays yield onset, enhances strain dispersion, and promotes elastic recovery, while ventral polarization leads to premature strain localization and plastic deformation. These outcomes align with the dorsally thickened rachises observed in flight-specialized birds and reflect their adaptation to asymmetric aerodynamic forces. In addition, we conducted a conceptual exploration of radial (cortex–medulla) redistribution, suggesting that even inner–outer asymmetry may contribute to directional stiffness tuning. Together, our findings highlight how the flight feather rachis integrates cortical material asymmetry to meet directional mechanical demands, offering a symmetry-informed framework for understanding biological shaft performance. Full article

This study takes limestone crushed stone concrete as the research object and systematically investigates its mechanical property changes and microstructural damage characteristics under different confining pressures using triaxial compression tests, scanning electron microscope (SEM) tests, and digital image processing techniques. The results show that, in terms of macro-mechanical properties, as the confining pressure increases, the peak strength increases by 192.66%, the axial peak strain increases by 143.66%, the elastic modulus increases by 133.98%, and the ductility coefficient increases by 54.61%. In terms of microstructure, the porosity decreases by 64.35%, the maximum pore diameter decreases by 75.69%, the fractal dimension decreases by 19.56%, and the interfacial transition zone cracks gradually extend into the aggregate interior. The optimization of the microstructure makes the concrete more compact, reduces stress concentration, and thereby enhances the macro-mechanical properties. Additionally, the failure characteristics of the specimens shift from diagonal shear failure to compressive flow failure. According to the Mohr–Coulomb strength criterion, the calculated cohesion is 6.96 MPa, the internal friction angle is 38.89°, and the breakage angle is 25.53°. A regression analysis established a quantitative relationship between microstructural characteristics and macro-mechanical properties, revealing the significant impact of microstructural characteristics on macro-mechanical properties. Under low confining pressure, early volumetric expansion and rapid volumetric strain occur, with microcracks mainly concentrated at the aggregate interface that are relatively wide. Under high confining pressure, volumetric expansion is delayed, volumetric strain increases slowly, and microcracks extend into the interior of the aggregate, becoming finer and more dispersed. Full article

This study investigated the beneficial effects of individual and co-inoculation with Lactobacillus delbrueckii subsp. lactis N102 and Lactobacillus sakei H1-5 on improving safety parameters, sensory characteristics, and non-volatile metabolite profiles in dry-fermented sausages. Comprehensive analyses were conducted throughout the 20-day maturation period (0, 6, 13, 16, and 20 days), including physicochemical monitoring (moisture content, malondialdehyde (MDA) levels, biogenic amine concentrations, and sodium nitrite residues); sensory evaluation (color parameters and textural properties); and ¹H NMR-based metabolomic profiling. Key findings revealed strain-specific advantages: the N102 inoculation significantly delayed lipid oxidation, achieving the lowest final MDA concentration (4.5 mg/kg) among all groups. Meanwhile, H1-5 supplementation notably improved color attributes (a*/b* ratio = 1.34). The co-inoculation strategy demonstrated synergistic effects through (1) accelerated acidification (pH 5.3 by day 6); (2) enhanced textural properties (significantly increased hardness and elasticity vs. control); (3) optimized water distribution (free water reduced to 0.56% with 64.73% immobilized water); and (4) a significant reduction in sodium nitrite residues (70% decrease) and complete elimination of phenylethylamine (total biogenic amines: 702.94 mg/kg). ¹H NMR metabolomics identified 30 non-volatile metabolites, and the co-inoculation significantly increased the amount of essential amino acids (leucine, isoleucine), flavor-related compounds (glutamic acid, succinic acid), and bioactive substances (gooseberry, creatine). These metabolites enhanced antioxidant capacity, freshness, and nutritional value. Our findings demonstrate that strategic co-cultivation of food-grade lactobacilli can synergistically enhance both the techno-functional properties and biochemical composition of fermented meat products, providing a viable approach for quality optimization in industrial applications. Full article

Al₃BC, with its remarkably high modulus of elasticity (326 GPa) and hardness (14 GPa), coupled with a low density (2.83 g/cc), stands out as a promising reinforcement material for Al matrix composite. To study feasibility of solid-solid reaction (SSR) by forming an in situ Al₃BC reinforcing phase within the matrix, this study developed an Al₃BC/Al composite via mechanical alloying, followed by sintering at 1000 °C/1 h, and subsequent hot pressing at 400 °C/40 MPa. The reaction kinetics and corresponding electron microscopy images suggest that the aluminum (Al)-boron (B) reacts with graphene nanoplates (GNPs) to form both clusters and a heterogeneous multi-structured Al₃BC reinforcements network dispersed within the fine-grain (FG) Al matrix. The heterostructure contributes to a good balance between strength (~284 MPa) and ductility (~17%) and stiffness (~212 GPa). Superior strain hardening ability (n = 0.3515) endorses remarkable load-bearing capacity (σ_c = 1.63) and thereby promotes excellent strength-ductility synergy in the composite. The fracture morphology reveals that reasonable ductility primarily relies on the crack deflection by the FG-Al matrix, playing a critical role in delaying fracture. The potential importance of the matrix microstructure in the overall fracture resistance of the composite has been highlighted. Full article

This paper takes as its starting point the distributed parameter models for both torsional and axial vibrations of the oilwell drillstring. While integrating several accepted features, the considered models are deduced following the Hamilton variational principle in the distributed parameter case. Then, these models are completed in order to take into account the elastic strain in driving signal transmission to the drillstring motions—rotational and axial (vertical). Stability and stabilization are tackled within the framework of the energy type Lyapunov functionals. From such “weak” Lyapunov functionals, only non-asymptotic Lyapunov stability can be obtained; therefore, asymptotic stability follows from the application of the Barbashin–Krasovskii–LaSalle invariance principle. This use of the invariance principle is carried out by associating a system of coupled delay differential and difference equations, recognized to be of neutral type. For this system of neutral type, the corresponding difference operator is strongly stable; hence, the Barbashin–Krasovskii–LaSalle principle can be applied. Note that this strong stability of the difference operator has been ensured by the aforementioned model completion with the elastic strain induced by the driving signals. Full article

This study investigates the influence of curing temperature (explored at 10 °C, 20 °C, and 30 °C) on the volume changes of alkali-activated slag (AAS) pastes with the aim of expanding existing knowledge on alkali-activated materials (AAMs). The focus was on autogenous and thermal strains, internal relative humidity (IRH), heat flow and cumulative heat, setting times, and workability. The results indicate that increasing the curing temperature to 30 °C reduces autogenous shrinkage, likely due to changes in the elastic modulus and viscoelastic properties, while promoting swelling, especially for higher molarities. The coefficient of thermal expansion (CTE), related to thermal strains, is higher when the curing temperature is increased, but its development is delayed. The IRH is influenced more by the activating solution’s molarity than by curing temperature, although temperature does affect the initial IRH. The study also revealed that higher curing temperatures accelerate chemical reactions and reduce setting times. The initial workability was significantly affected by the solution-to-binder ratio, while higher temperatures decreased workability, especially at higher molarities. These findings contribute to the understanding of how curing temperature influences the durability of AAS pastes, offering insights into optimized construction practices under varying environmental conditions. Full article

With the widespread application of small-sized bolts in aerospace and other fields, the demand for measuring their connection structures is increasing. Currently, although ultrasonic longitudinal wave methods are commonly used for bolt pretension stress measurement, their accuracy is limited for small-sized bolts. This paper proposes a piezoelectric acoustic resonance method (PZTAR) for small-sized bolt pretension stress measurement based on acoustic elasticity theory, ultrasonic resonance principles, and a bolt stress–strain model. The method involves analyzing the ultrasonic time-domain signals of small-sized bolts under load in the frequency domain to better evaluate the changes in the ultrasonic frequencies under different pretension stress. The effectiveness of this method is verified through pretension stress measurement experiments. The results indicate that the proposed ultrasonic resonance method achieves an average error of less than 5% for M5 specification bolts. Compared to traditional ultrasonic time delay methods, the proposed method demonstrates higher measurement accuracy. Additionally, the ultrasonic resonance method exhibits better robustness during the measurement process. Full article

Fruit firmness in sweet cherries (Prunus avium L.) is a critical quality parameter highly valued by consumers as it is associated with fruit freshness. In general, firm fruit also cope better with storage and handling. Gibberellic acid (GA) is commonly used by sweet cherry producers to increase firmness, soluble solids content and fruit size. This study evaluated the effects of GA on the rheological properties of sweet cherry fruit at harvest and postharvest storage. Specifically, GA’s influence on susceptibility to mechanical damage during handling was evaluated. The following GA treatments were applied to two sweet cherry cultivars ‘Bing’ and ‘Lapins’: T0, control, T30—GA at 15 ppm applied at pit-hardening and straw-colour stages; T45—GA at 25 ppm at pit-hardening and GA at 20 ppm at straw-colour; and T60—GA at 30 ppm applied at pit-hardening and straw-colour. The results indicate that GA delayed harvest by two to four days in both cultivars, with ‘Lapins’ also showing a significant increase in fruit size. Regardless of spray concentration, GA increased the modulus of elasticity and fruit resistance evaluated as stress at the maximum point at harvest. These effects persisted after 35 days of storage at 0 °C and an additional three days of shelf-life at 15 °C. While the strain or deformation capacity of the fruit at bioyield at harvest was constant across treatments, it was, however, lower in the GA-treated fruit than in the controls during storage at 0 °C under the high-humidity conditions of modified atmosphere packaging. The less mature fruit harvested at colour 3.0 (red/mahogany) were stiffer (reduced deformation) and more sensitive to induced mechanical injury than the fruit harvested later at colour 3.5 (mahogany). The GA treatments increased fruit resistance to damage without increasing tissue deformability. Other questions associated with stiffer tissues and lower deformability during storage at 0 °C under high humidity should be further studied, specifically cultivars that are naturally high in box-cracking sensitivity during storage. Full article

Strain rockburst is a severe failure phenomenon caused by the release of elastic strain energy in intact rocks under high-stress conditions. They frequently occur in deep tunnels, causing significant economic losses, casualties, and construction delays. Understanding the factors influencing this disaster is of significance for tunnel construction. This paper first proposes a novel three-dimensional (3D) discrete element numerical analysis method for rockburst numerical analysis considering the full stress state energy based on the bonded block model and the mechanics, brittleness, integrity, and energy storage of the surrounding rock. This numerical method is first validated via laboratory tests and engineering-scale applications and then is applied to study the effects of compressive and tensile strengths of rock mass, tunnel depth, and lateral pressure coefficient on strain rockburst. Meanwhile, sensitivity analyses of these influencing factors are conducted using numerical results and systematic analysis methods, and the influence degree of each factor on the rockburst tendency is explored and ranked. The results reveal that laboratory tests and actual engineering conditions are consistent with numerical simulation results, which validates the rationality and applicability of the novel rockburst analysis method proposed in this paper. With the increase in compressive strength, the stress concentration degree, energy accumulation level, maximum stress difference, and maximum elastic strain energy within the rock mass all increase, leading to a stronger rockburst tendency. Tunnel depth and the lateral stress coefficient are positively correlated with rockburst tendency. As the lateral pressure coefficient and tunnel depth increase, rockburst tendency exponentially increases, while the maximum stress difference and maximum elastic strain energy within the rock mass also increase. The influence degree of each factor is ranked from highest to lowest as follows: tensile strength, lateral pressure coefficient, compressive strength, and tunnel depth. The research results provide theoretical support and technical guidance for the effective prediction, prevention, and control of rock burst disasters in deep tunnels. Full article

Machine-harvested seed cotton was taken as the research object to further clarify its creep performance, minimize its power consumption during the loading process, and obtain a better loading method. The uniaxial compression creep test was carried out using the Instron universal material test bench to apply cyclic loading treatment. The test factors included cyclic loading times, cyclic stress peak, and cyclic loading frequency. The energy consumption curve of the machine-harvested seed cotton during cyclic loading was obtained through OriginPro 2019b software, and its energy change law was analyzed. Creep strain was divided into two parts, namely, initial creep strain and creep strain increment, to elucidate the creep mechanism. The Burgers model was chosen to describe the creep strain increment. Results show that machine-harvested seed cotton exhibits energy consumption hysteresis during cyclic loading. The compression energy rapidly decreases with increasing cyclic loading times and then stabilizes. Meanwhile, the compression energy increases with increasing cyclic stress peak and cyclic loading frequency. The creep strain mechanism is also the same, which first rapidly increases and then levels off. Cyclic loading times, cyclic stress peak, and cyclic loading frequency have different effects on creep strain increment, instantaneous elastic modulus, hysteresis elastic modulus, viscosity coefficient, delay time, and relative deformation index. Finally, disregarding power consumption and interaction, extending the cyclic loading time, and increasing the cyclic stress peak while simultaneously minimizing the cyclic loading frequency can reduce the relative deformation index in the creeping stage. Accordingly, the deformation retention ability in the creep is improved, but the compression energy in the cyclic loading increases. The results can provide theoretical and data support for studying the theoretical basis of the rheological properties of machine-harvested seed cotton, the design of seed cotton baling devices, and the study of bale (mold) forming quality. Full article

The deterioration of the surrounding rock at the tunnel bottom is a damage mechanics issue that occurs under disturbance load. To investigate the anisotropic characteristics of mechanical behavior and the AE response mechanism of layered sandstone, uniaxial compression tests and acoustic emission (AE) monitoring were conducted. The results show that the layer structure causes remarkable anisotropic characteristics in the wave velocities. The strain characteristics and mechanical parameters of layered sandstone exhibit obvious deterioration effects. The local strain and overall strain show a synergistic feature, with the local strain path being more complex and the deformation response being extremely sensitive. The peak stress and elastic modulus both exhibit V-type distribution rules, slowly decreasing first, then rapidly decreasing, and finally increasing rapidly, with the boundary points of the layer angle being 45° and 67.50°. The peak stress and elastic modulus show a nonlinear exponential correlation with the layer angle, and the sandstone belongs to the intermediate anisotropy level. The rupture pattern shows significant anisotropic characteristics, with the failure modes including tension failure, including tension failure I and tension failure Ⅱ, shear failure, and tension–shear composite failure. The fractal dimension shows a negative correlation with the layer deterioration effect. The AE activity exhibits a phased response characteristic to the aging deformation of layer structure. The more obvious the layer deterioration effect is, the longer the AE delay is. The AE intensity of tensile failure sandstone is generally greater than that of oblique shear failure. Full article

The Jeffreys-type heat conduction equation with flux precedence describes the temperature of diffusive hot electrons during the electron–phonon interaction process in metals. In this paper, the deformation resulting from ultrafast surface heating on a “nanoscale” plate is considered. The focus is on the anomalous heat transfer mechanisms that result from anomalous diffusion of hot electrons and are characterized by retarded thermal conduction, accelerated thermal conduction, or transition from super-thermal conductivity in the short-time response to sub-thermal conductivity in the long-time response and described by the fractional Jeffreys equation with three fractional parameters. The recent double-strip problem, Awad et al., Eur. Phy. J. Plus 2022, allowing the overlap between two propagating thermal waves, is generalized from the semi-infinite heat conductor case to thermoelastic case in the finite domain. The elastic response in the material is not simultaneous (i.e., not Hookean), rather it is assumed to be of the Kelvin–Voigt type, i.e., $\sigma =E\left(\epsilon +{\tau }_{\epsilon }\dot{\epsilon }\right)$, where $\sigma$ refers to the stress, $\epsilon$ is the strain, $E$ is the Young modulus, and ${\tau }_{\epsilon }$ refers to the strain relaxation time. The delayed strain response of the Kelvin–Voigt model eliminates the discontinuity of stresses, a hallmark of the Hookean solid. The immobilization of thermal conduction described by the ordinary Jeffreys equation of heat conduction is salient in metals when the heat flux precedence is considered. The absence of the finite speed thermal waves in the Kelvin–Voigt model results in a smooth stress surface during the heating process. The temperature contours and the displacement vector chart show that the anomalous heat transfer characterized by retardation or crossover from super- to sub-thermal conduction may disrupt the ultrafast laser heating of metals. Full article