Search Results (1,618)

Based on the three-dimensional Grain-Based Model, the influence of the micro-strength and micro-modulus of the intragranular structures on the mechanical behavior of the model was explored from the point of force chains. The force chain characteristic of the sample is quantified, and then the force chain characteristics of the samples were quantitatively analyzed to reveal the evolution mechanism of the overall mechanical parameters and fracture characteristics of the samples when the micro-parameters of the intragranular contact changed. It is found that with the increase in contact micro-strength, bonding can withstand a higher level of concentrated stress. In the loading process, the slippage between particles occurs, but the overall slippage distance decreases due to the decrease in the number of fracture bonds, which leads to an increase in the strength and deformation resistance of the sample. With the increase in the contact micro-modulus, the allowable distance of particle slippage decreases. The lower force chain can make the slippage distance of particles reach the threshold value, and the external load easily causes the generation of cracks. Therefore, the overall strength of the sample decreases, and the overall deformation of the sample decreases. The research results can provide some references for the construction of the heterogeneity model, quantitative analysis of the force chain network, and calibration of model micro-parameters. Full article

Resistance spot welding of aluminum alloys causes the electrode materials to degrade rapidly. This is due to diffusion processes occurring between the sheet materials and the copper electrodes at process temperatures of up to 600 °C. This significantly limits the electrode life, resulting in less than 60 weld cycles before the joint quality becomes insufficient. Thin-film diffusion barriers can increase electrode life and improve joint quality. This article describes the generation of barrier layers of nickel and tungsten using physical vapor deposition. These layers directly influence the welding process by altering the electrical resistance and friction coefficients in the contact area. Nanoindentation is used to determine the specific properties of the barrier layers within the 2.5–3 µm layer thickness range. Hardness and modulus of elasticity are determined by indentation tests. Scratch tests determine the friction coefficients and adhesion strength of the coating against plastic deformation. Nanoindentation is also used to investigate the degradation process of the electrode base material and barrier layers. This reveals which damage mechanisms occur with uncoated electrodes and demonstrates how thin-film diffusion barrier coatings can prevent aluminum diffusion. Full article

China’s loess deposits exhibit high vulnerability to deformation under precipitation and snowmelt, posing significant risks to infrastructure. This study utilized enzyme-induced carbonate precipitation (EICP) to enhance the mechanical properties of Yili loess. Comparative analyses of untreated and EICP-treated samples were conducted using unconfined compression strength (UCS) tests, unconsolidated–undrained (UU) triaxial shear tests, and scanning electron microscopy (SEM). Results demonstrated that urease activity increased markedly between 25–65 °C, while calcium carbonate production peaked at 55 °C before declining. EICP treatment elevated UCS by 52% relative to untreated soil and altered the failure mechanisms: untreated specimens failed through penetrating shear cracks, whereas treated specimens exhibited compressive failure with vertical fissures. Triaxial tests confirmed enhanced properties in EICP-stabilized loess, showing 8.3–10.7% higher failure strength and 15.7% greater cohesion (increasing from 31.3 kPa to 36.2 kPa), while the internal friction angle remained largely unchanged. Microstructural analysis revealed that EICP generated continuous cementitious layers and crystal bridges of vaterite, transforming particle contacts from point-to-point to surface-to-surface interfaces. Simultaneously, crystal precipitation reduced pore sizes and increased tortuosity. These micro-scale modifications improved interparticle friction constraints and stress transfer efficiency, thereby enhancing the macroscopic mechanical performance. The findings validate EICP’s efficacy for stabilizing collapsible loess deposits and provide insights for geohazard mitigation in similar engineering contexts. Full article

The low hardness of copper alloys, which are the substrate material used for continuous casting molds, makes them prone to plastic deformation, wear, and high-temperature oxidation, leading to premature failure and the formation of surface defects on billets. In this work, the microstructure, phase composition, mechanical, and tribological properties of Cr₃C₂–NiCr coatings deposited by high-velocity oxy-fuel (HVOF) spraying onto copper substrates used in molds were investigated. This research was driven by the need to extend the service life of copper molds in continuous steel casting processes. It was established that spraying parameters have a decisive influence on porosity, coating thickness, microhardness, and friction behavior under conditions simulating billet contact with the working surface of the mold. Among the investigated regimes, the coating deposited at a powder feed rate of 11.39 m/s exhibited a dense lamellar structure and the highest level of microhardness. Tribological tests confirmed that this coating exhibited the lowest coefficient of friction, whereas the other coatings were characterized by higher porosity and poorer wear resistance. Thus, the results emphasize the necessity of optimizing spraying parameters to develop highly effective HVOF protective coatings for copper molds operating under extreme thermomechanical loads during steel casting. Full article

In the field of shipping engineering, guide walls serve as core flow-guiding structures for river regulation and waterway maintenance. Their structural stability, construction efficiency, and maintainability directly determine shipping safety and construction costs. Currently, guide walls in mountainous rivers predominantly utilize cast-in-place monolithic structures, which suffer from issues such as complicated construction, high cement consumption, and poor adaptability. This study proposes a novel prefabricated reinforced guide wall, consisting of a base plate, prefabricated concrete units, intra-layer bolts, and inter-layer reinforcement bars, and develops a nonlinear numerical framework, integrating contact mechanics, metal plasticity, and finite element analysis to investigate the mechanical behavior of the proposed wall structure under hydraulic loads. The results show that the prefabricated reinforced guide wall exhibits stable stress and deformation responses and maintains reliable inter-layer stability. Benefiting from its hollow prefabricated configuration, which replaces part of the concrete with rockfill, the proposed system substantially reduces cement demand and supports low-carbon and sustainable construction. This study provides both theoretical insights and engineering evidence for the safe, efficient, and sustainable application of prefabricated reinforced guide walls in mountainous river locks. Full article

In light of frequently occurring wellbore instability such as wellbore collapse and sand production that often occur in drilling and the completion of shale oil and gas development, we propose one-run shape memory thermosensitive screen technology that can expand spontaneously at a specific temperature to help strengthen the formation. Based on the theory of thermal expansion and large deformation of shape memory materials, the expansion process of the thermosensitive screen is calculated by the finite element method. After expanding to the wellbore wall, the effects of the screen squeezing force on the formation production parameters are evaluated theoretically. The analysis shows that the radial compressive stress of the thermosensitive screen decreases with the increase in the radial distance, but as the original outer diameter of the thermosensitive screen is greater than the wellbore diameter, it can provide extrusion force for the wellbore wall. According to the in situ stress model, the extrusion force after the screen contacts the wellbore can effectively improve the stress distribution near the wellbore and reduce the impact of sand production caused by formation instability. Moreover, in shale oil and gas completion, it can effectively increase the bottom hole flowing pressure and drawdown pressure. Full article

Based on actual topography measurement data, this study adopts a paraboloid of revolution to characterize asperity geometry and establishes a lateral contact model that accounts for substrate deformation and covers the full elastic–plastic process. The proposed model achieves smooth transitions in contact behavior, effectively avoiding non-physical oscillations and discontinuities in the elastoplastic regime exhibited by existing models. Comparative results with multiple classical models demonstrate that the proposed model maintains strict monotonicity and continuity in predicting contact load, average contact pressure, and contact stiffness. This significantly improves prediction accuracy and physical consistency, providing a more reliable theoretical tool for modeling precision mechanical joint interfaces. Full article

This study developed and characterized zein-based edible films enriched with curcumin as natural pH-sensitive indicators for monitoring fish freshness. Colorimetric films were prepared with different curcumin concentrations (1–7% wt) and evaluated for physicochemical, mechanical, optical, and antioxidant properties. Increasing curcumin content reduced water vapor permeability (0.085–0.110 g·mm/m²·h·kPa), lowered water contact angles (<90°), and enhanced hydrophilicity. Films exhibited high brightness, with decreased a* and increased b* values, while light transmission decreased, improving UV barrier properties. Colorimetric response (ΔE*) across pH 3–10 was more pronounced at higher curcumin levels, confirming pH-sensitivity. Antioxidant activity significantly increased with curcumin loading (up to 24.18 µmol Trolox/g). Mechanical analysis revealed decreased tensile strength but improved elongation at break, bursting strength, and deformation, supported by SEM images showing more homogeneous, micro-porous structures at 7% curcumin. Zein films containing 7% (wt) curcumin (Z/CR7) were applied to gilthead sea bream (Sparus aurata) fillets stored at 4 °C for 13 days. Results showed lower TBARS and TVB-N values in Z/CR7 compared to the control, indicating delayed lipid oxidation and spoilage. Colorimetric changes in the films corresponded with fish freshness deterioration, providing a clear visual indicator. Microbiological results supported chemical findings, though antimicrobial effects were limited. Curcumin-enriched zein films demonstrated strong potential as intelligent, biodegradable packaging for real-time monitoring of seafood quality. Full article

The primary aim of this study is to develop an axisymmetric numerical model, employing the finite element approach, to simulate a two-wrinkling tube in T6 aluminum. The method uses an electric potential applied to the tube mesh, which passes through a solid die to induce the wrinkling process, facilitated by contact elements between the tube and the die. A lateral incremental voltage electric potential (0–50 kV), due to an electric coil, and applied axial and compressive displacement (0–12 mm) was considered. The materials’ properties were established as nonlinear, with elastoplastic behavior. The results were analyzed, which allowed the tube deformation with two wrinkles, comparable with previous results. Full article

Auxetic structures, characterized by a negative Poisson’s ratio and unique form-fitting deformation, are adopted for designing a bra pad that would facilitate bras with a flexible and adaptive fit. This study compares the pressure distribution between auxetic and traditional molded bra pads, highlighting the advantages of auxetic materials in applying uniform pressure and addressing health concerns. Seven athletic female participants with a bra size of 75B comprise the study sample. Anthropometric data of naked breasts are collected by using three-dimensional (3D) scanning to obtain the underbust and full bust dimensions in the standing and leaning forward positions, while the pressure distribution is measured with the Novel Pliance^® pressure measurement system in three poses: standing, static cycling, and dynamic cycling. The results show that the auxetic designs of bra pads consistently apply a more uniform pressure distribution compared to traditional foam pads, with mean pressures of 2.92 kPa for auxetic pads compared to 4.81 kPa for traditional foam pads during static cycling. Moreover, auxetic pads reduced maximum pressure by 25% compared to molded cups, and spatial variability was halved (SD 0.85 kPa vs. 1.70 kPa). Notably, at the bra neckline, auxetic pads exhibit increased pressure as the body leans forward, demonstrating their ability to adapt to changing breast shapes while maintaining adequate bra-breast contact. In contrast, in the lower breast area, the auxetic pads show a decrease in pressure, which indicates their capacity to accommodate variations in breast girth or volume without exerting excessive force. These findings highlight the superior adaptability and wear comfort provided by an auxetic structure, which shows its potential to address the dynamic support needs of active women. Overall, the auxetic designs of a bra pad in this study represent a significant advancement in sports bra technology and offer a promising alternative to traditional molded cups in activewear design. Full article

This study examines the modernization of the 61-4179 TVZ passenger coach for transporting light automobiles up to 3 tons, addressing the efficiency of multifunctional rail use. The objective was to assess how additional mass–dimensional loading influences strength, load distribution, and the dynamic stability of the vehicle–track system. Finite element simulations in ANSYS Workbench 2021 R2 determined stress distribution, deformations, and safety margins, while multibody dynamics modeling in Universal Mechanism evaluated wheel–rail contact forces, carbody accelerations, and stability coefficients. Field tests on curves with radii of 350 m and 300 m at 60 km/h validated the models. Carbody accelerations were 0.65–0.68 m/s², below the 0.7 m/s² regulatory limit; wheelset attack angles remained under 0.01 rad; and derailment safety coefficients were 1.6–1.8, all meeting international standards. Uniform load distribution maintained stability and suppressed oscillations. However, critical scenarios (wheel wear, extreme flange clearance, higher speeds) produced parameters approaching threshold values. To mitigate risks, clearance adjustment per δ₀ standards, a 1:20 guard-rail inclination, and optimized crossing profiles are proposed. These measures reduced lateral dynamic forces by 12–15% and raised the strength coefficient by 1.2–1.3. The results confirm technical feasibility, operational safety, and extended service life, supporting sustainable multimodal transport development. Full article

The premium electric-vehicle market demands exceptionally quiet transmissions because the absence of engine masking makes gearbox noise more perceptible. Virtual NVH (noise, vibration, and harshness) evaluation requires coupling elastic deformation, gear–tooth contact, and vibration transmission through bearings and housing within a single environment. This study develops an integrated workflow in MSC ADAMS for predicting the NVH behavior of a 23/81-tooth helical gear pair. Finite element-based flank stiffness is imported, and a nonlinear contact model is applied to flexible teeth. Baseline simulation at 50 Nm and 200 rpm yields a static transmission error (TE) of 7.5 µm and a dynamic peak-to-peak TE of 0.7 µm, with the fundamental mesh tone at 77 Hz. Increasing tip relief by +0.10 mm lowers RMS TE by 31% and the first mesh order by 3.1 dB while raising the flank pressure from 1.65 GPa to 1.88 GPa. The workflow efficiently supports early-stage gear-noise optimization prior to the development of physical prototypes. Full article

Digital Image Correlation systems are increasingly being used for non-contact measurement of deformation and strain in sheet metal components. However, the accuracy of such measurements can be significantly affected by various external and system-related factors. If these are not properly considered, substantial errors may be introduced. In this study, a short and longer flat sheet specimen were clamped in a vise to investigate how overhang and clamping stability influence the accuracy of the measured deformation fields. Two different measurement volumes were also evaluated to assess their effect on the results. These factors were evaluated through targeted experiments, and the resulting data were analyzed and interpreted. Based on the findings, recommendations were formulated to enhance the reliability of Digital Image Correlation measurements in both laboratory and industrial environments. Full article

This article is based on ABAQUS 2022 finite element software to establish a finite element model of the hydraulic forming process of bimetallic composite pipes. The results show that the larger the bulging pressure, the earlier the circumferential elastic deformation of the outer wall of the lining pipe is fully restored during unloading. Under the action of the base pipe, the compression elastic deformation of the lining pipe is greater, and the bonding strength between the base pipe and the lining pipe is higher; as the bulging pressure increases, the rebound amount of the outer wall of the liner slightly decreases, while the rebound amount of the inner wall of the base pipe gradually increases, and the difference in rebound amount between the inner wall of the base pipe and the outer wall of the liner pipe gradually increases; before plastic deformation occurs on the inner wall of the base pipe, its circumferential rebound increases rapidly with the increase in bulging pressure. When plastic deformation occurs on the inner wall of the base pipe, the rate of increase in circumferential rebound decreases; the residual contact stress between the base pipe and the liner increases linearly with the increase in bulging pressure. Full article

Deep in situ pressure coring provides an accurate means of determining oil and gas reserve parameters. The key to achieving pressure coring at depths exceeding 5000 m lies in the ultimate bearing strength and stability of the pressure controllers. Due to the limited downhole space and the inherent technical demands of pressure coring, traditional pressure coring technology typically has an ultimate bearing pressure capacity of less than 70 MPa. The structural model of the pressure controller is designed. The stress–strain distribution of the pressure controller under external load is numerically simulated. A contact stress optimization scheme and critical sealing gap of pressure controllers are proposed. It was found that the saddle pressure controllers can ensure the fit clearance of the sealing surface and effectively control the deformation of the valve cover within 0.015 mm. The saddle pressure controllers have demonstrated an ultimate bearing strength exceeding 140 MPa, with minimal leakage. These findings have significant implications for accurate assessment of deep petroleum resources. Full article