Search Results (771)

Within the framework of consistent couple stress theory (CCST) and employing Hamilton’s principle, we derive a Galerkin weak formulation to analyze the three-dimensional (3D) size-dependent free vibration characteristics of a simply supported, functionally graded (FG) magneto-electro-elastic (MEE) doubly curved (DC) microscale shell subjected to a uniform temperature change. Incorporating the differential reproducing kernel (DRK) interpolants into the weak formulation, we further develop an element-free Galerkin (EFG) method. The microscale shell of interest is composed of two-phase MEE materials, and its material properties are assumed to vary through its thickness according to a power-law distribution of the volume fractions of the constituents. The results show that the natural frequency solutions obtained using the EFG method are in excellent agreement with the reported 3D solutions for laminated composite and FG-MEE macroscale plates, with the material length-scale parameter and the inverse of the curvature radii set to zero. The effects of the material length-scale parameter, temperature change, inhomogeneity index, and mid-surface radius and length-to-thickness ratios on the FG-MEE microscale shell’s free vibration characteristics in a thermal environment are examined and appear to be significant. Full article

The thermal safety and longevity of lithium-ion batteries are critically constrained by excessive temperature rise and spatial thermal non-uniformity, particularly during high-rate discharges. Most existing numerical investigations rely on simplified heat generation models that fail to capture the spatiotemporal heterogeneity of electrochemical heat sources, leading to compromised predictive accuracy. To address this deficiency, this study develops a comprehensive three-dimensional electrochemical–thermal coupled framework, integrating the Newman pseudo-two-dimensional (P2D) electrochemical model with conjugate heat transfer and laminar flow dynamics. The predictive robustness of this framework is rigorously validated against experimental data across multiple discharge rates (3 C and 5 C). The validated model is then deployed to evaluate a water-cooled microchannel cold plate designed for prismatic $\mathrm{L}\mathrm{i}\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_4$/graphite cells under a demanding 5 C discharge. A systematic parametric investigation is conducted to quantify the effects of ambient temperature (293–343 K), microchannel number (2–6), and coolant inlet velocity (0.1–0.6 m/s) on the maximum battery temperature (${\mathrm{T}}_{\mathrm{m}\mathrm{a}\mathrm{x}}$) and temperature difference ($\mathsf{\Delta }\mathrm{T}$). Results demonstrate that the proposed system exhibits exceptional environmental robustness: over a 50 K ambient temperature span, ${\mathrm{T}}_{\mathrm{m}\mathrm{a}\mathrm{x}}$ increases by merely 2.0 K, remaining safely below the 323 K industry limit. Densifying the channel count from 2 to 6 further reduces ${\mathrm{T}}_{\mathrm{m}\mathrm{a}\mathrm{x}}$ by 1.55 K and narrows $\mathsf{\Delta }\mathrm{T}$ to 4.25 K, successfully satisfying the strict 5 K temperature uniformity standard. Furthermore, the thermal benefit of elevating inlet velocity exhibits a pronounced diminishing-return trend governed by the asymptotic reduction in bulk coolant temperature rise, dictating a critical trade-off against the quadratically escalating pumping power. Ultimately, these findings provide robust theoretical guidelines for the rational design of safe and energy-efficient battery thermal management systems. Full article

To investigate the influence of working fluid composition on the thermo-hydraulic performance of plate heat exchangers (PHEs) under single-phase sensible heat transfer conditions, a three-dimensional steady-state numerical model was developed for a transverse corrugated channel with a chevron angle of 60°. The governing equations were solved using the finite volume method implemented in ANSYS Fluent, in conjunction with the standard k–ε turbulence model. The analysis considered pure refrigerants R134a and R245fa, as well as their mixtures with mass ratios of 0.2, 0.5, and 0.8, with thermophysical properties assumed to be temperature-independent constants. The results indicate that as the mass fraction of R134a decreases from 1.0 to 0, the heat transfer coefficient (h) decreases from 1025 to 815 W/(m²·K), primarily attributed to the combined effects of reduced thermal conductivity and increased viscosity. Among the investigated cases, the R134a/R245fa mixture with a mass ratio of 0.8 provides the most favorable performance trade-off, exhibiting a heat transfer coefficient only 3.0% lower than that of pure R134a while achieving a 12.5% reduction in flow resistance compared with pure R245fa. Furthermore, the heat transfer coefficient is found to be weakly affected by heat flux in the range of 8000–20,000 W/m²; in contrast, increasing the mass flow rate from 0.001 to 0.005 kg/s enhances heat transfer coefficient by 65.1%, accompanied by a significant increase in pressure drop. Comparisons with established single-phase correlations for corrugated channels show average deviations of 6.5% for the Nusselt number and 3.8% for the friction factor. The present study provides useful guidance for working fluid selection and operational optimization of PHEs in applications dominated by sensible heat transfer, such as specific stages of heat pump cycles and medium-temperature waste heat recovery. Full article

To explore the influence mechanism of welding process parameters on the residual stress and temperature field of complex welded components, this paper takes H-shaped steel, which is widely used in engineering, as the research object. Based on the thermal-force coupling finite element method, a three-dimensional numerical model of its welding process is established using the ANSYS Workbench platform. Based on the heat conduction equation and structural constraint theory, in accordance with the classification criteria for thin plates and medium-thick plates in the standards of the International Institute of Welding, and in combination with the typical structural size characteristics, six sets of comparative working conditions were designed. The influence of two key parameters, namely, the welding heat source parameters and welding speed, on the welding residual stress and temperature field was analyzed in detail. The research results show that increasing the welding heat input will raise peak welding temperature and expand the range of the high-temperature zone, resulting in a significant increase in residual tensile stress in the weld zone after cooling. Increasing the welding speed can effectively reduce heat accumulation and decrease the temperature gradient, thereby lowering the peak residual stress by approximately 10% to 15%. Research reveals that, under the premise of ensuring thorough penetration, adopting a process combination of “lower heat input and higher welding speed” can effectively suppress the generation of welding residual stress in H-beams. The research results can provide a theoretical basis for the optimization of welding processes in actual production. Full article

This study investigates the interaction between the skin and stiffeners under tension and the structural failure mechanisms of aluminum alloy stiffened panels after battle damage, employing an integrated approach of experimental testing and numerical simulation. The variation in the residual strength of the stiffened panels with the characteristics of ruptures was explored, and an assessment method for residual strength was proposed based on the net-section failure criterion. The results indicate that the residual strength of the stiffened panels is closely related to the location and size of the rupture. For panels with ruptures of equal area, the residual strength is lowest for those with web damage, followed by those with flange damage, and highest for those with skin damage only. By employing an area-based conversion method, the three-dimensional stiffened panel was simplified to a two-dimensional plate. A stress averaging coefficient was introduced for large eccentric ruptures, while a conversion factor was applied for small eccentric ruptures to modify the residual strength assessment. The results demonstrate high accuracy. This study provides an efficient and precise method for evaluating the residual strength of damaged stiffened panels, offering a theoretical basis for aircraft battle damage repair. Full article

Composite soil–steel corrugated bridges, which are widely used in road, railway, and civil engineering, are recognized as durable, sustainable, and cost-effective structures. Due to their interactions with the surrounding soil, relatively thin corrugated steel plates are usually used in these bridges. Larger spans are associated with larger cross-sections, and deep corrugations with a 500 mm pitch and a 237 mm depth are already in use worldwide. However, the behavioral benefits of high-strength steel and additional strengthening elements for CSS structures have rarely been investigated with regard to local buckling in the straight regions of the corrugation. This study analyzed the influence of high-strength steel and innovative corrugated cross-sections strengthened with circular steel pipes on the utilization ratio of steel plates in composite soil–steel structures. Two-dimensional numerical models of three bridges with spans of 26 m, 17.5 m, and 12 m and surrounded by soil were developed to identify internal forces from permanent and temporary actions. Plate utilization was designed according to the Swedish, Canadian, and American methods, considering local buckling in the 500 × 237 mm and 381 × 140 mm corrugation profiles. It was found that the use of higher-strength steel material, as well as the introduction of steel pipes, significantly reduced the plate thickness of regular corrugations. The results show that the use of higher-strength steel reduced the cross-section area of regular and innovative corrugations by 30–40%. Moreover, the cross-section area of the innovative profile was 5% to 36% lower than that of the regular corrugation profile. Nevertheless, the results show that the local buckling approach proposed by the Swedish design method could be considered conservative and should be revised. In addition, the method of preventing local buckling by reducing the plastic moment capacity could be neglected when using thicker plates and lower steel grades. Full article

Metal-chalcogenide compounds with perovskite-type compositions have drawn increasing attention for their optical properties for solar energy conversion. Herein, a new α-type polymorph of the ternary sulfide SrHfS₃ is described, crystallizing in the NH₄CdCl₃ structure type. The yellow-colored plate-shaped crystals were synthesized at 1173 K using an elemental tin flux in an evacuated sealed tube. Its crystal structure was characterized at room temperature using single crystal X-ray diffraction to form in the orthorhombic Pnma space group, with the refined cell parameters of a = 8.5041(4) Å, b = 3.8004(2) Å, c = 13.8935(6) Å, and V = 449.02(4) ų. The structure comprises five independent crystallographic sites, having one Sr, one Hf, and three S sites. The structure can be described as containing one-dimensional chains of distorted HfS₆ octahedra extending down the b-axis to form ${\displaystyle \genfrac{}{}{0pt}{}{1}{\infty }}[$HfS₃]²⁻ strips of edge-sharing octahedra. The Sr atoms act as charge-balancing space fillers in the structure. High-purity bulk samples of α-SrHfS₃ could be prepared for measurement of its bandgap by optical diffuse-reflectance spectroscopy, showing a direct bandgap of 2.1(1) eV. Results of electronic structure calculations are consistent with this bandgap and type. The conduction and valence band edges stem from the respective empty Hf d-orbitals and the filled S p-orbital states. In summary, crystal growth of the α-type polymorph of SrHfS₃ has been demonstrated using a Sn flux approach, which can facilitate future broader synthetic explorations at lower temperatures. Full article

The methodical work describes all the necessary steps for establishing a stable oral ex vivo biofilm using saliva and crevicular plaque samples from periodontal healthy donors. First, cover slips were preconditioned with saliva supernatants and subsequently inoculated with crevicular plaque suspensions. Ex vivo biofilm formation was characterized by confocal laser scanning microscopy (cLSM) after 1, 4, 24, 48 and 72 h of anaerobic cultivation. Exemplarily, the inhibitory characteristics of blackcurrant fruit extracts [all-fruit juice (AFJ); alcoholic fraction from berry skins (AFBS)] were observed on 1, 4 and 24 h-aged ex vivo biofilms. Chlorhexidine (CHX, 0.2%) served as positive control. After direct contact (3 min), biofilms were dispersed, plated onto agar and anaerobically cultivated for 24 h. Early ex vivo biofilms (1 h-biofilm) showed scattered microbial colonies. After 4 h of cultivation, a multilayered biofilm was formed. Biofilm mass gradually increased, displaying a complex polymicrobial structure after 24 h. At 72 h, the biofilms had a dense three-dimensional appearance. Treatment with AFJ and CHX was more efficient in inhibiting biofilm growth compared to AFBS. Early biofilms (1 h, 4 h) were more susceptible to AFJ and CHX compared to 24 h-biofilms. The introduced model can be recommended for testing the efficiency of plaque-controlling agents. Full article

Background: In children with cerebral palsy, bony acetabular deficiencies are common and may be associated with progressive hip subluxation, abnormal joint loading, and ultimately hip dislocation. Hip reconstruction surgery is typically performed to prevent dislocation, and this includes acetabular reshaping using acetabuloplasty. The location of acetabular deficiency may vary among individuals; however, only radiographs are used for planning and intraoperative correction in many centers. Precise reconstruction and preop planning are necessary for the accurate correction of acetabular coverage. This study compares conventional hip reconstruction with a 3D-guided technique using individual preop 3D planning and 3D-printed guides during surgery to determine which method allows for a more accurate correction. We hypothesize that the patient-specific 3D planning leads to more precise anatomical correction of acetabular coverage compared to conventional freehand osteotomy. Methods: This study was registered in the German Clinical Trial Register (DRKS-ID: DRKS00031356) on 14 July 2023. In a randomized controlled trial, various imaging-based parameters were used to assess the bony anatomy preoperatively and postoperatively. Preoperative and 6-week postoperative computed tomography (CT) scans are part of routine clinical care. Additionally, an immediate postoperative CT scan was performed. One hip was operated on using individualized 3D preoperative planning, while the other hip was corrected using a conventional surgical approach. A standardized subtrochanteric osteotomy was performed for the varisation, derotation, and shortening of the proximal femur. This osteotomy was followed by acetabuloplasty under fluoroscopic control. For the 3D-planned operation, patient-specific cutting and repositioning guides were produced based on preoperative CT imaging. Patients with bilateral cerebral palsy (GMFCS levels I–V), aged 4–18 years, with an open triradiate growth plate and a migration index ≥ 40% in at least one hip were included. In a preliminary retrospective part, this project reproduces the existing three-dimensional acetabular index (3-DAI) and compares it with established radiographic methods to determine the utility and reliability of a reconstructed 3D CT measurement technique. A further component of the retrospective part is the creation of an age-adjusted database of typically developed hips and the development of a 3D head coverage index (3D-HCI) as a new 3D parameter to express acetabular coverage; therefore, it will be used as a secondary parameter and correlated to the 3DAI in the prospective part. Conclusions: Improved precision may have meaningful clinical implications for long-term joint congruency, load distribution, pain, and mobility outcomes. Full article

Finger seals operate over extended periods under complex conditions involving high-pressure differentials, elevated rotational speeds, and rotor radial runout. Intense convective heat transfer arises within the seal, significantly impacting its structural deformation. To elucidate the influence of temperature on finger-seal deformation during convective heat transfer, the present study derives heat transfer energy equations for finger seals based on the Local Thermal Non-Equilibrium (LTNE) model. A three-dimensional porous-media flow-field model incorporating the LTNE framework, along with a solid thermal-deformation model, is developed. The effects of pressure differential and interference-fit magnitude on the structural deformation and average contact pressure of finger seals are analyzed under both the Local Thermal Equilibrium (LTE) and LTNE models. The results indicate that the LTNE model predicts a higher maximum seal temperature and a lower leakage rate compared to the LTE model. In both models, the deformation of individual seal-blade layers increases with rising pressure differentials and interference-fit magnitudes. Furthermore, the overall blade deformation is more pronounced under the LTNE model, suggesting a substantial thermal influence on sealing performance. The effects of pressure difference and interference fit on the thermal deformation of the seal plate are similar: both have the greatest impact on radial deformation, followed by circumferential deformation and axial deformation. Within the pressure difference range, the radial deformation of the third-layer seal plate in the LTNE model increases by 14.55%. When the interference fit increases from 0.05 mm to 0.2 mm, the radial deformation of each layer of the seal plate in the LTNE model increases by 0.18 mm. The average contact pressure increases with both pressure differential and interference-fit magnitude across both models. At a given pressure differential, the LTNE model yields a higher average contact pressure than the LTE model, with a maximum observed difference of 0.01 MPa. When the interference-fit magnitude is small, the pressure difference between the models remains minimal; however, at the maximum interference-fit, the difference reaches 0.08 MPa. Full article

The manipulation of vector beams (VBs) with longitudinally variant polarization states is an important research topic and has potential applications in classical and quantum fields. In this study, we propose a half-wave plate dielectric metasurface composed of two interleaved sub-metasurfaces to generate longitudinally separated dual-channel vectorial structured light fields. The propagation and Pancharatnam–Berry phases are employed to construct hyperbolic, helical, and opposite gradient phases for focusing wavefronts, generating circularly polarized (CP) vortices, and deflecting CP vortices with the same chirality in opposite directions. Consequently, dual-channel higher-order or hybrid-order Poincaré (HOP or HyOP) beams are generated along the optical axis under elliptically polarized illumination, and their polarization states evolve along an arbitrary pair of antipodal meridians on the HOP or HyOP sphere by varying the ellipticity of the incident light, the propagation-phase topological charge, and the rotation order of the meta-atom. The consistency between the theoretical and simulated results demonstrates the feasibility and practicability of the proposed method. This study is significant for compact, integrated, and multifunctional optical devices, and provides an innovative strategy to extend optical field manipulation from two-dimensional to three-dimensional space. Full article

The impact of large boulders transported by debris flows is a primary cause of structural damage to mitigation works. However, quantitative modeling remains difficult because of the scarcity of field measurements and the complexity of the flow medium. In this study, a theoretical model for boulder impact force in debris flows is developed using dimensional analysis based on the Buckingham theorem, subsequently simplified to two dimensionless parameters, and then validated through a series of controlled laboratory experiments. Marble spheres were used as impactors and were released to strike a rigid steel plate under three types of media: clear water, bentonite slurry, and debris flows containing particles of different size classes. The experiments were designed to isolate and quantify the influence of the flow rheology and the suspended solid phase on impact forces. The results show that the impact coefficient c is strongly governed by the debris flow yield stress, bulk density, and the size of suspended particles, following the relationship c = 0.183[τ/(rgd₁)]^−0.1(d/d₀)^0.05. Based on this relationship, a generalized formula for calculating boulder impact forces in debris flows is proposed. The model is further evaluated using field monitoring data from Jiangjiagou, Yunnan Province. The back-calculated boulder diameters fall predominantly within the range of 0.1–0.3 m (76.3–86.8%), which is consistent with field observations. These results indicate that the proposed model captures the essential physical mechanisms governing boulder impacts and provides a rational basis for selecting design parameters in debris flow mitigation engineering. The array-type piezoelectric impact sensing system designed in this study achieves high-precision and high-stability measurement of the impact force of large boulders in debris flows, providing a new sensing technology for debris flow impact monitoring. Full article

In this study, a three-dimensional simulation of a walking-beam reheating furnace was developed to improve the steel slab reheating process and reduce surface oxidation kinetics using computational fluid dynamics (CFD). Combustion, heat transfer, fluid dynamics, and chemical reaction models were integrated into the numerical framework of this study. In addition, dynamic mesh remeshing was coupled through user-defined functions (UDFs), enabling the simultaneous simulation of slab movement and evolution of the involved transport phenomena. Turbulence was modeled with the realizable k-ε formulation, combustion with the Eddy Dissipation model, and radiation with the P-1 model coupled with WSGGM to include CO₂ and H₂O gas radiation. Scale formation was modeled using customized functions based on Arrhenius-type kinetics and Wagner’s oxidation model, evaluating its growth as a function of time, temperature, and furnace atmosphere. The predicted thermal evolution inside the furnace was validated using industrial data, yielding an average deviation of 5%. Furthermore, the proposed operating conditions led to an average slab temperature of 1289.77 °C at the exit of the homogenization zone, which was 16 °C higher than that under the current operation but still within the target range (1250 ± 50 °C). The reduction in combustion air decreased energy losses and improved product quality, lowering the molar oxygen content in the furnace atmosphere from 4.9 × 10² mol to 6.7 × 10¹ mol. Additionally, annual savings of 4,793,472 kg of natural gas and 13,884 tons of steel were estimated owing to reduced oxidation losses. The proposed air–fuel adjustment led to estimated annual energy savings (equivalent to 4,793,472 kg of natural gas) and a reduction in material loss due to oxidation from 4.5% to 3.75% (an absolute reduction of 0.75 percentage points; relative reduction ≈ 16.7%), which has a significant industrial impact on metal conservation and descaling cost reduction. Although there are CFD studies on plate overheating and scale growth separately, this work presents three main contributions: (1) the integration, within a single numerical framework, of combustion, radiation, species transport, oxidation kinetics, and actual plate movement using a dynamic mesh; (2) validation against continuous industrial records (16 thermocouples) and quantification of operational benefits such as fuel savings and reduced material loss; and (3) a comparative analysis between actual and optimized conditions, which standardize the air–methane ratio. Full article

Squeezed branch piles, originally developed for building and bridge foundations, have been downsized and deployed at larger pile spacing for reinforcing embankments over soft soils. However, the working mechanism of squeezed branch pile-supported embankments remains unclear. In this study, a three-dimensional numerical model of this embankment was established based on field tests. The analyses consider different pile types (squeezed branch piles and straight piles) and pile-head structures (beam-type cap and plate-type cap). These concrete components were modeled utilizing an advanced concrete model, which captures the strain-softening/hardening and yielding behavior. Simulation results show that squeezed branch piles provide better settlement control in the subsoil beneath the embankment than straight piles for the studied cases. The beam-type cap with squeezed branch piles behaves as a pile-beam foundation that reduces maximum settlement by around 38% compared to that of the plate-type cap, while the plate-type cap system functions as a composite foundation that enhances surcharge capacity by about 35–40%. The instability of the embankment is driven by tensile failure in concrete: The beam-type cap leads to a localized failure along the ground beam, and the plate-type cap system induces a progressive failure centered on the squeezed branch piles. Within the plate-type cap, the dimensions of the pile-head plate significantly influence settlement control and the stability of the embankment in soft soil. Full article

Thermal runaway accidents in lithium batteries necessitate effective thermal management. This study proposes a liquid cooling plate with internal spiral-array fins and investigates its performance under electrochemically coupled temperature-dependent heat generation conditions. A pseudo-two-dimensional (P2D) electrochemical model simulates battery discharge at 0.5C–2C rates to obtain heat generation characteristics, which serve as inputs for a fluid–solid coupled heat transfer model. The effects of spiral fin parameters—pitch (S) and height (h)—are systematically analyzed. Three main contributions are presented: spiral fins induce secondary flow that disrupts thermal boundary layer development and enhances fluid mixing, with smaller pitch extending the flow path and increasing radial velocity; a performance evaluation criterion (PEC)-based analysis identifies the optimal parameter range that balances heat transfer enhancement and pressure drop penalty; and increasing the fin height raises the finned area proportion and swirl intensity, suppressing bypass flow and strengthening heat transfer, with effects more pronounced at higher discharge rates. Key quantitative findings show that at 2C discharge, the optimized configuration (S = 3 mm, h = 0.5 mm) achieves a comprehensive performance index of 2.19 and reduces the maximum temperature by 25.32% compared to smooth channels. This work integrates electrochemical and thermal models to provide a new approach for optimizing spiral fin microchannels tailored to lithium battery operation. Full article