Search Results (344)

This essay reinterprets William Faulkner’s Light in August through the ethical problem of civil religion, understood as the use of shared narratives that bind communities but may also legitimate exclusion and violence. Focusing on the Reverend Gail Hightower, the essay traces Faulkner’s sustained critique of mythologized history, racialized communal narratives, and rigid appeals to duty that culminate in mob violence against Joe Christmas. Placing Faulkner in dialogue with Immanuel Kant’s rejection of moral exceptions and statutory religion, the essay examines Hightower’s refusal—and belated willingness—to bend truth in the face of injustice. It argues that while Light in August exposes the dangers of civil religion as a closed and coercive narrative, it also gestures toward a tragic ethical possibility: that narrative flexibility, under conditions of violence and epistemic collapse, may serve to interrupt injustice rather than authorize it. Full article

Pultruded glass fibre-reinforced polymer (GFRP) profiles are promising structural cores for lightweight sandwich panels, but their strong longitudinal response is accompanied by weak transverse resistance and local web instability. A matched experimental programme examined rectangular hollow pultruded GFRP profiles and vacuum-infused sandwich panels under four-point bending, short-span three-point bending and flatwise compression in H and V orientations. Changing from H to V increased the peak loads of individual profiles by 9.35% in four-point bending and by 26.06% in short-span loading but reduced the flatwise compressive peak load by 30.12%. For integrated panels, the same reorientation increased the four-point bending peak load by 22.74%, caused only a marginal change in short-span capacity and reduced the flatwise compressive peak load by 28.24%. Failure involved local web buckling, web shear damage, longitudinal splitting, laminate delamination and interfacial debonding. Continuous face sheets and wrapping laminates restrained local deformation and contributed to substantial post-damage resistance, consistent with load redistribution within the integrated section. Relative to a baseline comprising three individual profiles and the corresponding hollow FRP reference panel, integrated-panel capacities increased by 15.76%, 37.71% and 78.44% under four-point bending, short-span loading and flatwise compression, respectively. These results identify profile orientation and transverse web stability as key design parameters for pultruded-profile-core sandwich panels. Full article

Conventional design paradigms for vehicle underbody armor face an inherent trade-off: enhancing blast protection invariably incurs a prohibitive weight penalty. Here, we investigate a mechanical pre-stressing strategy for high-strength steel V-shaped vehicle underbody structures. A conventional V-shaped baseline structure was first subjected to a 6 kg TNT blast test, and the measured response was used to validate the numerical model. Based on the validated numerical model, four mass-equivalent (100 kg) configurations were subsequently compared numerically under escalating threats (2~8 kg TNT): pre-stressed steel, homogeneous steel, and all-metallic honeycomb sandwich panels (comprising high-strength steel face sheets and an aluminum alloy core) with both positive and negative Poisson’s ratios. The numerical results predict that the pre-stressed steel configuration exhibits the smallest maximum permanent floor deformations among the four configurations, with values of 22 mm, 46 mm, 131 mm, and 208 mm under 2, 4, 6, and 8 kg loads, respectively. Mechanistically, we reveal that for V-shaped geometries, residual-stress-induced stiffening and geometric arching are profoundly more effective than core crushing in controlling global bending, while the auxetic steel-faced aluminum honeycomb offers only marginal improvements over its conventional counterpart. This study offers a potential pathway for overcoming the weight–protection trade-off in underbody armor design. While the numerical predictions are encouraging, direct experimental validation of the pre-stressed configuration remains necessary prior to practical application. Full article

Nomex honeycomb core sandwich composites are attractive for lightweight structural applications because of their high specific stiffness. However, drilling required for mechanical joining can introduce both surface and subsurface damage and may change the mechanical and dynamic response of the structure. This study examines Nomex aramid honeycomb sandwich composites with C/C/C, C/G/C, G/C/G, and G/G/G face-sheet configurations using three-point bending, drilling, image analysis, ultrasonic C-scan, and acoustic impact measurements. The C/C/C configuration reached an average bending load 36.05% higher than G/G/G and reduced the entry and exit side delamination areas by 88.91% and 78.89%, respectively. Although C/C/C produced the highest thrust forces during drilling, it also showed the smallest surface and internal damage regions, indicating that thrust force alone does not fully describe hole quality. C/G/C also exhibited less damage than G/C/G; however, these two hybrid configurations differ in both carbon/glass content and ply position, so the contribution of each factor cannot be separated independently. After drilling, the natural frequency decreased, and the damping ratio increased in all configurations. Overall, the carbon-rich face sheets provided higher bending resistance and more effectively limited drilling-induced damage. Full article

Dual-stator single-rotor (DSSR) axial flux permanent magnet synchronous motors (AFPMSMs) offer high torque density but face reliability challenges due to unbalanced magnetic forces (UMF) and bending moments caused by eccentricity faults. This study investigates the electromagnetic performance of a DSSR AFPMSM under static, dynamic, axial, and radial eccentricities to reveal specific fault signatures and physical mechanisms. The methodology relies on three-dimensional transient finite element analysis (3-D FEA) and is validated by experimental tests on a 500 W prototype. Results indicate that while static and dynamic eccentricities have negligible effects on average torque, they induce significant bending moments where static eccentricity generates a constant moment and dynamic eccentricity produces an alternating one, both proportional to the eccentricity severity. Crucially, axial eccentricity disrupts magnetic symmetry, causing a 17.6% no-load back-EMF imbalance between stators and increasing net axial UMF to 53.2 N at a 40% eccentricity factor. Conversely, radial eccentricity shows minimal impact, confirming the topology’s robustness against radial misalignments. These findings provide essential baseline data for the vibration analysis and condition monitoring of DSSR AFPMSMs. Full article

Bio-inspired helicoidal laminates can redirect damage under transverse loading, but their response as sandwich face sheets remains unclear because the core changes both deformation and load transfer. This study experimentally and numerically investigated the quasi-static penetration of 73-ply carbon/epoxy laminates and Nomex honeycomb sandwich panels with cross-ply, quasi-isotropic, uniform helicoidal (5°, 10°, and 20°), and hybrid helicoidal layups. A fully ply-resolved model was developed for the monolithic laminates, whereas an eight-sublaminate model with an explicitly represented honeycomb core was used for the sandwich panels. H73(10–5) achieved the highest monolithic-laminate peak load of 5.23 kN, 46.1% above CP73 and 35.5% above QI73. The sandwich panels exhibited two load peaks separated by a core-crushing plateau. S-H73(5–10) produced the highest first peak load of 8.99 kN, while S-H73(10–5) achieved the highest penetration energy of 108.37 J. Experiments, simulations, and fractographic observations showed that the intact core constrained upper-face-sheet bending and promoted localized indentation-assisted punching-shear perforation. The crushed core subsequently transferred load to the lower face sheet, which failed through bending- and membrane-dominated tearing. Full article

Scientific evaluation of open-pit slope stability under the disturbance of underground goaf is critical to the safe production of open-pit coal mines. Taking an open-pit coal mine in Inner Mongolia as the engineering background, this study investigates the influence mechanism of underground goaf on slope stability. With discrete element numerical simulation, the movement law of overlying strata above the goaf is revealed, and the heights of the “three zones” and boundary movement angles are determined. Furthermore, limit-equilibrium theory is adopted to analyze slope stability affected by goafs from three perspectives: goaf span, occurrence position and inter-goaf spacing. The results indicate that under partial extraction conditions, goaf span is positively correlated with the height of the caving zone and negatively correlated with the boundary movement angle. As the goaf width increases, the mining-induced deformation field expands progressively, and a distinct bending-subsidence zone develops in the 50 m wide single-goaf case, resulting in a complete caving–fractured–bending-subsidence zonation. For adjacent goafs, smaller inter-goaf spacing promotes overlap of the mining-induced deformation fields and generally enhances overburden disturbance. As the spacing increases, the interaction between adjacent goafs tends to weaken, although the degree of reduction depends on goaf width and the deformation parameter considered. Therefore, the spacing of approximately 50 m observed in the present simulations is interpreted as a site-specific transition range rather than a universal critical threshold. Two landslide modes are identified in the Baozhixil open-pit mine: circular arc sliding and composite sliding controlled by the weak interlayer of No. 1 coal seam. Slope stability is negatively correlated with goaf span and positively correlated with the horizontal distance between the goaf and the slope face. For the analysis of inter-goaf spacing, slope stability shows a positive correlation with the proportion of non-collapse deformation area within the sliding mass. Full article

Structurally integrated lithium-ion batteries (LIBs) in bionic underwater vehicles face increasingly complex internal short circuit (ISC) risks under mechanical abuse. In this study, a three-dimensional bidirectional mechanical–electrical–thermal coupling model is established to reconstruct the evolution from structural damage to ISC triggering in cylindrical LIBs under indentation conditions. A constitutive inversion method incorporating load, contact area, and volume evolution is proposed to calibrate the jellyroll stress–strain response for different indenter diameters. An ISC criterion based on separator thickness is then introduced, and local short-circuit paths are realized through dynamic topology updates of the distributed equivalent circuit model network. The calibrated model reproduced the experimental load response, voltage decay, temperature rise, and damage morphology. The systematic investigation into ISC behavior shows that indenter diameter governs competition among local shear, local bending, and global compression, while loading position determines structural constraint and boundary effects. Rather than corresponding to the minimum ISC load, the most hazardous condition (4 mm indenter diameter and 18 mm loading position) exists where local stress concentration and weakened structural constraints jointly promote rapid separator failure, shortening the ISC triggering time to 79.2 s. These findings provide guidance for battery safety assessment and structural protection design in underwater vehicles. Full article

Polymer-fiber weft-knitted textiles are widely used in functional apparel and moisture-management materials, but their complex loop topology, yarn-level porosity, and interlayer hierarchy make simulation-oriented geometric modeling challenging. Conventional control-point and interpolated-curve methods often have limitations in representing knitting actions, maintaining yarn-path continuity, and generating meshable geometries. This study proposes a rule-driven geometric modeling method for polymer-fiber weft-knitted structures using the yarn centerline as the basic geometric carrier. Knitting actions, including knit, tuck, float, plating, and double-needle-bed assignment, are converted into reusable local path-generation rules and integrated through pattern-matrix input, action recognition, parametric centerline generation, continuous stitching, and standardized output. The method represents single-bed and double-bed structures within a unified framework, including plain, jacquard, plated, tuck, rib, interlock, half-cardigan, full-cardigan, and purl structures. Compared with an interpolated-curve method, the curvature-jump rate of four representative structures decreases from 40.78–69.23% to 0–0.31%, with markedly reduced maximum bending angles. Mesh-generation results show continuous meshes with improved element quality for complex double-bed structures. A moisture-transfer simulation of a fully plated plain-knitted structure gives one-way transport indices of −122.3187 and 122.2472 for face- and back-side liquid entry, with relative errors of 1.74% and 0.50% compared with experiments. These results indicate that the proposed method provides reproducible and meshable geometric input for structure–property modeling and moisture-transfer prediction of polymer-fiber knitted textiles. Full article

This paper presents a methodology to evaluate the entire process of thermal evolution and fracture failure within stay cables subjected to sheath fires. Computer software FDS 2021 and ABAQUS 2021 are applied to build a sequentially thermos–mechanics coupled method integrating thermal, structural, and fracture dynamic analyses in stay cables under sheath fire exposure conditions. Herein, three representative fire scenarios including full-circumferential, top-side, and bottom-side ignition are reconstructed. Further, 127 individual wires, accounting for interstitial cavity radiation and contact heat transfer, are utilized to perform analysis on sectional temperature in stay cables. The results indicate that the ignition mode dictates the cross-sectional temperature gradient, with localized ignitions inducing highly asymmetric thermal fields and pronounced internal bending moments. Elevated temperatures trigger a progressive load redistribution from the degraded fire-facing wires to cooler internal layers. Ultimately, abrupt global fracture occurs when the residual ultimate load-carrying capacity intersects with the actual applied tension, resulting in a fracture morphology that closely corresponds to the spatial thermal distribution. Furthermore, the structural capacity degradation exhibits three distinct time-dependent stages: a slow degradation stage, a sharp decline stage, and a recovery stage. Among the analyzed scenarios, full-circumferential ignition induces the most drastic overall capacity reduction, while bottom-side ignition poses a markedly greater rupture risk than top-side ignition. Full article

This paper mainly investigates the ice-impact resistance of PVC foam sandwich beams for polar ship protective structures through low-velocity impact experiments and nonlinear finite element simulations. An experimentally validated elastic–plastic coupled model, accounting for ice crushing and large structural deformation, was used to examine the effects of core density and face-sheet thickness distribution on the ice-impact response of sandwich beams. Results show that the upper face sheet undergoes local indentation and global bending, the lower face sheet mainly bends globally, and the foam core exhibits local compression and overall bending, while compressive deformation accompanied by ice crushing and spalling occurs at the front part of the ice impactor. Moreover, the effective structural stiffness decreased during plastic loading as local indentation and core compression developed, whereas the unloading stiffness was higher than the effective stiffness during plastic loading. Energy dissipation primarily comes from ice crushing, face-sheet plasticity, and core compression. Increasing core density reduces deflection and core compression but increases peak force. Among the three face-sheet configurations examined at a constant total thickness, the configuration with a thinner upper face sheet and a thicker lower face sheet produced a smaller final deformation of the lower face sheet. This study provides a useful reference for ice-resistant design of sandwich structures in polar ships. Full article

Cost is one of the decisive factors when selecting a fibre type for structural strengthening. This study therefore tested the hypothesis that a low-cost fibre can still provide a substantial improvement in the mechanical performance of strengthened timber beams. Four-point bending tests were carried out on 25 pine beams, comprising an unstrengthened reference series and four series strengthened with glass fibre reinforced polymer (GFRP) sheets, each series consisting of five specimens. The beams had nominal dimensions of 80 mm × 80 mm × 1600 mm. The reinforcement was bonded exclusively to the external surfaces, with a focus on the tension zone. Two variables were examined: the number of sheet layers and the extent of coverage of the timber surface. The reinforcement ratio ranged from 0.38% to 1.15%. The response of the beams was assessed in terms of load-bearing capacity, stiffness, ductility, and failure mode. Bonding three layers of sheet to the bottom face of the beams increased the load-bearing capacity by up to 58.20%. The effect on stiffness was less pronounced, with a maximum increase of 20%, which is attributable to the relatively low elastic modulus of the sheets. However, the ductility of the beams increased significantly (up to 126.14%, based on energy considerations), a result that can be directly attributed to the composite’s high adhesion and high elongation at rupture. The transformed cross-section method and finite element simulations were used to predict the behaviour of the strengthened elements, and both showed good agreement with the test results within the elastic range. It is concluded that GFRP sheets are a rational strengthening solution, although satisfactory effectiveness was obtained only at higher reinforcement ratios; at least two layers are recommended for the configurations tested. The effect of the strengthening configuration on the load-bearing capacity, on the deflection at maximum load and on the ductility was statistically significant, whereas its effect on the bending stiffness was not. Full article

The current study investigated the impact of facial three-dimensional shape geometry and respirator-face interface mechanics on the fit of N95 respirators in 21 Hong Kong Chinese adults. Three-dimensional facial scanning, quantitative fit testing of four N95 respirators (3M 1860, 1870+, 9105, and 9502+), and facial dimensions extraction using Geomagic Wrap were conducted in this study. The seven fit test exercises were performed in the current investigation, while finite element analysis (FEA) was used for studying respirator-face contact mechanics in a stratified subset of 14 participants wearing 3M 1870+ geometry. Among all evaluated models, 3M 1870+ had the highest pass rate. Pearson correlation analysis showed only nominal, uncorrected associations between the fit factor and nose length (r = 0.574, p = 0.007) as well as neck circumference (r = 0.434, p = 0.050). None of the anthropometric correlations remained statistically significant after Bonferroni correction for multiple comparisons (n = 38) (adjusted alpha level = 0.00132). Threshold post hoc observations of the bitragion coronal arc, neck circumference, nose height and nose length should therefore be considered as hypothesis generation and not as screening criteria. Fit factors decreased in dynamic movements, especially when bending. FEA-predicted contact area correlated strongly with experimental fit factor (r = 0.974, 95% CI: 0.918 to 0.992, p < 0.001), thus confirming the association of simulation and fit performance measurement but not serving as independent validation of the model. These preliminary results could be helpful for future respirator fit studies and respirator design for Hong Kong Chinese adults. Full article

The contradiction between high compliance and low load-bearing capacity of flexible manipulators limits their engineering applications. Meanwhile, the theoretical modeling of the deformation and variable stiffness characteristics of flexible joints still faces considerable challenges. This paper proposes a positive-pressure double-airbag gap-constrained particle-jamming variable stiffness method and develops a novel actively variable stiffness pneumatic flexible bending joint with an integrated configuration of actuator, variable stiffness device (VSD), and primary structure. Based on classical elasticity theory and Coulomb–Amontons’ law of friction, theoretical models for the bending angle and tangential stiffness are established and verified through prototype experiments. With VSD activation, the joint reaches a bending angle of 56.35° at 0.4 MPa. At 40° forward bending, VSD activation increases the tangential stiffness from 0.167 N/mm to 0.832 N/mm, with the stiffness ratio between 40° and 0° increasing from 1.56 without VSD to 4.80 with VSD activation. Model predictions agree well with experimental data, yielding mean relative errors of 6.77% for the bending-angle model with VSD and 6.76% for the forward tangential-stiffness model with VSD activation. A coupling effect between bending deformation and stiffness is observed. The results demonstrate that the proposed joint achieves substantial stiffness regulation, providing a basis for its application in flexible robotic systems. Full article

Gob-side entry retaining by roof cutting and pressure relief (CRRE) eliminates coal pillar waste and mitigates mining-induced stress concentration. Although widely applied in mines shallower than 1000 m, systematic research on asymmetric deformation mechanisms and matched control technologies under ultra-deep conditions (>1000 m, σH > 60 MPa) remains limited. This study investigates the 5307 working face of Anju Coal Mine (burial depth: 1127–1195 m) using theoretical analysis, FLAC3D numerical simulation, and 480 m of field monitoring. The stress evolution, deviatoric stress field response, and asymmetric deformation mechanisms of the surrounding rock under ultra-deep mining conditions are systematically analyzed, based on which a targeted collaborative control technology is proposed. The key findings indicate that (1) CRRE significantly attenuates advanced abutment pressure compared with conventional pillar retention, with an average stress reduction of 20.1 ± 1.2% (95% CI: 17.8–22.4%, p < 0.01). (2) During the advanced mining stage, the second invariant of deviatoric stress exhibits a saddle-shaped distribution with a pronounced concentration at the mid-rib, identifying this as the dominant zone for rib bulging failure. (3) In the post-mining entry-forming stage, the roof deviatoric stress field demonstrates marked asymmetric evolution, with the distortion energy on the solid-coal side substantially exceeding that on the gob side; moreover, the low-position roof strata exhibit high distortion and poor stability, rendering them prone to bending fractures. Grounded in these mechanisms, a full-cycle differentiated surrounding rock control technology is developed, integrating pre-mining directional roof pre-splitting, active tough support reinforcement, post-mining temporary roof control and pressure relief, and gangue retaining with rib collaborative protection. The key parameters include a roof cutting height of 7 m, a cutting angle of 15°, NPR constant-resistance anchor cables with W-steel belts, and temporary support extending 300 m behind the working face. Field monitoring reveals staged deformation evolution, with stabilization achieved 250 m behind the working face. Maximum roof subsidence, floor heave, and total roof-floor convergence were 180 mm, 329 mm, and 422 mm, respectively, below the 500 mm allowable threshold for ultra-deep retained entries. Full article