Search Results (34,877)

Dissimilar friction stir welding (FSW) of titanium alloys offers a route to spatially optimized aerospace structures, but the asymmetric thermomechanical environment produces heterogeneous microstructures and textures whose interaction with mechanical performance is not well characterized. A near-α/α+β combination of titanium alloys, Ti–6242 SG (advancing side, ADV) and Ti–54M (retreating side, RET), was welded across a matrix of rotation speeds (225–325 rpm) and traverse speeds (100–150 mm·min⁻¹), spanning rotation-to-traverse-speed ratios N/v of 1.80–2.75, which was used throughout as an empirical processing index that orders the conditions of this matrix rather than as a measure of specific heat input. Microstructure, phase identification, relative diffracted-intensity trends, and crystallographic textures were characterized by 2D-XRD at three cross-section locations (ADV, weld nugget center [CEN], RET) and correlated with transverse tensile properties and fracture locations. Partial pole figures were plotted in the simple-shear reference frame with ideal-orientation overlays, intensities in multiples of a random distribution (m.r.d.). The CEN develops the strongest textures, dominated by a basal {002}_α component (20–31 m.r.d.) with poles near the normal direction; this concentration lies away from the ideal shear fiber loci and is more readily explained by orientation inheritance during the β→α transformation on cooling than by direct shear, although unambiguous identification of variant selection would require orientation-resolved measurements. The RET develops {101}_α and {100}_α pole concentrations clustering near the ideal P-fiber loci, consistent with deformation-related texture development, intensifying with both rotation and traverse speed. The ADV shows mixed textures varying non-monotonically with parameters. Two conditions of nearly identical N/v obtained from different parameter combinations (225 rpm/125 mm·min⁻¹ and 275 rpm/150 mm·min⁻¹) nevertheless develop measurably different streak morphologies, microstructures, textures, and tensile responses, showing directly that N/v orders but does not determine the thermomechanical state. Yield strength is uniform (≈900–940 MPa) across the full matrix, consistent with a Schmid-factor estimate in which the basal-near-ND CEN texture gives a very low resolved shear stress on basal systems under transverse loading; joint efficiencies reach ≈90–96%. Ductility, in contrast, tracks consolidation quality rather than texture severity: fracture strain rises almost monotonically with N/v, from ≈0.6–1.4% at N/v ≈ 1.8 (defect-driven, erratic failure) to ≈5.4–6.0% at N/v = 2.60, despite the latter condition carrying the strongest RET pyramidal texture. Full-field strain measurement shows the weld nugget to carry the lowest strain and the highest apparent stiffness of any zone in every condition for which the load record is reliable, with strain accumulating on the advancing side. Consolidated conditions fracture on the advancing side where deformation concentrates, whereas the lowest N/v and longest-exposure conditions fracture in the nugget center; all fracture surfaces are ductile, with the crack path following continuous α layers at prior-β grain boundaries. A favorable processing range within the investigated parameter matrix is N/v ≈ 2.2–2.6, with the best overall combination at 325 rpm and 125 mm·min⁻¹ (N/v = 2.60: UTS ≈ 1010 MPa, ≈5.4–6.0% elongation). Within the parameter range examined here, consolidation quality is the first-order design variable for this dissimilar system, with the zonal texture architecture setting the yield strength level. Full article

Wildfires near overhead transmission line corridors can cause localized conductor heating, thermal elongation, increased sag, and reduced ground clearance. However, traditional sag-calculation formulas and simplified equivalent-temperature methods have difficulty accurately representing wildfire-induced nonuniform temperature rise. To address this limitation, a fluid–thermal–stress multiphysics model was developed for an LGJ 300/40 ACSR conductor. A prescribed flame-temperature field and surrounding airflow were calculated using a CFD model to obtain the conductor’s nonuniform temperature distribution, which was then transferred to a structural finite-element model to determine thermal expansion and sag deformation. The effects of fire-source location were also investigated. The results show that nonuniform temperature rise leads to sag responses significantly different from those predicted using the three-section equivalent-temperature method. When the average conductor temperature reached approximately 130 °C, the maximum sag increased to about three times the cold-state value. Changing the fire-source location resulted in maximum differences of 73.3 °C in average conductor temperature and 37.1% in maximum sag. These quantitative relationships provide a practical reference for assessing conductor-to-ground clearance and evaluating wildfire-induced sag risk of overhead transmission lines. 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

A multiscale computational framework is presented to assess the effect of voids that may arise from a scarf repair and its influence on the post-repair lifetime of wind turbine blades. The approach links a full scale blade model with a detailed repair region model and a microscale representation of polymer adhesives containing voids. Boundary conditions from the global blade model are transferred to the scarf repair model, which subsequently provides input to a microscale representative volume element (RVE) of the adhesive containing voids using the submodelling technique. This RVE is combined with a continuum damage mechanics formulation to simulate high-cycle fatigue and estimate the lifetime for different void contents. The effect of void content resulting from scarf repair is evaluated under both quasi-static and high-cycle fatigue loading, enabling lifetime predictions. In the simulations, it was demonstrated that the lifetime of repaired blade is 4 times lower for the repair with 4% void content as compared with the repair with 1% void content. Full article

Precise signal extraction and geophysical interpretation of Global Navigation Satellite System (GNSS) coordinate time series constitute the core foundation for establishing the International Terrestrial Reference Frame (ITRF) and inverting surface mass redistribution. This paper reviews major advances in this field across four dimensions: model framework, signal characteristics, extraction methods, and geophysical mechanisms. Key findings include: (1) Maximum Likelihood Estimation (MLE) has become the recognized standard for linear trend extraction: by jointly estimating deformation parameters and the noise covariance, it corrects the up to 5–10-fold underestimation of velocity uncertainty that arises in conventional least-squares analyses when colored noise is present but a white-noise covariance is assumed; (2) in CMONOC benchmark tests reported by Wu et al., Variational Mode Decomposition (VMD) achieves an average 69.8% residual RMS reduction at 97.9% of stations—results that are promising but not yet independently replicated on other networks—while the self-supervised model GNSS-FM (currently an unreviewed preprint) represents an emerging intelligent analysis paradigm; (3) the combined effect of atmospheric, non-tidal ocean and hydrological loading explains about 42% of the residual power of the annual vertical signal globally after pole tide correction and reduces the weighted mean vertical annual amplitude from 4.19 mm to 3.19 mm, while for horizontal components the fraction explained by current loading models is much smaller (amplitude ratio, explained variance and RMS/WRMS reduction are distinct metrics and are not directly interchangeable). This paper further highlights that the annual period was reported to fluctuate between 363 and 367 days at the ten CMONOC stations analyzed by Li et al.—a time variability that, if general, challenges fixed-frequency signal separation methods, although apparent period changes may also arise from amplitude/phase modulation, spectral leakage, finite-record effects, colored noise or data gaps—and it identifies thermoelastic deformation (TED) as a long-neglected but potentially quantifiable component, based on a recently released preprint dataset that has not yet undergone peer review. Finally, key research prospects are outlined, including physics-informed fusion methods, self-supervised foundation models, and a unified multi-source inversion framework. Full article

This study investigated the shear behavior of large-scale reinforced concrete (RC) columns strengthened with either Engineered Cementitious Composite (ECC) or Ferro-Engineered Cementitious Composite (Ferro-ECC) jackets, with the latter incorporating expanded steel wire mesh (ESWM), thereby distinguishing the contribution of the ECC jacket from the additional contribution of ESWM. Ten large-scale specimens were tested without axial compression under monotonic four-point loading to evaluate the effects of mesh type, number of mesh layers, and transverse reinforcement under two deficiency scenarios: excessive stirrup spacing (250 mm) and complete absence of stirrups. Structural performance was assessed in terms of load–deflection response, cracking behavior, failure mode, stiffness, deformability, energy absorption, and shear capacity. The experimental cracking moments and ultimate shear capacities were evaluated against widely used design codes, and modified prediction models were proposed to account for the contributions of ECC and ESWM strengthening. The results showed that ECC strengthening alone significantly enhanced the shear performance of both stirruped and unstirruped RC columns, increasing the ultimate load by approximately 92–118% relative to the corresponding control specimens. The use of hybrid ECC–ferrocement jackets further increased the ultimate load by 106–123% with a single mesh layer, while two mesh layers resulted in increases of up to 164% and 244% for the stirruped and unstirruped columns, respectively. Strengthening delayed the initiation of flexural and diagonal cracking, increased crack distribution, and maintained service-load crack widths within acceptable limits (≈0.10–0.30 mm). Initial stiffness increased by up to 136%, deformation capacity improved by 25–60%, and energy absorption increased by 121–240% for ECC alone and up to 6.21 times with ECC–mesh systems. Coarse mesh was more effective in single-layer configurations, whereas fine mesh provided superior performance in double-layer systems through enhanced crack control. The proposed cracking and shear prediction models showed good agreement with the experimental results. Full article

Permafrost degradation is intensifying differential settlement, structural deformation, and secondary periglacial hazards along linear infrastructure in cold regions, underscoring the need for monitoring approaches that integrate corridor-scale screening with fine-scale quantification. This study investigated highways, railways, transmission tower foundations, and buried pipelines in the permafrost region of Northeast China using multi-temporal UAV-borne LiDAR point clouds and synchronous visible-light imagery acquired by a DJI Matrice 300 unmanned aerial vehicle equipped with a DJI Zenmuse L1 sensor (DJI, Shenzhen, China). A synergistic optical–LiDAR framework was developed for distress identification and multidimensional quantification. The overall root mean square errors (RMSEs) at flight altitudes of 50 m and 100 m were 3.25 cm and 4.13 cm, respectively. By integrating texture and boundary information from synchronous visible-light imagery, elevation and volumetric metrics from LiDAR-derived digital elevation models (DEMs) and digital surface models (DSMs), and structural attitude parameters extracted from three-dimensional (3D) models, the framework enabled the parametric quantification of pavement cracking, differential shoulder settlement, railway embankment slump, transmission tower inclination, thaw settlement and ponding in pipeline trenches, and secondary icing. Snow-depth retrievals agreed well with field measurements (R² = 0.87, RMSE = 1.32 cm), indicating that UAV-LiDAR can extend monitoring into snow-covered periods. These findings provide a methodological basis for distress detection, screening of hazard-prone sections, and risk-informed operation and maintenance of linear infrastructure in permafrost regions. Full article

Rapid seismic intensity estimation supports situational awareness, emergency response, and the assessment of earthquake-induced structural risk. Instrument-based systems provide authoritative measurements, but limited deployment density and installation cost can restrict spatial coverage. Video sensing offers a complementary route by converting the visible motion of a calibrated target into physical motion indicators; its reliability, however, depends on stable frame-wise localisation under illumination variation, blur, and target deformation. This paper presents FAMTrack, a vision-based seismic intensity prediction framework whose tracking module augments a one-stream Vision Transformer with a parallel Frequency-Aware Matching branch that encodes patch-wise Fourier amplitude and phase. A Cross-Domain Fusion Module exchanges spatial and frequency evidence through bidirectional cross-attention without modifying the detection head or tracking loss. On LaSOT, FAMTrack-256 attains a 75.1% AUC, 4.0 percentage points above OSTrack-256. On GOT-10K, it reaches 77.9% AO, a gain of 4.2 points. In the held-out seismic-video evaluation, FAMTrack reduces the displacement RMSE from 0.523 to 0.332 mm and improves window-level intensity prediction accuracy from 80.0% to 86.7% relative to OSTrack-256. Under the fixed calibrated-video pipeline and the evaluated controlled conditions, these results indicate that frequency-aware localisation is associated with improved public-benchmark tracking, motion recovery, and seismic intensity estimation. Full article

Non-destructive in situ tests, such as the plate bearing (plate load) test, are widely used to estimate the equivalent deformation modulus (e.g., $E_{v2}$) of existing road embankments. However, the depth of influence sampled by such a test is governed by the loading plate diameter, so a single test yields only an average, diameter-dependent modulus rather than the actual variation in stiffness with depth. This study investigates whether systematically varying the plate diameter and inverting the resulting settlement–diameter (dispersion) curves can recover the full depth-dependent stiffness profile, $E\left(z\right)$. Synthetic settlement–diameter curves were generated using a Boussinesq-based forward model for four families of reference stiffness profiles, representing normal (stiffness increasing with depth) and reverse (stiffness decreasing with depth) linear and exponential trends, combined with six Poisson’s ratios and five profile slopes/exponents (30 cases per profile family, 120 cases in total). Two inversion strategies were applied to back-calculate $E\left(z\right)$ from each dispersion curve: a classical Occam-type, smoothness-constrained (Tikhonov-regularized) nonlinear inversion, and a direct, closed-form simplified inversion method (SIM) based on differencing the apparent-modulus-versus-diameter curve. The results were benchmarked against the known reference profiles. Once calibrated so that its governing parameters depend only on Poisson’s ratio and the shape of the measured dispersion curve, SIM could be applied blindly—without knowledge of the reference profile or a starting model, requiring only an assumed Poisson’s ratio and the established calibration—and recovered $E\left(z\right)$ with markedly lower error than Occam’s inversion (WAD = 2.2–4.7% and RMSPE = 2.6–5.8%, versus 7.4–19.1% and 9.4–28.3%, respectively, across the four profile families). For the Poisson’s ratio most typical of earth materials, $\nu =0.3$, the calibration further collapses to a single parameter set common to all four families investigated ($I=0.66$; $c=1.3$ for stiffness increasing with depth, $c=2.5$ for stiffness decreasing with depth), which attains WAD ≤ 4.2% across all four families with no calibration equation at all. Notably, Occam’s inversion reproduced the settlement–diameter curve itself with good accuracy in most cases, yet this close data fit did not guarantee an accurate stiffness profile—a direct manifestation of the intrinsic non-uniqueness of the settlement-based inverse problem. These findings are bounded by their evidence base: noise-free data from the same forward operator used in the inversion, smooth profiles, a calibration evaluated on the cases that produced it, and an Occam comparison specific to L-curve-selected regularization. Within these limits, SIM is a promising alternative to regularized inversion; measurement noise, layered profiles and field validation are the next steps. Full article

To improve the static and dynamic stiffness of the LV500 horizontal CNC lathe and reduce machining errors, this study focuses on integrated structural simulation, bed–saddle collaborative optimization, and standardized precision evaluation. A whole-machine structural model is established in SolidWorks, and static, modal, and harmonic response co-simulations are performed in ANSYS, followed by multi-objective optimization of the two key weak components. MATLAB is used to process the dynamic simulation data. Based on a Renishaw XL-80 laser interferometer and the accompanying CARTO software, axis accuracy detection and measurement uncertainty evaluation are performed, forming a reproducible full-process engineering analysis system applicable to similar machine tools. The simulation results show that the maximum structural deformation after optimization is 0.016 mm, and the first-order natural frequency increases from 86.99 Hz to 92.55 Hz. Experimental tests demonstrate positioning accuracies of 3.0 μm (U = 0.38 μm, k = 2) for the X-axis and 3.3 μm (U = 0.45 μm, k = 2) for the Z-axis. Owing to the enhanced static–dynamic stiffness after structural optimization, the workpiece machining error can be stably controlled within 0.01 mm. In this study, a unified whole-machine model enables continuous static and dynamic analysis. The coupling stiffness of assembled components is considered in the modeling process, and the static and dynamic performance of the whole machine is improved through dual-component collaborative optimization. The inclusion of metrological-level uncertainty evaluation enhances the reliability of the experimental data. The proposed method provides a standardized engineering scheme for the static and dynamic performance optimization of similar horizontal CNC lathes. Full article

Coal rib instability is a critical challenge in steeply inclined, large-mining-height longwall faces containing coal seam partings. Taking the No. 4103 working face of Changcheng No. 1 Coal Mine as an engineering case, this study integrates theoretical analysis, numerical simulation, and field verification to investigate the underlying failure mechanisms. A segmented shear–slip mechanical model is developed using limit-equilibrium analysis to derive the stability margin, through which the coupled effects of seam dip, mining height, and parting properties on rib stability are quantified. Three-dimensional distinct-element simulations further reveal that rib deformation follows a consistent spatial pattern—middle section > upper section > lower section—and that the position and number of partings modify the load-transfer path and failure-surface continuity. Based on these findings, a coordinated control strategy is implemented, incorporating zoned differential support, dynamic adjustment of mining parameters, and localized reinforcement. Field application substantially reduces the frequency and depth of rib spalling and improves support stability and production continuity. The results provide a practical basis for coal rib control under comparable steeply inclined, large-mining-height conditions. Full article

Background: Artificial cranial modification (ACM) in pre-Hispanic Andean populations provides a natural model for investigating whether marked deformation of the cranial vault is associated with corresponding changes in palatal morphology and craniofacial integration. Methods: Three-dimensional geometric morphometrics was used to quantify neurocranial and palatal shape in 19 Peruvian crania (9 modified, 10 unmodified). Analyses included Generalized Procrustes Analysis, principal component analysis, Procrustes ANOVA, morphological disparity tests, directional asymmetry assessment, and two-block partial least squares (PLS) analysis of neurocranial–palatal covariation. Results: Modified crania showed significant neurocranial shape divergence from unmodified individuals, whereas palatal mean shape, principal component scores, and within-group disparity did not differ significantly between groups. Directional asymmetry was significant in both groups, but differences in mean asymmetry between groups were modest. Two-block PLS analysis yielded a first-axis correlation of r-PLS = 0.694; however, this association was not statistically significant (p = 0.488), and the RV coefficient indicated only low-to-moderate integration between neurocranial and palatal shape (RV = 0.341). Conclusions: These findings indicate that pronounced neurocranial deformation is associated with substantial changes in cranial vault morphology but limited alteration of palatal shape. The absence of significant neurocranial–palatal covariation suggests that the palate behaves as a comparatively constrained component of the craniofacial complex, supporting a model of partial craniofacial integration during growth. Full article

The integration of complementary sensing modalities provides a basis for accurate crack identification in advanced aircraft structures. In this context, PZT transducers are sensitive to incipient damage through guided-wave interrogation, whereas strain gauges capture quasi-static deformation. Prevailing fusion paradigms, however, encounter an interpretability–adaptability dilemma. Model-based approaches lack robustness to sensor degradation, while data-driven attention methods sacrifice transparency. To resolve this trade-off, an Evidence-guided Attention Neural Network (EANN) is proposed. Its central methodological contribution lies in repositioning Dempster–Shafer (D-S) evidence theory from a terminal fusion operator to an upstream credibility feature extraction module. Evidence-derived credibility features, comprising belief entropy, inter-source similarity, and Kalman-filtered residuals, drive the attention weight optimization and endow the learned channel weights with physically interpretable evidential meaning. Ablation experiments confirm that the observed improvement arises from the interaction between the evidence-guided credibility representation and adaptive attention weighting, with neither component sufficient on its own. The framework fuses quasi-static strain measurements with active piezoelectric guided-wave interrogation, which offers high sensitivity to incipient damage but remains vulnerable to channel degradation. Experiments on aluminum tensile plates and trapezoidal wing skin specimens show that EANN maintains identification accuracy under simulated sensor anomalies and partial failures by attenuating compromised channels without explicit fault detection, providing an uncertainty-aware fusion framework for online structural health monitoring of aerospace structures. Full article

Auxetic polymers offer a route to deformation-activated sealing by transforming axial deformation into lateral expansion, enabling controlled conformity and retention within perforated structures. This paper presents the design-space-guided optimisation of a multi-material polymeric auxetic plug for mechanically activated sealing of circular perforation surrogates relevant to military ground-vehicle structures using a controlled thin-wall surrogate validation framework. The sealing combines an SLA-printed Elastic 50A photopolymer auxetic body with TPU 95A load-transfer and priming components. A parameterised re-entrant unit cell was optimised using response-surface design of experiments coupled with nonlinear finite-element analysis. The optimised geometry, with a height of 6 mm, length of 5 mm, strut thickness of 1.25 mm, and re-entrant angle of 31°, achieved a predicted negative Poisson’s ratio of −2.66 under 20% axial strain. Experimental validation using additively manufactured unit cells confirmed the intended auxetic deformation response. The optimised structure was then integrated into a multi-material plug and tested against a solid polymer benchmark, achieving sealing to approximately 22 kPa with improved anchoring across the tested 22–25 mm perforation range. The results establish a mechanism-driven pathway from polymer auxetic unit-cell optimisation to plug-level pressure-sealing performance, demonstrating the potential of multi-material auxetic architectures as deformation-activated sealing systems for temporary repair of perforated military ground-vehicle structures. Full article

Ground deformations induced by underground mining significantly affect the geometric condition and serviceability of buildings located in mining areas. Conventional assessments are commonly based on ground deformation indicators, which do not necessarily reflect the actual structural response. This study presents a terrestrial laser scanning (TLS)-based methodology for assessing the three-dimensional deformation of an eleven-storey residential building located in the Legnica–Głogów Copper District (LGCD), Poland. The analysis was performed using a high-density point cloud acquired from ten scanning positions. Following registration and filtering, building geometry was reconstructed and corner positions were determined from 123 horizontal cross-sections. Horizontal displacements, tilt profiles, and rotation about the vertical axis were subsequently analysed within a local coordinate system. The results revealed pronounced spatial variability in both displacement magnitude and direction. The maximum horizontal displacement reached approximately 0.18 m, corresponding to a local tilt of 5.9 mm/m. Corner displacements at the highest common observation level ranged from 8.6 mm to 178.3 mm, indicating that the observed geometry is inconsistent with a simple rigid-body model subjected to uniform tilting. Analysis of geometric changes with height further identified an overall increase in torsional rotation with height, accompanied by local variations. Comparison of TLS-derived geometry with a theoretical mining-induced ground deformation model showed that the measured structural response does not directly reproduce the underlying ground deformation pattern. The largest discrepancies occurred along the building longitudinal axis, indicating that structural stiffness and soil–foundation–structure interaction significantly modify the transfer of ground movements to the superstructure. These results demonstrate the capability of TLS for detailed assessment of mining-affected buildings and provide quantitative insight into the relationship between ground deformation and actual structural response. Full article