Search Results (697)

The CAELESTIS project aims to promote the development and design of innovative aircraft and engine structures through an integrated ecosystem of simulations and digital tools, enabling synergy across all stages of the manufacturing process. The component selected was an Outlet Guide Vane (OGV), a static engine part composed of a central composite section and titanium inserts at both ends, joined in a single manufacturing step. A detailed investigation of the joints between these materials was carried out using surface treatments of different natures to evaluate properties that directly influence the final joint quality. Optical analysis techniques were employed to characterize the morphology, roughness and surface free energy (SFE), complemented by mechanical tests to determine the adhesion and shear strength. All specimens were manufactured using the Resin Transfer Molding (RTM) “one-shot” process. Full article

Accurate classification of rock fracture modes is essential for understanding rock mass instability mechanisms. To address the limitation of traditional acoustic emission (AE) classification methods that treat a single AE signal as a single fracture event, overlooking its composite nature from multiple fracture events and leading to misclassification, this study proposes a novel rock fracture mode classification method based on AE spectral analysis. This study details the development framework, theoretical model, classification criteria, application process, and experimental validation of the new rock fracture mode classification method. Uniaxial compression tests on granite, marble, and limestone, along with rockburst simulation tests on granite, were conducted to validate the classification of fracture modes. In rockburst simulations, shear fracture signals accounted for 48% on average, composite signals 40%, and tensile signals 12%. The method effectively distinguishes multiple fracture events within a single AE signal, accurately classifies fracture modes, and elucidates the dynamic evolution of fracture modes during the rockburst precursor stage, offering significant advantages for rock fracture mode classification and mechanistic insight. Full article

In earthquake engineering and hydraulic engineering, the dynamic mechanical behavior of cohesive soils is crucial to ensure structural stability. However, most existing dynamic constitutive models fail to adequately account for the influence of strain history, which is essential for accurately predicting soil behavior under seismic loading. This study conducted a series of cyclic single-shear tests on both in situ and disturbed Changsha cohesive soils. Hysteresis curves were obtained under varying shear strain amplitudes to investigate the degradation patterns of the dynamic shear modulus and the evolution of the damping ratio. Furthermore, multi-cycle loading tests under constant strain amplitude were carried out to clarify the correlation between damping ratio, dynamic shear modulus, and the number of loading cycles. A simplified practical dynamic model, applicable to general cohesive soils, is proposed. This model incorporates the effect of strain history and provides a valuable reference for analyzing the dynamic response of soils subjected to earthquake actions. Full article

Sugarcane is an important economic crop in southern China. Affected by typhoons, it is prone to lodging, which not only increases the difficulty and loss rate of mechanical harvesting but also reduces the sugar content. The mechanical properties of the sugarcane root–soil system are crucial to its lodging resistance. However, accurate discrete element parameters are still lacking for DEM-based research on the mechanical properties of this system. Therefore, this study adopts a method combining the angle of repose test, shear force test, and discrete element simulation of single roots to calibrate DEM parameters. Using the angle of repose and maximum shear force of a single root as response values, Plackett–Burman, steepest ascent, and Box–Behnken tests are sequentially carried out with Design-Expert 13 software to calibrate the contact and bonding parameters of individual sugarcane roots. The relative errors between the physical and simulation test results for the angle of repose and shear force are 1.29% and 0.66%, respectively. This study provides a reference for the establishment of discrete element simulation models for sugarcane roots and for the subsequent development of sugarcane root–soil composite models. Full article

In extreme scenarios such as nuclear explosions and high-energy radiation detection in space, UV-cured adhesives are usually used as coupling media to bind tapered optic fiber arrays with intensified charge-coupled devices or complementary metal–oxide semiconductors and a tapered optic fiber array for effective optical signal transmission. To address the issue of weak bonding strength caused by the small binding area between charge-coupled devices or complementary metal–oxide semiconductors and TOFA, a stage-wise curing process was investigated and proved to be efficient through comparison with the single curing process. The effect of interval time between the initial and final curing on coupling strength was characterized by tensile strength, shear strength and shock acceleration testing, and the samples were exposed to high and low temperatures for evaluation of their environmental adaptability. The curing mechanism was analyzed by surface morphology of the adhesive layer after decoupling and an energy-dispersive X-ray spectroscopy elemental analysis of interface layer. The results show that when the interval time is extended from 5 min to 60 min, the shock acceleration of the coupling device decreases by 26.1%, while the tensile and shear strengths also decrease by 49.4% and 60.7%, respectively. The decline in coupling strength is attributed to oxygen inhibition during interval time. The exposure of the adhesive surface to the air allows oxygen to diffuse into and react with active the free radicals that remain from the initial curing, which inhibits further polymerization and generates a thin, incompletely cured weak boundary layer. These findings provide insights for optimizing stage-wise curing processes and improving the reliability of coupled imaging devices. Full article

To address the difficulty of directionally cutting thick, hard key strata in gob-side entry retaining using conventional blasting or hydraulic fracturing, this paper proposes a high-pressure water-jet slotting-induced pre-cracked weakening belt (PCWB) roof-cutting technology. Several finite-length PCWBs are arranged within the key stratum and designed to coalesce into a plane, inducing through-going roof failure along a pre-determined path. A fixed–fixed key strata beam model combined with linear elastic fracture mechanics shows that the double-belt configuration forces the bending moment and shear force to concentrate in a thin rock bridge, where bending and shear stresses are amplified by about 1.5–2.8 times and 1.2–1.7 times, respectively, for 2–4 m thick key strata, providing a mechanical basis for preferential tensile–shear failure. Two-dimensional RFPA2D simulations reveal “width-dominated, length-assisted” control of cutting performance and identify an optimal weakening belt geometry of about 400 mm in width and 200 mm in length. Three-dimensional numerical modeling of parallel slot pairs indicates that intra-pair spacing of about 40 mm produces a continuous, directional weakening belt, whereas smaller or larger spacing causes, respectively, destructive interference or loss of connectivity. High-pressure water-jet tests (320 MPa, 0.33 mm nozzle, 1.30 mm/s traverse speed) on limestone blocks confirm that single slots can penetrate the full thickness and that cracks from adjacent slots coalesce through the rock bridge, forming a wide, straight fracture band. Field application in the Dongjiang Mine (3.5 m limestone key stratum, ~400 m depth) shows that the first weighting is advanced from the 7th to the 3rd day, peak support resistance is reduced from 8.8 to 7.4 MPa, and periodic weighting becomes more frequent and smoother. The PCWB technology is therefore suitable for panels with 2–4 m thick hard key strata at similar depths, offering precise key stratum severance, active stress relief, and safe, controllable construction. Full article

Background/Objectives: Autoimmune thyroiditis affects physical and cognitive development in children. Therefore, early detection can prevent symptoms that could lead to lifelong changes. Autoimmune thyroiditis can frequently accompany type 1 diabetes (T1DM) and celiac disease (CD). The goal in this study is to evaluate its usability as a screening method by assessing thyroid elasticity in children with negative thyroid autoantibodies and T1DM or CD. Methods: This cross-sectional, case–control, single-center study was conducted with children who had applied to the Pediatrics outpatient clinic of Kayseri City Education and Research Hospital (Turkey). The study included three groups of cases (T1DM, CD and control). The value of the shear wave elastography (SWE) color map was recorded in kPa. Comparisons between two independent groups were conducted using either Student’s t-test or the Mann–Whitney U-test, while categorical variables were analyzed with the Chi-square test. A correlation analysis was conducted to evaluate the relationship between the variables. Results: The study cohort comprised 185 children, of whom 71 had T1DM, 54 had CD, and 60 constituted the healthy control group. The participants ranged in age from 4 to 17.9 years, with a mean age of 11.4 ± 3.8 years. The gender distribution did not differ significantly between the groups. Anti-thyroid peroxidase (TPOAb) levels did not differ significantly between the groups (p = 0.894). Thyroid volume or standard deviation score did not differ significantly between the groups. Corresponding SWE values in the T1DM, CD and control groups were 7.7 (6.0–9.3), 5.9 (5.2–7.9) versus 7.1 (6.0–9.6), respectively (p = 0.002). Correlations were significantly associated between SWE scores and anti-thyroglobulin (TgAb), thyroid volume, mean hemoglobin A1c (HbA1c), and time elapsed from a diagnosis of CD. Conclusions: The SWE scores were observed to be higher in children with T1DM compared to those with CD. Full article

Classical soil mechanics models are inadequate for predicting the traction of wheeled vehicles under high-velocity off-road conditions due to the complex dynamic soil response. To address this, this study proposes a velocity-segmented dynamic compression-shear model for aeolian sandy soil, enhancing classical theories with velocity-dependent corrections for the 0–10 m/s range. A theoretical patterned wheel–soil interaction model is developed, incorporating lug effects via an equivalent radius. Furthermore, a comprehensive vehicle traction model is established by integrating the soil model with a dynamic equilibrium iteration method that couples suspension dynamics, pitch attitude, and axle load distribution. Validation results demonstrate that the single-wheel traction theoretical model achieves an error of less than 18%, while the full vehicle traction model reaches a 73% prediction accuracy for drawbar pull and sinkage, as verified through soil bin tests and full-vehicle experiments. This research provides theoretical framework for the real-time and accurate prediction of wheeled-vehicle traction performance on unprepared terrain, offering significant improvements for high-velocity off-road mobility analysis. Full article

Steel–concrete composite beams are widely used in building and bridge engineering; however, the impact response of Steel–Coarse Aggregate–Ultra-High Performance Concrete (Steel–CA–UHPC) composite beams remains insufficiently quantified, and no beam-specific dynamic capacity formula is available. To address this gap, companion static testing and drop-weight impact tests were performed on full-scale simply supported steel–CA–UHPC composite beams under single and repeated impacts, followed by development of a strain-rate-dependent dynamic increase factor (DIF) model and a capacity prediction framework. The companion static specimen reached 448 kN, whereas the 5 m impact cases produced peak forces of 930.0–940.4 kN, corresponding to 2.08–2.10 times the static level, with the initial peak forming within 1.0–1.1 ms. Dynamic failure was marked by rapid mid-span cracking of the CA–UHPC slab and brittle shear fracture of studs, while repeated impacts mainly accelerated cumulative damage before the final high-energy strike. Static–dynamic displacement comparison further revealed much more abrupt deformation concentration under impact loading. A revised static capacity formula reduced the prediction error from 4.46% for the code-based method and 1.00% for the literature model to 0.74%. Combined with the fitted DIF–strain-rate relation, the proposed framework reproduced the measured dynamic capacities with errors of −4.63% to 9.75%. The study provides member-level evidence and a practical DIF-based method for evaluating the impact resistance of steel–CA–UHPC composite beams. Full article

Metallic Shear Plate Dampers (MSPDs) are essential components in passive vibration control systems and require rapid post-earthquake inspection to assess damage and determine replacement needs. Traditional visual inspection methods suffer from low efficiency and limited ability to detect concealed damage. This study proposes a novel MSPD damage detection method based on active sensing and the k-nearest neighbor (KNN) algorithm, featuring high accuracy, efficiency, and low cost. Quasi-static tests were conducted to simulate various damage states. Sweep-frequency excitation was applied using a charge amplifier, and piezoelectric sensors were employed to generate and receive stress wave signals corresponding to different damage conditions. The acquired signals were processed using wavelet packet transform (WPT) and energy spectrum analysis to extract discriminative time–frequency features, which were used to train and validate the KNN model. Results show that the model achieved a validation accuracy of 98.9% using all valid data and 98.1% using a single excitation-sensing channel. When tested on an MSPD with a similar overall structure but lacking stiffeners, the model achieved an accuracy of 92.6% in distinguishing between healthy and damaged states. This indicates that the proposed method has good robustness and practical potential for MSPDs with similar damage evolution and failure modes despite certain structural variations. Full article

The exploitation of deep oil and gas resources faces challenges posed by complex high-temperature and high-pressure environments. Understanding the mechanical behavior of reservoir rocks under such conditions is therefore critical for ensuring engineering safety. Most existing studies utilize reservoir rock samples at ambient temperature or subjected to high-temperature pretreatment for conventional triaxial tests. However, research on the mechanical response under the coupled conditions of real-time high temperature and in situ true triaxial stress remains limited. To address this gap, this study employed a self-developed in situ true triaxial testing system capable of simultaneous high-temperature and high-pressure loading. Systematic in situ true triaxial mechanical tests were conducted on granite under temperatures up to 200 °C and confining pressures up to 200 MPa. After fracturing, the three-dimensional crack morphology was obtained using CT scanning, and quantitative characterized based on the average crack width and fractal dimension, systematically investigating the effects of temperature, intermediate principal stress (σ₂), and minimum principal stress (σ₃) on the mechanical parameters and fracture characteristics of granite. In this study, the results indicate that over the temperature range of 25–200 °C, the peak strength and elastic modulus decrease by approximately 11–18% and 15–40%, respectively, while the peak strain increases by 4–20%. The failure mode transitions gradually from a tensile–shear composite fracture at room temperature to a predominantly shear fracture at elevated temperatures. The rock brittleness is reduced, thus the damage zone expands, and macroscopic fractures decrease. Correspondingly, the average fracture width decreases from approximately 0.66 mm to 0.55 mm, and the fractal dimension increases from about 2.28 to 2.38. An increase in σ₂ leads to a 19–26% increase in peak strength and a 33–75% increase in elastic modulus, while also increasing the average fracture width and decreasing the fractal dimension. Also, the rock brittleness increases, and the failure mode shifts from tensile–shear composite fracture to shear fracture. An increase in σ₃ results in an approximately 11% increase in peak strength, a 30% increase in peak strain, and a 21% decrease in elastic modulus, accompanied by a decrease in average fracture width and an increase in fractal dimension. This suppresses the formation of a single dominant fracture surface, consequently increasing the complexity of the fracture morphology. This research reveals the mechanical response and failure laws of deep granite under high-temperature and true triaxial conditions, providing important insights for understanding the mechanical properties of deep reservoir rocks and for the design of drilling and fracturing operations. Full article

This study evaluated eleven resin cements used as core build-up materials by examining the following properties: (a) push-out force between root dentin and the fiber post; (b) pull-out force between the fiber post and the core build-up material; (c) shear bond strength of the resin cement to root dentin; (d) flexural strength of the resin cement; and (e) flexural modulus of elasticity of the resin cement. The purpose of this investigation was to clarify the relationships between recently available universal adhesives, core build-up materials, resin cements, and fiber posts. All experiments were performed at two evaluation periods: after 1 day of water storage (Base) and after 20,000 thermocycles (TC 20k). For the push-out test, simulated post spaces were prepared in single-rooted human premolars. The specimens were sectioned perpendicular to the long axis into 2 mm-thick slices and then subjected to push-out testing to assess the bond strength of the dentin–resin cement–fiber post complex. No significant differences in bonding performance were found between Base and TC 20k. These findings suggest that universal adhesives used for pretreatment of multiple substrates in fiber post cementation can provide not only strong but also durable adhesion over time. Full article

To address the prominent problem of early rutting distress in asphalt pavements under heavy-load traffic in China, this study proposes a composite modifier consisting of direct coal liquefaction residue (DCLR), styrene–butadiene–styrene block copolymer (SBS), and styrene–butadiene rubber (SBR). The preparation process and formula were optimized through single-factor experiments and orthogonal tests. Systematic investigations were conducted on its conventional performance, water damage resistance, aging resistance, fatigue performance, rheological properties, and microscopic mechanism, with comparisons made against base asphalt, single DCLR-modified asphalt, SBS-modified asphalt, and SBS/SBR-modified asphalt. The results indicate that the optimal preparation process for the novel composite high-modulus modified asphalt is as follows: DCLR particle size of 0.3 mm, addition in molten state, shear temperature of 170 °C, shear rate of 5000 r·min⁻¹, shear time of 50 min. The optimal formula is 10% DCLR + 3% SBS + 2% SBR + 3% compatibilizer, with the addition sequence of “DCLR → SBS + compatibilizer → SBR”. This asphalt exhibits a softening point of 77.8 ± 2.1 °C, a Brookfield viscosity at 135 °C of 1.928 ± 0.105 Pa·s, and a grading of 5 for adhesion to aggregates; the rutting factor at 64 °C reaches 10.8 ± 0.9 kPa (6.43 times that of the base asphalt), the creep stiffness at −12 °C is 136 ± 12.5 MPa, and the low-temperature limit temperature is −17 °C; the freeze–thaw splitting strength ratio (TSR) is 94.6 ± 1.8%, and both aging resistance and water damage resistance are significantly superior to those of the control group asphalts (p < 0.05). The novel composite high-modulus modified asphalt showed improved overall laboratory performance and may be suitable for heavy-load traffic and complex climatic conditions, however, field validation is needed. Full article

This study aims to investigate the influence of clay mineral content on the rheological properties and long-term deformation stability of clays, and to establish a unified model capable of quantitatively describing the nonlinear rheological behavior of clays with different mineral compositions. Direct shear rheological tests were conducted on specimens prepared with different mixing ratios of bentonite, kaolin, and quartz. Combined with micro-mechanism analysis, the controlling factors of clay rheological behavior were explored. The experimental results show that the creep stress threshold, elastic viscosity, and average plastic viscosity decrease significantly with increasing clay mineral content. The rheological deformation exhibits distinct nonlinear characteristics, and clay mineral content plays a controlling role in the rheological behavior. Based on experimental and mechanistic analysis, a unified rheological model was established, which reflects the material origin of rheology and captures nonlinear rheological characteristics. This model can predict the entire time-history mechanical behavior of clays with different mineral compositions across the three stages of instantaneous deformation, decay rheology, and steady-state rheology under different shear stress levels using a single set of parameters. Validation was performed through direct shear rheological tests under 50 working conditions for five types of clay specimens, demonstrating good consistency between the model calculations and experimental results. The unified rheological model reveals the material origin and physical essence of clay rheology, demonstrates high universality, and advances the understanding of the influence of mineral composition on rheology from the current phenomenological qualitative description to quantitative calculation for the first time, significantly enhancing its engineering application value. This provides a more reliable tool for predicting long-term deformation and assessing the stability of clay foundations. Full article

Carbonate reservoirs in the Shunbei area develop pronounced fracture networks after acidized hydraulic fracturing and thus have the potential to be repurposed as underground gas storage (UGS) after hydrocarbon depletion. Characterizing their mechanical behavior is essential for safe UGS operation; however, deep to ultra-deep natural cores are difficult to obtain, and conventional macroscopic tests often cannot provide parameters that meet engineering requirements. To address this issue, nanoindentation combined with QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) was employed to quantify microscale mineral distributions and the mechanical properties of the major constituents. The investigated rock is calcite-dominated (89.62%), with minor quartz (9.89%) and trace feldspar-group minerals (1.89%). Minerals are randomly embedded, and soft–hard phase boundaries are widely distributed. A finite–discrete element method (FDEM) model was then constructed and calibrated in ABAQUS. The discrepancies in uniaxial compressive strength and elastic modulus relative to laboratory results were 6.51% and 9.91%, respectively, indicating good agreement in both mechanical response and failure mode. Parametric analyses using three additional models with different mineral proportions show that damage preferentially initiates at mineral phase boundaries and stress concentration zones induced by end constraints. Microcracks then propagate and coalesce into a dominant compressive–shear band, and final failure is mainly governed by slip along the shear band with localized tensile cracking. With increasing quartz and feldspar contents, enhanced heterogeneity and a higher density of phase boundaries lead to a higher density of crack nucleation sites and increased crack branching, and the failure pattern transitions from a single shear-band–controlled mode to a more network-like fracture system. Moreover, macroscopic strength is not determined solely by the intrinsic strength of individual minerals; heterogeneity and phase-boundary characteristics strongly govern microcrack behavior, such that higher hard-phase contents may result in a lower peak strength. Full article