Search Results (832)

The reliability of high-strength bolted connections is critical to the safety of large-scale engineering structures. This study proposes a non-contact quantitative method for detecting bolt loosening based on the self-magnetic flux leakage (SMFL) effect. Systematic experiments were carried out on M14-12.9 bolts, using nine independent specimens tested under six torque levels, to reveal the intrinsic relationship between bolt preload and the “magnetic valley” feature of the surface leakage field. For quantitative evaluation, the absolute value of the differential peak magnetic field, |ΔPMF|, is defined as the core feature parameter. The results show that, in the reference specimen group, |ΔPMF| exhibits a pronounced linear relationship with the applied torque (R² > 0.96), and the corresponding linear regression parameters display good consistency across the nine specimens (RSD ≈ 4%). Comparative tests on two additional bolt specifications clarify how bolt strength grade and geometric size influence the detection sensitivity and linearity. To address lift-off effects, measurements on a representative specimen at four lift-off heights were used to construct a simplified bivariate linear compensation model, which significantly reduces lift-off-induced bias within the working range h = 10–16 mm. Finally, a hierarchical diagnostic scheme for bolt loosening that incorporates lift-off compensation is established on the basis of |ΔPMF|, providing a feasible approach for rapid assessment of bolt loosening under complex service conditions. Full article

Background: Fetal growth restriction (FGR) is a major contributor to adverse perinatal outcomes and is primarily driven by placental insufficiency and chronic fetal hypoxia. While arterial Doppler abnormalities are widely used in clinical surveillance, less is known about venous hemodynamics and intracardiac structural adaptations in FGR. In particular, the clinical relevance of foramen ovale (FO) morphometry and inferior vena cava (IVC) Doppler parameters in different FGR phenotypes remains incompletely understood. This study aimed to evaluate FO measurements and IVC Doppler indices in early- and late-onset FGR and to investigate their associations with adverse perinatal outcomes. Methods: This prospective observational study included 240 singleton pregnancies: 120 fetuses with FGR and 120 gestational age-matched appropriate-for-gestational-age controls. FGR was defined according to Delphi consensus criteria and classified as early onset (<32 weeks) or late onset (≥32 weeks). Ultrasonographic assessment included FO and right atrium dimensions, FO-to-right atrium (FO/RA) ratio, IVC diameter, and IVC Doppler indices (pulsatility index [PI], preload index [PLI], and peak velocity index for veins [PVIV]). A composite adverse perinatal outcome (CAPO) was recorded. Receiver operating characteristic (ROC) curve analysis and multivariable logistic regression were performed. Results: Compared with controls, fetuses with FGR exhibited significantly smaller FO dimensions, lower FO/RA ratios, reduced IVC diameters, and higher IVC Doppler indices (all p < 0.05). The FO/RA ratio demonstrated the highest discriminative performance for CAPO (AUC 0.722). In multivariable analysis, a 0.1-unit increase in the FO/RA ratio was independently associated with a reduced risk of CAPO (OR 0.57), whereas higher IVC PI values were associated with an increased risk (OR 2.64). IVC Doppler alterations were less pronounced in early-onset FGR. Conclusions: FO morphometry and IVC Doppler parameters reflect complementary stages of fetal cardiovascular adaptation in fetal growth restriction, with FO changes representing early adaptive responses and IVC Doppler alterations indicating more advanced hemodynamic compromise, and this may provide additional value for perinatal risk stratification. Full article

In conventional band sawing, the long-span compression of the flexible saw blade often results in large fluctuations in cutting force, low cutting efficiency, and poor force predictability. To address these issues, this study investigates the dynamic cutting force modeling and experimental validation of ultrasonic vibration-assisted band sawing using 304 stainless steel as the workpiece material. Based on an analysis of the band sawing mechanism, an ultrasonic vibration-assisted approach is proposed to modify the contact conditions between the saw blade and the workpiece. A dynamic model of the saw blade is established using the string vibration equation, and a multi-tooth dynamic cutting force prediction model is further developed by incorporating variable cutting depth characteristics under ultrasonic vibration. Comparative experiments are conducted between conventional sawing and ultrasonic vibration-assisted sawing to validate the proposed model. At feed rates of 0.1–0.4 mm/s and preload values of 0.1–0.5 mm, the proposed model predicts dynamic cutting forces with good agreement to experimental results, achieving an average relative error of 5.44%. Under typical cutting conditions for difficult-to-machine materials, ultrasonic vibration-assisted sawing reduces the average cutting force and feed force by approximately 15% and 18%, respectively, while decreasing surface roughness along the feed direction by about 21%, thereby improving sawing efficiency and surface quality. Full article

Background/Objectives: Under general anesthesia, maintaining patients’ blood pressure (BP) is important to prevent organ ischemia. When bleeding occurs, it is sometimes difficult to increase BP with boluses of fluids or transfusions, and vasoconstrictors must be administered. This study investigated circulatory dynamic changes in patients who bled during surgery and were administered phenylephrine, particularly left ventricular end-diastolic volume (EDV), effective arterial elastance (Ea), and left ventricular end-systolic elastance (Ees), calculating each value from the left ventricular–arterial coupling (Ees/Ea). Methods: We calculated Ees/Ea using electrocardiograms, arterial pressure waveforms, and phonocardiograms using an esophageal stethoscope. We investigated the changes in patients’ EDV, Ea, and Ees during two periods: phenylephrine administration and after BP elevation. Results: The seven participants comprised three men and four women. Between the two periods, linear mixed-model analysis revealed that mean arterial pressure (MAP), Ea, and Ees significantly increased over time (MAP; β = 8.7, p < 0.01, Ea; β = 0.22, p < 0.05, Ees; β = 0.73, p < 0.05), while no significant changes were observed in other parameters such as heart rate and EDV. Conventional parameters demonstrated that stroke volume variation significantly decreased (β = −2.0, p = 0.01), systemic vascular resistance index significantly increased (β = 200, p < 0.01), while no significant change was observed in cardiac index (β = −0.03, p = 0.7). In patients administered phenylephrine due to BP decrease from bleeding, significant changes in afterload and cardiac contractility occurred without changes in preload. Conclusions: Our noninvasive method for calculating EDV, Ea, and Ees can be valuable for monitoring hemodynamics under anesthesia. Full article

Aiming at analyzing the load characteristics and friction torque of triple-row hub bearings for new energy vehicles, this work established a comprehensive theoretical and experimental methodology for predicting the internal load distribution and friction torque. Firstly, considering the preload effect via an initial negative clearance, deformation coordination and force balance equations for the triple-row bearing under axial load were formulated, to analyze the external loads under various driving conditions. Based on contact deformation theory, a quasi-static model was developed to combine radial, axial, and moment loads. The Newton–Raphson iterative algorithm was employed to solve the ball load distribution equations, and the correctness was verified by using the finite element method. Furthermore, accounting for the elastic hysteresis, differential sliding, and spin sliding, the theoretical models for friction torque components were established, to investigate the influence of structural parameters and the total friction torque under different driving conditions. Finally, to confirm the effectiveness and the precision of the model, a finite element simulation and experimental measurements of friction torque were conducted, respectively, which showed good agreement with theoretical calculations. The main innovations include proposing a mechanical modeling method for triple-row hub bearings that accounts for preload effects, and establishing an integrated friction torque analysis model applicable to multiple driving conditions. This work provides theoretical support and a methodological foundation for the design of next-generation hub bearings for new energy vehicles. Full article

Cardiogenic pulmonary edema (CPE) is a life-threatening manifestation of acute heart failure characterized by rapid accumulation of fluid in the interstitial and alveolar spaces, leading to severe dyspnea, hypoxemia, and respiratory failure. The condition arises from elevated left-sided filling pressures that increase pulmonary capillary hydrostatic pressure, disrupt alveolo-capillary barrier integrity, and impair gas exchange. Neurohormonal activation further perpetuates congestion and increases myocardial workload, creating a vicious cycle of hemodynamic overload and respiratory compromise. Respiratory support is a cornerstone of management in CPE, aimed at stabilizing oxygenation, reducing the work of breathing, and facilitating ventricular unloading while definitive therapies, such as diuretics, vasodilators, inotropes, or mechanical circulatory support (MCS), address the underlying cause. Among available modalities, non-invasive ventilation (NIV) with continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) has the strongest evidence base in moderate-to-severe CPE, consistently reducing the need for intubation and providing rapid relief of dyspnea. High-flow nasal cannula (HFNC) represents an emerging alternative in patients with moderate hypoxemia or intolerance to mask ventilation, and should be considered an adjunctive option in selected patients with less severe disease or NIV intolerance, although its efficacy in severe presentations remains uncertain. Invasive mechanical ventilation is reserved for refractory cases, while extracorporeal membrane oxygenation (ECMO) and other advanced circulatory support modalities may be necessary in cardiogenic shock. Integration of respiratory strategies with hemodynamic optimization is essential, as positive pressure ventilation favorably modulates preload and afterload, synergizing with pharmacological unloading. Future directions include personalization of ventilatory strategies using advanced monitoring, novel interfaces to improve tolerability, and earlier integration of MCS. In summary, respiratory support in CPE is both a bridge and a decisive therapeutic intervention, interrupting the cycle of hypoxemia and hemodynamic deterioration. A multidisciplinary, individualized approach remains central to improving outcomes in this high-risk population. Full article

Membrane proteins remain the most challenging targets for structural characterization, yet their elucidation provides valuable insights into protein function, disease mechanisms, and drug specificity. Structural biology platforms have advanced rapidly in recent years, notably through the development and implementation of nanodiscs—discoidal lipid–protein complexes that encapsulate and solubilize membrane proteins within a controlled, native-like environment. While nanodiscs have become powerful tools for studying membrane proteins, faithfully reconstituting the compositional asymmetry intrinsic to nearly all biological membranes has not yet been achieved. Proper membrane leaflet lipid distribution is critical for accurate protein folding, stability, and insertion. Here, we share a protocol for reconstituting tailored compositional asymmetry within nanodiscs through membrane extraction from giant unilamellar vesicles (GUVs) treated with a leaflet-specific methyl-β-cyclodextrin (mβCD) lipid exchange. Nanodisc asymmetry is verified through a geometric approach: biotin-DPPE-preloaded mβCD engages in lipid exchange with the outer leaflet of POPC GUVs solubilized by the lipid-free membrane scaffold protein (MSP) Δ49ApoA-I to form nanodisc structures. Once isolated, nanodiscs are introduced to the biotin-binding bacterial protein streptavidin. High-speed atomic force microscopy imaging depicts nanodisc–dimer complexes, indicating that biotin-DPPE was successfully reconstituted into a single leaflet of the nanodiscs. This finding outlines the first step toward engineering tailored nanodisc asymmetry and mimicking the native environment of integral proteins—a potentially powerful tool for accurately reconstituting and structurally analyzing integral membrane proteins whose functions are modulated by lipid asymmetry. Full article

The structural health monitoring of bolted connections is important for ensuring the safety and reliability of engineering systems, yet conventional sensing technologies struggle to balance detection range and sensitivity. This study presents a flexible sensor with a hybrid capacitive–resistive sensing mechanism, designed to overcome the limitations of single-mode sensors. By integrating a hierarchically structured composite layer with tailored material properties, the sensor achieves a seamless transition between sensing modes across different pressure ranges. It exhibits high sensitivity in both low-pressure and high-pressure regions, enabling the reliable detection of preload variations in bolted connections. Experimental validation confirms its cyclic durability and rapid response to mechanical changes, demonstrating good potential for real-time monitoring in aerospace and industrial systems. Full article

Humans could sensitively perceive and identify objects through dense mechanoreceptors distributed on the skin of curved fingertips. Inspired by this biological structure, this study presents a general conformal integration method for flexible tactile sensors on curved fingertip surfaces. By adopting a spherical partition design and an inverse mode auxiliary layering process, it ensures the uniform distribution of stress at different curvatures. The sensor adopts a 3 × 3 tactile array configuration, replicating the 3D curved surface distribution of human mechanoreceptors. By analyzing multi-point outputs, the sensor reconstructs contact pressure gradients and infers the softness or stiffness of touched objects, thereby realizing both structural and functional bionics. These sensors exhibit excellent linearity within 0–100 kPa (sensitivity ≈ 36.86 kPa⁻¹), fast response (2 ms), and outstanding durability (signal decay of only 1.94% after 30,000 cycles). It is worth noting that this conformal tactile fingertip integration method not only exhibits uniform responses at each unit, but also has the preload-free advantage, and then performs well in pulse detection and hardness discrimination. This work provides a novel bioinspired pathway for conformal integration of tactile sensors, enabling artificial skins and robotic fingertips with human-like tactile perception. Full article

Bolted connections are critical in deep-sea engineering, yet classical theories (such as VDI 2230) implicitly assume atmospheric pressure conditions, neglecting the volume contraction of components due to hydrostatic pressure. This fundamental flaw hinders accurate prediction of preload retention—especially when bolts and clamped components exhibit differential compressibility (a common scenario in practical applications). To bridge this scientific gap, this paper establishes the first analytical model for bolt preload under pressure-induced volumetric contraction based on deformation coordination relations. The derived closed-form expressions explicitly quantify residual preload as a function of deep-sea ambient pressure, component bulk modulus, and geometric parameters. Model predictions closely match finite element calculations, showing that stainless steel bolts clamping aluminum alloys under 110 MPa pressure can experience up to a 40% preload reduction. This theoretical framework extends classical bolt connection mechanics to high-pressure environments, providing a scientific basis for optimizing deep-sea connection designs through material matching and dimensional control to effectively mitigate pressure-induced preload loss. Full article

This paper presents research on an online preload detecting method for power transformer windings that is highly sensitive, survivable and repeatable. Traditional frequency response analysis methods exhibit limitations in sensitivity, accuracy, and interference resistance, making it difficult to detect small loosening. Although the FBG offer superior performance, quartz optical fibers exhibit limited deformation capacity and are susceptible to damage from short circuit impacts. To identify FBG placement locations with minimal impact exposure, this study compared FBG sensors at different installation positions through 42 short circuit impacts. Results confirmed that the FBG positioned at the top of pressure board experienced the least impact damage. Subsequently, a transformer equipped with this online preload detecting system underwent 12 short circuit impact tests. Simulation results and hoisting cover findings aligned with the FBG online detecting data. This study proposes an experimentally validated online preload detecting method, providing a reliable and reproducible technical pathway for transformer condition assessment. Full article

In complex mechanical systems involving multiple parts and contact interfaces, failure modes are not only statistically correlated but may also interact through underlying physical mechanisms. These interactions, often neglected in current reliability analysis, can lead to significant deviations in failure predictions, especially in rotor systems and actuators. Taking aeroengine turbine rotor assemblies as an example, multiple failure modes, such as wear, fatigue and slip at contact interfaces, affect key mechanical property parameters including assembly preload, cylindrical interference fit and cooling performance. These variations lead to evolving stress/strain and temperature fields with increasing load cycles, thereby inducing physical interactions among different failure modes. This study systematically analyzes the interaction mechanisms among multiple failure modes within a turbine rotor assembly. A mechanics model is established to quantify these interactions and their effects on failure evolution. Furthermore, a time-dependent reliability evaluation method is proposed based on Monte Carlo simulation and the Probability Network Evaluation Technique. A case study illustrates that both continuous-type and trigger-type interactions significantly affect the failure probabilities of wear and low-cycle fatigue. The results emphasize the necessity of accounting for interaction of multi-failure modes to improve the accuracy of failure prediction and enhance the design reliability of turbine rotor assemblies. Full article

Metal-composite joints, leveraging the high specific strength/stiffness and superior fatigue resistance of carbon fiber reinforced polymers (CFRP) alongside metallic materials’ excellent toughness and formability, have become prevalent in aerospace structures. Fastener flexibility serves as a critical parameter governing load distribution prediction and fatigue life assessment, where accurate quantification directly impacts structural reliability. Current approaches face limitations: experimental methods require extended testing cycles, numerical simulations exhibit computational inefficiency, and conventional machine learning (ML) models suffer from “black-box” characteristics that obscure mechanical principle alignment, hindering aerospace implementation. This study proposes an integrated framework combining numerical simulation with explainable ML for fastener flexibility analysis. Initially, finite element modeling (FEM) constructs a dataset encompassing geometric features, material properties, and flexibility values. Subsequently, a random forest (RF) prediction model is developed with five-fold cross-validation and residual analysis ensuring accuracy. SHapley Additive exPlanations (SHAP) methodology then quantifies input features’ marginal contributions to flexibility predictions, with results interpreted in conjunction with theoretical flexibility formulas to elucidate key parameter influence mechanisms. The approach achieves 0.99 R2 accuracy and 0.11 s computation time while resolving explainability challenges, identifying fastener diameter-to-plate thickness ratio as the dominant driver with negligible temperature/preload effects, thereby providing a validated efficient solution for aerospace joint optimization. Full article

Preterm infants in neonatal intensive care units (NICUs) experience impaired neurodevelopment and dysregulated stress responses, partly due to a lack of tactile stimulation. Although massage therapy offers proven therapeutic benefits by stimulating C-tactile afferents through (gentle) dynamic touch, existing methods are limited by clinical staff variability and resource constraints. This work presents a compact soft-pneumatic actuator array (SPAA) utilizing four nylon–TPU actuators (modules) connected in series or in parallel to perform a sequential actuation; this array is designed to deliver safe, shear-free, and massage-like normal compression tailored for preterm infants. Actuator performance was characterized using a load-cell and a pressure sensor under different preloads (10–30 g), establishing operating internal pressures of 20–50 kPa, which produced target force ranges between 0.1 and 0.3 N. Two SPAA architectures were evaluated: (i) parallel manifold with branch resistances and (ii) series chain with graded outlet resistances, using passive fluidic sequencing for controlled activation. The series configuration achieved repeatable sequential actuation with programmable delays, essential for mimicking therapeutic massage patterns. These results demonstrate that passive soft-pneumatic sequencing can reliably deliver dynamic tactile stimuli within neurophysiological and safety constraints, laying the groundwork for standardized, automated neonatal massage therapy in NICUs. Full article

ANSYS software was used to analyze the moment-rotation relationship of semi-rigid steel structure joints with bolted connection. A parametric study was conducted to examine the influence of eight key variables—including bolt number, bolt grade, angle steel grade, bolt diameter, angle steel thickness, angle steel width, preload magnitude, and friction coefficient—on the bending behavior of semi-rigid joints with bolted connection. Parametric analysis reveals that the initial rotational stiffness is most significantly influenced by the bolt diameter, the width and thickness of the angle steel, the bolt preload, the coefficient of friction, and the bolt number. The stiffness exhibited an average increase of 50.6% for every 4 mm increment in bolt diameter from 12 mm to 24 mm. Expanding the angle steel width from 50 mm to 75 mm resulted in a substantial 88.5% average increase in stiffness, while a further width increase from 75 mm to 110 mm led to a smaller average increase of 17.4% per 17.5 mm. Similarly, the stiffness rose by an average of 33.8% for every 2 mm increase in the thickness of the angle steel within the 4 mm to 10 mm range. A 25% increase in bolt preload correlated with a modest average stiffness gain of 2.7%. The rate of stiffness improvement diminished with increasing friction coefficient. In contrast, the initial rotational stiffness exhibited a relationship that is approximately linear with respect to the quantity of bolts. Regarding the ultimate bending moment, the key influencing factors were identified as bolt diameter, preload, coefficient of friction, and number of bolts. The ultimate moment demonstrated a non-monotonic relationship with bolt diameter, characterized by an initial increase, followed by a decrease, and then a sharp subsequent rise. Linear enhancements in the ultimate moment were observed with increases in both bolt preload and coefficient of friction. Furthermore, the ultimate bending moment showed a gradual increase with the number of bolts. Based on the results, a bending moment-rotation curve model of joints with bolted connection is established, and the expression of each parameter in the model is calculated. This model can be applied to simulation of the bending performance of semi-rigid joints with bolted connection. Full article