Search Results (123)

This paper develops a novel design formula to estimate the residual strength of corroded stiffened cylindrical structures. It extends a previously established ultimate strength formulation for intact cylinders by introducing a corrosion-induced strength reduction factor. The foundational formula considers failure mode interactions like yielding, local buckling, overall buckling, and stiffener tripping. This research utilizes recent experimental and numerical investigations on corroded ring-stiffened cylinder models. Experimental results validate the numerical analysis method, showing good agreement in collapse pressures (2–4% difference) and shapes. The validated numerical method is then subject to an extensive parametric study, systematically varying corrosion characteristics. Results indicate a clear relationship between corrosion volume and strength reduction, with overall buckling being more sensitive. Based on these comprehensive results, a new empirical strength reduction factor (${\rho }_c$) is derived as a function of the corrosion volume ratio ($V_{non}$). This factor is integrated into the existing ultimate strength formula, allowing direct residual strength estimation for corroded structures. The proposed formula is rigorously verified against experimental and numerical data, showing excellent agreement (mean 1.00, COV 5.86%). This research provides a practical, accurate design tool for assessing the integrity and service life of corroded stiffened cylindrical structures. Full article

The contact characteristics of radial tires are crucial for optimizing stress distribution, deformation, and wear. The non-uniform contact stress behavior induced by complex tread patterns remains under-explored in existing tire mechanics research. Taking the 205/50R17 radial tire as a representative case, a reverse modeling approach was employed to develop an accurate finite element model for tires incorporating intricate tread pattern features. The fidelity of the proposed tire simulation model was confirmed utilizing high-precision contour profiling techniques. The impact of diverse usage conditions and design parameters on the tire outer profile and ground contact characteristics under static and free-rolling states was analyzed. Experimental observations demonstrate that the increased inflation pressure leads to a proportional decrease in contact area. Under incremental vertical loading, the contact patch develops progressively into a saddle-shaped geometry featuring elevated shoulder regions and a recessed central zone. Increasing the belt angle compromises its hoop-stiffening function, thereby inducing elliptical contact patch geometry. Larger design diameters compromise contact length symmetry in shoulder regions. Variation in shoulder thickness at 85% of the tread width results in a significant difference in contact length between the left and right tread blocks in the rolling state. This work enables refinement strategies for both tread configurations and tire dimensional designs in industrial applications. Full article

Peripheral artery disease (PAD) is a chronic progressive accumulation of atherosclerotic lesions with varying degrees of arterial obstruction determining ischemic symptoms of the involved extremities. PAD is associated with decreased bioavailable nitric oxide due to endothelial cell dysfunction and the development and progression of vascular arterial stiffening (VAS). Atherosclerosis also plays an essential role in the development and progression of vascular arterial stiffening (VAS), which is associated with endothelial cell activation and dysfunction that results in a proinflammatory endothelium with a decreased ability to produce bioavailable nitric oxide (NO). NO is one of three gasotransmitters, along with carbon monoxide and hydrogen sulfide, that promotes vasodilation. NO plays a crucial role in the regulation of PAD, and a deficiency in its bioavailability is strongly linked to the development of atherosclerosis, VAS, and PAD. A decreased arterial patency may also occur due to a reduction in the elasticity or diameter of the vessel wall due to the progressive nature of VAS and atherosclerosis in PAD. Progressive atherosclerosis and VAS promote narrowing over time, which leads to impairment of vasorelaxation and extremity blood flow. This narrative review examines how atherosclerosis, aging and hypertension, metabolic syndrome and type 2 diabetes, tobacco smoking, and endothelial cell activation and dysfunction with decreased NO and VAS with its increased damaging pulsatile pulse pressure result in microvessel remodeling. Further, the role of ischemia and ischemia–reperfusion injury is discussed and how it contributes to ischemic skeletal muscle remodeling, ischemic neuropathy, and pain perception in PAD. Full article

A hyperparameter-optimized Kriging surrogate model was developed for the structural collapse behavior framework presented in this paper. The assessment is conducted on a stiffened panel subject to axial load and lateral pressure, typical of the deck structure of a bulk carrier ship. This behavior is characterized using nonlinear finite element analysis to determine the collapse response. The surrogate model’s hyperparameters were optimized using a Genetic Algorithm to achieve the best performance, and the trained framework can predict ultimate strength. By following this approach, the problem can be reformulated as a multi-objective optimization task. This framework involves associating the Kriging surrogate model with a multi-objective evolutionary optimization algorithm based on Genetic Algorithms to balance the trade-off between the weight and ultimate strength of the stiffened panel. The results confirm the applicability of the Kriging surrogate framework to predict the ultimate strength and assess the collapse analysis of the stiffened panels, ensuring accuracy through GA-based hyperparameter optimization. Full article

Stiffened panels are extensively used in aerospace applications, particularly in wing and fuselage sections, due to their favorable strength-to-weight ratio under in-plane loading conditions. This research employs the commercial finite element software Ansys-19 to analysis the critical buckling and ultimate collapse load of an aluminum stiffened panel having a dimension of 1244 mm (Length) × 957 mm (width) × 3.5 mm (thickness), with three stiffener blades located 280 mm away from each other. Both the critical buckling load and post-buckling ultimate failure load of the panel are validated against the experimental data found in the available literature, where the edges towards the length are clamped and simply supported, and the other two edges are free. For nonlinear buckling analysis, a plasticity power law is adopted with a small geometric imperfection of 0.4% at the middle of the panel. After the numerical validation, the investigation is further carried out considering four different lateral pressures, specifically 0.013 MPa, 0.065 MPa, 0.085 MPa, and 0.13 MPa, along with the compressive loading boundary conditions. It was found that even though the pressure application of 0.013 MPa did not significantly impact the critical buckling load of the panel, the ultimate collapse load was reduced by 18.5%. In general, the ultimate collapse load of the panel was severely affected by the presence of lateral pressure while edge compressing. Three opening shapes—namely, square, circular, and rectangular/hemispherical—were also investigated to understand the behavior of the panel with openings. It was found that the openings significantly affected the critical buckling load and ultimate collapse load of the stiffened panel, with the lateral pressure also contributing to this effect. Finally, in critical areas with higher lateral pressure load, a titanium panel can be a good alternative to the aluminum panel since it can provide almost twice to thrice better buckling stability and ultimate collapse load to the panels with a weight nearly 1.6 times higher than aluminum. These findings highlight the significance of precision manufacturing, particularly in improving and optimizing the structural efficiency of stiffened panels in aerospace industries. Full article

This paper presents a comprehensive on-site decision-making framework for assessing the structural integrity of a jacket-type offshore platform in the Gulf of Mexico, installed at a water depth of 50 m. Six critical analyses—(i) static operation and storm, (ii) dynamic storm, (iii) strength-level seismic, (iv) seismic ductility (pushover), (v) maximum wave resistance (pushover), and (vi) spectral fatigue—are performed using SACS V16 software to capture both linear and nonlinear interactions among the soil, piles, and superstructure. The environmental conditions include multi-directional wind, waves, currents, and seismic loads. In the static linear analyses (i, ii, and iii), the overall results confirm that the unity checks (UCs) for structural members, tubular joints, and piles remain below allowable thresholds (UC < 1.0), thus meeting API RP 2A-WSD, AISC, IMCA, and Pemex P.2.0130.01-2015 standards for different load demands. However, these three analyses also show hydrostatic collapse due to water pressure on submerged elements, which is mitigated by installing stiffening rings in the tubular components. The dynamic analyses (ii and iii) reveal how generalized mass and mass participation factors influence structural behavior by generating various vibration modes with different periods. They also include a load comparison under different damping values, selecting the most unfavorable scenario. The nonlinear analyses (iv and v) provide collapse factors (Cr = 8.53 and RSR = 2.68) that exceed the minimum requirements; these analyses pinpoint the onset of plasticization in specific elements, identify their collapse mechanism, and illustrate corresponding load–displacement curves. Finally, spectral fatigue assessments indicate that most tubular joints meet or exceed their design life, except for one joint (node 370). This joint’s service life extends from 9.3 years to 27.0 years by applying a burr grinding weld-profiling technique, making it compliant with the fatigue criteria. By systematically combining linear, nonlinear, and fatigue-based analyses, the proposed framework enables robust multi-hazard verification of marine platforms. It provides operators and engineers with clear strategies for reinforcing existing structures and guiding future developments to ensure safe long-term performance. Full article

The subject of the present work is the development and implementation of a novel testing facility to carry out an experimental campaign on an advanced fuselage panel manufactured from both thermoplastic and metallic materials, as well as the validation of its numerical simulation. The experimental arrangement was specifically designed, assembled, and instrumented to have multi-axial loading capabilities. The investigated load cases comprised uniaxial in-plane compression, lateral distributed pressure, and their combination. The introduction of pressure was enabled by inflatable airbags, and compression was applied up to the onset of local skin buckling. Calibration of the load introduction and inspection equipment was performed in multiple steps to acquire accurate and representative measurements. Data were recorded by external sensors mounted on a hydraulic actuator and an optical Digital Image Correlation (DIC) system. A numerical simulation of the fuselage panel and the test rig was developed, and a validation study was conducted. In the Finite Element (FE) model, several of the experimental configuration’s supporting elements and their connections to the specimen were integrated as constraints and boundary conditions. Data procured from the tests were correlated to the simulation’s predictions, presenting low errors in most displacement/strain distributions. The results show that the proposed test rig concept is suitable for stiffened panel level testing and could be used for future studies on similar aeronautical components. Full article

The size of ships has increased considerably in recent decades. This growth impacts the stress magnitude in the bottom hull plates, which constantly suffer from biaxial compression and lateral water pressure, potentially leading to buckling. Adding stiffeners is an effective alternative to increase mechanical buckling resistance if placed in a proper way. Several researchers have investigated the influence of stiffeners on plates under different loading conditions. However, the behavior under combined biaxial compression and lateral pressure has not yet been widely explored. This work aims to verify and validate a computational model to analyze the elastoplastic buckling of plates under biaxial compression and lateral pressure, applying it in a case study to define the ideal geometric configuration to increase ultimate buckling resistance, using the constructal design method and exhaustive search technique. In this study, a portion of the volume from a reference plate without stiffeners was converted into stiffeners to determine the optimal geometry for maximizing ultimate buckling resistance. The numerical model was verified and validated, and the case study identified the optimal plate configuration with five longitudinal and four transverse stiffeners, with a height-to-thickness ratio of 8.70, achieving a 284% increase in ultimate buckling resistance compared to the reference plate. These results highlight the importance of geometric evaluation in structural engineering problems. Full article

This study demonstrates the use of a dual-sample arm swept-source optical coherence tomography (SS-OCT) instrument coupled with air-puff stimulation to assess corneal displacement in an ex vivo porcine eye model. The air-puff SS-OCT system enables correction of corneal deformation for eye globe retraction, providing a comprehensive quantitative analysis of corneal apex deformation dynamics under varying intraocular pressure (IOP) levels and air-puff stimulus strengths. Spatio-temporal characterization of those stimuli was performed. The results showed that the cornea stiffened with increased IOP, and reducing the stimulus amplitude decreased the correlation between parameters describing corneal dynamics and IOP. However, maximum displacement and corneal response time exhibited very strong correlations regardless of the strength of the applied air-puff. These findings suggest that softening air-puff stimulation may impact the accuracy of non-contact tonometers in measuring IOP and corneal biomechanical properties. Full article

Carbon fiber-reinforced epoxy composites, known for their high specific stiffness, specific strength, and toughness are one of the primary materials used for composite nozzles in aerospace industries. The high temperature vibration behaviors of the composite nozzles, especially those that withstand internal pressures, are key to affecting their dynamic response and even failure during the service. This study investigates the changes in frequencies and the vibrational modes of the carbon fiber reinforced epoxy nozzles, focusing on a three-dimensional (3D) orthogonal woven composite, with high internal temperatures from 25 °C to 300 °C and non-uniform internal pressures, up to 5.4 MPa. By considering the temperature-sensitive parameters, including Young’s modulus, thermal conductivity, and thermal expansion coefficients, which are derived from a self-built representative volume element (RVE), the intrinsic frequencies and vibrational modes in composite nozzles were examined. Findings reveal that 2 nodal diameter (ND) and 3ND modes are influenced by $E_{xx}$ and $E_{yy}$ while bending and torsion modes are predominantly affected by shear modulus. Temperature and internal pressure exhibit opposite effects on the modal frequencies. When the inner wall temperature rises from 25 °C to 300 °C, 2ND and 3ND frequencies decrease by an average of 30.39%, while bending and torsion frequencies decline by an average of 54.80%, primarily attributed to the decline modulus. Modal shifts were observed at ~150 °C, where the bending mode shifts to the 1st-order mode. More importantly, introducing non-uniform internal pressures induces the increase in nozzle stiffening in the xy-plane, leading to an apparent increase in the average 2ND and 3ND frequencies by 17.89% and 7.96%, while negligible changes in the bending and torsional frequencies. The temperature where the modal shifts were reduced to ~50 °C. The research performed in this work offers crucial insights for assessing the vibration life and safety design of hypersonic flight vehicles exposed to high-temperature thermal vibrations. Full article

The pressure response of crystalline 9,9′-spirobifluorene up to 8 GPa was studied by means of Raman spectroscopy using a diamond anvil cell as a pressure chamber. With increasing pressure, the observed Raman peaks shifted to higher frequencies, reflecting the bond hardening upon volume reduction, which was much more pronounced for the initially weaker intermolecular interactions than for the stronger intramolecular covalent bonds. The significant changes in the Raman spectrum and the pressure evolution of the frequencies at ~1.3 GPa for both the intermolecular and the intramolecular Raman peaks signaled a pressure-induced structural and molecular conformation transition with a little hysteretic behavior (~0.5 GPa) upon pressure release. For P > 4 GPa, the reversible decrease of the pressure coefficients of the majority of the intermolecular and some intramolecular peak frequencies indicated another structural modification of the studied molecular crystal. A value of ~9 GPa for the bulk modulus of the system at zero pressure was estimated from the logarithmic pressure coefficients of the frequencies of the intermolecular modes in the low-pressure phase. These coefficients were reduced by ~6 times at 4.2 GPa, indicating that the considerable stiffening of the material in the high-pressure phase emanated from the selective strengthening of the intermolecular interactions. Full article

Ultimate strength is critical for hull structures because it determines the maximum load the structure can withstand before catastrophic failure. Aluminium honeycomb sandwich panels provide excellent energy absorption and a high strength-to-weight ratio. However, further investigation of honeycomb sandwich panel structural performance is needed in typical marine conditions. This study focuses on the numerical analysis of honeycomb sandwich panels employing the nonlinear finite element method through the commercial software ANSYS. It investigates their performance under uniaxial compression and varying lateral pressure conditions while considering different cell edge lengths and core height configurations. Several structural configurations are compared to the experimental work published in the literature. Enhanced by experimental accuracy, the present study is a further step in expanding the application of honeycomb sandwich panels for ship hull applications that may lead to light and energy-efficient structures. Full article

Hypertension exerts a profound impact on the microcirculation, causing both structural and functional alterations that contribute to systemic and organ-specific vascular damage. The microcirculation, comprising arterioles, capillaries, and venules with diameters smaller than 20 μm, plays a fundamental role in oxygen delivery, nutrient exchange, and maintaining tissue homeostasis. In the context of hypertension, microvascular remodeling and rarefaction result in reduced vessel density and elasticity, increasing vascular resistance and driving end-organ damage. The pathophysiological mechanisms underlying hypertensive microvascular dysfunction include endothelial dysfunction, oxidative stress, and excessive collagen deposition. These changes impair nitric oxide (NO) bioavailability, increase reactive oxygen species (ROS) production, and promote inflammation and fibrosis. These processes lead to progressive vascular stiffening and dysfunction, with significant implications for multiple organs, including the heart, kidneys, brain, and retina. This review underscores the pivotal role of microvascular dysfunction in hypertension-related complications and highlights the importance of early detection and therapeutic interventions. Strategies aimed at optimizing blood pressure control, improving endothelial function, and targeting oxidative stress and vascular remodeling are critical to mitigating the systemic consequences of hypertensive microvascular damage and reducing the burden of related cardiovascular and renal diseases. Full article

Trimethylamine N-oxide (TMAO), a gut microbiome-derived metabolite, participates in the atherogenesis and vascular stiffening that is closely linked with cardiovascular (CV) complications and related deaths in individuals with kidney failure undergoing peritoneal dialysis (PD) therapy. In these patients, arterial stiffness (AS) is also an indicator of adverse CV outcomes. This study assessed the correlation between serum TMAO concentration quantified with high-performance liquid chromatography and mass spectrometry and central AS measured by carotid–femoral pulse wave velocity (cfPWV) in patients with chronic PD. Of the 160 participants included, 23.8% had a cfPWV of ≥10 m/s, which fulfilled the AS criteria. Multivariable logistic regression analysis revealed that TMAO, age, and waist circumference were positively associated with AS. Multivariable stepwise linear regression showed that underlying diabetes, advanced age, waist circumference, systolic blood pressure, and logarithmic-transformed TMAO were independently correlated with cfPWV. The area under the receiver operating characteristic curve for TMAO in differentiating AS from non-AS was 0.737. In conclusion, serum TMAO level was significantly independently correlated with central AS among participants undergoing PD for end-stage kidney failure. Full article

While power transformer manufacturers are well versed in electrical aspects such as ampere-turns and amps per square inch, optimizing electrical efficiency, voltage regulation, and insulation, there is a potential oversight regarding the intricate mechanical challenges associated with electrical design. As transformers evolve in size and capacity, mechanical forces become increasingly significant, necessitating a closer examination of the mechanical aspects of electrical design. This study focuses on the design of power transformer tank walls. To address the challenge associated with larger tank wall deflection (for both the high-voltage and low-voltage sides) during pressure tests, different stiffeners such as flat stiffeners, changed flat stiffener dimensions, flat bar supports for stiffeners, and H-beams were added to the tank wall and modeled for finite element analysis. The tank wall design was optimized for higher mechanical strength, lower deflection, and lower mass by assessing the von Mises stress and deformation of different stiffeners. The findings of this study will contribute to a better understanding of how design adjustments affects mechanical strength, stress distribution, and overall reliability, providing valuable insights for the industry. Full article