Pressure Loading Research Articles

Ultimate Strength Analysis of Aluminium Honeycomb Sandwich Panels Subjected to Uniaxial Compressive Loads and Lateral Pressure

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.

Design of compliant thermal actuators using topology optimization involving design-dependent convection and pressure load

This study presents a topology optimization method for thermal actuators that accounts for boundary conditions influenced by variables such as thermal convection and pressure load. Thermal actuators with gripper-like designs are essential for handling hot and brittle materials. The objective of this study is to design actuator shapes that achieve an optimal balance between flexibility and stiffness in high-temperature environments. Unlike previous studies that consider load conditions imposed on fixed boundaries within the design domain, this research introduces a high-temperature fluid as the driving source and employs a novel approach to boundary condition setting by integrating fictitious physical problems. This approach allows for the precise specification of various boundary conditions across multiple domains. A weighted-sum method is applied to optimize three objective functions related to deformability, stiffness, and thermal diffusibility of the actuators. To address the issue of excessively thin structures compromising deformability and the poor convergence of the optimization process, stress constraints based on the optimization history are introduced. The proposed method is validated through numerical examples, demonstrating improvements in structural deformability while controlling deformation on the target surface plane. The numerical results confirm that the objective function decreases and stress is suppressed, verifying the effectiveness of the proposed approach.

Impact of foam metal hoods on pressure waves generated by high-speed trains traversing tunnels

The high-speed trains traveling at 400 km/h will generate severe alternating pressure and potential sonic boom when passing through tunnels. This paper proposed foam metal hoods (FMH) to mitigate the pressure waves induced by trains traversing tunnels. 1:20 scaled moving-model experiments were conducted to investigate the mitigation mechanisms of FMH on micro-pressure waves (MPW), residual pressure, and aerodynamic loads on the train and tunnel. The impact of FMH's installation position and length on MPW and residual pressure were discussed. The results indicate that the entrance FMH can weaken the expansion wave generated by the tail train entering the tunnel, thereby reducing the pressure amplitude on the train surface and tunnel wall. FMH can reduce the reflection intensity of pressure waves, effectively lowering the root mean square (RMS) of residual pressure. Installing FMH at both ends can reduce the RMS of residual pressure in the middle of the tunnel by 25%. The exit FMH enables the initial wavefront to gradually release pressure outward, thereby reducing MPW intensity. The radiation range of the MPW iso-surface is narrowed by energy consumption as the wavefront passes through the porous structures. The mitigation ratio of MPW intensifies as the length of the exit FMH increases. Using a 4-m-long exit FMH can decrease the MPW amplitude by 83.2% at 20 m from the FMH exit. The FMH facilitates a low-noise environment near tunnel portals, reducing the aerodynamic loads on the tunnel structures, and mitigating the train aerodynamic loads.

A kinematic hardening constitutive model for anomalous multiaxial ratcheting behaviors of zirconium alloy tubes under combined cyclic axial load and internal pressure at 648 K

A kinematic hardening constitutive model for anomalous multiaxial ratcheting behaviors of zirconium alloy tubes under combined cyclic axial load and internal pressure at 648 K

Research on dynamic well control in riserless mud recovery system

In order to promote the development of RMR (Riserless Mud Recovery) system well control technology and ensure the safe operation of deep water drilling operations, the overflow control equation of RMR system considering the lifting force of subsea pump is established and verified, the conventional overflow monitoring method and the overflow monitoring method based on subsea pump parameter variation are compared and analyzed. the dynamic well control process of the RMR system after overflow under the two modes of constant subsea pump displacement and constant inlet pressure of subsea pump is simulated, and the influencing factors of inlet pressure of subsea pump are further analyzed. The results show that although the temperature effect is taken into account in the model established in this paper, the time error of the mud pool increment, the inlet pressure and the displacement of subsea pump after reaching the overflow criterion is less than 22.5% compared with Froyen's model. The conventional overflow monitoring method has fast response and small change, while the overflow monitoring method based on subsea pump parameter change is on the contrary, and the two should be used together. Both the constant inlet pressure of subsea pump mode and the constant subsea pump displacement mode can control overflow, but from the stability of subsea pump, service life and well control safety, the constant displacement mode is better. In the case of large formation pressure, low drilling fluid density, overflow criteria and circulating displacement, the pressure response adjustment speed of the subsea pump inlet is faster, and the back pressure load of the subsea pump inlet can be effectively alleviated by appropriately increasing the circulating displacement and drilling fluid density. This study has enriched the theoretical system of RMR system in overflow control, and has certain guiding significance for the development of deepwater and ultra-deepwater drilling safety technology.

Cumulative blood pressure load and cognitive decline in older adults: An observational analysis of two large cohorts.

Cumulative blood pressure metrics may provide greater precision for measuring temporal risk exposure, especially in later life where data are mixed regarding associations of high blood pressure (BP) on cognitive function. We examined the relationship between greater cumulative exposure to high BP in later life and several domains of cognitive function. Individual cognitive assessment scores and BP measurements in older adults (age ≥70 years) at baseline and over approximately 8 years of follow-up were available in the population-based Canadian Victoria Longitudinal Study (VLS) and Swedish Gothenburg H70 Birth Cohort Studies (H70). Linear mixed models were used to quantify associations between cumulative systolic and diastolic BP and change in cognitive scores. Each additional 100mmHg increase in cumulative BP was related to greater decline in the Rey Auditory Verbal Learning Test (RAVLT) List A, trials 1-5 total score over follow-up: -0.23 (95% confidence interval [CI] -0.32, -0.13) for systolic BP and -0.41 (95%CI -0.58, -0.23) for diastolic BP. Similarly increases cumulative systolic and diastolic BP were related to greater declines Digit Symbol Substitution Task (DSS) scores: -0.59 (95%CI -0.80, -0.38) and -1.04 (95% CI -1.40, -0.67), respectively. There were no associations of cumulative BP and temporal changes in general cognition, other measures of verbal episodic memory, or semantic fluency. Higher cumulative BP is associated with greater declines in RAVLT measured immediate memory span and complex attention, information processing speed and visuospatial scanning in older adults, but the scale of change is small. Additional research is required to further define these relationships and identify opportunities for prevention.

Reliability Assessment of the Casted Steel Function Block in Gasoline Fuel Rails

In this study, the reliability of the casted function block, a critical component of the fuel rail assembly (FRA), is examined under the pressure and thermal loads typically encountered in an engine compartment. The function block serves a dual purpose: it acts as a holder for the fuel rail, securing it to the cylinder head (CH), and it includes the injector cup, which connects the injectors to the rail. This component is manufactured as a single piece using casting methods. To assess the stress experienced by the function block, Finite Element Analysis (FEA) techniques are employed. Additionally, a specialized mechanical pulse test is developed to determine the fatigue limits of the casted function block. This testing is crucial for understanding how the component will perform under cyclic loading conditions. The failure probability of the function block is quantified by generating S-N (stress-cycle) curves based on the results from the mechanical pulse tests. These curves illustrate the relationship between the applied stress and the number of cycles to failure, allowing for a comprehensive analysis of the component's durability. Ultimately, the study demonstrates that the failure probability of the casted function block is estimated to be less than 1 ppm (parts per million) for serial production. This finding confirms that the function block meets the stringent reliability requirements necessary for automotive applications, ensuring its performance and safety in the demanding environment of an engine compartment.

Tailoring Robust 2D Nanochannels by Radical Polymerization for Efficient Molecular Sieving.

Two-dimensional (2D) nanochannels have demonstrated outstanding performance for sieving specific molecules or ions, owing to their uniform molecular channel sizes and interlayer physical/chemical properties. However, controllably tuning nanochannel spaces with specific sizes and simultaneously achieving high mechanical strength remain the main challenges. In this work, the inter-sheet gallery d-spacing of graphene oxide (GO) membrane is successfully tailored with high mechanical strength via a general radical-induced polymerization strategy. The introduced amide groups from N-Vinylformamide significantly reinforce the 2D nanochannels within the freestanding membranes, resulting in an ultrahigh tensile strength of up to 105MPa. The d-spacing of the membrane is controllably tuned within a range of 0.799-1.410nm, resulting in a variable water permeance of up to 218 L m-2h-1 bar-1 (1304% higher than that of the pristine GO membranes). In particular, the tailored membranes demonstrate excellent water permeance stability (140 L m-2h-1 bar-1) in a 200-h long-term operation and high selectivity of solutes under harsh conditions, including a wide range of pH from 4.0 to 10.0, up to a loading pressure of 12bar and an external temperature of 40°C. This approach comprehensively achieves a balance between sieving performance and mechanical strength, satisfying the requirements for the next-generation molecular sieving membranes.

Using Machine Learning to Predict the Stress-strain State of a Ring Plate

This article is devoted to the problem of prediction of the stress-strain state of a ring plate using neural networks. The article shows how to train the neural network to estimate the von Mises stress of a ring plate under external uniform pressure. Machine learning, one of the six disciplines of Artificial Intelligence (AI) without which problems of having machines acting humanly could not be accomplished. Applications of ANNs to engineering structures arise in a variety of industries such as engineering, automotive, space structures, etc. ANNs allow to develop models e.g. for the stress-strain state estimation of some type of solids. Thus, the development of machine learning methods for predicting the behavior of engineering structures is urgent. The paper describes the scheme for using machine learning in the stress-strain state analysis of a ring plate. Additional input parameters of the data set are the following: outer radius, inner radius, thickness of the plate, Young’s modulus, Poison’s coefficient, and pressure load. The training set is generated by the finite element method. Initial parameters of the training set have been randomly generated. The artificial neural network merges numerical and one-hot input layers. One hot The developed regression model allows to predict von Mises stresses for a ring plate. The developed model allows to predict the von Mises stress with 10% of the mean absolute percentage error. The key advantage of an artificial neural network is the speed of prediction. The ANN predicts the von Mises stress almost instantaneously (milliseconds) comparing the finite element method

Crack Arrest Analysis of Components With Compressive Residual Stress

ABSTRACTA finite element analysis and fracture mechanics methodology for determining the autofrettage pressure required to cause crack arrest in components under varying pressure loading are presented. Superposition of the autofrettage residual stress distribution and working load stress distribution is combined with ANSYS Separating Morphing and Adaptive Remeshing Technology (SMART) to determine the effective stress intensity factor as the crack grows. The condition for crack arrest is identified by comparison with a crack arrest model defining the crack propagation threshold stress intensity factor range for microstructurally short, physically short, and long cracks. The crack propagation threshold models of El Haddad and Chapetti are implemented and applied to fatigue analysis of stainless steel and low carbon steel double notch tensile test specimens with preinduced compressive residual stress. Based on comparison with fatigue test results, the Chapetti model is selected for use in the analysis of a 3D aluminum alloy valve body. The calculated minimum autofrettage pressure required to give crack arrest under a given working load cycle is found to be in good agreement with experimental observations from the literature.

Heuristic-based vehicle arrangement for ro-ro ships

In this paper, a two-level search strategy fused with an improved no-fit polygon algorithm and improved bat algorithm is proposed to obtain the layout points of multiple vehicles. Additionally, a space–time scheduling strategy is proposed using the Improved D*Lite Algorithm (ID*Lite) and improved Bezier curve to generate the trajectories of individual vehicles. Furthermore, a conflict resolution strategy is introduced to address the collision conflict problem during multi-vehicle scheduling. The proposed strategies aim to achieve the objectives of shortest scheduling time and smallest array space in order to reduce the time and space cost of vehicle loading on ro-ro carriers. Through a comparison with other algorithms (e.g., at high loading pressure, Scenario 3), the strategies presented in this paper demonstrate advantages such as higher deck utilization (92.234%), shorter path length, fewer collision conflicts, and more balanced weighting. Mainstream methods only focus on a certain part of vehicle transportation, we not only use more stable parking spot generation algorithm and parking order generation algorithm, but also more high-speed multi-vehicle path-finding algorithm, path optimization strategy, multi-vehicle scheduling strategy, which innovatively form a complete vehicle planning process, and at the same time, as an algorithmic framework that can be generalized to any 2d or 3d scenarios.

Experimental Determination of the Equivalent Moment of Inertia and Stresses of Aluminium Profiles with Thermal Breaks

This paper presents the results of experimental tests and computer simulations on the stiffness of composite aluminium mullions used in unitised façades. The elements analysed were subjected to bending in order to simulate the actual operating conditions of aluminium façades subjected to significant wind pressure or suction loads. The basic mechanical and physical properties of the materials from which the analysed type of aluminium façade is made (Aluminium EN AW-6060 in the T66 temper and polyamide PA66 25GF), the test method, and the results obtained are described. As a result of the tests, equivalent moments of inertia of the composite profile (aluminium profile with the thermal break) were determined, which are strongly dependent on the strength of the connection between the individual elements, the asymmetry of the cross-section, and the properties of the thermal break. Strain measurements carried out using FBG (Fiber Bragg Grating) strain sensors installed in the profiles under tests allowed for determining the actual stress values of the aluminium profiles under consideration. The results obtained were compared to theoretical (numerical) values, indicating discrepancies at higher load values. The methodology presented in this article is to be used to monitor the deformation of the aluminium façade mullions of HRB (High-Rise Buildings).

Comparison of the effects of orthoses on hallux valgus angle and plantar pressure in individuals with hallux valgus.

Hallux valgus (HV) is a condition characterized by the lateral deviation of the first phalanx and medial deviation of the first metatarsal, leading to subluxation of the first metatarsophalangeal joint. Various orthotic applications are employed in the treatment of HV deformity. This study aimed to compare the effects of a toe separator (TS) and dynamic orthosis (DO) on hallux valgus angle (HVA), plantar pressure (PP), and quality of life (QoL). Thirty individuals aged between 18 and 65 years who had mild to moderate HV deformity were included in our study. Participants were randomized into TS and DO groups. Pretest and post-test evaluations at 4 weeks included goniometric measurement for HVA, PP measurement using the Sensor Medica device, QoL assessment using the American Orthopaedic Foot & Ankle Society-Hallux MTP-IP Scale and Manchester-Oxford Foot Questionnaire, and numerical evaluation scale for orthosis satisfaction. No statistically significant changes were observed in HVA measurements (p > 0.05). In the DO group, significant differences were observed in PP assessment for right rearfoot loading (p = 0.048) and total average pressure measurement of the right foot (p = 0.025). QoL assessments were observed significant differences in the DO group compared with the TS group (p < 0.05). After a 4-week period of wearing the TS and DO orthoses, no change in HVA was observed. In the DO group, a more balanced load distribution between the right and left foot (50.2% left, 49.8% right) and a more pronounced effect in reducing deformity-related pain and improving QoL by increasing functionality were noted.

Mechanical Behavior of Hollow Corrugated Sandwich Cylinders Under Inner Pressure Loading

Taking pressure-bearing equipment as a prototype, the mechanical behavior of hollow corrugated sandwich cylinders under inner pressure loading was investigated. Considering the hollow cylindrical shell with finite length, the elastic closed-form solutions of hollow corrugated sandwich cylinders under inner pressure loading were presented. The optimization for minimum weight was performed. The stress distribution characteristics of the structures with different topological parameters were discussed. It can be found that an inflection point of the structure loading efficiency exists during an increase in the pressure, providing that under lower inner pressure loading, the loading efficiency of hollow corrugated sandwich structures is not invariably superior to homogeneous structures, yet while subjected to higher inner pressures, the sandwich structures exhibit a significant advantage in load-bearing efficiency.

Effects of Radially Variable Sweep Vanes on Rotor–Stator Interaction Noise

Abstract This article presents a three-dimensional semianalytic cascade model for the prediction of rotor–stator interaction noise, which includes the effects of radially variable sweep angle and chord length to better account for the latest trends in the fan-stage stator design of turbofan aero-engines. The theoretical modeling and solution method are first introduced, with special attention paid to the singularity problem brought by the nonuniformity of the stator vanes in the radial direction. The tonal rotor–stator interaction noise for stators with a radially varying sweep angle or a radially varying chord length is then calculated and analyzed. It is discovered that the phase variation in unsteady pressure loading near the stator leading edge greatly affects the resulting tonal interaction noise, while the sweep of a stator trailing edge shows less influence on the rotor–stator interaction. The duct mode characteristic of the cut-on modes has proved to be an important factor in the design of a swept stator. In addition, the soft vane design can further reduce the tonal interaction noise on a swept stator cascade.

The Model is Designed Based on TPMS and Verified by Simulating Mechanical Properties

The three-period minimal surface (TPMS) metal porous structure represents a novel design suitable for lightweight and multifunctional applications. This study designed three types of TPMS porous structures: Diamond, Gyroid, and Primitive, and investigated their deformation behavior through finite element simulation. Results indicate that the Gyroid structure demonstrates exceptional mechanical properties and energy absorption, achieving a strength limit of 186.44 MPa. The Gyroid porous structure exhibits a uniform layer-by-layer fracture pattern with a fracture zone at a 45° angle to the direction of pressure loading at 30% strain. Conversely, at 20% strain, the Diamond and Primitive porous structures exhibit initial shear band failures at the unit cell junctions.

Nonlinear buckling and postbuckling of FG-CNTRC sandwich plates with multi-layer corrugated FG-CNTRC core

This paper proposes an analytical solution for the nonlinear buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) sandwich plates under axial compressive and external pressure loads is analytically examined in this paper. The considered plates are designed with the multi-layer corrugated FG-CNTRC core and face sheets. The CNT distribution laws of the multi-layer corrugated core are proposed to ensure the material continuity between FG-CNTRC face sheets and multi-layer corrugated core. Classical plate theory (CPT) with geometrical nonlinearities is utilized to formulate the fundamental expressions. In addition, the Ritz energy method is used to achieve the expressions of compression and pressure postbuckling curves, and axial critical buckling loads. The investigations numerically display the influences of multi-layer corrugated core, material, and geometrical properties on the nonlinear buckling and postbuckling behavior of plates.

Energy optimization design for the driving source for rock fragmentation by high-voltage pulsed discharge (RHPD)

The energy parameter of the driving source for rock fragmentation by high-voltage pulsed discharge (RHPD) determines the effectiveness of rock fragmentation. The mapping relationship between the energy parameter of the RHPD driving source and the stress parameter is established, and an energy optimization design criterion for the RHPD driving source is proposed. The time-varying impedance of the plasma channel is simulated, and the spatial and temporal distribution of stress within the rock under the channel pressure loading is analyzed. A rock fragmentation criterion based on the stress impulse criterion is proposed, and a nonlinear constrained mathematical model for the energy optimization design for the RHPD driving source is developed. Using the existing driving source and load parameters as examples, the feasibility and accuracy of the proposed energy optimization design criterion for the RHPD driving source are verified, which provides theoretical guidance for the design of the RHPD driving source.

Beveled microneedles with channel for transdermal injection and sampling, fabricated with minimal steps and standard MEMS technology.

Microneedles hold the potential for enabling shallow skin penetration applications where biomarkers are extracted from the interstitial fluid (ISF) and drugs are injected in a painless and effective manner. To this purpose, needles must have an inner channel. Channeled needles were demonstrated using custom silicon microtechnology, having several needle tip geometries. Nevertheless, all the proposed fabrication sequences are not compatible with mass production based on mature, standard microfabrication techniques. Furthermore, ISF extraction was also demonstrated with channeled needles but under poorly controlled conditions and over long periods of time, the latter being impractical for medical use. A range of factors may impede or slow ISF extraction that require controlled experiments. In this work we address the above tasks in terms of microfabrication sequence design, tip geometry design and experimental validation under controlled conditions. We report the development and fabrication of a silicon channeled microneedle array using conventional, industrial micromechanic processes. With only 2 lithography steps, a hypodermic needle tip profile is achieved. Using the fabricated microneedles, fluid extraction is experimented on chicken skin mockups. Extraction tests are carried out by inducing a controlled pressure gradient between the two ends of the microneedle channels, generated by loading the chip or by applying vacuum to the chip's backside. The extraction of more than 1 μL of fluid in 20 minutes is demonstrated with a maximum applied pressure gradient of 500 mbar. A correlation between the extraction rate efficiency and needles' density is observed, both for short and long extraction times. These results provide the first demonstration of in vitro interstitial fluid collection under controlled experimental conditions using silicon hollow microneedles fabricated with standard micro electro mechanical systems (MEMS) fabrication technology and minimal steps. Based on the obtained data, a comparison is drawn between pressure load and vacuum as drivers for ISF extraction, according to modelling and controlled experiments.

The Potential of Polymers and Glass to Enhance Hydrogen Storage Capacity: A Mathematical Approach.

This manuscript contributes to understanding the role of hydrogen in different materials, emphasizing polymers and composite materials, to increase hydrogen storage capacity in those materials. Hydrogen storage is critical in advancing and optimizing sustainable energy solutions that are essential for improving their performance. Capillary arrays, which offer increased surface area and optimized storage geometries, present a promising avenue for enhancing hydrogen uptake. This work evaluates various polymers and glass for their mechanical properties and strength with 700 bar inner pressure loads within capillary tubes. A theoretical mathematical approach was employed to quantify the impact of material properties on storage capacity. Our results demonstrate that certain polymers (e.g., Zylon AS, Dyneema SK99) and glass types (S-2 Glass) exhibit superior hydrogen storage potential due to their enhanced strength and low density. These findings suggest that integrating the proposed materials into capillary array systems can significantly improve hydrogen storage efficiency (15-37 wt.% and 37-40 g/L), making them viable candidates for next-generation energy storage systems. This study provides valuable insights into material selection and structural design strategies for high-capacity hydrogen storage technologies.