Search Results (100)

This study presents a closed-form analytical solution for large-deformation pressure-induced stress and displacement fields in thick-walled, functionally graded (FG) hyperelastic polyvinyl chloride (PVC) cylinders subjected to internal pressure. The formulation inherently satisfies incompressibility—an aspect not guaranteed by standard finite element methods (FEMs)—and provides explicit expressions for all stress and deformation components. Using a Mooney–Rivlin model with an exponential–logarithmic gradation law, the study examines bi-layer and tri-layer configurations under varying property-changing scenarios. The governing equations are reduced to a single nonlinear scalar relation for the radial mapping constant, ensuring computational efficiency. Analytical predictions demonstrate excellent agreement with FEM results (errors < 1%) and recover homogeneous limits, and demonstrate that continuous gradation significantly reduces stress concentrations compared to discrete layering. The proposed model offers an efficient tool for designing pressure-resistant FG hyperelastic components for engineering applications such as pipes, hoses, biomedical devices, and protective casings. Full article

In response to the current limitation where conventional constant volume combustion apparatuses are generally confined to pressure ratings of 5–20 MPa, insufficient for the demands of ultra-high-pressure combustion fundamental research, this study designs and verifies a high-pressure-resistant constant volume combustion apparatus with a rated working pressure of 250 MPa. The strength design and safety factor calculation for the combustion chamber main body were conducted based on the Lame thick-walled cylinder elastic theory. A finite element numerical simulation method was systematically employed to perform static analysis, transient impact response analysis, and high-cycle fatigue-life assessment of the key components of the apparatus. The results indicate that under a 250 MPa design internal pressure load, the maximum circumferential stress at the inner wall of the combustion chamber main body is 328.0 MPa, with a safety factor greater than 1.5, complying with relevant safety codes for high-pressure vessels. Under transient loading simulating combustion impact, the maximum equivalent stress of all structural components is below the material yield strength, with a maximum elastic deformation of less than 0.06 mm, demonstrating excellent structural stiffness and impact resistance. Fatigue assessment with a design-life target of 1.0 × 10⁶ pressure cycles shows that the cumulative damage values for all components are significantly less than 1.0, meeting the reliability requirements for long-term cyclic service. This apparatus integrates functional modules such as high-pressure precision gas mixing, high-energy reliable ignition, high-speed transient parameter acquisition, and safe product collection, providing a stable, controllable, and safe experimental platform for in-depth research on the combustion mechanisms of gaseous fuels under ultra-high-pressure conditions. Full article

Interface debonding between the casing and cement sheath (CC interface) is a major cause of wellbore failure in hot dry rock geothermal wells. By adding iron filings to cement and varying their distribution along the radial direction, a cement sheath with gradient mechanical properties is obtained. This sheath is called a functional gradient cement sheath. In this paper, a theoretical mechanical model of the functional gradient cement sheath is established. Its mechanical parameters are obtained from laboratory experiments. Analytical solutions for the stress and displacement fields of the casing–functional gradient cement sheath–formation system are derived using elastic thick-walled cylinder theory. The effectiveness of the functional gradient cement sheath in preventing CC interface debonding is then studied. The results indicate the following: (1) cement block samples containing iron filings were prepared with particle sizes of 0.5 mm, 1 mm, and 2 mm and with iron filing-to-cement mass ratios of 0%, 10%, 20%, 30%, and 40%. The compressive strength and elastic modulus of these samples both varied with the iron filing content. As the iron filing content increases, the compressive strength and elastic modulus generally increase, but they decrease under certain conditions. (2) With the total mass of iron filings fixed, the influence of different elastic modulus distributions (exponential, linear, quadratic parabolic, and uniform) on the functional gradient cement sheath was investigated. It was found that the quadratic parabolic distribution of the elastic modulus yields the best mechanical properties. (3) The influence law of the size and dosage of iron filings on the functional gradient cement sheath was studied. Based on the experimental data (0%, 10%, 20%, 30%, 40%), three representative contents (15%, 30%, 45%) were selected for theoretical analysis. It was found that when the iron filing size was 0.5 mm and the dosage was 15%, the stress and displacement on the inner wall of the functional gradient cement sheath were the minimum. Full article

This research analyses the mechanical behaviour of the insertion process between two cylinders that are commonly employed in non-rigid joints. Through comprehensive analysis, the study reveals the dynamics of insertion force, particularly by highlighting the impact of initial collisions on subsequent deformations and the ultimate evolution of insertion forces. Contrary to intuitive assumptions, our findings reveal that higher interference levels between cylinders do not uniformly correlate with increased maximum insertion force levels; instead, for certain cylinder combinations, higher interference generates lower maximum insertion force levels. Additionally, the significance of the thickness ratio as a pivotal determinant in predicting overall behaviour and insertion force, which is a variable that is often overlooked in conventional analyses, has been underscored. Furthermore, it has been demonstrated that the applicability of analytical equations that were developed as part of thick-walled cylinder theory diminishes when mechanical joints undergo plasticity, which underscores the need for alternative modelling approaches. Through finite element simulations, fidelity when representing insertion processes, with errors below 15%, not only capturing peak insertion forces but also delineating the nuanced evolution of forces and cylinder deformations, has been attained. Conversely, the analytical method employed from the examined literature yielded unrealistic insertion force estimations that proved inadequate for scenarios that involve substantial interference. Full article

Multi-layered shrink-fitted pressure vessels are critical for high-pressure applications, where structural integrity relies on inducing residual compressive stresses to mitigate operational tensile loads. This study presents a comprehensive analytical framework and automated sizing algorithms for both isotropic (metallic) and orthotropic (composite) thick-walled cylinders. Given fundamental design constraints, specifically the internal pressure, inner diameter and layer count, the models determine the optimal radial interferences required for assembly. For metallic configurations, geometric discretization is analytically derived from the Tresca yield criterion to guarantee uniform maximum equivalent stresses across all layers. For composite assemblies, a discrete optimization routine based on Classical Laminate Theory and the Tsai–Wu failure criterion is implemented to identify physically manufacturable repeated-sublaminate configurations, layer thicknesses and macroscopic equivalent properties. In both scenarios, interfacial contact pressures are derived by enforcing strict kinematic compatibility. The analytical stress fields and theoretical contact pressures are subsequently validated against Finite Element Method (FEM) simulations. Ultimately, the proposed algorithms provide an efficient and robust design tool capable of defining precise manufacturing tolerances and structural parameters for advanced high-pressure containment systems. Full article

To elucidate the wear evolution and failure mechanisms of VL-type composite seals in aviation hydraulic actuators under multiple operating conditions, a two-dimensional plane-strain finite element model was developed for a VL seal consisting of a PTFE L-ring and an NBR O-ring. The model incorporated the Mooney–Rivlin hyperelastic constitutive law and the Archard wear model. The effects of O-ring compression ratio, hydraulic pressure, sliding velocity, and temperature on cumulative wear, wear rate, and contact state were systematically investigated. The results show that the compression ratio has a nonlinear influence on wear. Within 8–16%, the peak wear increases approximately linearly with compression ratio; above 16%, the peak wear reaches a plateau and a secondary wear zone appears, indicating a transition from single-contact to multi-contact sealing. Hydraulic pressure promotes wear over the range of 4–28 MPa, and at 28 MPa the opposite lip edge of the L-ring comes into contact with the cylinder wall, weakening the sealing effectiveness. Within 0.1–0.3 m/s, wear increases approximately linearly with sliding velocity. However, under high velocity and insufficient hydraulic pressure, the L-ring may undergo inversion, resulting in complete seal failure. Temperature exhibits a non-monotonic effect: material softening reduces local contact stress and wear from −55 to 80 °C, whereas excessive softening at 135 °C causes the peak wear rate to increase again. A parametric analysis scheme involving an increased L-ring height and thickness, a reduced O-ring cross-section diameter, and reserved deformation space raises the critical compression ratio for stable single-contact sealing from 16% to above 20%. These findings clarify the contact-stress/contact-area competition mechanism governing VL seal wear and provide guidance for the design of aviation hydraulic actuator seals. Full article

Accurate prediction of Rate of Penetration (ROP) in carbonate formations remains constrained by the arbitrary selection of geomechanical input parameters in empirical drilling models. This study presents the first systematic field-based evaluation of sixteen geomechanical properties—grouped into three categories: strength parameters (uniaxial compressive strength (UCS), confined compressive strength (CCS), shear strength, thick-walled cylinder strength (TWC), friction angle, and cohesion), elastic moduli (Young’s modulus, shear modulus, bulk modulus, bulk compressibility, dynamic combined modulus (DCM), Poisson’s ratio, brittleness index), and in situ stress parameters (overburden pressure, minimum, and maximum horizontal stresses)—to identify optimal predictors for ROP modeling across PDC bit sizes of 12.25″ and 8.5″. Continuous wireline log data from two vertical carbonate wells in the Middle East (Well A: 1000–3370 m; Well B: 1945 to 3128 m; total intervals of 2370 m and 1183 m, respectively) penetrating formations comprising limestone, dolomite, sandstone, shale, anhydrite, and marly limestone were used. All sixteen geomechanical properties were computed using Interactive Petrophysics (IP) software with lithology-specific empirical correlations and validated against laboratory core measurements (R² = 0.79–0.95). Pearson and Spearman correlation analyses quantified parameter–ROP relationships, and the Al-Abduljabbar empirical model, recalibrated via multiple nonlinear regression, served as the evaluation framework. DCM consistently exhibited the strongest negative correlation with ROP across both bit sizes and achieved the highest model accuracy (R² = 0.54, AAPE = 25.33%), significantly outperforming the Bourgoyne and Young model (R² = 0.26, AAPE = 36.55%). A statistically validated scale-dependent effect was identified: Fisher’s Z-transformation tests confirmed that the correlation reversal between CCS and UCS across bit sizes is statistically significant (CCS: Z = −16.84, p < 0.001; UCS: Z = −6.75, p < 0.001), establishing CCS as the superior predictor at 12.25″ and UCS as the superior predictor at 8.5″—a finding not previously reported in the ROP literature. This reversal is attributed to the larger contact area of the 12.25″ bit, which promotes confinement-dominated rock failure better described by CCS, whereas the smaller bit produces localized stress concentration better represented by UCS. These results establish that (1) optimal geomechanical input selection is bit-size dependent, (2) nonlinear modeling outperforms linear frameworks for strength–ROP relationships, and (3) parameter relevance outweighs coefficient tuning in model robustness. DCM is recommended as the most operationally practical universal input, requiring only conventional compressional sonic and density logs. This study provides a systematic framework for geomechanical parameter selection with direct implications for drilling optimization in heterogeneous carbonate reservoirs. Full article

In shale gas extraction, solid particles such as fracturing proppants cause erosion in production and transmission pipelines. Cyclone desanders are widely used for gas–solid separation, but high-velocity sand-laden fluids frequently induce equipment failure, leakage and safety risks. Therefore, research on erosion and protective measures is essential. This study focuses on the desander at the M shale gas wellhead, where wall thickness was measured at three monitoring points to determine erosion rates. A CFD-based numerical erosion model for the cyclone desander was developed using ANSYS Fluent within the ANSYS Workbench 19.2 environment (ANSYS, Inc., Canonsburg, PA, USA). The model was validated by comparing simulation results with field data, revealing the distribution patterns of the velocity field, pressure field, and erosion rate. The study analyzed the impact of nine factors on desander erosion: inlet aspect ratio, cylinder radius, cone length, dust discharge port diameter, exhaust port diameter, particle size, particle concentration, inlet velocity, and operating pressure, clarifying the erosion variation patterns for each factor. SPSSAU V25.0 (Beijing Qingsi Technology Co., Ltd., Beijing, China) was employed to analyze the significance of these nine factors, identifying six significant influencing factors: inlet aspect ratio, cylinder diameter, dust discharge port diameter, particle size, particle concentration, and inlet velocity. Subsequently, response surface analysis was performed using Design-Expert 13 (Stat-Ease, Inc., Minneapolis, MN, USA) to obtain the relationship between the factors and their impact on maximum erosion, leading to the establishment of a predictive model for the maximum erosion rate. In addition, geometry optimization, local wall thickening, coating protection, material selection, and bionic rib structures were discussed as erosion-mitigation strategies. The optimized geometry reduced the erosion rate at the inlet and dust discharge outlet by 20.4% and 21.8%, respectively, while the bionic rib structure reduced the maximum erosion rate by 58%. Full article

The surface quality of machined gears is closely related to operational energy efficiency and service durability, which affect the achievement of dual carbon goals in sustainable manufacturing. This study proposes a radial pre-stressed grinding method for gear manufacturing. Firstly, an analytical model for the radial pre-stress exerted on the gear inner hole was established by virtue of thick-walled cylinder theory. Secondly, a simulation and experiment were conducted under the same pre-stress conditions to obtain the radial stress. The theoretical, simulated, and experimental results were compared and discussed. Then, gear grinding simulations were performed at different pre-stress levels, grinding depths and grinding speeds. Finally, the grinding parameters were optimized by means of response surface methodology (RSM). This study recommends incorporating gears manufactured with radial pre-stressing into relevant industrial standards for green and low-carbon development. The results indicate that applying radial pre-stress to the gear inner hole significantly influences surface roughness and residual compressive stress after grinding, whereas it exhibits a minimal effect on grinding force. After optimization, compared with the initial simulation results, surface roughness is reduced by 12.5%, the absolute value of residual compressive stress is increased by 52.6%, and grinding force is decreased by 2.1%. The implementation of radial pre-stressed grinding in gear manufacturing requires institutional support, including its integration into green standard institutions, the development of technical specifications, and the establishment of promotion mechanisms. Such integration can be facilitated through national ‘Green Factory’ initiatives, comprehensive intellectual property protection, and targeted personnel training. Full article

Implementing compressed air energy storage (CAES) in lined caverns provides a promising technical solution for large-scale energy storage, and the reasonable selection of sealing materials is essential for its success. Flexible membrane materials including sprayable polymers, rubber sheets, and airbags have recently been considered economical and practical sealing options. However, research on flexible membrane sealed CAES caverns remains limited, particularly regarding their mechanical response and parameter sensitivities. To address this gap, an elastic multilayer thick-walled cylinder model verified by physical model tests is proposed. Analytical solutions for the stress and displacement fields of the surrounding rock and concrete lining are derived, and a calculation scheme is designed to evaluate the influence and sensitivity of key parameters. Results indicate that under high internal pressure, both the lining and surrounding rock undergo radial compression without yielding, whereas the lining experiences adverse tensile stresses in the hoop direction. The maximum hoop tensile stress reached the order of 1~3 MPa under typical CAES operating pressures, and tensile-compressive stress transformation may occur in the lining under certain parameter combinations. Sensitivity analysis further shows that internal pressure, in situ stress, surrounding rock elastic modulus, and cavern radius are the dominant factors influencing the mechanical behavior of the system, while geometric and lining parameters have secondary but non-negligible effects. The findings provide theoretical support for the stability analysis and material design of flexible membrane sealed CAES caverns and offer useful guidance for determining allowable operating pressures and selecting lining configurations. Full article

Sarcocystis is a genus of heteroxenous, globally distributed coccidian parasites. Limited research has been conducted on the natural infection of Sarcocystis in rodents in the Middle East. In this study, the Libyan jird (Meriones libycus) was identified as the natural intermediate host of the new species Sarcocystis meriones, based on morphological and molecular data. Microscopic sarcocysts were detected in the thigh muscles of 8.5% (4/47) of Libyan jirds captured from a semi-desert area in Amghara, Eastern Kuwait. Under the light microscope, sarcocysts were filamentous with blunt ends and thin walls, measuring 1550 × 89 µm. Transmission electron microscopy analysis showed the densely packed protrusions measure 1.2 × 0.5 µm and resemble thuja or a cylinder and having lateral microvilli, while the ground substance layer was 0.5–0.6 µm thick and type 22-like. Based on four genetic loci (18S rRNA, 28S rRNA, ITS1, and cox1), S. meriones was genetically most similar to S. myodes and S. ratti, infecting voles and mice of the genus Apodemus and black rats (Rattus rattus), respectively. Phylogenetic results suggest predatory mammals as potential definitive hosts of S. meriones. Further studies are needed to reveal host specificity, geographical distribution, and the impact of the parasite on the host’s health of the newly described Sarcocystis species. Full article

Tomato brown rugose fruit virus (ToBRFV) has been causing severe agricultural damage worldwide since its recent discovery. While related to tobacco mosaic virus, its properties and infection mechanisms are poorly understood. To uncover their structure and nanomechanics, we carried out atomic force microscopy (AFM) measurements on individual ToBRFV particles. The virions are rod-shaped with a height and width of 9 and 30 nm, respectively. Length is widely distributed (5–1000 nm), with a mode at 30 nm. ToBRFV rods displayed a 22.4 nm axial periodicity related to structural units. Force spectroscopy revealed a Young’s modulus of 8.7 MPa, a spring constant of 0.25 N/m, and a rupture force of 1.7 nN. In the force curves a step was seen at a height of 3.3 nm, which is related to virion wall thickness. Wall thickness was also estimated by predicting coat protein structure with AlphaFold, yielding a protein with a length of 7.3 nm. Accordingly, the structural element of ToBRFv is a right circular cylinder with an equal height and diameter of ~22 nm and a wall thickness between 3.3 and 7.3 nm. Thus, at least four to nine serially linked units are required to encapsidate a single, helically organized RNA genome. Fragmentation of ToBRFV into these cylindrical structural units may result in a facilitated release of the genome and thus efficient infection. Full article

Deep shale gas reservoirs are vital sources of unconventional natural gas and present unique challenges for exploration and development due to their multiscale flow characteristics and elastoplastic deformation behavior of reservoir rocks. Accurately predicting permeability in these reservoirs is crucial. This study introduces a novel model utilizing fractal theory and a thick-walled cylinder model to characterize stress-dependent apparent gas permeability. The model incorporates various flow mechanisms, including viscous flow, transition flow, Knudsen diffusion, surface diffusion, real gas effects, and gas slip effects. It enables predictions of how permeability changes with elastoplastic behavior and affects the pore volume fractions of different flow mechanisms. Experimental validation during elastic and elastoplastic deformations confirms the model’s accuracy, with each parameter having clear physical significance. Key findings reveal that, at the same effective stress, apparent gas permeability increases with pore radius fractal dimension, temperature, and Young’s modulus, while decreasing with capillary tortuosity fractal dimension. Additionally, during plastic deformation, greater magnitudes of plastic strain lead to more pronounced changes in apparent gas permeability compared to elastic deformation. These insights emphasize the importance of incorporating elastoplastic behavior in studies of deep shale gas reservoirs. Full article

Complex non-Newtonian glues are widely used in electrical vehicle (EV) manufacturing plants. In this paper, we focus on initial transient and compressibility issues which are closely associated with high pressure, boundary conditions, and flexible tubes, as well as their respective fluid–structure interaction effects. Both thixotropic and power law non-Newtonian nearly compressible fluid models have been employed to couple with flexible tubes with two different sets of material properties, namely, Young’s modulus and density. In addition to thick-wall cylindrical pressure vessel solutions, different pressure and velocity boundary conditions have also been studied with the consideration of initial transient and steady solutions for acoustic models. Moreover, the radial direction displacement distributions through the tube wall thickness and axial directions compare well within 4 to 9 percentage points with theoretical solutions of thick-wall cylinders under internal and external pressures. Finally, inverse optimization methods have been employed for the calibration of key parameters in comparison with experimental and computational results. Full article

Hydrodynamic coefficients of subsea suspended pipelines are crucial for fatigue and stability assessments. The effect of the gap height to diameter ratio e/D (0.1 ≤ e/D ≤ 2.0) and boundary layer thickness to diameter ratio δ/D (0.5 ≤ δ/D ≤ 3.0) on the force coefficients under unidirectional current conditions with the Reynolds numbers Re in the range of 1 × 10⁴ ≤ Re ≤ 1 × 10⁵ are investigated via numerical simulations. The results show that the average drag coefficient increases, whereas the average lift coefficient decreases gradually with the increasing e/D. The vortex shedding is inhibited by the wall for e/D < 0.24, starts at e/D = 0.24, becomes stronger with the increase in e/D in the range from 0.24 to 0.5, and approximates to that behind a wall-free cylinder for e/D > 0.5. The effect of δ/D can be eliminated if the coefficients are normalized by the undisturbed flow velocity at the height of the center of the pipeline. Moreover, empirical prediction formulas are proposed describing the drag and lift coefficients as the function of e/D, which can be applied to engineering designs related to free spans. Full article