•Inspired from meniscus buffer structure and reinforced concrete special geometry.•ETC coating with PDMS exhibits excellent mechanical properties and durability.•Flexible ETC coating with PDMS would ...firmly adhere on metal substrates.•ETC coating with PDMS shows efficient and stable preservative performance.•Erosion rate of 37.55% is reduced on ETC with PDMS compared to no buffer coating.
Inspired by human meniscus, a superhydrophobic inner pipeline coating with has been developed to mitigate the erosion and corrosion damages to gas transportation pipeline. The erosion-resistant coating, consisting of modified TiO2 nanoparticles (NPs), multi-walled carbon nanotube (CNTs), and epoxy resin (EP), is built on a buffer layer made of polydimethylsiloxane (PDMS). The optimized buffer layer thickness (100 μm) was determined by finite element simulation when mixing ratio between the curing agent and PDMS was 1:30. The erosion resistance of the prepared coating was quantified by an erosion ring experiment. Finally, erosion resistance of materials produced by different filler types (fibrous and spherical) were compared. The erosion resistance of the material is significantly improved by the tensile force of the fiber filler, similar to the steel in reinforced concrete. The result shows that the buffer-structure coating can reduce the magnitude of erosion rate significantly. Compared to the coating with no buffer structure, the maximum reduction of erosion rate is up to 37.55 %. In addition, the water contact angle (CA) of the sample could maintained over 150° after various mechanical shocks, such as 350 times of 90° bending test, 1500 times of sand impact test, and 4H pencil hardness test. Compared with the 316L steel sample, the corrosion potential of the coating in 3.5 wt% NaCl solution increased from −0.18 V to 0.04 V, making it potentially applicable for the corrosive environment of submarine pipelines.
This paper focuses on modeling the water absorption and the resulting internal stress behavior of steel/rubber composites. A three-dimensional finite element model, which includes the internal ...microstructure of bundled long steel wire reinforced composite, is established to accurately simulate water diffusion behavior. The water diffusion coefficient and rubber matrix's hygroscopic expansion parameter are estimated by experiments. The outcomes demonstrated that the earliest stages of water diffusion of steel/rubber composites conformed to the Fickian model. Then the weight gain continued to increase and followed the Langmuir model instead of Fickian model owing to the presence of bound water. Both the free water and bound water in steel/rubber composites were modeled by FE software. The internal stress caused by the differential swelling between steel and rubber was revealed and quantitatively analyzed through finite element simulation. The internal stress is the main cause of damage initiation in the steel/rubber composites, which was in good agreement with experimental measurements.
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•The water absorption mechanisms of steel/rubber composites were systematically studied.•There were two stages of water absorption behavior of steel/rubber composites due to the existence of free and bound water.•The FE model of composite's true internal geometry were established to simulate the water diffusion behavior.•The evolution of internal stress analysis by FE method was in good agreement with experimental results.•The internal stress is the main cause of damage initiation in the steel/rubber composites.
Damaged Reinforced Concrete (RC) beams are commonly strengthened by bonding Carbon Fiber Reinforced Polymer (CFRP) strips to their soffits. However, inaccessible or narrow soffits limit the use of ...bottom-bonded CFRP strips. The Side Bonded (SB) CFRP technique overcomes this, yet studies on SB-CFRP-reinforced beams' fatigue behavior are limited. This paper presents a Finite Element (FE) model for simulating the fatigue behavior of RC beams externally strengthened with SB-CFRP sheets. The model incorporates cyclic-dependent CFRP-concrete interface degradation. Existing experimental results are utilized to validate its accuracy. Computational analyses are undertaken to explore the effects of CFRP dimensions, load and prestress levels, and end-U-shaped wrapping on fatigue performance. A simple model is proposed to predict fatigue life considering load and prestress levels. The FE model effectively predicts fatigue performance. Parametric studies indicate that narrow CFRP strips are unable to prevent concrete failure under high loads. Fatigue failure modes include rebar ruptures and CFRP delamination. Besides, the end-U-shaped wrapping reduces interface damage, extending fatigue life. The study emphasizes the sensitivity of vibration excitation method to CFRP debonding. The proposed equation efficiently predicts the fatigue life of RC beams with externally bonded CFRP strips on their sides.
•Development of a FE model for simulating fatigue in RC beams strengthened with SB-CFRP.•Consideration of cyclic-dependent degradation at the CFRP-concrete interface in the model.•Investigation of parameter effects on fatigue performance through numerical studies.
•A novel class of chiral structures is presented.•Two deformation mechanisms potentially leading to auxetic behaviour can act.•The hexastarchiral structure is studied using numerical and experimental ...methods.•The numerical and experimental results showed good agreement.•Hexastarchirals extend the range of Poisson's ratios attained by the hexachiral.
A novel class of chiral structures having intersecting ligaments acting as the node is presented in this study. Depending on the geometric parameters, this arrangement may allow both the ligaments connecting the nodes together as well as the ligaments that compose the node itself to bend upon the application of a uniaxial force. Hence, such structures are capable of deforming through two distinct mechanisms, i.e. bending of the ligaments between the nodes and bending of the ligaments in the nodes. The novel six ligament (hexa) arrangement, a structure derived from the hexachiral, was chosen for the purpose of investigating these novel designs. This was studied through the use of finite element simulations and mechanical testing of 3D printed specimens. Analysis of the results supports the suggestion that a hierarchical deformation system exist. The value of the Poisson's ratio was found to be dependent on the relative thickness of the respective ligaments.
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This study implemented indoor scaled drainage testing and three-dimensional (3D) finite element simulations to analyze the seepage behavior of ultra-wide cross-section porous asphalt concrete (PAC) ...pavement with voids of 18 %, 20 % and 22 %. The seepage water level curves under the rainfall intensity of 0.5, 1, 2, 10, 50 and 100 years recurrence intervals were obtained by scaled test. The Seep3D software was used to analyze the seepage state of the ultra-wide cross-section porous pavement. Results indicated that void ratio was the paramount factor affecting the drainage capacity, which decreasing porosity significantly intensifies roadway surface water depth over 25 %. Water level curves obtained in scaled test showed similar trends to pore water pressure curves in 3D simulation. According to the theory of non-uniform gradual seepage, the pore water pressure can be used to effectively characterize the seepage state inside the porous pavement. Implementing cross drain with 10 m spacing maximally alleviated inundation by 23 %. Spacing intervals of 50 m, 30 m, and 20 m proportionately mitigated peak value by 4 %, 7 % and 12 % respectively.
•Design and develop a new indoor scaled drainage device.•Using a combination of scaled experiments and 3D simulations.•Propose strategy to weaken water accumulation in complex road sections.
The subsurface fluid injection can cause pressure increase within faults, leading to earthquake occurrences. However, the factors controlling earthquake rupture due to pressure perturbation remain ...poorly understood. To resolve this problem, we simulate the physical processes of earthquake nucleation and rupture on strike-slip faults perturbated by pressure migration based on the slip-weakening law. Multiple kinds of factors, including background stress, fluid injection rates, the area of the pressurized region, fault geometry, and fault friction coefficients, are considered in our simulations. Our simulation results reveal that the ratio of shear stress to normal stress rather than their absolute values controls the rupture behavior. With the large stress ratios, high injection rates, and large pressurized areas, earthquakes are prone to propagate as runaway ruptures. Additionally, faults with large aspect ratios of length to width are also favorable for causing runaway ruptures. In contrast, the factors of fault strike, dip angles and friction coefficients have minor influence on rupture behavior.
•Different damage states of CFRP honeycomb sandwich structure are revealed through low-velocity impact experiments.•A refined finite element model suitable for plain weave CFRP composite is ...established to accurately predict the impact response of the structure.•The energy absorption mechanism of CFRP honeycomb sandwich structure is investigated.•The impact-induced damage is characterized by industrial tomography technology (CT) without destroying the sandwich structure.•Reducing the cell side length is a better way to improve the impact resistance of CFRP honeycomb sandwich structure.
The objective of this study is to examine the response and failure of honeycomb sandwich structures made of carbon fiber reinforced polymer (CFRP) composites under low-velocity impacts. Four impact tests with varying energies are performed to induce four distinct damage states in the sandwich structure: no discernible damage, damage to the top face sheet and a portion of the core, damage to the lower face sheet, and total penetration. The damage characteristics of the sandwich structures is analyzed by using industrial tomography technology (CT) without destroying them. A refined finite element model is established to further explain the deformation behavior and energy absorption mechanism of the structure, clarifying the effects of the honeycomb core's structural parameters, such as wall thickness, cell side length, and core height. To enhance the precision of simulation outcomes, a model for the onset and progression of damage in plain woven composites is incorporated into the user-defined material subroutine. The experiments and simulations demonstrate a high level of consistency in terms of peak loads, failure mode, and energy absorption.
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It is rather challenging to obtain high-quality Ti joints by conventional friction stir welding because of the problem of over-heating. The welding process and final microstructures and properties of ...the joints are controlled by both plastic deformation and recrystallization. However, for a long time, studies have only focused on recrystallization mechanisms but ignored deformation modes. In this study, a defect-free ultrafine-grained Ti joint with a joint efficiency of 100% was for the first time produced by submerged friction stirring (SFS) technology. We utilized transmission electron microscopy with a two-beam diffraction technique and electron backscatter diffraction to systematically investigate the deformation mode versus the grain refinement mechanism. The finite element method was utilized to simulate the temperature field throughout the joint for the microstructural explanation. During the whole SFS, prismatic slip occurred, and the other dominant deformation mechanisms changed from {101¯2} twinning and basal slip to pyramidal <a + c> slip. The variation of slip modes was largely dependent on the twinning and temperature rise. The ultrafine-grained microstructure was attributed to the successive refinement effect of the twin-dislocation interaction, dislocation absorption, dynamic grain boundary migration and texture-induced grain convergence. The effect of the temperature, strain and strain rate on the microstructural evolution mechanisms was discussed. Based on our work, we expect the wide application of SFS in producing ultrafine-grained bulk Ti materials and high-quality joints.
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This paper presents numerical modeling and simulation of damage that occurred to an aluminum plate due to a hydrodynamic impact. The model is developed based on a published experiment that was ...carried out by dropping a thin stiffened aluminum hollow box into the water from a prescribed height. The hydrodynamic impact causes damage in the middle of the plate which had an initial circular hole in the middle. The ABAQUS/CAE is used to model this experiment by using the Coupled Eulerian-Lagrangian method. The ductile damage property of the aluminum is defined to model the failure. The results show that the numerical simulation can predict the acceleration of the specimen close to that observed during the experiment. The simulation can also replicate the damage of the plate. A parametric study shows that one of the parameters that may affect the shape of the damage is the boundary condition definitions of the plate.
•The feasibility of the ICOG corona ring is verified by simulation analysis.•The opening distance, installation orientation and insulating layer thickness of the opening corona ring are simulated and ...analyzed, and the parameters of the ICOG corona ring are determined.•The electric field of the ICOG corona ring in the case of bird droppings is simulated and analyzed.•Through the bird droppings simulation test, the anti-bird performance of the ICOG corona ring is verified.
In the bird-related faults of transmission lines, the bird droppings flashover fault caused by the short-circuiting of bird droppings to the corona ring is extremely significant. To decrease the flashover probability of bird droppings and improve the convenience of installation, this paper proposes a method of coating the insulating layer on the open-gap corona ring, and verifies the insulation performance of the insulation coated open-gap (ICOG) corona ring through simulation and experiment. In this paper, the feasibility of corona ring coating insulating layer is verified by finite element simulation, and the influence of ICOG corona ring structure on the surface electric field distribution of composite insulator is studied. Finally, the impact of various bird droppings parameters on the flashover of the ICOG corona ring is investigated through experiments and compared with the flashover of an ordinary corona ring. The simulation results show that when the opening distance is 50–70 mm, the opening is toward the tower side, and the thickness of the insulating layer is 5 mm, the surface field strength of the composite insulator is the smallest. The experimental results show that the flashover probability of bird droppings increases with the increase of conductivity and viscosity of bird droppings. After the open-gap corona ring is coated with the insulating layer, the area where the bird droppings flashover occurs is reduced by about 20 %, which can better play the role of anti-bird flashover and has better convenience. This paper provides a certain reference for the anti-bird control of transmission lines.
