Erosion Mechanism Research Articles

An improved small-scale test setup for assessing backward erosion piping

Backward erosion piping is one of the erosion mechanisms that lead to embankment dam incidents, whereby foundation granular materials are transported to the downstream toe leaving a shallow pipe in place. Most previous studies have focused on secondary erosion as the responsible process for the pipe progression. On the other hand, a few experimental investigations have considered primary erosion by restricting the pipe pathway within a confined channel for easier monitoring of local gradients. This paper presents a modified small-scale setup with the hole-type exit configuration to capture local hydraulic conditions associated with the progression of the pipe in a realistic and unconstrained pathway. Horizontal compaction and a more accurate measurement and acquisition system are other improvements added to this setup. The test outcomes of the two fine sands have revealed that the scale factor of Sellmeijer’s model can be used to predict the critical global hydraulic gradient for the specific geometry of the small-scale setup with the hole-type exit. Moreover, the progression of the pipe remains unaffected by loading history. Results also confirm the previous findings regarding the mutual influence of local gradient and pipe tip progression.

Spatial and temporal distribution and environmental determinants of freeze-thaw erosion intensity in Qiangtang grasslands, China

Context Analysing freeze-thaw erosion is of great significance to ecological environment protection and land resource utilisation in high altitude areas. Aims We used seven indicators (temperature, precipitation, vegetation cover, elevation, slope, slope orientation, and sand content) to calculate the freeze-thaw erosion intensity index for different seasons from 2000 to 2019. Methods We used a graded weighted evaluation model and a geographical detector method to analyse spatiotemporal pattern and driving factors of freeze-thaw erosion intensity in Qiangtang grasslands. Key results (1) From 2000 to 2019, the total area of freeze-thaw erosion was higher in the non-growing season than in the growing season. The area of moderate and above-average freeze-thaw erosion increased over time in the non-growing season but decreased in the growing season. The spatial distribution of freeze-thaw erosion was mainly determined by the annual range of precipitation and temperature, which reflect the intensity and frequency of freezing and thawing cycles. (2) Vegetation cover was an indirect factor that influenced the soil moisture and stability. The slope was another important factor that affected the spatial distribution of freeze-thaw erosion in different regions. Conclusions The results show that in 2000–2019 the area of freeze-thaw erosion showed a downward trend. The erosion degree in the non-growing season is on the rise. Implications Our study provides new insights into the dynamics and mechanisms of freeze-thaw erosion in Qiangtang grasslands and contributes to the understanding and management of water and climate change impacts on this region.

Gradient erosion mechanism of ultra-low water binder ratio cement-based materials (ULWC) at low temperature: From molecular structure to macroscopic pore structure

The study of damage mechanisms is crucial for enhancing the service performance of low-temperature concrete. This study reveals the gradient erosion mechanism of ULWC behavior under low-temperature. The study employs in-situ detection techniques to analyze the effects of low-temperature on the C-S-H and crystal structures, including internal stress and chemical composition. It also uses 1H NMR and CT to compare the frost heave of gradient pores with the matrix contraction. The results indicate that low-temperatures lead to irreversible degradation of crystal structures and collapse of C-S-H, resulting in spontaneous shrinkage. Furthermore, in the gradient pore structure, the frost heave of gel pores opposes the shrinkage of the matrix, ultimately leading to the reorganization of C-S-H grain stack structure and the refinement of micropores and degradation of macropores. Therefore, the gradient erosion mechanism suggests that although low temperature may disrupt the chemical structure of ULWC, it will refine the pores in the microstructure.

Erosive wear and particle attrition in multi-stage solar particle receivers and screw conveyors: A CFD-DEM approach with machine learning and artificial neural networks

A coupled finite volume and discrete element method (CFD-DEM) numerical model is developed to unravel the fundamental mechanisms of granular transport, surface erosive wear and particle attrition in multistage solar particle receivers (MSPR) and screw conveyors (SC). Additionally, various regression-based supervised machine learning (ML) and artificial neural networks (ANN) are trained and optimized with the goal of quickly quantifying erosion and attrition thereby overcoming (a) the inherent challenges of high computational expense of CFD-DEM simulations and (b) exorbitant time required to post-process and extract DEM results. This study is the first of its kind to harness a synergistic numerical framework (CFD-DEM, ML, ANN) to unravel the fundamental mechanisms of erosion and attrition in MSPRs, non-vibrationally induced SCs, and vibrationally-induced SCs. It is found that the packing distribution, particle curtain width, and severity of particle scattering in a MSPR exhibits a subtle variation with particle diameter. In the context of SCs, the magnitudes of erosion and attrition are contingent on the particle diameter and flow operating conditions such as screw blade velocity, vibrational frequency and vibrational amplitude. Interestingly, a vibrationally-induced SC (VI-SC) exhibits superior performance in terms of low erosion and attrition unlike non-vibrationally induced SC (NVI-SC). It is found that MSPRs with 750–1000 µm particles and SCs with 750–1000 µm coupled with vibrational frequencies and vibrational amplitudes of 5 Hz and 0.007 m, respectively, are the preferred configurations due to minimum particle scattering, low erosive wear and low particle attrition. The trained and optimized ML models such as XGBoost, CatBoost, and Multilayer Perceptron (MLP) exhibit superior performance in predicting erosive wear and particle attrition on unseen DEM data, whereas the Multiple Linear Regression (MLR) and Gaussian Process Regression (GPR) ML exhibit poor performance prediction. For the first time, new information on fundamental granular flow dynamics, erosive wear and particle attrition in MSPRs and SCs is discerned. The methodology allows scientists to quickly examine material degradation for a myriad of industrial applications such as concentrated solar thermal (CST), among others.

Effect of SiC dominated with ZrB2 particles on the ablation and mechanical properties of carbon/novolac‐epoxy (EPN1180) composite at 3000°C

AbstractThis study investigates the mechanical properties and erosion resistance of high temperature–pressure carbon‐epoxy novolac insulation reinforced with ZrB2/SiC particles. For this reason, at first, five samples were fabricated using the hot press, which included resin epoxy novolac EPN1180 base without reinforcement and four samples containing resin with 20:80, 30:70, 40:60, and 50:50 of SiC: ZrB2 particles respectively. After manufacturing of the samples, the mechanical properties were evaluated through bending and tensile testing, followed by erosion resistance properties by the use of oxyacetylene flame erosion tests. Chemical composition and surface morphology analysis of the composites were conducted using energy‐dispersive spectroscopy, scanning electron microscopy, and x‐ray diffraction analysis. Results indicate that the addition of ceramic particles enhances both mechanical properties and erosion resistance of the composite. The pure resin sample exhibited the highest weight loss and thickness reduction, while the sample containing 40% SiC and 60% ZrB2 demonstrated the least weight loss and thickness reduction about 55% and 83% respectively compared to pure sample. Additionally, the sample with 30% SiC and 70% ZrB2 had the lowest backside temperature. Furthermore, the sample with 20% SiC and 80% ZrB2 exhibited the highest mechanical properties, with a tensile strength of 422.5 MPa and flexural strength of 587.11 MPa. Morphological analysis revealed the presence of phases such as SiO2, ZrO2, and ZrSiO4 attributable to the ZrB2/SiC particles, contributing to the enhancement of erosion resistance.Highlights Examines volume ratios of ZrB2/SiC. Discovers the best particle ratio (20%SiC, 80%ZrB2) for mechanical properties. Identifies the best particle ratio (30% SiC, 70% ZrB2) for erosion resistance. Reveals key phases enhancing erosion resistance with advanced analysis methods. Linear and mass ablation rate improved by 83% and 55% (best formation).

Study on the mechanism of soil erosion by submerged water jet vertical scouring in cohesive soils

The water jet trenching technique is widely used in the burial of submarine pipelines. However, its application in cohesive soils often leads to complexity in trench morphology and challenges in predicting trench dimensions due to unclear soil erosion mechanisms. These issues significantly impact pipeline burials. To investigate the soil erosion mechanism of water jet trenching in cohesive soils, two-dimensional physical simulation experiments of submerged vertical water jet erosion were conducted. The influence of jet pressure, impingement height, and nozzle diameter on the shape of the scour hole was analyzed. The erosion damage patterns of water jets on cohesive soils were studied, and a theoretical model for the development of scour holes was established. The study revealed that when the jet velocity reaches 1000 m/s and the nozzle diameter reaches 1 mm, a contracted neck forms at the upper part of the scour hole. The appearance of the contracted neck is due to excessive jet impact energy causing impact shear failure in the soil. The effective height and width of the contracted neck increase with jet pressure and nozzle diameter and decrease with impingement height. Based on Prandtl's bearing capacity model, a model for predicting impact shear failure in cohesive soils was established, and a predictive formula for the effective height and diameter of the neck was proposed. Experimental validation confirmed the accuracy of the predictive formula. These findings provide theoretical support for the application of water jet trenching techniques in cohesive seabed soils.

Erosion performance of direct-aged Al2O3-reinforced plasma-sprayed composite coatings at high-temperature conditions

The present investigation evaluates the influence of furnace heat-treatment (HT) on the microstructure, microhardness, fracture toughness and erosion resistance of three plasma sprayed composite coatings: a Inconel625–30 wt% micron-sized Al2O3 (In625-MHT) coating, a Inconel625–30 wt% nano-sized Al2O3 (In625-NHT) coating and a Inconel625–15 wt% micron-sized Al2O3 + 15 wt% nano-sized Al2O3 (In625-BHT/bimodal) coating. High temperature solid particle erosion tests were conducted at 900 °C temperature and with at two different impingement angles (90 and 30) in simulated environment using standard erosion-test rig. Coatings were subjected to detailed mechanical and microstructural analysis in order to better understand their erosion mechanism and structure–property correlation. By healing pores and cracks, the furnace HT increases the coatings’ erosion resistance in the order of In625-BHT, In625-NHT, and In625-MHTcoating. In addition, the mechanical properties of In625-BHT coating like porosity (1.0 ± 0.09%), micro-hardness (1299 ± 25Hv) and fracture toughness (5.9 MPa√m) are significantly improved after HT. The presence of grooves and lips on the surfaces of uncoated substrates provides clear evidence that the erosion mechanism involves the combined processes of micro-ploughing and micro-cutting indicating ductile erosion mode. However unimodal and bimodal composite coatings demonstrated a brittle erosion mode.

Dynamic analysis of a class of fractional‐order dry friction oscillators

This article investigates a class of Duffing nonlinear dynamic systems with fractional‐order dry friction and conducts in‐depth research on the stability, chaotic characteristics, and erosion of the safety basin of this system; the results are verified through numerical simulation. First, the average method is used to approximate the amplitude–frequency relationship of the system, and the accuracy of the analytical results is verified through numerical experiments. Second, the Melnikov method is used to obtain the conditions for the system to enter chaos in the Smale horseshoe sense, and the Melnikov curve is drawn for further verification. Then, bifurcation diagrams are drawn for the changes in various parameters in the system, with a focus on analyzing the influence of friction factors on chaotic bifurcation. By applying the definition and calculation principle of the maximum Lyapunov exponent, and drawing and utilizing the maximum Lyapunov exponent graph, the chaotic state that the system enters under different parameters is more clearly defined. Finally, the evolution law of the safety basin under various parameter changes, especially dry friction changes, is analyzed, and the erosion and bifurcation mechanism of the safety basin is studied. Comparing with the bifurcation diagram, it reveals that chaos primarily contributes to the erosion of the safety basin.

Synthesis and characterization of cellulose fibers modified zinc phosphate/hydroxyapatite core-shell as enhanced carrier of cisplatin: Loading, release, and cytotoxicity

The uncontrolled administration of the cisplatin drug (CPTN) resulted in numerous drawbacks. Therefore, effective, affordable, and biocompatible delivery systems were suggested to regulate the loading, release, and therapeutic effect of CPTN. Zinc phosphate/hydroxyapatite hybrid form (ZP/HP) and core-shell nano-rod morphology, as well as its functionalized derivative with cellulose (CF@ZP/HP), were synthesized by the facile dissolution precipitation method followed by mixing with cellulose fibers, respectively. The developed CF@ZP/HP displayed remarkable enhanced CPTN loading properties (418.2 mg/g) as compared to ZP/HP (259.8 mg/g). The CPTN loading behaviors into CF@ZP/HP follow the Langmuir isotherm properties (R2 > 0.98) in addition to the kinetic activities of the pseudo-first-order model (R2 > 0.96). The steric assessment validates the notable increase in the existing loading receptors after the functionalization of ZP/HP with CF from 57.7 mg/g (ZP/HP) to 90.5 mg/g. The functionalization also impacted the capacity of each existing receptor to be able to ensure 5 CPTN molecules. This, in addition to the loading energies (<40 kJ/mol), donates the loading of CPTN by physical multi-molecular processes and in vertical orientation. The CPTN releasing patterns of CF@ZP/HP exhibit slow and controlled properties (95.7 % after 200 h at pH 7.4 and 100 % after 120 h at pH 5.5), but faster than the properties of ZP/HP. The kinetic modeling of the release activities together with the diffusion exponent (>0.45) reflected the release of CPTN according to both erosion and diffusion mechanisms. The loading of CPTN into both ZP/HP and CF@ZP/HP also resulted in a marked enhancement in the anticancer activity of CPTN against human cervical epithelial malignancies (HeLa) (cell viability = 5.6 % (CPTN), 3.2 % (CPTN loaded ZP/HP), and 1.12 % (CPTN loaded CF@ZP/HP)).

Study on the stressing state features of basalt fibre concrete lining structure under sulphate erosion

Basalt fibre (BF) is an environmentally friendly material with excellent corrosion resistance. When tunnels cross gypsum rock strata, the gypsum rock will dissolve sulphate and erode the supporting structure, thus affecting the safe operation of the tunnels in the long term. Adding BF to the supporting structure of gypsum rock tunnels can improve its resistance to sulphate erosion. This paper took Wuzhishan Tunnel as a case, and first determined the sulphate concentration of the gypsum rock stratigraphic environment at the site; then, analysed the change of mechanical properties of basalt fibre concrete (BFC) before and after sulphate erosion by mechanical tests; finally, examined the deformation and force characteristics of the BFC secondary lining structure by numerical simulation. The results showed that the bridging effect of BF fibres and the stable spatial network structure formed inside the concrete enhanced the mechanical properties of BFC and its ability to resist sulphate erosion. However, due to the agglomeration effect of BF fibres, too much BF would reduce the mechanical properties and erosion resistance of BFC. At a BF content of 6 kg/m³, BFC had the strongest ability to resist sulphate erosion, and the cube compressive strength, axial compressive strength, and modulus of elasticity of BFC were the highest, with 47.8 MPa, 33.6 MPa, and 38.7 GPa, respectively. The dense calcium silicate hydrate (C-S-H) gel, generated near the BF, enhanced the connection between the cementitious and the aggregate, inhibited the development of microcracks within the concrete, and reduced the erosion channels for sulphate ions. The maximum displacement of the BFC secondary lining structure was reduced by 20.15 % compared to plain concrete (PC) after sulphate erosion. The secondary lining structures consisting of both BFC and PC were stressed the most at footing. The secondary lining structure composed of BFC had better deformation resistance and higher strength than PC.

Ectonic Model and Erosion Mechanisms in a Pulsed Vacuum Arc Initiated by a Spark Discharge along the Dielectric Surface

Ectonic Model and Erosion Mechanisms in a Pulsed Vacuum Arc Initiated by a Spark Discharge along the Dielectric Surface

Experimental Study of Sediment Erosion in Pelton Turbine Bucket

Abstract In hydroelectric power plants (HPPs), sediment-laden water flows through entire turbines, causing components to be damaged over time. Pelton turbine components serve abrasive erosion from particle hardness, and rough surface when subjected to high flow velocities and various jet impingement angles. In this study, an experiment was conducted to examine the erosion-prone areas of a small-scale Pelton turbine bucket under actual flow conditions. For the experiment, the Pelton bucket was painted with four distinct layers of paint: red, yellow, green, and blue. These layers served as indicators, helping us to visually track the erosion process. The setup was specifically designed to inject sediment upstream of the nozzle. It operated for a significant period of 0- 30 minutes, and every 5 minutes, the erosion pattern was noted with the nozzle fully open at 10 l/s and a net head of 6m with jet impingement angle 75°, 90°, and 105°. After operating for 0-30 minutes in sediment-laden flow conditions, a pattern of erosion was revealed, showing the hot spots (areas more susceptible to erosion) during the investigation at jet angles of 75°, 90°, and 105°. The most severe erosion areas are in the bucket domain, specifically at the splitter region and the deeper upper and lower parts of the brim. The erosion mechanism was influenced by the jet diameter and impingement angle on the bucket splitter. The experiment revealed that the outer regions of the bucket, where the flow was directed outward, suffered the most severe erosion, providing evidence of particle separation at high accelerations.

Designing sandwich-zigzag multilayered TiN coatings for corrosion-erosion coupling damage protection

Coatings are utilized to enhance the surface properties of materials. This study aimed to modify the TiN coating with a novel sandwich-zigzag intermediate layer and delve into the intricate damage mechanisms under harsh corrosion-erosion coupling environments. Due to the infiltration of NaCl into the coating and the subsequent formation of TiO2, the sandwich-zigzag TiN coatings exhibited a reduction in mechanical behavior and erosion resistance when exposed to salt spray at 550 °C for 50 h. Moreover, the erosion rates of the as-corroded TiN coatings displayed an opposite trend compared to that of the as-deposited coatings, showing that the erosion rate was highest at the erosion angle of 30°. Nevertheless, the presence of the zigzag-TiN intermediate layer benefited the coating by preventing stress accumulation and heterogeneous interface. This ultimately improved the erosion resistance of the coatings by more than 2 times at universal erosion angle compared to that of the substrates under the synergistic effects of corrosion and erosion.

Transmural gastric mesh migration after hiatal hernia repair: Case report and literature review

IntroductionMesh reinforcement of the hiatus has been shown to reduce the hernia recurrence rate. But serious related complications have been reported including bleeding, erosion or migration, infection, stricture, and adhesions. Complete transmural gastric migrations of the mesh have been rarely cited in the literature. CaseWe herein report a case of a 62-year-old woman who presented for dysphagia and weight loss, 2 years after hiatal hernia repair with mesh cruroplasty. On endoscopy, complete transmural mesh migration into the stomach was identified, but it was difficult to remove. The mesh was then removed surgically. DiscussionThe possible mechanism of mesh erosion can be related to the anatomy of the distal esophagus, fixation, position, and distance of the mesh to the esophagus when placed at surgery. Endoscopic mesh retrieval is the first line of treatment when safe and feasible. Other surgical treatments in case of failure of endoscopic removal are case by case depending on the position of the mesh and the extent of organ injury. Surgery can be done laparoscopically or via laparotomy. ConclusionIn conclusion, dysphagia may manifest during the early postoperative period after mesh repair antireflux surgery, but such dysphagia usually resolves; if it doesn’t or if it worsens, mesh migration must be excluded

Effect of VC content on the microstructure, ablation and oxidation resistance of the protective oxide layer of C/C-ZrC-VC-SiC composites

A third reinforcement vanadium carbide (VC) is introduced to improve the compactness, ablation and oxidation resistance of the protective oxide layer of C/C-ZrC-SiC composites, and the effect of VC content on the microstructure and properties of the oxide layer is studied. Results showed that the compactness of the oxide layer gradually increased with the increase of VC content. Excessive oxide melt leaded to an increase in the evaporation and mechanical erosion. Z2V1S6 exhibited the best ablation and oxidation resistance, which was attributed to the formation of a tightly bound composite oxide bi-layer with a dense ZrO2-SiO2-V2O3 inner layer and a ZrO2 skeleton outer layer bonded by SiO2-V2O3 melt.

Arc erosion behavior of Ag-8 wt.%ZrO2 contact materials with CuO additions

To clarify the effect of CuO on the arc erosion behavior of AgZrO2 contact materials, the Ag-8 wt.%ZrO2 contact materials without and with CuO addition were prepared by the combination of three-dimensional vibrating mixing and hot-pressing sintering, and the electrical contact tests were performed 5000 times on a JF04D electrical contact testing system. The effect of CuO additive on the arc erosion behavior of Ag-8 wt.%ZrO2 contact material was studied, and the arc erosion mechanism was discussed as well. The results show that an appropriate CuO addition can significantly improve the hardness, electrical conductivity and arc erosion resistance of Ag-8 wt.%ZrO2 contact material. At 0.5 wt%CuO, the optimal combination of relative density, hardness and electrical conductivity can be achieved, which are 99.48 %, 79.0 HV and 79.3 %IACS, respectively. Furthermore, the Ag-8 wt.%ZrO2 contact material with 0.5 wt%CuO addition exhibits the lowest arc energy and shortest arc duration, least mass loss, and silver splashing as well as the formation of pores are also significantly inhibited, displaying excellent arc erosion resistance. This can be ascribed to the improved electrical conductivity and enhanced interface bonding together with CuO decomposition under high temperature arc.

Investigation of the erosion mechanism of fluorine-free mold flux on the submerged entry nozzle under the influence of negative electric field

Fluorine-free mold flux is receiving increasing attention due to the environmental and health problems associated with using fluorinated flux in casting. However, the erosion problem in the submerged entry nozzle is still exists and not solved. Therefore, in this study, the electric field is used to improve the erosion resistance capability of the nozzle. The results show that a thick protective adhesion layer is formed on the surface of the slag-line material under the action of a negative electric field due to an electrochemical reaction. This protective layer further reacts with the CaO/SiO2 content of the fluorine-free slag-line material to generate an interfacial reaction layer composed mainly of Ca2SiO4 and CaZrO3. Due to the presence of Ca2SiO4 in the interfacial reaction layer, a small amount of crystalline transformation occurs during the cooling process. Thus, under the protection of the double protective layer generated by the action of the negative electric field, the slag-line material is not subject to the erosion of the fluorine-free mold flux, and the erosion rate is only 0.37%.

SEM of Erosive Wear Mechanisms of Kevlar Fiber Reinforced Composites

SEM of Erosive Wear Mechanisms of Kevlar Fiber Reinforced Composites

Aerothermal Loads on a Representative Porous Mesostructure at Flight Conditions Using Direct Simulation Monte Carlo

Spacecraft require thermal protection systems (TPS) in order to survive the extreme conditions present during atmospheric entry missions. Porous ablators are a class of TPS materials that have been used successfully on several entry missions, although they can be difficult to model because of their complex nature at the micro- and mesoscales. Specifically, the processes that lead to mechanical erosion (spallation) of these materials are poorly understood. In order to gain insight into the spallation process, the current work computes aerothermal loads on a mesostructure representative of FiberForm (the substrate of phenolic impregnated carbon ablator) by leveraging a simulation framework involving loosely coupled Computational Fluid Dynamics-Direct Simulation Monte Carlo (CFD-DSMC) simulations of hypersonic boundary layers. CFD boundary layers are extracted from two altitudes, 68.9 and 81 km, along the Stardust entry trajectory and are imposed as boundary conditions on a DSMC simulation over an artificially generated mesostructure, which is representative of the charred layer of the TPS material. In order to produce high-quality results, the DSMC boundary conditions require careful consideration; specifically, Chapman–Enskog distributions are needed to account for large velocity and temperature gradients. Visualizations of the DSMC flowfield indicate excellent agreement with the original CFD data, and the aerothermal loads (heat flux and traction force) on the surface were examined using probability density functions. Additionally, the effects of pyrolysis blowing through the mesostructure on the surface properties are also determined.

Atomic oxygen erosion mechanism of polyimide via reactive molecular dynamics simulation and density functional theory calculation

Atomic oxygen (AO) causes serious oxidative degradation on polymeric materials in the space environment, yet understanding its reaction mechanism is a challenging task. Herein, we primarily investigate the reaction sites and reaction paths of pure polyimide material to AO erosion and propose a modification strategy involving electron-withdrawing groups to enhance the material's resistance to AO with density functional theory (DFT) and reactive force field molecular dynamics (ReaxFF MD). DFT calculations reveal that AO erosion is an electrophilic reaction, which preferentially interacts on the benzene ring with pronounced electron density distribution on the third part of the polyimide molecule. ReaxFF MD simulations validate this finding and provide additional reaction pathways that are divided into the early-stage reactions and later secondary reactions. In the early stage, only small number of AOs take part in the reactions that include the formation of CO bonds and ring opening processes. These reactions are relatively slow and majorly determine the AO resistance of the material. In the subsequent stage, AO predominantly reacts with reactive species and radicals generated from earlier reactions, leading to fast degradation. With these findings, we propose a strategy to enhance the AO resistance by introducing electron-withdrawing functional groups in the polyimides. As exemplified, the polyimide with -CF3 group shows 21.1% lower erosion yield than unmodified polymer. The present study gives a deep insight for the mechanism of AO erosion on polyimide by exploring its reaction sites and provides valuable theoretical guidance for improving the material's resistance to erosion.