Erosion Experiments Research Articles

Slurry erosion characteristics and erosion mechanisms of stainless steel

In the present study, slurry erosion experiments of stainless steel SUS-304 were carried out using new advanced erosion test rig, where the multiphase flows of alumina sand and water were utilized as the erodents. The results show that erosion rate was initially high and gradually reduced over the testing time. In addition, the erosion rate increased with an increase in impact velocity. The surface roughness increased with either increasing testing time or impact velocity. Further, the surface profiles of “W” shape were observed for all eroded samples. Microstructural characterization reveals two different erosion regimes: plastic deformation mechanism dominated at high impact angles, while plowing/cutting mechanism dominated at low impact angles. A correlation between the erosion rate, erosion profile and microstructure is also discussed.

Microstructure and Cavitation Erosion Properties of Ceramic Coatings Fabricated on Ti-6Al-4V Alloy by Pack Carburizing

In this study, Ti-6Al-4V alloy was processed by pack carburizing to improve the cavitation erosion behavior. X-ray diffraction and scanning-electron microscopy (SEM) analysis showed that a uniform and crack-free ceramic coating formed on the surface of the treated samples. The coating layer comprised primary TiC and less oxide. Cavitation erosion experiment results indicated that the treated samples have the factor of 3.44 to 6.68 increase in cavitation erosion resistance (Re) as compared with the as-received sample. The ceramic coatings with high hardness and good metallurgical bonding were responsible for the enhanced cavitation erosion properties. When the coatings were treated at condition of high temperature and/or long time, the Re was enervated due to the thin oxide film formed at the outermost surface. Cavitation erosion mechanism for the coatings was characterized as brittle mode by SEM observation of the worn surfaces.

Size distribution analysis of colloid generated from compacted bentonite in low ionic strength aqueous solutions

An experimental methodology is presented, with the objective of investigating erosion and colloid generation from compacted bentonite, to evaluate its possible effects on radionuclide migration in a deep geological repository (DGR) in crystalline rock.Bentonite erosion studies were performed using a natural bentonite and considering two possible scenarios existing in a DGR in crystalline rock: the first one, where the water hydrating the bentonite is stagnant (static scenario) and the second one where the water can flow at the bentonite surface, simulating the existence of a water conducting fracture (dynamic scenario).In particular, the size of the generated colloids was analysed, as it is a very important parameter for transport and retention/filtration processes in crystalline rock and, ultimately, for colloid-driven radionuclide transport. The analysis of the size distribution of colloids, detected in erosion experiments, was carried out by the very sensitive single particle counting (SPC) technique.As bentonite colloids are particularly stable and mobile in low ionic strength (I) solutions, these chemical conditions were considered of particular interest.Results showed that the quantity of colloids generated from compacted bentonite depends on the chemistry of the water, and that the presence of calcium in the electrolyte inhibits the maximum generation of colloidal particles. The maximum concentration of bentonite colloid in solution corresponds to particles with a size around 50–100nm.The size distribution of bentonite colloids was similar in all the analysed cases, but the concentration of particles of smaller size (50–100nm) was always higher in the absence of calcium, indicating the clear effect of this element on their aggregation.Results also evidenced the importance of water/clay interactions: these can be of extreme importance for the evaluation of erosion and stability of colloids in a DGR at a long term.

Experimental Investigation of Electrode Erosion of Trigatron in Microsecond Arc Discharge Process

Trigatrons have been widely used in many fields. However, the performance of trigatrons typically degrades as operational time increases. Among many influence factors, electrode erosion is a primary cause of trigatrons failure. In this paper, the peak current and pulsewidth of trigatrons are in the order of kiloampere (kA) and microsecond (μs), respectively, with an electrode size in the order of millimeters (mm). The discharge images show that the arc appearance looks filamentary in shape during the early period of the discharge. As the discharge process progresses, the arc expands and moves radially to the side surface of the anode. Simultaneously, electrode erosion experiments are conducted on the trigatrons in an atmospheric environment. Experimental results show that the erosion level becomes more serious with an increase of gap distance and discharge current. The weight loss of Mo and W electrodes with erosion times are very close to a linear distribution, however, weight loss rate of W-Cu electrodes increases more dramatically with an increase of erosion times. The erosion of WCu electrode is more pronounced than Mo and W electrodes the volume erosion rate of W is smaller than Mo, but the mass erosion rate of W is higher than Mo. Many cracks always appear on the W and Mo electrode surfaces, which are due to frequent and intensive interaction between the expansion and shrinkage of the electrode material.

Erosion Experiment of Self-Excited Oscillation Pulsed Jet

In order to improve the erosion effect of jet under submergence condition, experimental studies of erosion generated from the self-excited pulsed jet was carried out by using developed self-excited oscillation nozzle. The erosion volume and depth of pulsed jet were measured and taking mortar block as an erosion part. The results were that the standoff has significant influence on erosion effect. The erosion volume firstly decreases with increases in cavity length and then increases to a peak value. Erosion volume of pulsed jet is significantly higher than that of continuous jet, the erosion depth of two jet has slight difference.

Aeolian comminution experiments revealing surprising sandball mineral aggregates

Abstract We have undertaken a set of wind erosion experiments on a simple and well defined mineral, quartz. In these experiments wind action is simulated by end over end tumbling of quartz grains in a sealed quartz flask. The tumbling induces collisions among the quartz grains and the walls of the flask. This process simulates wind action impact speed of ∼1.2 m/s. After several months of tumbling we observed the formation of a large number of spherical sand aggregates, which resemble small snowballs under optical microscopy. Upon mechanical load the aggregates are seen to be more elastic than quartz and their mechanical strength is comparable, though slightly lower than that of sintered silica aerogels. Aggregates of this kind have not been reported from field sites or from closed circulation systems. However, sparse occurrence might explain this, or in nature the concentration of the aggregate building particles is so low that they never meet and just appear as the most fine grained tail of the sediment particle size distribution.

Repeated erosion of cohesive sediments with biofilms

Abstract. This study aims to explore the interplay between biofilms and erodability of cohesive sediments. Erosion experiments were run in four laboratory annular flumes with natural sediments. After each erosion the sediment was allowed to settle, mimicking intermittent physical processes like tidal currents and waves. The time between consecutive erosion events ranged from 1 to 12 days. Turbidity of the water column caused by sediment resuspension was used to determine the erodability of the sediments with respect to small and moderate shear stresses. Erodability was also compared on the basis of the presence of benthic biofilms, which were quantified using a Pulse-Amplitude Modulation (PAM) Underwater Fluorometer. We found that frequent erosion lead to the establishment of a weak biofilm, which reduced sediment erosion at small shear stresses (around 0.1 Pa). If prolonged periods without erosion were present, the biofilm fully established, resulting in lower erosion at moderate shear stresses (around 0.4 Pa). We conclude that an unstructured extracellular polymeric substances (EPS) matrix always affect sediment erodability at low shear stresses, while only a fully developed biofilm mat can reduce sediment erodability at moderate shear stresses.

Sediment Erosion and Transport Experiments in Laboratory using Artificial Rainfall Simulator

Catchments soil erosion, one of the most serious problems in the mountainous environment of the world, consists of a complex phenomenon involving the detachment of individual soil particles from the soil mass and their transport, storage and overland flow of rainfall, and infiltration. Sediment size distribution during erosion processes appear to depend on many factors such as rainfall characteristics, vegetation cover, hydraulic flow, soil properties and slope. This study involved laboratory flume experiments carried out under simulated rainfall in a 3.0 m long × 0.8 m wide × 0.7 m deep flume, set at 17° slope. Five experimental cases, consisting of twelve experiments using three different sediments with two different rainfall conditions, are reported. The experiments consisted of detailed observations of particle size distribution of the out-flow sediment. Sediment water mixture out-flow hydrograph and sediment mass out-flow rate over time, moisture profiles at different points within the soil domain, and seepage outflow were also reported. Moisture profiles, seepage outflow, and movement of overland flow were clearly found to be controlled by water retention function and hydraulic function of the soil. The difference of grain size distribution of original soil bed and the out-flow sediment was found to be insignificant in the cases of uniform sediment used experiments. However, in the cases of non-uniform sediment used experiments the outflow sediment was found to be coarser than the original soil domain. The results indicated that the sediment transport mechanism is the combination of particle segregation, suspension/saltation and rolling along the travel distance.

Modelling the Effect of Particle Size Distribution in Multiphase Flows with Computational Fluid Dynamics and Physical Erosion Experiments

It is known that particle size has an influence in determining the erosion rate, and hence equipment life, on a target material in single phase flows (i.e. flow of solid particles in liquid only or gas only flows). In reality single phase flow is rarely the case for field applications in the oil and gas industry. Field cases are typically multiphase in nature, with volumetric combinations of gas, liquid and sand. Erosion predictions of multiphase flows extrapolated from single phase flow results may be overly conservative. Current understanding of particle size distribution on material erosion in multiphase flows is limited. This work examines the effect of particle size distribution on material erosion of a cylindrical aluminium rod positioned in a 2" vertical pipe under slug and distributed bubble regimes using various water and air volume ratios. This is achieved through physical erosion experiments and computational fluid dynamics (CFD) simulations tailored to account for particle dynamics in multiphase flows.

Erosion Behaviors of Impeller Material FV520B in Centrifugal Compressor

To study the erosion behaviors and mechanism of impeller material FV520B in centrifugal compressor, the erosion experiments with polygonal alumina particles were carried out on the high-speed erosion testing system. Microstructure of the erosion zone was analyzed by SEM to reveal the erosion mechanism. An erosion model to calculate the erosion rate of FV520B was developed. The results showed that, FV520B exhibited the erosion characteristics of typical plastic materials, the highest erosion rate occurred at the impact angle of 24°, the lowest erosion rate occurred at normal impact angle. The velocity index at the impact angle 24° and 90° were 3.37 and 3.68, it grew as the impact angle increased. The erosion mechanism of FV520B was micro-cutting and deformation wear, at low impact angles, the erosion was dominated by micro-cutting wear, while at high impact angle greater than 60 °, the erosion was dominated by deformation wear. Also the predictions of the erosion model were in good agreement with the results of experiments, indicating that this model can be used to estimate the erosion rate of compressor impeller under different working conditions.

Ultrasonic cavitation erosion of gas nitrided Ti–6Al–4V alloys

Ultrasonic cavitation erosion experiments were performed on Ti–6Al–4V alloys samples in annealed, nitrided and nitrided and subsequently heat treated state. The protective oxide layer formed as a result of annealing and heat treatment after nitriding is eliminated after less than 30min cavitation time, while the nitride layer lasts up to 90min cavitation time. Once the protective layer is removed, the cavitation process develops by grain boundary erosion, leading to the expulsion of grains from the surface. The gas nitrided Ti–6Al–4V alloy, forming a TixN surface layer, proved to be a better solution to improve the cavitation erosion resistance, compared to the annealed and nitrided and heat treated state, respectively. The analysis of the mean depth of erosion rate at 165min cavitation time showed an improvement of the cavitation erosion resistance of the nitrided samples of up to 77% higher compared to the one of the annealed samples.

Laboratory soil piping and internal erosion experiments: evaluation of a soil piping model for low‐compacted soils

ABSTRACTMechanistic models have been proposed for soil piping and internal erosion on well‐compacted levees and dams, but limited research has evaluated these models in less compacted (more erodible) soils typical of hillslopes and streambanks. This study utilized a soil box (50 cm long, 50 cm wide and 20 cm tall) to conduct constant‐head, soil pipe and internal erosion experiments for two soils (clay loam from Dry Creek and sandy loam from Cow Creek streambanks) packed at uniform bulk densities. Initial gravimetric moisture contents prior to packing were 10, 12 and 14% for Dry Creek soil and 8, 12, and 14% for Cow Creek soil. A 1‐cm diameter rod was placed horizontally along the length of the soil bed during packing and carefully removed after packing to create a continuous soil pipe. A constant head was maintained at the inflow end. Flow rates and sediment concentrations were measured from the pipe outlet. Replicate submerged jet erosion tests (JETs) were conducted to derive erodibility parameters for repacked samples at the same moisture contents. Flow rates from the box experiments were used to calibrate the mechanistic model. The influence of the initial moisture content was apparent, with some pipes (8% moisture content) expanding so fast that limited data was collected. The mechanistic model was able to estimate equivalent flow rates to those observed in the experiments, but had difficulty matching observed sediment concentrations when the pipes rapidly expanded. The JETs predicted similar erodibility coefficients compared to the mechanistic model for the more erodible cases but not for the less erodible cases (14% moisture content). Improved models are needed that better define the changing soil pipe cross‐section during supply‐ and transport‐limited internal erosion, especially for piping through lower compacted (more erodible) soils as opposed to more well‐compacted soils resulting from constructing levees and dams. Copyright © 2013 John Wiley & Sons, Ltd.

Sequential resuspension of biofilm components (viruses, prokaryotes and protists) as measured by erodimetry experiments in the Brouage mudflat (French Atlantic coast)

Resuspension thresholds in terms of friction velocity were experimentally quantified for the prokaryotes, protists and for the first time, viruses of intertidal mudflat biofilms. Differences in resuspension thresholds could be related to the type, behaviour and size of microorganisms and their association with particles. Free microorganisms (viruses, bacteria and some nanoflagellates) were resuspended by weak flow at friction velocities lower than 2cms−1. Chlorophyll a, some nanoflagellates and attached bacteria were resuspended together with the bed's muddy sediment, which required friction velocities larger than 3cms−1. Diatoms smaller than 60μm were resuspended at velocities between 3 and 5cms−1, while those larger than 60μm were resuspended at higher friction velocities (5.5 to 6.5cms−1).The thresholds of resuspension also depended on the micro-scale position of microorganisms in the sediment (horizontal and vertical distributions). In the field, the vertical distribution of chlorophyll a (a proxy of microphytobenthos) was skewed, with a maximum in the first 2mm of sediment. Along the neap–spring tidal cycle, chlorophyll a revealed an increase in MPB biomass in the first 2mm of the sediment, in relation to light increases with exposure durations. The horizontal distribution of chlorophyll a could be inferred from erosion experiments. During the initial phase of biofilm growth, the distribution of chlorophyll a seemed horizontally homogeneous, and was uniformly eroded at the beginning of the increase in chlorophyll a. From these results, we can make a hypothesis: in the subsequent phase of biofilm growth until the maximum of emersion duration, the eroded quantity of chlorophyll a was larger than expected based from chlorophyll a vertical distribution, suggesting that biofilm horizontal distribution became patchy and enriched chlorophyll a was preferentially eroded. When emersion duration and biofilm growth decreased, the trend was reversed, and eroded quantity of chlorophyll a was lower than expected from chlorophyll a vertical distribution, suggesting that areas with low chlorophyll a were preferentially eroded. Such erosion patterns when biofilm growth decreased probably resulted from the bulldozing activity of a surficial sediment bioturbator, the gastropod Peringia ulvae. Our study did not directly prove this horizontal distribution but it should be further discussed. This distribution needs to be studied to acquire real evidence of patchy distributions.

Sediment availability on burned hillslopes

[1] Erodibility describes the inherent resistance of soil to erosion. Hillslope erosion models typically consider erodibility to be constant with depth. This may not be the case after wildfire because erodibility is partly determined by the availability of noncohesive soil and ash at the surface. This study quantifies erodibility of burned soils using methods that explicitly capture variations in soil properties with depth. Flume experiments on intact cores from three sites in western United States showed that erodibility of fire-affected soil was highest at the soil surface and declined exponentially within the top 20 mm of the soil profile, with root density and soil depth accounting for 62% of the variation. Variation in erodibility with depth resulted in transient sediment flux during erosion experiments on bounded field plots. Material that contributed to transient flux was conceptualized as a layer of noncohesive material of variable depth (dnc). This depth was related to shear strength measurements and sampled spatially to obtain the probability distribution of noncohesive material as a function of depth below the surface. After wildfire in southeast Australia, the initial dnc ranged from 7.5 to 9.1 mm, which equated to 97–117 Mg ha−1 of noncohesive material. The depth decreased exponentially with time since wildfire to 0.4 mm (or < 5 Mg ha−1) after 3 years of recovery. The results are organized into a framework for modeling fire effects on erodibility as a function of the production and depletion of the noncohesive layer overlying a cohesive layer.

Experimental Tooling Design of the Jet Erosion

Erosion is a failure phenomenon which caused by relative motion between the surface of a fluid and material, it often results in the failure of the device, affects the normal operation of equipment. This paper describes the design of a erosion experimental device combined with the characteristics of the existing types of erosion experimental advantages, disadvantages and metal material erosion experiment. The device consists of a plurality of tank, pump, spray tanks, cam nozzle, pipeline and so on. It can control to the impact velocity, impact angle.

A Study on Erosion Performance of Monocrystalline Silicon in Ultrasonic Vibration-Assisted Abrasive Water Jet Machining

Ultrasonic vibration-assisted machining (UVAM) is an effective and promising technology for processing hard and brittle materials, it has been explored in many experimental and theoretical investigations. In this paper, a study on the erosion performance of monocrystalline silicon with UVAM is presented and discussed. In the erosion experiments, monocrystalline silicon wafers were eroded by the abrasive water jet machine assisted with an ultrasonic vibration system. A contrast experiment was carried out firstly to study the influence of the ultrasonic vibration, and then an orthogonal experiment investigation was carried out to understand the effect of process variables (the abrasive particle diameter, jet impact angle, standoff distance, abrasive mass flow rate and ultrasonic vibration power) on the depth of erosion and material removal rate (MRR). The experimental results revealed that ultrasonic vibration-assisted abrasive water jet erosion (UVA-AWJE) can obviously improve the depth of the erosion and MRR compared with those in traditional AWJE and the variation trends of the effect of the abrasive particle diameter, jet impact angle, standoff distance and abrasive mass flow rate on the erosion performance in UVA-AWJE are very similar to those effect in the traditional AWJ machining.

Research of Micro-Abrasive Suspension Jet Erosion Morphology and Material Removal Mechanism

This paper introduces the micro-abrasive suspension jet polishing technology in precision machining technology. In order to understand the micro-abrasive suspension jet erosion morphology and material removal mechanism, the erosion experiments of micro-abrasive suspension jet on 40CrMnMo7 special steel work-piece were taken. We found that when the incident angles are 90°, 60°, 30°, the polishing area is respectively annular shape, horseshoe shape and blade shape. During the erosion process, as the incident angle becomes smaller, most amounts of abrasive particles impact angles will also be small, and these cause more material removal. When the particles impact the work-piece with small angles, most particles play shearing action on the work-piece and leave the work-piece nanoscale scratches; while the particles impact the work-piece at large angles, extrusion and blow are formed by the majority of the particles on the work-piece, leaving different small size pits.

Study on mechanical and erosion wear performance of granite filled glass-epoxy hybrid composites

In this study, a new class of low cost hybrid composites consisting of glass-epoxy and filled with four different weight proportions (0 wt%, 10 wt%, 15 wt% and 20 wt%) of granite particulates (a solid waste generated from stone processing industries) are developed. Mechanical study reveals that hardness, tensile modulus and impact energy of these composites are improving with filler addition while a steady decline in tensile and flexural strength is observed. The erosion rates of these composites are evaluated at different impingement angles (30–90°), impact velocities (33–68 m/s) and erodent sizes (100–250 µm) following the erosion test experiments in an air jet type test rig. An optimal parameter setting is determined for minimum erosion rate and subsequently validated by conducting confirmation experiment as per Taguchi methodology. Erosion test results indicate that the incorporation of granite particulates results in improvement of erosion wear resistance of glass-epoxy composites. Different modes of material removal, wear craters and other qualitative attributes are examined by a scanning electron microscopy during erosion experiment of the samples.

From soil aggregates to riverine flocs: a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics

AbstractParticles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity. Their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles. To‐date, hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix. However, lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column. In order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment, soil particle behaviour was tested under controlled laboratory conditions. Seven flume erosion and deposition experiments, designed to simulate a natural erosive event, and five shear cell experiments were performed using three contrasting materials: two of them were poorly developed and as such can not be considered as soils, whilst the third one was a calcareous brown soil. These experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport. Large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence. Indeed, at the maximum applied bed shear stress, the aggregated particles median diameter was found to be three times larger for the well‐developed soil than for the two others. Differences were smaller in the falling limb, suggesting that soil aggregates underwent structural changes. However, characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs, but rather into hybrid soil aggregate–floc particles. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Modeling simple experiments of biochar erosion from soil

Summary Biochar is often promoted as an amendment to improve soil quality. However, researchers have recently noted that biochar and similar substances preferentially erode from soil, which may reduce its effectiveness. Identifying the erosion mechanisms may help develop strategies for retaining biochar in soil. To investigate the role of raindrop impact biochar erosion, we applied the Hairsine–Rose erosion model to small-scale experiments that simulated rainfall on a simple biochar-soil mixture. The Hairsine–Rose model simulated the biochar concentrations in runoff well for the early part of the experiments but under-predicted the concentrations for longer times. At the end of the simulated rainfall experiments, biochar content in the soil increased with depth in the soil column from 1% near the surface to 8% in underlying soil layers; similar distributions have been observed for soil, which drives upwards diffusion. By superimposing the Wallach diffusion model on the Hairsine–Rose model we were able to simulate biochar concentrations at both short and long times. We speculate that the relatively dense sand particles are displacing the biochar and we are investigating this further. Our findings suggest that long-term sequestration of biochar in soil is unlikely in soils or parts of the landscape with limited infiltration capacity.