Erosion Experiments Research Articles

Solid particle erosion of glass epoxy composite strengthened by metal powder

In the present study, the solid particle erosion behavior of glass-epoxy composite strengthened by metal powder has been studied. Four types of specimens were tested; one is composite specimen without metal powder, the others with metal powder, the percentages of which were 5%, 10%, and 20% by weight, respectively. Steady state erosion rates of these composites have been evaluated at various impingement angles (changed from 15° to 90° by 15° increments) with different impact velocities (34 m/s, 53 m/s and 80 m/s). The erosion experiments have been carried out by using silica sand particles (450 ± 50 μm) as erodent. The results show that the erosion rate of the composites with and without powder is the highest when the particles impact angle is between 15° and 30°. In addition, the erosion quantity of the composites were nearly the same for the specimens with and without metal powder.

Tribological behavior of plasma sprayed Cr2O3–3%TiO2 coatings

► Tribological behaviors of plasma-sprayed conventional and nanostructured ceramic coatings using pin on disc type dry sliding and pot type slurry erosion test were investigated in the present work. ► The experimental results indicated that there were two main wear mechanisms, plastic smearing and adhesive tearing, in the worn coatings under dry sliding. ► The main mass removal mechanisms observed in all the coatings subjected to slurry erosion were the formation and propagation of brittle cracks resulting in the detachment of coating surface material. Tribological behaviors of plasma-sprayed conventional and nanostructured Cr 2 O 3 –3%TiO 2 ceramic coatings (i.e., CC3T and NC3T, respectively) using pin on disc type dry sliding and pot type slurry erosion test were investigated in the present work. The experimental results indicated that there were two main wear mechanisms, plastic smearing and adhesive tearing, in the worn coatings under dry sliding. Plastic smearing corresponded to a lower average friction coefficient and wear rate, while adhesive tearing corresponded to higher values. The erosive environment selected for the slurry erosion experiments include 10, 20 and 30% of SiO 2 slurry concentrations in water with particle size 75–106 μm. The main damage mechanism observed in all the coatings submitted to slurry erosion were the formation and propagation of brittle cracks resulting in the detachment of coating surface material. Microstructural investigation was also carried to investigate the wear and erosion mechanism of the coatings using FE-SEM and EDS analysis. Properties like microhardness and porosity were also investigated for these coatings. Tribological performance of NC3T was better as compared to CC3T as observed in the present work.

Research on the Corrosion Resistance of Manganese Slag Cement Stabilized Macadam Base

In this study, the unconfined compressive strength and anti-corrosion capacity and erosion resistibility were evaluated. Different admixture amounts of manganese slag cement were used as constituents of stabilized macadam base specimens. On the prepared specimens mechanical property test、continuous immersion experiment and anti erosion experiment were carried out for the research on the corrosion resistance of manganese slag cement stabilized macadam base. It was observed that corrosion resistance and scour resistance performances were significantly improved with the incorporation of manganese. The performance of corrosion resistance reduce after first enhance when slag manganese slag cement stabilized macadam base are marinated with acid rain. During continuous acid rain marinate, the anti-corrosion capacity is improved on the first 21day, but it is observed declined rapidly after 21day acid rain marinate and finally manganese slag cement stabilized macadam base is lose its workability because of full corrosion.

Influence of the type of interface on the tribological characteristics of ICVI generated SiCf/SiC composites

► SiC/SiC composites with carbon interface show better wear and erosion resistance in addition to good mechanical properties. ► The intermediate heat treatment given to the SiC/SiC composites with boron nitride interface improves the tensile properties, fracture toughness etc. but wear resistance and erosion point of view it degrades. ► SiC/SiC composites with boron nitride interface improves show poor wear and erosion resistance. The SiC f /SiC ceramic matrix composites find applications in structural, wear resistance and high temperature applications as they are quite superior to their monolithic counter parts due to their improved flaw tolerance, large work of fracture and non-catastrophic failure behaviour. In this investigation, three types of SiC f /SiC composites, i.e., SiC f /SiC composite with carbon interface, SiC f /SiC composite with boron nitride interface and SiC f /SiC composite with boron nitride interface subjected to an intermediate heat treatment have been made via isothermal and isobaric chemical vapour infiltration technique using Nicalon ceramic grade SiC fibres. The density achieved in all the three types of composites is around 2.6–2.7 g/cc. The sliding wear/friction and solid particle erosion experiments were carried out on these composites using a pin-on-disc set up and jet erosion test rig respectively. The composites with carbon interface show higher hardness, lower sliding wear and erosion losses compared to the composite with boron nitride interface with and without intermediate heat treatment. To substantiate the slide wear and erosion data, scanning electron microscopic features have been examined.

Effect of microstructure on slurry erosion behaviour of weld hardfacing alloys

In the present work, the slurry erosion behaviour of weld hardfacing alloys was investigated by systematic variation of identified test parameters and the response data were generated from a suitably designed experimental plan. The identified groups of parameters were operational parameters; velocity, slurry concentration, and particle size of the erodent; and relative hardness of erodent particle and the microstructural parameter, carbide volume fraction (CVF). The slurry erosion experiments of hardfacing alloys with different Cr and C content were conducted using a pot-type slurry erosion tester with silica sand slurry of different concentration over a range of velocities. The slurry erosion volume loss of hardfacing alloys exhibited different trends under different test conditions with identified parameters. The slurry erosion volume loss decreased with increasing CVF and He/ Ht, (ratio of hardness of erodent to hardness of target) except under severe erosion test conditions where the reverse trend was observed. An empirical correlation was proposed, in which the slurry erosion rate was expressed as a product of operational parameters, microstructural parameter, and relative hardness of erodent particles. Scanning electron microscopy observations were focused on gaining additional information associated with the mechanism of material removal under different experimental conditions.

Effect of microparticle properties on erosion in solid-steam mixtures

Based on a custom-built experimental apparatus, irregular microparticles of different sizes and microparticles of the same size but of different shape were added to wet steam, and erosion experiments were performed on polished medium carbon steel specimens. After the experiments, the eroded surfaces were analyzed by scanning electron microscopy and the degree of damage was evaluated by area loss. The results indicated that microparticle size significantly affects the degree of erosion damage. With an increase in size, variations in the method of damage mainly cause different degrees of damage on an eroded surface. Microparticle shape hardly affects the number of craters. Compared with spherical microparticles, irregular microparticles cause indentations more easily and result in more severe abrasion on the material’s surface.

Erosion behaviour of epoxy based unidirectionl (GFRP) composite materials

In the present work, the solid particle erosion behaviour and wear mechanism of commercial epoxy based unidirectional glass fibre reinforced plastics (GFRP) composites were investigated. The erosion experiments have been carried out using irregular silica sand (SiC) particles (150 ± 15 μm) as an erodent. The erosion losses of these composites were evaluated at various impingement angles (30°, 60° and 90°) with the change of both of erosion time and pressure. The erosion behaviour of (GFRP) has changed from ductile to brittle at 60° impingement angle and the erosion loss was the highest. The morphology of eroded surfaces was observed under scanning electron microscope and damage mechanisms were discussed.

High Temperature Erosion Behavior of Mo-Si-Ni-Al Metal-Ceramic Composite Cladding Layer Produced by TIG Welding

In this paper, the Mo-Si-Ni-Al metal-ceramic composite cladding layer on the surface of the 304 stainless steel was applied by using tungsten inert gas (TIG) method. The phase composition and microstructure of the cladding layer were characterized by XRD, SEM and EDS. With the high temperature erosion experiment in the range of 873-1073 K, the erosion behavior of the Mo-Si-Ni-Al cladding layer was studied. The maximum total mass loss was observed in the specimen, which was tested at 923 K and 45°erosion angle. The high temperature erosion mechanism of the Mo-Si-Ni-Al cladding layer was discussed.

Quantifying and modeling post-failure sediment yields from laboratory-scale soil erosion and shallow landslide experiments with silty loess

Rainfall events on steep hillslopes can cause both soil erosion and shallow landslides. These processes interact with each other and need to be studied in an integrated way to understand hillslope sediment yields. The main aim of this research is to study post-failure sediment yield following landslides that alter local slope gradients. A laboratory flume under a rainfall simulator was used to quantify erosion and shallow landslides in fine-grained silty loess soils. The flume was divided into an upper and a lower section; the slopes of which could be altered. A total of 12 experiments were conducted on slopes ranging from 35° to 47° in the upper and 5° to 10° in the lower flume sections. Shallow landslides were triggered in four of the 12 experiments. Sediment and runoff were collected from the flume outlet every minute during landslides and every 10 min before and after landslides. Changes in the soil slope after landslides occurred were recorded. Results showed that peak sediment yields were related to landslide occurrence and proximity to the outlet. Post-failure reduction in sediment yields was related to the evolution of the hillslope after slope failures. A simple rule-based soil redistribution model of runout distance was validated using the experimental results. The Water Erosion Prediction Project (WEPP) model was used to simulate runoff and soil erosion during pre- and post-failure rainfall events. Predicted runoff rates and sediment yields using WEPP were in good agreement with those measured in both pre- and post-failure events, indicating that the model can be used successfully as part of an integrated approach to modeling sediment yields in landslide-prone landscapes.

Effects of salinity and organic matter on sedimentation and resuspension of the sediment

The effect of the salinity and organic mattter, such as Extraceller Polymeric Substances on the settlement of the suspended sediment and erosion of the estuarine sediment was studied. The surface sediments were sampled at the tidal river of the Chikugo River where the turbidity maximum is observed to use flocculation and erosion experiments. The results of the experiments showed that concentration-based settling velocity of the suspended mud increaces with increases of salinity. Suspended mud with EPS has much higher settling velocity comparing with the EPS removed sediment. On the other hand, flux based settling velocities of each sediments were almost same regardless of whether EPS was removed or not. Erosion thresholds of the sediments whose EPS were removed had lower than those of raw sediments

Role of cation mixing in the sol formation of Ca/Na-montmorillonite

Compound Ca/Na-montmorillonites were prepared by mixing given amounts of homoionic Ca-montmorillonite with given amounts of homoionic Na-montmorillonite. Colloidal sol formation in deionized water of these mixed Ca/Na-montmorillonites were investigated by means of turbidity measurements or through swelling pressure evolution in specially constructed swelling pressure test cells. It is concluded that the sol phase is absent in homoionic Ca-montmorillonite, which is interpreted as a manifestation of ion-ion correlations that are strong for divalent ions. Using the swelling pressure test cells it was found that Na-montmorillonite readily penetrates filters with pore size 2 μm, whereas in the case of Ca-montmorillonite no material was lost through the filters even at a pore size of 100 μm. However, mixed Ca/Na-montmorillonite with 20% or more sodium swells extensively and give rise to rapid increase in turbidity and behave qualitatively the same as homoionic Na-montmorillonite with respect to sol formation. This is also confirmed in erosion experiment using the swelling pressure test cells as well as in sedimentation tests monitored with a turbidimeter. Montmorillonite with 90% or more calcium in the interlayer behaves similar to homoionic Ca-montmorillonite. Thus it is concluded that 90% of the clay layer charge needs to be compensated by Ca 2+ for correlation interactions to prevent sol formation.

EROSION RATE OF COHESIVE SEDIMENT WITH DIFFERENT CLAY-CONTENT-RATIO

Erosion rate formula of cohesive sediment had been derived by the first author, but the there was very few information about it in the range that clay-content-ratio Rcc was less than 0.3. A series of erosion experiments were conducted in order to understand the effect of Rcc on the erosion rate. As a result, it was confirmed that the formula was valid in the range of Rcc between 0.1 and 1.0. The influence of watercontent-ratio on the test sample was discussed on the basis of experimental results. A deformation process and a stable profile of cohesive straight channel with a different value of Rcc were also investigated in order to understand the erosion process of cohesive sediment from a different point of view.

Technical Note A New Method for Replicating Complex Microtopographic Surfaces in Laboratory Soil Box Experiments

Current laboratory methods for creating rough soil surfaces for surface runoff, infiltration, and soil erosion experiments are limited in their ability to duplicate rough surfaces with uniform soil properties (e.g., bulk density) throughout the soil profile. A new method for replicating rough soil surfaces with uniform bulk density was developed. The new method utilizes a laboratory-scale soil box and surface mold constructed with desired rough surface microtopography. For experiments, the surface mold was set on a plane parallel with the bottom of the soil box at a height governed by the desired soil profile depth. The soil box was then rotated 90, soil was incrementally packed in 5-cm layers in the void volume between the mold and the soil box, the soil box was then rotated 90 back to horizontal, and the surface mold was removed. The ability to replicate rough surface microtopography was verified by creating five rough soil surfaces using the aforementioned method, scanning the surfaces using an instantaneous-profile laser scanner to obtain high resolution DEMs, and determining their maximum ponding area (MPA) and maximum depression storage (MDS) using a Puddle Delineation (PD) program. Each surface was then evaluated by comparing the computed MDS and MPA against the actual surface mold values. The average MPA and MDS relative errors of the five surfaces from the mold surface were 1.85% and 1.86%, respectively. A separate rough surface also was packed for evaluating bulk density of the packed soil using the replication method. Based on the two-tailed t-test, bulk density was statistically uniform for 12 sample locations across the soil surface and throughout the soil profile. The new method proved efficient and effective at producing soil surfaces with identical rough surface microtopography and uniform bulk density.

Erosive Wear Studies of Glass fiber- and Carbon Fiber-reinforced Polyetheretherketone Composites at Low Particle Speed

In this study, solid particle erosive wear behavior of randomly oriented short glass fiber and carbon fiber-reinforced polyetheretherketone (PEEK) composites was investigated. The solid particle erosion experiments were carried out at six different contact angles (15—90°) and at low particle speed using brown fused aluminum oxide (Al2O3) particles (500—710 µm) as an erodent. The PEEK composites showed semi-ductile erosion behavior, with a maximum wear amount at a contact angle of 45°. The fiber type and the contact angle had a significant influence on erosion behavior. Glass fiber-reinforced PEEK composites showed better erosive wear resistance than carbon fibre-reinforced composites. Scanning electron microscopy studies were conducted to understand the wear mechanisms involved during the erosive wear.

Advances in sediment transport modelling

A detailed description of how recently-developed sediment dynamics formulations are incorporated into the United States Environmental Protection Agency's Environmental Fluid Dynamics Code is presented. The new approach is an extension of previous models and accounts for multiple sediment size classes, has a unified treatment of suspended load and bedload, and appropriately replicates bed armouring. The resulting flow, transport, and sediment dynamics model is an improvement to previous models because it may directly incorporate site-specific data, while maintaining a physically consistent, unified treatment of bedload and suspended load. Experimental data from a noncohesive sediment erosion experiment in a straight channel help validate the numerical model. In this simulation, unknown parameters representing the active layer thickness and the erosion rates of the two largest sediment size classes when they are newly deposited are identified from the available data.

Supramolecular Hydrogels from Cisplatin-Loaded Block Copolymer Nanoparticles and α-Cyclodextrins with a Stepwise Delivery Property

A stepwise anticancer drug delivery system based on an injectable supramolecular hydrogel was presented. In this system, poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAA) block copolymer nanoparticles containing cisplatin were released by erosion of the hydrogels and then the cisplatin was released from the nanoparticles by exchanging with chloride ions. By mixing α-cyclodextrins (α-CDs) and the PEG-b-PAA micelles with their PAA cores loaded with the cisplatin in water, the novel supramolecular hydrogels were generated by threading α-CDs onto the PEG segments and forming physical cross-links of molecular necklaces. The gelation properties could be tuned by changing concentrations of the polymers and cisplatin, their feeds, and by adding PEG homopolymers or Pluronic copolymers as additives. Structures and properties of the supramolecular hydrogels containing cisplatin were studied by wide-angle X-ray diffraction (XRD) and rheology measurements, respectively. The thixotropic effect of the hydrogels and their reversible sol-gel transition were confirmed. In vitro hydrogel erosion experiments were conducted and cisplatin release in saline and pure water was quantified. Hydrogel erosion produced discrete nanoparticles from which cisplatin was released completely in saline. In contrast, the hydrogels were eroded into nanoparticles in pure water, but no cisplatin could be released. In vitro cytotoxicity studies showed that the cisplatin-loaded hydrogels inhibited the growth of human bladder carcinoma EJ cells with a similar potency as that of the free cisplatin, whereas the hydrogels without cisplatin showed no cytotoxicity. These results suggested that the cisplatin-coordinated PEG-b-PAA/α-CD supramolecular hydrogels hold great potential as an injectable system for sustained delivery of cisplatin in cancer therapy.

Rill erosion in natural and disturbed forests: 1. Measurements

Rill erosion can be a large portion of the total erosion in disturbed forests, but measurements of the runoff and erosion at the rill scale are uncommon. Simulated rill erosion experiments were conducted in two forested areas in the northwestern United States on slopes ranging from 18 to 79%. We compared runoff rates, runoff velocities, and sediment flux rates from natural (undisturbed) forests and in forests either burned at low soil burn severity (10 months or 2 weeks post‐fire), high soil burn severity, or subject to skidding of felled logs. The runoff rates and velocities in the natural sites (2.7 L min−1 and 0.016 m s−1, respectively) were lower than those in all the disturbed sites (12 to 21 L min−1 and 0.19 to 0.31 m s−1, respectively), except for the 10‐month old low soil burn severity site where the velocity (0.073 m s−1) was indistinguishable from the natural sites. The mean sediment flux rate in the natural sites also was very small (1.3 × 10−5 kg s−1) as compared to the rates in the disturbed areas (2.5 × 10−4 to 0.011 kg s−1). The hillslope gradient did not affect the runoff or sediment responses. The sediment flux rates generally were greater in the initial stage of each inflow period than in the steady state condition, but there was no corresponding transient effect in runoff rates. Rill erosion modeling implications based on these data are presented in part 2 of this study.

Effects of artificial soil surface management on changes of aggregate stability and other soil properties

Studies of size distribution, stability of the aggregates, and other soil properties are very important due to their influence on tilth, water infiltration, and nutrient dynamics and more importantly on accelerated erosion but are affected by soil surface management. Both chemical e.g. pH, organic carbon, (OC), exchangeable cations e.g. calcium (Ca), magnesium (Mg) and physical properties such as aggregate size and stability are dynamic properties, which vary in response to forces affecting soil environment. This study was carried out to have a long and detailed understanding of how artificial surface soil covering materials can protect the soil physical and chemical properties from the ravages of soil erosion. Such endeavor would allow us to make suitable modification to soil conservation practices to enhance soil stability and importantly soil productivity. Data measured for eight years on induced erosion experiments on a Ferralsol covered by artificial soil netting locally called sombrite at Campinas, Brazil, were used to examine the effects of accelerated soil erosion on soil chemical and physical properties. Each erosion plot had an area of 25 x 4 m. Four soil treatments were chosen: bare (control) and three artificially covered soils. Changes of soil properties observed in relation to aggregation were bulk density, total and aeration porosity, available water capacity and changes in soil chemical properties. From pooled data stepwise multiple regressions were done to find out the relationship of aggregate stability with pH, calcium, and organic matter. There were no significant differences (P=0.05) in mean weight diameters (MWD) and size distribution irrespective of whether samples were collected from the upper middle or lower parts of the erosion plots. There were very gradual decline in mean weight diameters (MWD) and size distribution of water-stable aggregates during the study period. Bulk density increased appreciably on bare soils but remained almost constant in artificially covered soils. However, using Duncan tests, the treatment differences were not significant (P=0.05). Non-significant correlation (P=0.05) between MWD and the soil chemical properties were observed. Coefficients of determination for pH, OC, MWD and Ca could not sufficiently assist in explaining changes in aggregate stability as a result of surface cover. Key words: artificial soil covers, soil surface management, soil properties, accelerated erosion, aggregate stability.

Erosive wear of a surface coated hydroturbine steel

In the present investigation, stellite-6, Cr3C2-NiCr and WC-Co-Cr coatings were deposited by D-Gun on a hot rolled 21Cr-4Ni-N steel meant for fabrication of hydro turbine underwater parts. The coatings have been characterized for microstructure, porosity, microhardness and crystalline nature. The erosion experiments were carried out using an air jet erosion test rig at a velocity of 120 ms−1 and impingement angles of 30° and 90°. Silicon carbide particles of size ranging between 500 and 700 μm were used as erodent. Scanning electron microscopy (SEM) technique was used to analyse the nature and mechanism of erosion. Erosion behaviour is observed to be influenced largely by the nature and extent of porosity in the surface coatings.

Evaluation of magnetic iron oxides as sediment tracers in water erosion experiments

Abstract Water erosion is one of the major concerns with regard to sustainability of agricultural systems in Mediterranean countries (e.g. olive farming areas in Southern Spain). The limitations of the technologies traditionally used in erosion measurement has created increased interest in the use of innovative erosion tracers useful for monitoring erosion and determining deposition rates in the field. In this work, we evaluated the potential of magnetic iron oxide (Fe3O4) as a soil tracer. Particle size distribution of the magnetic iron oxide, mobility under drainage conditions and the effect of the aggregate size distribution in blank and tagged soils were studied. The use of magnetic iron oxide to estimate soil losses at small-scale was also examined using a portable rainfall simulator and measuring magnetic susceptibility before and after each simulated rainfall. The properties of the magnetic iron oxide, including a particle size distribution similar to that of soil aggregates, strong binding to soil particles, little mobility in soil, very high magnetic susceptibility relative to the typically low background values of the studied soils, innocuous to environment and low cost, make it an effective soil tracer for estimating soil losses at a small-scale.