Steady-state Erosion Rate Research Articles

Pothole and channel system formation in the McMurdo Dry Valleys of Antarctica: New insights from cosmogenic nuclides

Large pothole and channel features (∼15m deep, ∼30m wide) carved into the Beacon Sandstone in the upland Dry Valleys of Antarctica have been used to infer catastrophic subglacial flooding beneath an expanded East Antarctic Ice Sheet that overran the Transantarctic Mountains during the mid-Miocene. Though the age and erosion rates of these geomorphic features have not been quantified, preservation of the potholes and channels has been attributed to negligible erosion under consistent polar desert conditions since the retreat of the ice sheet at ∼14Ma. We present cosmogenic 21Ne and 10Be data from samples collected along vertical transects of pothole and channel walls, as well as from intervening benches, within Battleship Promontory in the Convoy Range and within Sessrumnir Valley in the Western Asgard Range to constrain their exposure history. Measurements of fissiogenic 136Xe are used to estimate a nucleogenic 21Ne concentration in the Beacon Sandstone of 7.7±2.4×106atomsg−1 and to correct our 21Ne data for this component. Sample concentrations of cosmogenic 21Ne and 10Be are significantly lower than previously measured in the regional bedrock and reveal steady state erosion rates ranging from 99 to 171cmMa−1 in Battleship Promontory and from 59 to 383cmMa−1 in Sessrumnir Valley. Continuous exposure at such erosion rates would remove 8–54m of bedrock over a 14Ma period, a length scale similar to the features themselves, and suggests that these systems could have formed primarily through subaerial erosive processes. Alternatively, if the features formed subglacially in the Miocene, then a complex erosion and exposure history must have occurred to prevent the accumulation of cosmogenic nuclides to levels higher than those observed. Either prolonged and extensive ice cover of these features prior to 2Ma, or a threefold increase in erosion rates during the Plio–Pleistocene could produce the 21Ne and 10Be concentrations measured here. Ultimately, all of these scenarios imply that the upland Dry Valleys landscape has experienced greater changes over the last 14Ma than previously considered.

Morphology and solid particle erosion wear behavior of red mud composite coatings

In order to understand the tribological behavior of red mud composite coatings, the red mud and composite materials like fly ash, carbon and aluminum are being plasma sprayed. The coatings are investigated to know their morphological behavior and erosion wear characteristics. Plasma spraying is done at different plasma arc current like 200, 250, 300 and 400 amperes. Torch input powers maintained as 6, 9, 12 and 16 KW. The substrates chose are rectangular in shape having a dimension of 50 mm × 25 mm × 2 mm. commercially available aluminum, copper, mild steel and stainless steel being used as substrate. Room temperature solid particle erosion trials are carried out using a compressed air blasting type rig under impact angles of 30o, 60o and 90o. The present investigation uses an erosion apparatus of Sand Blast type. The test is conducted as per ASTMG-76 standards. It is analyzed that initially the cumulative coating mass loss increases rapidly and later on becomes almost stagnant. A transient regime in the erosion process exists, during which the incremental erosion rate decreases monotonically down to a steady state erosion rate.

Damage assessment of titania filled zinc–aluminum alloy metal matrix composites in erosive environment: A comparative study

The present research work, describes the development of particulate filled alloy composites consisting of ZA-27 alloy as a base material and titania particulate as reinforcing materials. The objective of the present work is to study the erosion wear behavior of particulate filled alloy composites by Taguchi experimental design technique at four different impact velocities (25–79m/s), erodent temperature (40–100°C), impingement angles (30–90°) and erodent size (250–550μm) respectively. A finite element simulation model (ANSYS/AUTODYN) for damage assessment in erosion is developed and validated by a well designed set of experiments. It is observed that the experimental results are in good agreement with the computational results and the proposed simulation model is very useful for damage assessment. However, a series of steady state erosion analysis is also conducted by varying the impingement angle and impact velocity one at a time while keeping other factors remains constant before studying the Taguchi experimental results. From this analysis it is observed that the peak erosion rate occur at about 60° impingement angle at constant impact velocity (66m/s), erodent size (450μm), stand-off-distance (75mm) and erodent temperature (60°C) for all the composites. However, the steady state erosion rate as a function of impact velocity for unfilled composite shows maximum erosion rate as compared to filled composites at constant impingement angle (45°), erodent size (450μm), stand-off-distance (75mm) and erodent temperature (60°C) respectively. Finally, the damage mechanisms of eroded surfaces are investigated using scanning electron microscope (SEM).

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.

Surface erosion induced by heavy ion backscattering analysis

Material removal induced by HIBS (Heavy Ion Backscattering Spectrometry) analysis has been investigated. For this purpose the thickness of thin metal films deposited on graphite was measured as a function of fluence of the Si and Ti projectile ion beam. Steady state erosion rates are in fair agreement with surface sputtering rates calculated by SRIM. For some layers however, the first few monolayers are removed at a much faster rate. A comparison with standard He RBS is made and consequences for the applicability of HIBS are discussed.

Pleistocene dynamics of the interior East Antarctic ice sheet

Current models describing past configurations of the East Antarctic ice sheet are poorly constrained by observations. Exposure dating of bedrock surfaces using in situ–produced cosmogenic nuclides provides an ideal tool for directly constraining former changes in ice sheet elevation. We present cosmogenic radionuclide 10 Be and 26 Al measurements in bedrock surfaces and glacially transported cobbles in the Grove Mountains, a group of nunataks within the slow-flowing interior ice sheet dome, hundreds of kilometers from the coastal ice margin and from ice streams. Samples were collected in vertical transects over 500 m of relief. Minimum bedrock and erratic exposure ages show a trend of increasing age with height above the ice sheet, spanning a period from 0.3 to 4.0 Ma and 50–900 ka, respectively. No evidence was found for thicker ice at the Last Glacial Maximum compared to modern ice thickness. The older bedrock exposure ages of 2.5–4.0 Ma require steady-state erosion rates of −1 . The measured two-isotope bedrock exposure ages are successfully modeled when changes in surface elevation of the ice sheet are described by a combination of linear long-term ice surface lowering and shorter term high-frequency glacial-interglacial oscillations. The best-fit model requires a long-term thinning rate of 50 m m.y. −1 and an elevation change of 100 m over a 100 k.y. glacial cycle.

Real-time and post-plasma studies of influence of low levels of tungsten on carbon erosion and surface evolution behaviour in D2 plasma

A profound influence of monolayer tungsten coverage of hard carbon films on the evolution of carbon surface erosion behaviour, surface chemistry and morphology in D2 plasma has been established by real-time ellipsometry, x-ray photoelectron spectroscopy and atomic force microscopy measurements. The erosion of tungsten-covered carbon showed two distinct stages of plasma material interactions: rapid tungsten removal during the initial erosion period and steady-state amorphous carbon removal accompanied by large-scale surface roughness development. The initial removal of tungsten takes place at a rate that significantly exceeds typical sputter yields at the ion energies used here and is attributed to elimination of weakly bonded tungsten from the surface. The tungsten remaining on the a-C : H film surface causes surface roughness development of the eroding carbon surface by a masking effect, and simultaneously leads to a seven fold reduction of the steady-state carbon erosion rate for long plasma surface interaction times (∼100 s). Results presented are of direct relevance for material transport and re-deposition, and the interaction of those films with plasma in the divertor region and on mirror surfaces of fusion devices.

Erosion Studies of Short Glass Fiber-reinforced Thermoplastic Composites and Prediction of Erosion Rate Using ANNs

Erosion behavior of polyetherketone (PEK) reinforced by short glass fibers with varying fiber content (0—30 wt%) has been studied. Steady-state erosion rates have been evaluated at different impact angles (15°—90°) and impact velocities (25—66 m/s) using silica sand particles as an erodent. PEK and its composites exhibited maximum erosion rate at 30° impact angle indicating ductile erosion behavior. The erosion rates of PEK composites increased with increase in amount of glass fiber. Also, artificial neural networks technique has been used to predict the erosion rate based on the experimentally measured database of PEK composites. The effect of various learning algorithms on the training performance of the neural networks was investigated. The results show that the predicted erosion rates agreed well when compared with the experimentally measured values. It shows that a well-trained neural network will help to analyze the dependency of erosive wear on material composition and testing conditions making use of relatively small experimental databases.

Solid particle erosion of unidirectional fibre reinforced thermoplastic composites

In the present study, the solid particle erosion behaviour of neat PEEK matrix and unidirectional glass fibre (GF) and carbon fibre (CF) reinforced polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) composites has been studied. The erosion experiments have been carried out by using silica sand particles (200±50μm) as an erodent. Steady state erosion rates of these composites have been evaluated at different impact angles and impact velocities. The neat PEEK exhibited peak erosion rate at 30° impingement angle whereas the composites exhibited a semi-ductile behaviour with peak erosion rate at 60° impact angle. The erosion rate of the glass fibre reinforced composites was higher than that of the carbon fibre reinforced composites. The results show that the fibre orientation has a significant influence on erosion rate only at lower impact angles. The erosion rate of the composites was higher when the particles impact perpendicular to the fibre direction than parallel to the fibres. The morphology of eroded surfaces was observed under scanning electron microscope and damage mechanisms were discussed.

Microstructure and wear resistance of low temperature hot pressed TiB 2

Fine-grained TiB 2 compacts have been hot pressed to 98–99% theoretical density at 1400 °C. The compacts were consolidated from sub-micron powders prepared by a high-energy ball milling technique. Titanium diboride (TiB 2) powders were obtained from the milling of commercially synthesized TiB 2 and also from the mechanical alloying (MA) of Ti and B precursors. The formation of TiB 2 from Ti and B powders by mechanical alloying was found to reach completion after 3 h, and wear debris from steel mill vials and media introduced 0.8 to 1.5 wt% Fe in the sintered compacts. The dry erosion resistance of the highest density compacts was examined using an ASTM standard test with an abrasive jet of Al 2O 3 impinging at a normal angle of incidence. Steady-state erosion rates of 0.5 mm 3/kg of erodent compare favorably with the measured value of 9 mm 3/kg for commercial, fine-grained WC–Co cermets under identical conditions. Microstructures, fracture surfaces, and erosion craters were also examined by electron microscopy.

Incubation Time and Cavitation Erosion Rate of Work-Hardening Materials

A phenomenological analysis of the cavitation erosion process of ductile materials is proposed. On the material side, the main parameters are the thickness of the hardened layer together with the conventional yield strength and ultimate strength. On the fluid side, the erosive potential of the cavitating flow is described in a simplified way using three integral parameters: rate, mean amplitude, and mean size of hydrodynamic impact loads. Explicit equations are derived for the computation of the incubation time and the steady-state erosion rate. They point out two characteristic scales. The time scale, which is relevant to the erosion phenomenon, is the covering time—the time necessary for the impacts to cover the material surface—whereas the pertinent length scale for ductile materials is the thickness of the hardened layer. The incubation time is proportional to the covering time with a multiplicative factor, which strongly depends on flow aggressiveness in terms of the mean amplitude of impact loads. As for the erosion rate under steady-state conditions, it is scaled by the ratio of the thickness of hardened layers to the covering time with an additional dependence on flow aggressiveness, too. The approach is supported by erosion tests conducted in a cavitation tunnel at a velocity of 65 m/s on stainless steel 316 L. Flow aggressiveness is inferred from pitting tests. The same model of material response that was used for mass loss prediction is applied to derive the original hydrodynamic impact loads due to bubble collapses from the geometric features of the pits. Long duration tests are performed in order to determine experimentally the incubation time and the mean depth of penetration rate and to validate the theoretical approach.

Solid particle erosion studies on polyphenylene sulfide composites and prediction on erosion data using artificial neural networks

Solid particle erosion behavior of polyphenylene sulfide, reinforced by short glass fibers with varying fiber content (0–40 wt%) has been studied. Steady-state erosion rates have been evaluated at different impact angles (15–90°) and impact velocities (25–66 m/s) using silica sand particles (200 ± 50 μm) as an erodent. PPS and its composites exhibited maximum erosion rate at 30° impact angle indicating ductile erosion behavior. Though PPS is a brittle thermoplastic, incubation period was found for neat resin and its composites at normal impact ( α = 90°). The erosion rates of PPS composites increased with increasing amount of glass fiber. Morphology of eroded surfaces was examined using scanning electron microscopy (SEM) and possible wear mechanisms were discussed. Also, artificial neural networks (ANNs) technique has been used to predict the erosion rate based on the experimentally measured database of PPS composites. The results show that the predicted data are well acceptable when comparing them to measured values. A well-trained ANN is expected to be very helpful for prediction of wear data for systematic parameter studies.

Solid particle erosion behaviour of ferrous and non-ferrous materials and correlation of erosion data with erosion models

The main objective of the present investigation was to study the erosion behaviour of ferrous and non-ferrous materials and also to examine the erosion model developed for normal and oblique impact angles by Hutchings. For this purpose, erosion studies of ferrous and non-ferrous materials have been conducted at different impingement angles (15–90°) and impact velocities (24–52 m/s). It was observed in this study that the erosion peak at about 60° impingement angle has been pronounced at higher impact velocity (52 m/s) for different materials. However at lower impact velocities, for different materials, the curves of steady state erosion rate versus impingement angle were rather shallow. A reasonable agreement between wear coefficients and hardness of the materials has been observed from one of the models developed by Hutchings. Erosion efficiency values (1.5–6%) indicate that microploughing will be the dominating wear mechanism. Scanning electron microscopy (SEM) study of eroded surface has revealed different wear mechanisms.

Solid-particle erosion behavior of high-performance thermoplastic polymers

Solid-particle erosion tests were carried out to study the effect of matrix material, impact angle, and impact velocity on the erosion behavior of seven types of thermoplastic neat polymers (i.e., polyetherimide, polyetheretherketone, polyetherketone, polyphenylene sulfide, polyethersulfone, polysulfone, and ultrahigh molecular weight polyethylene). Steady-state erosion rates of these polymers have been evaluated at different impact angles (15–90°) and impact velocities (25–66 m/s). Silica sand of particle size 200 ± 50 μm was used as the erodent. These polymers have exhibited maximum erosion rate (E max) at 30° impact angle indicating ductile erosion behavior. Some of these polymers have shown an incubation behavior at lower impact velocities for an impact angle of 90°. Correlations among steady-state erosion rate and mechanical properties and glass transition temperature (T g) were established. Morphology of eroded surfaces was examined using scanning electron microscopy and possible wear mechanisms were discussed.

Erosion of a model rosin-based marine antifouling paint binder as studied with quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry

In this study two surface sensitive methods, i.e. quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry, were used for erosion measurements of a rosin-based marine antifouling paint binder. Thin films of the binder were applied on sensor surfaces by the means of spin-coating and the effect of water velocity over the paint film, water temperature or ionic strength on erosion was investigated. Both the acoustic QCM-D model and the optical ellipsometry model gave comparable erosion results. The initial 2–50 nm rapid erosion of the top layer was followed by steady-state erosion rate until end of experiment. For example, the steady-state erosion rate was 12 nm/24 h in artificial seawater at 23 °C and with a flow of 200 μl/min over the paint surface as measured with QCM-D. The erosion rate increased with increased velocity and increased temperature. Ionic strength had no effect on the erosion rate of this model binder. At low water velocities the surface layer was highly dissipative indicating a water filled surface top layer or the formation of deposits on the surface. New characterization techniques that are able to study the erosion mechanisms on the nanometre scale are sought for as the binders get more technically complex containing, for example, nanoparticles or enzymes. Surface sensitive methods could be used to rapidly screen the effect of different binder chemistries or paint additives on the erosion during the paint development process.

Correction to “Slip rate of the Calico fault: Implications for geologic versus geodetic rate discrepancy in the Eastern California Shear Zone”

[1] In the paper “Slip rate of the Calico fault: Implications for geologic versus geodetic rate discrepancy in the Eastern California Shear Zone” by Michael Oskin, Lesley Perg, Dylan Blumentritt, Sujoy Mukhopadhyay, and Alexander Iriondo (Journal of Geophysical Research, 112, B03402, doi:10.1029/2006JB004451, 2007), erosion rates were miscalculated from 10Be concentrations of exhumed quartz monzonite boulders on the F alluvial fan at the Sheep Springs wash study area. The measured concentrations could be interpreted as steady state erosion rates between 1.6 and 1.9 cm/kyr through alluvium with bulk density of 2.0 g/cm3. At the corrected rates it would take >500 kyr to remove a 10-m-thick alluvial fan deposit. Thus these rates are consistent with preservation of older fan remnants in the study area. These slow alluvial fan erosion rates are also consistent with denudation rates of alluvial fans in the western Mojave Desert [Matmon et al., 2006]. In addition, the exposure age of quartz monzonite boulder sample CC04-025 in Table 3, from the B alluvial fan, is corrected to 59.4 ± 1.6 ka. These corrections do not affect our calculations of the slip rates for the Calico fault, which are based on cosmogenic dating of the better preserved K alluvial fan surface and on stratigraphic constraints that bound the age of the B alluvial fan.

Quantifying periglacial erosion in the Nepal high Himalaya

Quantifying erosion rates in high mountain environments is challenging because the erosional processes are often stochastic and catastrophic. Distinguishing between periglacial and glacial rates is especially challenging. In this study we focus on determining erosion rates from a glaciated alpine landscape where the bedrock sidewalls are eroding predominantly by blockfall. We utilize a topographically well-constrained, debris-covered glacier on the north slope of the Annapurna Range, central Nepal Himalaya, to quantify an average headwall retreat rate. By measuring supraglacial debris depths from 0.1 to 2.4 m and average short-term down-valley transport rates of 17 m/yr we calculate a yearly sediment flux of 5820 ± 1990 m 3/yr. The supraglacial debris originates from the steep, rocky headwall of the valley and we use the calculated flux with an estimated headwall contributing area to determine a slope-perpendicular headwall retreat rate of 1.3 ± 0.5 mm/yr, which corresponds to a vertical lowering rate of 0.42 ± 0.16 mm/yr and a horizontal retreat rate of 1.2 ± 0.5 mm/yr. This rate is significantly greater than the steady-state erosion rates that we determine for the valley ridge crests and sidewalls (0.08 ± 0.03 mm/yr and 0.20 ± 0.05 mm/yr, respectively) using concentrations of the in situ produced cosmogenic radionuclide, 10Be. Additionally, 10Be exposure ages of the lateral moraine crests and supraglacial debris suggest a glacial advance about 470 yr ago and a long-term supraglacial transport rate of about 10 m/yr. Using this long-term transport rate reduces our inferred headwall retreat and suggests that the up-glacial bedrock slopes are eroding at roughly the same rate. While our results do not quantify the rate of glacial erosion, the absence of a glacial gorge suggests that there may be a rough balance between glacial downcutting and the erosion of the valley sidewalls. Rates quantified here are almost an order of magnitude lower than fluvial incision rates of the upper Marsyandi River that drains the study area, suggesting that even glaciated catchments are not keeping pace with the rapidly down-cutting rivers of the Himalaya.

Erosion of geopolymers made from industrial waste

Solid-particle erosion studies were conducted on geopolymers derived from various combinations of granulated blast-furnace slag, flyash, sand, clay, and rock. The erodent particles were 390-μm angular Al2O3, which impacted at 30, 60, or 90° at a velocity of 50, 70, or 100 m/s. Steady-state erosion rates were obtained as weight of target lost per weight of impacting particles. Material-loss mechanisms were studied by scanning electron microscopy (SEM). All of the geopolymers responded to normal impact as conventional brittle solids, but impact at 30° led to anomalously rapid erosion, probably because of presence of microcracks and consequent enhanced removal of aggregates within the geopolymers. Erosion rates at 90° impact were proportional to erodent velocity to the 2.3–2.7 power. The geopolymers exhibited crushing strengths of approximately 32–57 MPa. Erosion rate correlated with density and strength for geopolymers of similar composition. All of the geopolymers that contained flyash were more resistant to erosion than was the geopolymer without flyash.

Solid-particle erosion of an anodized Mg alloy

Solid-particle erosion studies were conducted on a hardened Mg alloy (WE43A-T6) and the same alloy that had been anodized to produce a ≈12 μm oxide layer. Angular alumina particles of nominal diameter 63 or 143 μm traveling at 60 or 120 m/s impacted the targets at 20° or 90°. Steady-state erosion rates were determined as weight loss of a sample per weight of impacting particles. Under these erosive conditions, the oxide coating on the WE43A-T6 alloy was removed quickly. Weight-loss data indicated that the alloy underlying the anodized layer eroded measurably faster than the as-heat-treated alloy, but that below depths greater than ≈80 μm, the two alloys eroded at nearly equal rates. The near-surface more rapid erosion rates for the anodized alloy were attributed to loss of ductility due to internal oxidation from the anodizing process.

Weathering and transport of sediments in the Bolivian Andes: Time constraints from uranium-series isotopes

Rivers from the upper Rio Madeira basin (Bolivia) have been studied with uranium-series isotopes in order to constrain the timescales of weathering and sediment transfer from the Andes through the Amazon tropical plain. Uranium (U), thorium (Th) and radium (Ra) isotopes ( 238U– 234U– 230Th– 226Ra and 232Th) have been analyzed in the suspended load (> 0.2 μm) of rivers. Increasing 230Th excesses relative to 238U in suspended particles from the Andes to the tropical plain is interpreted as an increasing duration of weathering during sediment transport and storage in the foreland basin. Model calculations for ( 230Th/ 238U) and ( 226Ra/ 230Th) activity ratios in suspended particles using a continuous weathering model indicates that: (i) the timescale for production, storage and transport of sediments in the Andean Cordillera is only a few kyr, (ii) the storage time of suspended sediments in the foreland basin is 5 ± 1 kyr and (iii) the average transfer time of suspended sediments from the Andes to the confluence of Rio Madeira with the Amazon River is 17 ± 3 kyr. An implication of these short timescales is that the bedrock eroded must have lost part of its uranium during one or several past erosion cycles. This demonstrates the recycling of sediments through several erosion cycles before transfer to the oceans. The calculation of long-term (> 1 kyr), steady-state erosion rates indicates that they are much lower than present-day rates. This increase in denudation rates must be recent and could be explained by an increase in precipitation ∼ 4 ka ago, as suggested by palaeoclimatic evidences and the draining of transient sedimentary basins encountered on the Altiplano and easily eroded. This suggests that climatic variability rather than tectonics alone produces high erosion rates.