Sand Impact Research Articles

Test and Application on New Synchronous Grouting Materials for Earth Pressure Balance Shield

The type and properties of the grouting materials contribute great impact on the grouting effect. The new grout with hydrated lime, fly ash, bentonite, sand, water and water reducer as materials was developed, and the raw material requirements and performance requirements of the new grout were ascertained. Some experimental results were illustrated on the fineness modulus of sand and water reducer dosage impact on the properties of the new grout. The preliminary application results in Shanghai and Soochow metro showed that the new grout played a very good role on the surface subsidence control both in fine clay soil and sand strata.

A discrete particle approach to simulate the combined effect of blast and sand impact loading of steel plates

The structural response of a stainless steel plate subjected to the combined blast and sand impact loading from a buried charge has been investigated using a fully coupled approach in which a discrete particle method is used to determine the load due to the high explosive detonation products, the air shock and the sand, and a finite element method predicts the plate deflection. The discrete particle method is based on rigid, spherical particles that transfer forces between each other during collisions. This method, which is based on a Lagrangian formulation, has several advantages over coupled Lagrangian–Eulerian approaches as both advection errors and severe contact problems are avoided. The method has been validated against experimental tests where spherical 150 g C-4 charges were detonated at various stand-off distances from square, edge-clamped 3.4 mm thick AL-6XN stainless steel plates. The experiments were carried out for a bare charge, a charge enclosed in dry sand and a charge enclosed in fully saturated wet sand. The particle-based method is able to describe the physical interactions between the explosive reaction products and soil particles leading to a realistic prediction of the sand ejecta speed and momentum. Good quantitative agreement between the experimental and predicted deformation response of the plates is also obtained.

Observations of wind‐blown sand under various meteorological conditions at a beach

Field observations were conducted on a natural, open ocean beach system in Japan to investigate characteristics of wind‐blown sand transport under various weather conditions including a storm event. Data sets over periods of several hours included blown sand impact counts, three‐dimensional wind conditions, hourly precipitation, and moisture content of the sediment surface. The intermittent blown sand impact data shifted by 1 s ahead of the wind velocity correlated with the wind velocity during a no‐rainfall period (for an assumed dry surface) and in the longshore wind direction (for sufficiently long fetch length). The 5‐min mean wind velocity/impact counts relationship was well constrained by both second‐ and third‐order polynomial fitting of velocity under similar weather conditions. During a no‐rainfall period and in the longshore wind direction, the relationship between the wind velocity and sand flux estimated from the counts coincides with existing studies in wind tunnel experiments. The sand flux, however, decreased by 1 order of magnitude because of a change in the wind direction from longshore to cross‐shore and then by more than 1 order of magnitude because of an increase in the moisture content. Threshold wind velocity calculated using the time fraction equivalence method with the impact counts and the horizontal wind velocity in 5‐min sampling periods was approximately equal to the value predicted using Bagnold's equation during the no‐rainfall period and increased significantly during the rainfall phase. The sand flux sensor has several limitations for complex conditions in the field; however, it provides a number of characteristics of sand transport under various meteorological conditions.

Synergistic effects of fluid flow and sand particles on erosion–corrosion of aluminum in ethylene glycol–water solutions

The synergistic effects of fluid flow and sand particles on erosion–corrosion of 3003 aluminum (Al) alloy in ethylene glycol–water solution that simulates the automotive engine coolant were studied through a rotating disk electrode by electrochemical measurements. It was found that, in the absence of sand particles, the anodic current density of Al electrode decreases with the increase in electrode rotating speed, which is attributed to the enhanced electrode oxidation accompanying with accelerated oxygen diffusion and reduction. Mass-transport plays an important role in electrode process, as indicated by the presence of diffusive impedance. With the addition of sand particles, the de-stabilization of electrode is predominant and the anodic current density increases with the electrode rotation speed, which is attributed to the enhanced impact damage to electrode by sand particles. The electrode roughening effect due to sand impact is indicated by the presence of inductive loop in impedance plots. The variation of sand particle size does not have apparent effect on polarization behaviour of Al electrode, while an elevated temperature increases significantly the anodic current density of the electrode. There exists a synergism of fluid flow and sand impact on electrochemical corrosion behaviour of Al electrode.

Sand erosion testing of novel compositions of hard ceramics

The sand erosion rates of novel compositions of hard ceramics such as tungsten carbide, silicon nitride, silicon carbide, and partially stabilized zirconia have been tested in air-sand erosion facilities. A new testing facility that ensured stable and reproducible erosion testing with sand velocities and concentrations up to 250 m/s and 5 wt% in air, respectively, was built at IMI. Special rig design features allowed accurate sand consumption monitoring during each test. High-speed photography was used to determine the sand velocity distribution at each test setting. Parallel testing of these materials in the benchmark facility at the University of Southampton elucidated the test parameters critical for reproducibility of the results in different test configurations. High-speed visualization of the sand impact on the material surface demonstrated fragmentation of almost every sand particle in the range of velocities of 60 m/s and higher. The evidence of extensive fragmentation contributed to understanding the origin of the erosion resistance of hard ceramics. The values of the velocity exponent ( n) were typical of those reported in literature. However, unlike the expected erosion behavior of a brittle material, an ultrafine grained binderless tungsten carbide was more erosive at low impact angle.

Alleviation of erosion–corrosion damage by liquid–sand impact through use of chemicals

Erosion–corrosion is a complex mechanism of material degradation resulting from interactions between electrochemical and mechanical processes. The consequences of erosion–corrosion are severe with economic penalties resulting from premature failure of components, increased downtime and increased maintenance costs. This paper assesses the efficiency of corrosion inhibitors in reducing material damage occurring as a consequence of erosion and corrosion processes under CO 2 saturated conditions. The inhibitor action is measured using gravimetric and electrochemical analysis. It has been demonstrated that the inhibitors, effective in reducing corrosion in static conditions, can also reduce material degradation in erosion–corrosion environments. Inhibitor action in this study is through adsorption on the metal surface and effective elimination of charge transfer. Through reduction of corrosion processes, the inhibitor facilitates the reduction of corrosion-related damage. There also appears to be a role of the inhibitor in affecting the mechanical impact damage.

High velocity sand impact damage on CVD diamond

This paper describes a recent study of the damage mechanisms generated by high velocity-sand impact on diamond coatings deposited on tungsten substrates by chemical vapour deposition (CVD). The coatings were erosion tested using 90–355-μm diameter sand at a velocity of 268 m s −1 and the eroded coatings examined by scanning electron and acoustic microscopy. The images indicate that the circumferential cracks and pinholes are the main erosion features and are only located on debonded areas of the coating. This suggests that they could be formed by stress waves reflected from the coating–substrate interface, which interact with surface waves to generate circumferential cracks, the precursor to pinholes. The high spatial resolution of scanning acoustic microscopy enables the resolution of individual pinholes, thus, providing important evidence for identifying the mechanism responsible for the formation of circumferential cracks, the precursor to the pinholes. However, the acoustic images must be interpreted with care; in particular, it is important to compare microstructural features observed by acoustic microscopy with other techniques.

The sand erosion performance of coatings

This paper reviews studies of the performance of polymeric, metallic and ceramic including diamond coatings on steel and ceramic substrates when subjected to water–sand jet impingement erosion conditions. The coatings tested have been deposited by the thermal spray, electroless plating, PVD and CVD routes. The erosion conditions covered include sand impact velocities between 10 and 30 m/s with sand sizes 60–235 μm and at jet impingement angles of 30° and 90°. Tests compared the performance of the substrate material carbon steel AISI 1020 with the various polymeric, metallic and ceramic coatings. Coating and substrate erosion rates are plotted against mean particle impact energy, E k or E kV p 0.5 allowing easy surface selection once the erosion conditions of an application are known. The effect of jet impingement on the erosion resistance of selected coatings is presented. As with bulk materials, the slurry jet impingement angle and mean E k must be considered in coating selection. Of the softer coatings tested the flexible polyurethane coatings seem to have promise for future use in fluid-borne sand particle erosion environments. Pure epoxy coatings show typical brittle erosion behaviour, with fusion-bonded epoxy having mixed ductile and brittle behaviour and glass fibre reinforced epoxy showing strong ductile behaviour. CVD deposited coatings of either boron carbide or diamond are the most resistant surfaces tested and outperform bulk ceramics such as silicon carbide by orders of magnitude for E k <8 μJ and 90° jet impingement angle. Areas requiring further research to allow accurate prediction of coating life are highlighted.

Design and performance of a high velocity air–sand jet impingement erosion facility

This paper describes the design, construction and capabilities of a high velocity air–sand erosion rig. It has been designed with the aid of computational fluid dynamics to approximately simulate the erosion conditions often experienced by subsea choke valves used in the offshore oil industry. It has also been designed to evaluate the erosion performance of CVD diamond coatings at sonic velocity. The rig is of the gas-blast design in which solid particles, typically sand 60–660 μm in size, are injected into a high velocity air stream and accelerated down a 16-mm-diameter tube, 1 m in length, before striking the sample under test. Tests can be carried out with particle velocities of up to 340 m/s under a wide range of sand fluxes, impact angles and standoff distances. The results of pressure, velocity and sand flux calibration work are described. In addition, preliminary experimental data on tests carried out on mild steel, bulk and sprayed tungsten carbide are also presented. The flexibility of the air–sand rig allows the erosion behaviour of materials to be studied under a wide range of conditions.

Method for the prediction of erosion by logarithmic-nomal size distributed sand.

A prediction method for the erosion of mild steel by sand is studied. The prediction method is based on sand erosion results from the summation of erosion by a grain of sand and is proportional to the power law of particle diameter to erosion. Predicted erosion was compared with erosion test results which were done with a sand blast type test apparatus under a sand impact condition of 50 m/s air velocity and at 30° degrees to the test piece. Sieved sand and eleven kinds of logarithmic-normal size distributed commercial sands were used to compare calculated erosion with observed erosion. It is known that predicted erosion has an error of not over 18% for sieved sand and not over 56% for commercial sand.

Sediment Impact On Turbine Material: Case Study Of Modi River, Nepal

Hydropower is considered as one of the most economical and stable base energy source compared with other sources of energy of Nepal. Researches coherent to this field are not new but yet it is not sufficient, lots of tiles have to be kept for better understanding of hydropower effecting elements. Sand is the most affecting element that damages the turbine blades, so research on relation of sand and turbine is most. This research is done to find out the impact of sediment on turbine material. Modi River sediment at eight different stations has been taken as sample and its erosion rate in turbine blade sample specimen has been accounted in this study. Rotating disc apparatus has been utilized to find out the total impact of sand on turbine material. Four same kind of test turbine material is used on single rotating disc all at a time at same condition to define sand impact. Thirty gram (gm) of sediment mixed with three liters of water is used to strike sample pieces for five minutes. Two different tests of sediment samples of 8 different locations were studied. After all the test it is observed that the first test sand sample of location 1 and turbine material 1 has the highest impact with a weight loss of 7.764 mg and least impact in sand sample location 1 and sand sample 3 with a weight loss of 3.5 mg. Average weight loss of turbine material in first location is 5.929 mg which is the greatest impact and 4.0083 at eight locations which is the least. Relating to turbine material first rotating disc turbine specimen P0A has been affected highly with weight loss of 9.289 mg and less eroded on P5A rotating turbine specimen with weight loss of 1.2 mg. DOI: http://dx.doi.org/10.3126/kuset.v8i1.6047 KUSET 2012; 8(1): 88-96