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The possibility of using the microhardness method to determine the deformation of surface layers during cavitation wear of cast metal alloys is analyzed. The studies were carried out on two casting alloys: titanium alloy and AK12pch silumin. The experiments consisted of two stages. At the first stage, cylindrical samples were made from the listed alloys, which were compressed on a press to a different degree of plastic deformation, then cut in the middle along or across the axis of the sample. The obtained section was ground and polished, and then the microhardness of the obtained sections was measured and calibration graphs of the dependence of microhardness on the intensity of plastic deformation were built. The second stage included tests of alloys for cavitation wear on an ultrasonic magnetostrictive vibrator in fresh water at a frequency and amplitude of oscillations of the end of the concentrator of the device equal to 22 kHz and 28 µm, respectively. During the tests, the microhardness of the worn surface was periodically measured and the dependence of the microhardness on the duration of the cavitation effect was plotted. The maximum achievable value of microhardness during the incubation period of cavitation wear was determined from the maximum point on this dependence. According to the obtained maximum value of microhardness, the corresponding value of the intensity of plastic deformation of the worn surface was "removed" from the calibration curve. The causes of possible errors in determining the deformation of the surface of cast alloys worn during cavitation, when using the microhardness method, are established. [ABSTRACT FROM AUTHOR]

Currently, technological developments are undergoing development, including lubrication technology for hydrodynamic bearings. Various innovations have been discussed in research studies on hydrodynamic lubrication, one of which is textured bearings. In this study, the effect of artificial slip and inertia on the hydrodynamic lubrication performance of textured parallel slider bearings was observed. Especially when artificial slip conditions and the effects of inertia and cavitation are applied simultaneously to the textured bearing surface, the flow conditions greatly affect the value of the load carrying capacity. Therefore, this condition still needs to be investigated. This condition is approached computationally by using computational fluid dynamics (CFD) methods including the cavitation phenomenon. The results show the comparison of two condition i.e no-slip and full slip model. Based on computational studies, it shows that the difference occurs in the pressure distribution area. This phenomenon certainly affects the load support value. In the condition of full slip load support has a higher value. Slip also causes a decrease in friction between the fluids and a decrease in the cavitation effect on the thrust bearing. [ABSTRACT FROM AUTHOR]

Pressure regulators have been part of industries to address various requirement related to pressure settings. Being in industry since long time, lot of research's have already been done to address issues & improve performance. The published research papers had addressed the performance issues like cavitation (that happens due to sudden pressure drop causing the bubble formation at localized area which in term results in cavitation), high pressure, high-pressure differential(which is normally achieved by multistage of regulator as single stage regulator cannot work above certain pressure differential), pressure stability (by adding sensitive diaphragm & high precision controlled orifice seat),corrosion (by using high grade NACE complain material like 316L & duplex stainless steel),various failures (like galling, mushroom formation, pitting, diaphragm rupture) & safety (by designing regulator as per various internal standard like PED, ASME BPVC). Ergonomic aspect of pressure regulator considering the human comfort found missing. This paper addresses the ergonomic aspects pressure regulator to ease setting downstream pressure with non-stretching & frictionless material. Research will also address to make pressure regulator setting uniform torque across the pressure range making regulator more sensitive for precise pressure setting. It also addresses the requirement of high flow through controlled orifice by introducing a bypass system working in parallel with controlled regulator to achieve fast volume filling at high pressure. [ABSTRACT FROM AUTHOR]

A spillway is a hydraulic structure in a dam to release flood discharge and prevent overtopping. The flow through the spillway structure can trigger cavitation, endangering the stability of the construction indicated by an erosion of the ground floor of the spillway structure. This study aimed to examine the cavitation number associated with the safety of the spillway design. The research was conducted on the spillway of the Krueng Kluet Dam using a physical model at the Laboratory of River and Coast – Hydro Engineering Division, Civil Engineering Department, Syiah Kuala University = of Indonesia. The cavitation analysis was undertaken by collecting data on the pressure and velocity at each flow rate variation. The analysis results showed that the spillway of the Krueng Kluet Dam is at level 1 (no cavitation damage), level 2 (possibility of cavitation damage), and level 3 (cavitation damage) risk of damage. The spillway section with the possibility of cavitation damage (level 2) is in the distance 6,3 to 11,1 m from crest spillway, and cavitation damage (level 3) are in distance 10,4 to 11,1 for Q5 and Q1000. The cavitation that occurred at the bottom of the spillway can be prevented by treating the surface of the spillway structure (grinding rough elements) and using an aerator at the bottom of the spillway. [ABSTRACT FROM AUTHOR]

The phenomenon of cavitation in liquid flows occurs in many technical devices, and leads to a decrease in the reliability and efficiency of these devices. One such device is internal combustion engines with liquid cooling systems. Cavitation phenomena in the cooling cavities, together with the corrosive effect of coolants, lead to erosion-corrosion destruction of the cylinder liners. The article proposes criteria for assessing the intensity of erosion-corrosion damage, taking into account the design characteristics of engines, the degree of their forcing, parameters of the operating cycle, operating and water-chemical parameters of cooling. Calculations carried out for various brands of engines made it possible to identify factors affecting the intensity of erosion-corrosion destruction, which include the specific gravity and the degree of forcing. It is shown that the transition to high-temperature cooling and the improvement of the properties of coolants provides a decrease in the intensity of erosion-corrosion damage and increases the service life of engine cylinder liners. The results obtained can be used to adjust the schedules of maintenance and repairs of engines, as well as for the rational choice of cooling modes and properties of coolants. [ABSTRACT FROM AUTHOR]

The subject of rheology research, as a field of science, is the study of the behavior of various phase systems, primarily liquids and gases, subjected to loads over a certain period of time. These include mechanical loads, the influence of electric, magnetic and other fields that can significantly change the intramolecular structure of materials. The main effects of these interactions are elastic, plastic or so-called flowing. With regard to the properties of the tested changes, in liquids, which include epoxy resins, before the hardening process, viscosity (dynamic and kinematic) is most often tested. This property describes the ability of a fluid to resist shear stresses. Their value depends on pressure, temperature and shear rate in the considered medium. The afore-mentioned polymers are very often used in the processes of bonding building materials with different properties due to their good adhesion to the substrate. Nevertheless, the effectiveness of gluing depends largely on the parameters of the adhesive both during the application of the layer and after the hardening process. Adhesives used in construction are often modified by adding fillers. Their effective bonding with the resin can be ensured by the cavitation process. This phenomenon depends on local changes in pressure and temperature in the volume of the liquid subjected to external load. In the case of the described research, the energy of ultrasound (the so-called sonication) was used to homogenize the epoxy adhesive with the selected powder filler. The sonication process was investigated in terms of the cavitation phenomenon occurring in the polymer and its influence on the changes in the adhesive viscosity and the effectiveness of the filler application. As a result, suitability of sonication as a method of resin modification in terms of obtaining a composite material was assessed. [ABSTRACT FROM AUTHOR]

In this work, plasma discharge in the liquid phase under the action of intensive ultrasonic cavitation has been applied to synthesize iron oxide nanoparticles. The resulting nanoparticles were characterized by the range of methods of physical and chemical analysis - dynamic light scattering, scanning electron microscopy. It was shown that the particles had size about 100 nm, and were stable to aggregation and sedimentation. Using these nanoparticles and low-density polyethylene, a polymer composite material was obtained and characterized by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Gas Metal Arc Welding (GMAW) are well known due to its cost effective and easy accessibility. The technique is commonly used in shipping maintenance to repair corrosion and erosion affected propeller blades. Recently, studies of the Friction Stir Process (FSP) have shown its capability to generate a very fine microstructure and enhancement of the metal surface properties. This paper proposes an integrated approach for repairing larger sized nickel-aluminum bronze (NAB) components using a single robotic system. The process includes surface cleaning, weld deposition (WD), welding deposition Friction Stir Process (WD-FSP), surface and contour finishing. The mechanical properties, including hardness, cavitation erosion and corrosion performance, are tested on as-cast NAB, WD and WD-FSP surfaces. The weld deposition and WD-FSP surfaces showed an enhancement in hardness compared to as-cast NAB. As for cavitations erosion and corrosion, the weld deposition and WD-FSP sample exhibited an improvement in the cumulative mass loss and shifting of the electrode potential to the more noble section signifying that using the proposed approach is feasible for NAB repair. [ABSTRACT FROM AUTHOR]

An impeller a rotating component used to increases or decreases the flow and pressure of fluids, which has wide spread applications in aircraft sector, automobile industry, medical field and power plant technology. In real time applications bronze and hardened steel impellers quickly erode when presented to destructive mediums, for example, waste water, seawater, sewage,, chlorine, bromine, and numerous chemicals. They are dependent upon cavitation and electrolysis (galvanic erosion) which rashly demolishes the impeller drastically. The corrosion is the major problem of the impeller that increases pump operating and maintenance expenses which obligated the industries to search for alternative materials. The main criterion is to select the appropriate selection of material for the impeller to resist corrosion. Materials such as Caprolone (Nylon) and ABS (Acrylonitrile Butadiene Styrene) have been consider for the study considered which has chemical, thermal stability along with toughness and strength. The design and analysis of impeller is designed, analyzed using commercially available simulation tools. [ABSTRACT FROM AUTHOR]

The aim of present work is to analyse the effects of hot forging on slurry erosion behaviour of stainless steel SS420 experimentally. Samples of the material are heated at different temperatures ranging from 850°C to 950°C and after that the forging process is applied on the heated samples with the help of Birson Friction Screw Press Machine at constant strain rate 10s-1. The slurry erosion tests are conducted on the as-received and the hot forged samples with an impact velocity of slurry of 10 m/s and 10% slurry concentration (by weight). It is observed that the hardness of the hot forged samples increases with the process temperature and is more than that of the as- received sample. Slurry erosion resistance is found to be higher in the hot forged samples than the as-received sample. It is also seen that the slurry erosion resistance is maximum for hot forged Stainless steel SS420 at 950°C. [ABSTRACT FROM AUTHOR]

A specific operating mode was observed for Hall thrusters in the power range up to 5 kW when at least one of the following changes occurred: a decrease in gas flow rate, an increase in magnetic field magnitude, an extension of ceramics or a change in ceramics properties. The thruster operating in the observed mode has total efficiency from 5 to 20% lower than in the design mode. In this paper, relative erosion rate of boron nitride (BN) ceramics was measured for a Hall thruster with external ionization and acceleration region for both operating modes using passive spectral analysis. The Hall thruster has middle line diameter of 77mm and maximum power up to 2.5 kW. Estimations of the relative erosion rate were based on boron doublet linewith wavelengths of 249.677 and 249.773 nm. During the study, discharge voltage range was from 400 to 1000 V, mas flow rate range was from 2 to 6 mg/s. It was shown that the relative erosion rate for all operating conditions is lower for the operating mode with lower efficiency for chosen thruster. [ABSTRACT FROM AUTHOR]

Ultrasound sensors and inspection systems are frequently used to generate acoustic waves in metal structures capable of detecting and characterizing cracks, pits, erosion, inclusions, weld anomalies, and other material and structural features. One significant problem with piezoelectric transducers is the difficulty to achieve good coupling between the transducer and the surface being examined. This is particularly true in harsh conditions with high temperatures, cyclical hot and cold temperatures, highly radioactive fields found near nuclear reactors or spent nuclear fuel, caustic or corrosive fluids, and other extreme environmental conditions, as well as in long-term monitoring applications where repair or replacement of the sensor is difficult or expensive. Typically, coupling between the surface and the transducer is achieved with water, gel, grease, viscous shear coupling material, or pressure, which might not be possible or appropriate for long-term applications in which the impedance-matching materials wear away, evaporate, or simply stop functioning due to changes in surface conditions. Fluid couplings can evaporate or drain away from the transducer-substrate interface; glue-based couplings may foul or fail and are notoriously unreliable at high temperatures and in radioactive environments. This work explores the behavior of a magnetostrictive cold-spray patch that is metallurgically bonded to a stainless steel inspection target surface, and compares it to the performance of a standard adhesively-bonded ferrous-cobalt magnetostrictive strip solution. Cold-spray is a coating process where 10–100 micron diameter powdered metal is accelerated to Mach 2 to Mach 3 (2–3 x speed of sound) and impacted on the surface to be coated. Each powder particle forms a kinetic bond with the substrate or other coating particles to produce a metallurgically bonded layer. If the powder is nickel or cobalt with high magnetostrictive coefficients, this surface can serve as the base of a magnetostrictive sensor suitable for crack or pitting-damage inspection and monitoring that is not subject to temporal or environmental degradation. A commercially pure nickel (CPNi) cold-spray patch-based sensor on a 2 × 4 ft., ¼ and ½ in. thick plate was contrasted with a more conventional FeCo adhesive strip to determine feasibility and relative efficacy of the two magnetostrictive substrates. The magnetostrictive coefficient of CPNi is reported as 25–60 ppm while cobalt has a magnetostrictive coefficient of 40–120. Moreover, the FeCo strip is prepared with a magnetic bias treatment. As might be anticipated, the FeCo strip showed ∼7–19 dB stronger edge-wall reflection than the CPNi patch; however, both signals were readily detectable. This degree of different responses is manageable within the range of gain sensitivity to pit or crack flaws would be similarly detectable and, therefore, the cold-spray patch would be a viable alternative to a FeCo adhesive strip sensor that is not subject to adhesive degradation. Influences of magnetic bias and cold-spray patch thickness are also explored in this study. [ABSTRACT FROM AUTHOR]

Samples based on talc with 15 % of zeolite from Zlatokop, Serbia, sintered at 1200 ºC were prepared and tested in condition of cavitation erosion. The ultrasonic vibratory cavitation set up with stationary specimen was used. Mass loss was measured and degradation level of the samples using image analysis and Young modulus of elasticity was monitored. Obtained results showed good resistance to the cavitation erosion giving the possibility of future application in different conditions where cavitation erosion is expected. [ABSTRACT FROM AUTHOR]

To improve the dynamic characteristics and cavitation characteristics of large-flow pilot operated check valve. consider the pilot poppet as the research object, analyses working principle and design three different kinds of pilot poppets. The vibration characteristics and impact characteristics are analyzed. The simulation mode! is established through flow field simulation software. The cavitation characteristics of large-flow pilot operated check valve are studied and discussed. On this basis, high-pressure large-flow impact experimental system is used for impact experiment, and the cavitation index is discussed. Then optimal structure is obtained. Simulation results indicate that the increase of pilot poppet half cone angle can effectively reduce the cavitation area, reducing the generation of cavitation. Experimental results show that the pressure impact is not decreasing with increasing of pilot poppet half cone angle in process of unloading, but the unloading capacity. response speed and pilot poppet half cone angle are positively correlated. The impact characteristics of 60° pilot poppet. and its cavitation index is lesser, which indicates 60° pilot poppet is the optimal structure, with the theory results are basically identical. [ABSTRACT FROM AUTHOR]

Cavitation erosion can often be related to the strong unsteady characteristics of cloud cavitation. The current study focuses on the capability of LES to predict the unsteady behavior of the cavitating flow around a NACA0015 hydrofoil. The Large Eddy Simulation (LES) results can reproduce more unsteady phenomena than the unsteady Reynolds-Averaged Navier-Stokes (URANS) results, and can predict closer location of cavitation closure, resulting in more accurate shedding frequency and oscillation frequency of the lift and drag. It is indicated that the LES method can provide a sound numerical basis for further quantitative forecast of cavitation erosion. [ABSTRACT FROM AUTHOR]

The first observations of the destructive effects of cavitation have been made on marine propellers. As a result, researchers and shipbuilders requested materials, techniques that treated materials propellers, which confer resistance to cavitation erosion. Such a technique, very well mastered, is the volumetric heat treatment due to the knowledge of all the factors that define it. This paper presents the effect of treatment on behaviour and resistance type CuNiAlFeMn bronze (symbolized AMPCO M4) to cavitation erosion caused by vibrating piezoelectric crystal vibrating device T2 cavity found in the laboratory of U.P Timişoara. The resistance created by the application of this treatment is carried out based on the characteristic curves of erosion MDE (t) and MDER (t), compared with the material condition of the material delivered and CuNiAl III RNR standard, the reference for the ships propellers Romania. Comparison with state material delivered with the standard shows that the treatment you get a large increase in resistance due to increasing hardness of the surface layer exposed to cavitation. [ABSTRACT FROM AUTHOR]

Cavitation often occurs in inducer pumps used for space rockets. Silver plated coating on the inducer liner faces the damage of cavitation. Therefore, it is important to study about the cavitation erosion resistance for silver plated coating at several operating conditions in the inducer pumps. In this study, the cavitation erosion tests were carried for silver plated coating in deionized water and ethanol at several liquid temperatures (273K-400K) and pressures (0.10MPa-0.48MPa). The mass loss rate is evaluated in terms of thermodynamic parameter Z proposed by Brennen [9], suppression pressure p-pv (pv: saturated vapor pressure) and acoustic impedance pc (p: density and c: sound speed). Cavitation bubble behaviors depending on the thermodynamic effect and the liquid type were observed by high speed video camera. The mass loss rate is formulated by thermodynamic parameter Z, suppression pressure p-pv and acoustic impedance pc. [ABSTRACT FROM AUTHOR]

It's well known, that the imploding cavitation bubbles causes the damage on the solid surfaces. This process is then dangerous for the mechanical parts of the hydraulic machines. Proposed article dealing with the analysis of the type of the damage caused by the cavitation erosion according to the selected metallic material of the specimen. As is shown in the article, the type of the damage has a realtion to the hydraulic parameters of the flow (velocity, cavitation number). The optical and weight measerument methods will be used for the anlysis. [ABSTRACT FROM AUTHOR]

This paper reports the outcome of a numerical study of ultrasonic cavitation using a CFD flow algorithm based on a compressible density-based finite volume method with a low-Mach-number consistent flux function and an explicit time integration [15; 18] in combination with an erosion-detecting flow analysis procedure. The model is validated against erosion data of an ultrasonic horn for different gap widths between the horn tip and a counter sample which has been intensively investigated in previous material studies at the Ruhr University Bochum [23] as well as on first optical in-house flow measurement data which is presented in a companion paper [13]. Flow features such as subharmonic cavitation oscillation frequencies as well as constricted vapour cloud structures can also be observed by the vapour regions predicted in our simulation as well as by the detected collapse event field (collapse detector) [12]. With a statistical analysis of transient wall loads we can determine the erosion sensitive areas qualitatively. Our simulation method can reproduce the influence of the gap width on vapour structure and on location of cavitation erosion. [ABSTRACT FROM AUTHOR]

Till today, factors influencing the formation and collapse of densely distributed, interacting cavitation bubbles are only qualitatively understood. The aim of the present study is to investigate experimentally the influence of selected boundary conditions on the number and size distribution of cavitation bubbles created by an ultrasonic horn (sonotrode). Cavitation bubble clouds below the sonotrode were recorded by means of phase-locked shadowgraphy imaging. The time integrated number of cavitation bubbles was found to decrease exponentially with growing bubble radius. The number of bubbles was increased with growing actuation amplitude and gap width between the sonotrode tip and an opposing solid wall. Furthermore, it could be shown that the number of cavitation bubbles depends on the actuation phase. Future investigations will focus on establishing a statistical relation between the number and size distribution of cavitation bubbles in the near wall region and the resulting cavitation erosion on solid surfaces. [ABSTRACT FROM AUTHOR]

The article discusses a study that investigates a suitable coating for a rudder application for ships. Arc spraying using metallic wire as the feedstock is selected for coating deposition, and ten different coatings were prepared by arc spraying with wire feedstock of aluminum, zinc, copper, and iron. Evaluations of the cavitation erosion and marine corrosion behaviors of the arc-sprayed coatings are made and compared with conventional anti-corrosion paints used on devices such as hydraulic machinery.

High intensity pulsed ultrasound can achieve tissue erosion at a tissue-fluid interface. The mechanism for erosion is believed to be cavitation, as evidenced by a temporally changing acoustic backscatter. To understand the erosion mechanism, optical and acoustic observations are employed to monitor dynamics of the ultrasound generated bubble cloud at a tissue-fluid interface. The results show that the initiation of variable acoustic backscatter occurs due to formation of a bubble cloud. Pulses of several μsec in duration result in bubble cloud lasting hundreds of μsec, with cavitation nuclei persisting tens of msec. The dynamics of the bubble cloud highly depend on therapy pulse parameters. For example, the life-time and the size of the bubble cloud are greater with longer pulse duration, higher pulse intensity, and higher PRF. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]