Cavitating Water Jet Research Articles

Deformation and fracture behaviors of graded 2 titanium ultra-thin metallic sheets in water cavitation micro-forming

Water cavitation micro-forming (WCMF) with high quantum efficiency and excellent accuracy are essential for the applications in micro-forming. In this study, based on the size effects, an effective regulation of the cavitation micro-forming was realized. Surprisingly, micro-forming of graded 2 titanium ultra-thin metallic sheets was retained at field of special forming with WCMF. Based on the Hugoniot Elastic Limit of the material, the deformation and fracture behaviors of the case were effectively modified via water-jet shock time varying. In addition, the relationship between the deformation and the fracture of the material and the obtained water-jet cavitation shock time was established. Particularly, the cavitation energy displayed a high efficiency (within 90 s) and have a significant contribution to the appearance of the parabolic dimples. Therefore, this work opens up new opportunities for the development of special forming with excellent micro-forming performance through manipulation of water-jet cavitation shock time.

Performance Analysis of 7075 Aluminum Alloy Strengthened by Cavitation Water Jet Peening at Different Scanning Speeds

Shot peening technologies can improve the performance of materials and extend the service life of parts. Cavitation water jet peening (CWJP) is a new shot peening technology that uses the shear effect of a high-speed jet in a submerged environment to produce a cluster of bubbles, thereby achieving a significant increase in impact performance. In this paper, CWJP was used to strengthen the surface of the 7075 aluminum alloy (Al7075), and the effects of CWJP with different scanning speeds on its microstructure and mechanical properties were investigated. The morphology evolution revealed that the plastic deformation of the sample surface became more serious and the surface roughness increased with the decrease in scanning speed. The distribution of residual stress and microhardness along the depth direction of the Al7075 was measured before and after the CWJP impact, and it was found that CWJP causes work hardening on the surface of the Al7075 and can convert the subsurface tensile stress of the Al7075 into compressive stress. The mechanism of grain refinement of the Al7075 during plastic deformation was systematically revealed. Therefore, CWJP can effectively improve the surface properties of the 7075 aluminum alloy.

Water jet impact damage mechanism and dynamic penetration energy absorption of 2A12 aluminum alloy

This study aims to explore the waterjet cavitation impact (WCI) mechanism of 2A12 aluminum alloy and its dynamic penetration energy absorption after WCI treatment. The effects of WCI process parameters on the residual stress, surface quality, and microstructure of 2A12 aluminum alloy are investigated through experiment and simulation and, a dynamic penetration model of 2A12 aluminum alloy is established with ABAQUS software and finite element simulation is performed. The results show that WCI can greatly enhance the residual compressive stress of the target. Comprehensive evaluation of surface residual stress, surface quality, and plastic deformation layer reveals that a combination of small jet angle with large jet pressure, or large jet angle with medium jet pressure, delivers the best strengthening effect; the residual compressive stress and plastic deformation layer introduced by WCI can effectively increase the defensible performance of 2A12 aluminum alloy, making the projectile residual velocity far lower than before WCI treatment.

Comparison of the effect of water jet cavitation peening on stress corrosion cracking behavior of nickel-based alloy 600 and alloy 182 in high temperature water

PurposeThis paper aims to understand the effect of water jet cavitation peening (WJP) on stress corrosion cracking (SCC) behavior of alloy 600 and alloy 182 in high temperature water.Design/methodology/approachSurface and cross-section morphology, grain boundary microstructure, residual stress and strain distribution, hardness and surface roughness in water jet cavitation peened alloy 600 and alloy 182 were characterized.FindingsA superior stress corrosion cracking resistance was obtained in 600MA, which can be attributed to the formation of the ultrafine grain layer and the higher magnitude residual compressive stress.Originality/valueRelationship between WJP-induced microstructure and stress state change and SCC susceptibility was conducted. It could provide a theoretical basis for developing application of WJP in nuclear power plants.

CFD Simulation of the Cavitation Behaviour in Single Jet Process via Outlet Pressure

Cavitation effect is the most common phenomenon in the process of jet. In this work, the method of CFD numerical simulation is used to study the cavitation behaviour in the process of single hole jet. In order to obtain the mixing situation and change process of gaseous water and liquid water produced in the nozzle, the Euler multiphase flow model and the realizable k-epsilon model in the turbulence model are used. The simulation results show that the degree and frequency of liquid column breakage of cavitation water jet are far higher than those of ordinary water jet. And the structure of the nozzle also has the most ideal situation. When the nozzle inlet size is 20 mm, the nozzle diameter is 1 mm, and the nozzle length is 5 mm, which is most conducive to the growth and diffusion of cavitation bubbles. The cavitation effect increases with the increase of the inlet jet velocity, but the promotion effect does not increase significantly when the inlet velocity is greater than 2.5 m/s. From the perspective of energy consumption, the optimum velocity at this time is 2.5 m/s. And the pressure environment at the nozzle outlet also affects the cavitation phenomenon, mainly as follows: positive pressure can inhibit the cavitation effect, negative pressure can promote the cavitation effect, but the negative pressure has a limited effect on the degree of cavitation.

A critical comparative review of cavitation peening and other surface peening methods

Mechanical surface modification such as shot peening offer powerful enhancement of fatigue properties of metals and other materials. Cavitation usually causes surface damage in hydraulic machineries. However, careful selection of process parameters allowed developing an approach known as “cavitation peening.” Its advantage is surface roughness increase is lower than in conventional shot peening as there are no solid collisions involved. As cavitation is a hydrodynamic phenomenon, an understanding of both fluid dynamics and materials science is required. Cavitation peening is distinguished from “water jet peening,” in which water column impulse is used. Another flavor is “Submerged laser peening” that involves the use of a pulsed laser and can be considered a type of cavitation peening where cavitating bubbles are generated due to laser ablation. Ultrasound vibration, a popular method for generating cavitation for cleaning, has also been adapted for cavitation peening. The present comparative review presents key insights and achievements and addresses future directions that are required for advancing cavitation peening technology by considering the mechanisms of cavitation peening based on the reported data for water jet, pulsed laser, and ultrasonic cavitation peening. The data and methods are critically considered and summarized in comparison with shot peening. Strategic view of future challenges is presented. • Fatigue resistance enhancement using water jet, pulsed laser and ultrasonic cavitation peening was quantified • Cavitation peening using jet, pulsed laser & ultrasonic enhanced fatigue properties • Cavitation peening clearly distinguished from water jet peening • Cavitation peening benefits shown to exceed those by shot peening • Dislocation density induced by cavitation peening was lower than by shot peening • Importance of vortex cavitation is shown for experimental and numerical future work

Experimental study on the effect of dissolved CO2 on cavitation erosion intensity by submerged waterjet

Gas content has an important influence on the intensity of cavitation erosion, affecting the formation and collapse of cavitation nuclei. Previous studies have primarily focused on the influence of dissolved oxygen and nitrogen on cavitation erosion. Studying the effect of other gases on cavitation erosion can promote a better understanding of cavitation. This study first analysed the erosion morphology with various standoff distances under the same cavitation number. Subsequently, a typical erosion profile at a set distance was selected to study the effect of dissolved CO2 on submerged self-resonating waterjet cavitation erosion. The mass loss, maximum erosion height difference, and average roughness were used as indicators of cavitation erosion intensity. These three indicators show a similar trend with the change in cavitation erosion intensity. When the CO2 content was small, the dissolved CO2 primarily affected the cavitation intensity by affecting the pH of the water. With a further increase in air content, the inhibitory effect of gas content on the cavitation erosion intensity became apparent.

Development of processing technology using extremely high concentration cavitation energy by strong magnetic field

This work demonstrates a new processing technology termed magnetic energy intensive multifunction cavitation (MEI-MFC). In this technique, a strong magnetic field is used to concentrate the bubble energy while ultrasonic waves are applied from the perimeter of a water-jet cavitation jet. The cavitation bubbles are expanded while generating a swirling flow that increases the temperature and pressure of the bubbles. In addition, the presence of a strong magnetic field at the nozzle outlet and the collisions of charged bubbles induced by the Lorentz force cause a significant increase in the number of bubbles and the energy density. This enhanced cavitation processing technology can be applied to various materials to improve strength and to induce functionalization. The peening of austenitic stainless steel using this technique provides a highly corrosion-resistant surface while suppressing the formation of martensite and preventing sensitization by generating a new surface microstructure with a toughened layer directly underneath.

Improving the corrosion and stress corrosion cracking resistance of 316 L stainless steel in high temperature water by water jet cavitation peening

Water jet cavitation peening (WJP) was used to improve the corrosion and stress corrosion cracking (SCC) of cold worked 316L stainless steel (316L SS) in high temperature water. WJP induced changes in residual stress and microstructure of the surface layer on corrosion and SCC were investigated. The investigation was conducted by comparing the corrosion and SCC of the un-treated (UT) and WJP treated specimens by exposure tests and slow strain rate tensile (SSRT) tests. The results revealed that WJP obviously improved the corrosion and SCC resistance of 316L SS, which is attributed to the increase of residual compressive stress and the change of the microstructure of the surface layer.

Improving the Corrosion and Stress Corrosion Cracking Resistance of 316l Stainless Steel in High Temperature Water by Water Jet Cavitation Peening

Improving the Corrosion and Stress Corrosion Cracking Resistance of 316l Stainless Steel in High Temperature Water by Water Jet Cavitation Peening

Effect of Water Jet Cavitation Peening on Electrochemical Corrosion Behavior of Alloy 600 in Nacl Solution

Effect of Water Jet Cavitation Peening on Electrochemical Corrosion Behavior of Alloy 600 in Nacl Solution

A COMPARISON STUDY ON MICRO-BULGING AND SHORTLESS PEENING PROCESSES USING WATER JET CAVITATION

This paper presents a comparative study using a newly technology called water jets cavitation to fabricate micro feature on 304 stainless steel foils with a thickness of 100 µm and surface enhancement of 8090AlLi alloy sample with a thickness of 4 mm, where angular nozzle and a designed cavitation system were used with an incident pressure of 8-20 MPa. The bulged sample and the effect of incident pressure on the cavitation zone range were investigated. The experimental results indicated that the formed sample bulging depth of the outer ring shock zone and the bulging depth of the jet shock zone were not ideal, while the pits in the cavitation shock zone (that is, pits 2~4 and 10~12) obtained good geometric characteristics. Finally, the consistency of the maximum bulging depth was relatively good. The micro-bulged parts showed that the micro-pits in the cavitation shock zone had a large bulging depth and their uniformity was relatively good, indicating that the circular array feature micro-die has good performance in the cavitation water jet shock micro-bulging process. The effect of incident pressure on the range of cavitation zone, also indicated that the effective area of action of the cavitation water jet showed a ring. That is when the incident pressure was 20 MPa with a target distance of 120 mm, the maximum cavitation shock (bulging) zone showed rings of 3.5 ～21.1 mm with the 304 stainless steel foil and 3.5 mm~21.4 mm also with the 8090Al-Li alloy plate which were approximately same.

Comparison of advanced techniques for mechanical surface treatment of stainless steel parts

This work compares various mechanical surface treatment techniques applied to improve the properties of the AISI 304 austenitic stainless steel. Effects of laser shock peening (LSP), water jet cavitation peening (WjCP), water jet shot peening (WjSP), and ultrasonic impact treatment (UIT) on surface roughness, hardness, and residual stress were studied. The results demonstrate that as compared to the untreated specimen (Ra = 3.06 μm), all strain hardening methods demonstrate the decreased surface roughness parameters. The smallest Ra parameter of the wavy regular surface microrelief is formed after the ultrasonic treatment. The surface hardness (22.1 HRC5) was respectively increased by 30.7%, 38.4%, 69.6%, and 73.2% after the LSP, WjCP, WjSP, and UIT treatments. All peening techniques induced compressive residual stresses (ranged from –377 MPa to –693 MPa) in the near-surface layer. It is assumed that used treatments can increase wear/corrosion resistance and fatigue life in the studied steel.

INFLUENCE OF THE INLET PRESSURE ON IMPULSE CHARACTERISTICS OF ALUMINUM SAMPLES

In this work, the cavitation water jet technique was used to clean the inner walls of oil pipes after tertiary oil recovery. The surface morphology, depth of impinging pits, and corrosion resistance of aluminum samples after impingement with the cavitation water jet were examined using scanning electron microscopy (SEM), 3D microscopy, and an electrochemical workstation. When the inlet pressure was higher than 3[Formula: see text]MPa, the number of cavitation bubbles generated by the cavitation nozzle increased with an increase in inlet pressure. Moreover, the cleaning effect that the cavitation water jet had on the aluminum samples was higher than that of general water jet technology. There were no obvious changes to the surface of the aluminum samples when the inlet pressure was decreased to 13[Formula: see text]MPa. Meanwhile, the mass loss of aluminum samples also increased. However, the internal corrosion resistance of the pipe wall after impact was relatively low. These results indicate that the impinging efficiency of the cavitation water jet was obviously enhanced and the degree of damage to the oil pipe wall was low at an inlet pressure of 15[Formula: see text]MPa. The best target distance was 8–12[Formula: see text]mm, and at this point, the jet flushing effect was the best. Moreover, the jet velocity at the outlet cavity was 184[Formula: see text]m/s, and the jet strike area was 250[Formula: see text]mm2.

Effects of ambient pressure on the frequency characteristics of self-excited cavitating waterjet

The effects of ambient pressure on the self-excited cavitating waterjet(SECJ)’s frequency characteristics were experimentally studied under different operating conditions and nozzle resonant chamber geometries. The frequency characteristics were obtained by analyzing the waterjet’s dynamic pressure fluctuation and noise. Experimental results indicate that the fundamental self-excited frequency and its harmonics increase as ambient pressure rises from 0 to 5.5 MPa (corresponding 0 - 500 m water depth) under constant pressure drop ΔP=25MPa, which results in a higher-order resonance mode of the jet. The dimensionless parameters, including the Strouhal number Sd and cavitation number σ, were introduced to uncover ambient pressure’s influence mechanism. Dimensional analysis results indicate that the ambient pressure alters the self-excited frequency and modulates the frequency characteristics by changing the Strouhal number. The relationship between SdN and σ can be fitted as a power function SdN=Naσb (N is harmonic order, a and b are constant-coefficient). Based on this law and the mechanism of SECJ, the ambient pressure’s effects on the frequency characteristics can be predicted, which may be used to guide the optimization of SECJ system under a high ambient environment.

Automatic Edge Detection Applied to Cavitating Flow Analysis: Cavitation Cloud Dynamics and Properties Measured through Detected Image Regions

In a cavitating water jet, cavity clouds emerge and collapse with an unsteady, but periodic tendency where the frequencies depend on the working conditions. The presented work aims at examining and analyze the dynamic behavior and properties of the clouds under different circumstances. Computer vision and image processing were introduced as tools to define the cavitation clouds based on the Contour Recognition technique. A Canny operator and Otsu threshold fragmenting methods were used. The use of these methods allows for a better understanding of the cavitating jet clouds' behavior based on the pixel intensities and shows that for an arbitrary cloud the surface itself has a dynamic feature and depends on the cavity composition. The clouds' properties could be measured and correlated to the applied working conditions. Also, the oscillation frequencies of the area of the clouds could be determined. The analysis shows that the quality of the obtained results depends mainly on the input threshold values separating the foreground and background pixels. The difficulty of defining the threshold value is discussed in the paper, as well as the validity of using the Contour Recognition technique in this field.

Sonoluminescence from ultra-high temperature and pressure cavitation produced by a narrow water jet

This work developed a small-scale processing apparatus for ultra-high temperature and ultra-high-pressure cavitation (UTPC) incorporating a small diameter (0.1 mm) water jet nozzle. This instrumentation comprised a swirl flow nozzle (SFN) installed on the water jet nozzle so as to obtain UTPC from a multifunction cavitation (MFC) setup. Multi-bubble sonoluminescence (MBSL) assessments using two types of photon counting heads were employed to assess UTPC, MFC, ultrasonic cavitation (UC), water jet cavitation (WJC) and SFN-WJC. The SL intensity was found to increase in the order of SFN-WJC, WJC, UC, MFC to UTPC. Because UTPC produced the most intense emissions, this process evidently attained the highest processing temperature. Assuming a UC bubble temperature of 4000 K, the temperatures associated with UTPC, MFC and WJC were determined to be 5400–5900, 5300 and 3200–3300 K, respectively. The energy density of a single bubble during UTPC was calculated using the Rayleigh–Plesset and Planck equations for an initial bubble radius of 100 μm together with photon measurements from many bubbles and employing Planck's law. The highest SL intensity of UPTC is thought to exist due to the high energy density of UTPC. This research demonstrates that it is possible to increase the energy density of cavitation bubbles within a small reaction area.

Numerical Research of the Submerged High-Pressure Cavitation Water Jet Based on the RANS-LES Hybrid Model

The submerged high-pressure water jet has the characteristics of high velocity, strong turbulence, and severe cavitation. In order to reveal the formation mechanism of shear cavitation in the submerged high-pressure water jet and to grasp the turbulent structure and velocity distribution characteristics in the jet, the prediction ability of different turbulence models is studied first. The models represent the RANS model and RANS-LES hybrid model which are used to simulate the same cavitation jet, and the results are compared with the experimental results. The most reasonable model is then used to investigate the submerged high-pressure cavitation jet with different cavitation numbers. It is found that the calculation accuracy for small-scale vortexes has a great influence on the prediction accuracy of cavitation in the submerged jet. Both the DDES model and the SBES model can effectively capture the vortexes in the shear layer, and the SBES model can obtain more turbulence details. The result of the simulation under different cavitation numbers using the SBES model agrees well with the experimental result. Under the condition with low cavitation number, an intensive shear layer is formed at the exit of the nozzle, and small-scale vortexes are distributed along the shear layer. Mass transfer rate is relatively high in the region with a stronger vortex, which confirms that the low pressure in the vortex center is the main reason for the generation of cavitation in the shear layer. With the decrease of the cavitation number, the cavitation intensity increases obviously, while the nondimensional velocity along the radial direction changes little, which follows an exponential function.

Effects of Different Inlet Pressures on Impingement Characteristics of Aluminum

In this paper, the inner walls of oil pipes were cleaned using cavitation water jet technology after tertiary oil recovery. To improve cleaning efficiency and reduce damage caused by jet impingement, aluminum samples were used instead of oil pipe dirts. Scanning electron microscopy, 3D microscopy, and an electrochemical workstation were used to study the surface morphology, depth of impinging pits, and corrosion resistance of the aluminum samples after impingement with the cavitation water jet. According to the results, there were no obvious changes on the surface of the aluminum samples after impinging at inlet pressures lower than 13 MPa, but if the inlet pressure approached 15 MPa, the area of impinged pits on the surface of aluminum, the depth of impingement pits, and the mass loss of aluminum samples significantly increased, and the corrosion resistance of the oil pipe wall changed less after impingement. This proved that the impinging efficiency of the cavitation water jet was significantly improved and the degree of damage of the oil pipe wall was low near 15 MPa. If the inlet pressure was greater than 15 MPa, the impinging rate obviously increased, but the damage degree of the oil pipe wall was more serious.

Influence of thickness of hydrophobic polytetrafluoroethylene (PTFE) coatings on cavitation erosion of hydro-machinery steel SS410

Hydrophobic materials have the potential to replace the existing surface modification materials to combat the problem of cavitation erosion (CE), owing to their various capabilities like self-cleaning, anti-corrosion, anti-fogging, anti-icing, anti-fouling, and drag-reduction. Polytetrafluoroethylene (PTFE) as a hydrophobic material exhibits specific combination of properties such as low friction coefficient, chemically neutral, good impact strength and considerable thermal firmness, that allow PTFE to be used in a wide range of applications. Therefore, in this work, an effort has been made to explore the effect of thickness of hydrophobic PTFE coatings on CE of the hydro-machinery SS410 steel. Hydrophobic PTFE coatings with three variable thicknesses have been prepared on the hydro-machinery SS410 steel using sintering process. Using high-velocity submerged water jet cavitation erosion test rig, CE behaviour of PTFE coated and bare SS410 steel was evaluated under various combinations of operating parameters: namely jet velocity, stand-off distance (SOD), and impact angle. Contact angle was reported to be increased with the decrease in the thickness of PTFE layer, which may be due to the increased surface roughness of PTFE layer with decrease in thickness. CE resistance of PTFE coated material with a maximum thickness of 121 μm, was found to be highest for all the combinations of operating parameters, which may be attributed to its lowest fracture toughness and better cushioning effect. Further, it was observed that CE of the coated and SS410 steel was found to be maximum at the chosen maximum velocity, normal impact angle, and intermediate SOD. The signatures of pits with circular and elongated morphology were observed for normal and shallow impact angles, respectively. In case of lowest PTFE layer thickness, overlapped pits with relatively higher depth were observed, which might be responsible for higher CE of the same amongst all the PTFE coatings.